Guyot Science 2006
Department of Geosciences, Princeton University
Guyot Science 2006
A Summary of the Research Progress and Accomplishments Made by the Faculty Members of the Department of Geosciences During the Year 2006
The year January – December 2006 witnessed some important events and transitions for the Princeton Department of Geosciences. Tony Dahlen stepped down after five years as department chair and was succeeded by Bess Ward, a marine microbiologist and biogeochemist who has been a member of the faculty since 1998. George Philander accepted a Research Chair in Climate Studies at the University of Cape Town, where his mission is to raise the quality and visibility of South African climate and ocean science on the national and international stage. He remains an essential member of our faculty for half the year and is spending his spring semesters in South Africa. Guust Nolet was inducted into the American Academy of Arts and Sciences and was awarded the Bownocker Medal from Ohio State University. Previous recipients include several NAS members in the Geosciences, as well as Al Gore (2004). Jorge Sarmiento published a Chemical Oceanography textbook that was very well received and seems set to become the new standard in the field. Daniel Sigman, an isotope biogeochemist, and Thomas Duffy, a mineral physicist, were both promoted to full professor. Gerta Keller and T.C. Onstott continued to attract media and national attention, Gerta for her high visibility work on the controversy over the impact theory of mass extinction, and T.C. for his innovative biogeochemistry work in exotic environments such as deep gold mines and the Arctic Tundra. We were joined by two assistant professors, Adam Maloof, a geologist who applies paleomagnetism and other tools to the study of the ancient earth, and Frederik Simons, a geophysicist who is developing a variety of innovative new tools to study the struc- ture and evolution of planetary lithospheres as well as pioneering in the development of a freely drifting submersible vehicle to increase teleseismic coverage in the world’s oceans. Adam and Frederik participated in the Freshman seminar with Emeritus Professor Robert Phinney, continuing the tradition of serious field work for beginning students, which is so important in our undergraduate program. The recent research accomplishments of each member of the Geosciences faculty are described in the individual reports that follow. A list of faculty publications during the past two years, 2005-2006, is appended to each narrative report.
Geosciences Faculty: Back row, left to right: Allan Rubin (s), Bill Bonini (r), Jason Morgan (r, s), George Philander, Michael Oppenheimer (s), Kenneth Deffeyes (r), Tony Dahlen (s), Guust Nolet, John Suppe, Gregory van der Vink (s), Michael Bender, Jorge Sarmiento, Tullis Onstott, Lincoln Hollister, François Morel, Robert Phinney (r, s); Front row: Franklyn van Houten (r, s), Daniel Sigman, Gerta Keller, Adam Maloof, Bess Ward, Chairman, Frederik Simons, Nadine McQuarrie, Satish Myneni, Tom Duffy. (r) = emeritus; (s) = photo scanned. Photo by Bill Bonini with additions by Laurie Wanat.
Michael Bender During the past year, we continued two long-term Professor programs: measuring the O2/N2 and Ar/N2 ratio of air at Ph.D., 1970, Columbia University the 8 remote sampling sites of our observing network, and email: [email protected] measuring the O2/Ar ratio and triple isotope composition of O2 (hence net community production and gross primary production on a cruises transiting the Southern Ocean).
Highlights of our research during the past year: 1. Developing a method for measuring the 40Ar/38Ar ratio of air to high precision (± 0.01 ‰), and using it to determine, by analyzing gases from the Vostok and EPICA Dome C ice cores, the current rise rate. The results constrain the degassing rate of 40Ar from the solid Earth, providing a target for models of Earth degassing and also providing a tool The activities of my laboratory focus largely on studies of the to date very old ice samples by dating trapped gases from the geochemistry of O2, with applications to understanding the Dry Valleys and elsewhere (to an uncertainty of about ± 200 global carbon cycle and glacial-interglacial climate change. The kyr). geochemical properties we study are the concentration of O in 2 2. Participating in an expedition to Mullins Valley, Ant- air (which we measure to very high precision), and the relative arctica, led by Dave Marchant (Boston University) to sample abundance of the three stable O isotopes (16O, 17O, and 18O) in ice that underlies millions-year-old volcanic ashes. We O . There are two subjects for the isotopic studies: O in fossil 2 2 successfully drilled cores out to ash ages of 1.5 Ma, and will air extracted from ice cores, and dissolved O in seawater. 2 date these samples and begin reconstructing greenhouse gas The results inform us about a range of topics. Studies of concentration histories further back in time than heretofore the O concentration (or ratio of O /N ) in air constrain the 2 2 2 possible. fate of fossil fuel CO2 that does not remain in the atmosphere. 3. Completing a study of the O /N ratio of the Vostok These measurements allow us to partition the “missing” CO2 2 2 between the oceans and the land biosphere. They also constrain ice core and using the data, which vary with local summer- rates of seasonal biological production by the oceans. Finally, time solar insolation, to date the core by an orbital tuning they provide a test of models describing the global interaction approach (one aligns the O2/N2 variations with insolation of ocean circulation and biogeochemistry. variations). This work provides the most accurate chronol- ogy for the Vostok ice core prior to about 140 ka, and allows The isotopic measurements of 2O in ice-core trapped gases reflect the relative fertility of Earth’s biosphere, averaged over direct comparison of the timing of climate changes with about 1,000 years. the timing of changes in insolation induced by variations in Earth’s orbit about the sun. The triple isotope composition of 2O in seawater reflects the fraction of dissolved O2 from photosynthesis. O2 super- 4. Developing a greatly improved and simplified method saturation reflects net production (photosynthesis in excess of for continuously measuring the O2/Ar ratio of surface seawa- respiration); by combining measurements of O2 concentrations ter dissolved gases during ships’ transits. The data allow us and isotopes, we can determine rates of photosynthesis, respira- to continually calculate the air-sea flux of 2O derived from tion, net production, and organic carbon export in aquatic mixed layer photosynthesis in excess of respiration, hence net ecosystems. Of course rate determinations of these processes in community production. seawater have been made for many years; what makes our work new is that our approach does not require labor-intensive bottle 5. Integrating Southern Ocean data and models to dem- incubations at sea, and our measurements can be made on large onstrate a strong link between the observed spatial distribu- numbers of samples collected by colleagues on cruises of op- tion of net community production and modeled dissolution portunity, and returned to the lab. of iron in the surface waters, with a ratio of Fe deposition A second focus involves the geochemistry of Ar and will to NCP close to the estimated Fe/C ratio of phytoplankton. expand to include other noble gases. In seawater samples, Ar This correlation is arguably the strongest evidence for close gives a measure of physical supersaturation due to warming of regulation of carbon export by iron deposition throughout most of the Southern Ocean. This is Nicolas Cassar’s post- waters and bubble entrainment. In air samples, the Ar/N2 ratio reflects seasonal outgassing and ingassing due to temperature- doctoral research. driven solubility changes, and also to atmospheric mixing. In 6. Analyzing our atmospheric O2/N2 records, which the past atmosphere, the isotopic abundance of 40Ar, produced date back to 1991, to determine the rate of change in ocean by radioactive decay of potassium in the solid Earth, has carbon uptake during this period. The data show that ocean progressively risen with time. The recent rise rate reflects the uptake of CO2 is accelerating as the CO2 concentration of air outgassing rate of the contemporary Earth, and it also provides rises. This result is widely assumed, but has not previously a means of dating trapped gases in ancient ice (the older the ice, been demonstrated experimentally. We need to collect data the lower its 40Ar abundance). for at least one more year before we nail this down. Two-Year Bibliography Kaiser, Jan, Matthew K. Reuer, Bruce Barnett, and Michael L. Refereed articles: Bender, Marine productivity estimates from continuous Brook, E. J., J. W. C. White, Annie S. M. Schilla, Michael L. oxygen/argon ratio measurements by shipboard membrane Bender, Bruce Barnett, Jeffery P. Severinghaus, Kedrick C. inlet mass spectrometry, Geophysical Research Letters, 32, Taylor, Richard B. Alley, Eric J. Steig, Timing of millennial- doi:10.1029/2005GL023459, 2005. scale change at Siple Dome, West Antarctica, during the last Battle, Mark, Sara Mikaloff Fletcher, Michael L. Bender, Ralph glacial period, Quaternary Science Reviews, 24, 1333-1343, F. Keeling, Andrew C. Manning, Nicolas Gruber, Pieter P. 2005. Tans, Melissa B. Hendricks, David T. Ho, Caroline Simons, Bender, M. L., D. T. Ho, M. B. Hendricks, R Mika, M. O. Battle, Robert Mika, and Bill Paplawsky, Atmospheric potential P. P. Tans, T. J. Conway, B. Sturtevant, and N. Cassar, oxygen: New Observations and their implications for some atmospheric and oceanic models of the global oxygen and Atmospheric O2/N2 changes, 1993–2002: Implications for the carbon dioxide cycles, Global Biogeochemical Cycles, 20, partitioning of fossil fuel CO2 sequestration, Global Biogeo- chemical Cycles, 19, GB4017, doi:10.1029/2004GB002410, doi:10.1029/2005GB002534, 2006. 2005. Bender, M. L., G. Floch, J. Chappellaz, M. Suwa, J. M. Barnola, Hendricks, Melissa B., Michael L. Bender, Bruce A. Barnett, T. Blunier, G. Dreyfus, J. Jouzel, and F. Parrenin, Gas age- Peter Strutton, and Francisco Chavez, The triple oxygen ice age differences and the chronology of the Vostok ice core, 0-100 ka, Journal of Geophysical Research – Atmo- isotope composition of dissolved O2 in the equatorial Pacific: a tracer of mixing and biological production, Journal of spheres, 111, doi: 10.1029/2005JD006488, 2006. Geophysical Research - Oceans, 110, C12021, doi:10.1029/ Articles in press or submitted: 2004JC002735, 2005. Reuer, Matthew K., Bruce A. Barnett, Michael L. Bender, Paul Suwa, Makoto, Joseph C. von Fischer, Michael L. Bender, G. Falkowski, and Melissa B. Hendricks, New estimates Amaelle Landais, and Edward J. Brook, 2005 Chronology of Southern Ocean biological production rates from O2/Ar reconstruction for the disturbed bottom section of the GISP2 ratios and the triple isotope composition of O , Deep Sea Re- and the GRIP ice cores: implications for Termination II in 2 search, in press, 2005. Greenland, Journal of Geophysical Research - Atmospheres, 111, doi:10.1029/2005JD006032, 2005.
F. Anthony Dahlen the earth’s surface beneath the Coral Sea, east of Solomon Professor and south of Java are also evident in Raffa’sP -wave and S- Ph.D., 1969, University of wave tomographic images. These will be the last results from California, San Diego the Princeton tomography group that rely on measurements email: [email protected] made by other investigators. In future work, we will use our newly developed finite-frequency tomographic theory to invert a suite of P-wave and S-wave traveltimes and ampli- tudes, currently being measured in ten overlapping passbands by graduate students Karin Sigloch and Yue Tian, under the supervision of Guust Nolet. Fifth-year graduate student Tarje Nissen-Meyer made substantial progress during 2006 on his dissertation project, to compute exact 3-D waveform and traveltime sensitiv- ity kernels in a background spherical earth model, using an In 2006 I wrapped up my collaboration with Guust Nolet axially symmetric spectral element method (SEM). Once the and postdoctoral fellow Raffaella Montelli, to account for 2-D SEM is fully developed, it will be capable of comput- finite-frequency wavefront healing effects in global seismic ing the response of a spherical earth to a moment tensor or traveltime tomography. In this project, Raffa used 3-D finite- point force source up to 1-Hz frequency, substantially better frequency sensitivity kernels to invert long-period, cross-cor- than can be achieved with normal-mode summation codes. relation P-wave and S-wave traveltimes measured by Guy Individual 2-D computations are required for the monopole, Masters at Scripps Institution of Oceanography, together dipole and quadrupole components of the source. At the with short-period ISC traveltimes edited by Bob Engdahl at present time, these three source types have been successfully the University of Colorado. The results, published inScienc e implemented and fully benchmarked against both mode (2004) and Geochemistry, Geophysics, Geosystems (2006) pro- summation and an exact analytical solution in the simple vide persuasive evidence for the presence of a number of well- case of an earth model lacking a fluid outer core. These resolved convection plumes—including Ascension, Azores, results will be published in two back-to-back papers in the Canary, Cape Verde, Cook Island, Easter Island, Samoa and next issue of Geophysical Journal International. During the Tahiti—that originate in the vicinity of the core-mantle past several months, Tarje has optimized the mesher to deal boundary, as originally proposed by Jason Morgan more than with a realistic spherical earth model such as PREM, and thirty years ago. All of the observed plumes have a diameter implemented a displacement potential representation to ac- of several hundred kilometers, indicating that plumes convey count for the presence of the earth’s fluid core. The next steps a substantial fraction of the internal heat escaping from the are to fully parallelize the code for implementation on a small earth. Starting plumes that have not yet risen all the way to cluster, and to implement the rotations of the displacement
and strain fields and the temporal convolutions needed to multitaper methods of estimating spherical harmonic power compute the sensitivity kernels. This work is being conducted spectra from noisy data on a spatially localized portion of a in collaboration with Alex Fournier, who defended his Princ- sphere. These results are applicable to geodetic, planetary and eton Ph.D. dissertation in December 2003, and who is now cosmological data. Finally, we have begun to think about the a member of the faculty at the University of Toulouse. extension of our theoretical results to noise-cognizant multi- Guust Nolet and I are both very excited about a re- tapers, for application to data collected by the GRACE space cently launched collaboration with Ingrid Daubechies in the mission. These new tapers should be applicable to a variety of Princeton Department of Mathematics, to use wavelets and hydrological and climate problems, including the estimation possibly curvelets as a basis for finite-frequency tomographic of water balances in drainage basins, and the determination inversions. In 2006 we obtained our first results, which of contemporary icesheet melting rates in Greenland and have been submitted for publication in Geophysical Journal Antarctica. International. In this paper, postdoctoral scholar Ignace Loris Two-Year Bibliography l combined an 1-norm regularization method with a wavelet Refereed articles: basis to solve a toy 2-D tomographic problem of the canoni- Ampuero, J.-P. and F. A. Dahlen, Ambiguity of the moment ten- cal linear form Am = d, allowing for the possibility of sharp sor, Bull. Seismol. Soc. Amer., 95, 390–400, 2005. discontinuities superimposed on a smoothly varying back- Dahlen, F. A., Finite-frequency sensitivity kernels for boundary topography perturbations, Geophys. J. Int., 162, 525–540, ground; an iterative method is used to find a sparse solution 2005. m that contains no more fine-scale structure than is necessary Nolet, G., F. A. Dahlen, and R. Montelli, Travel times of seismic to fit the datad within the assigned errors. Ignace has now waves: a reassessment, in Seismic Earth: Array Analysis returned to a permanent faculty position at the Vrije Uni- of Broadband Seismograms, edited by A. Levander and G. verseteit in Brussels, and a new postdoc, Huub Douma, who Nolet, Geophysical Monograph, 157, American Geophysical Union, Washington, D.C., 37–47, 2005. received his Ph.D. from the Colorado School of Mines, has Dahlen, F. A. and G. Nolet, Comment on “On sensitivity kernels joined the project. Huub has begun to investigate whether for ‘wave-equation’ transmission tomography” by de Hoop seismic reciprocity can be used to speed up a number of cur- and van der Hilst, Geophys. J. Int., 163, 949–951, 2005. rently challenging or even prohibitive numerical computa- Zhou, Y., F. A. Dahlen, G. Nolet, and G. Laske, G., Finite-fre- tions in complex media. quency effects in global surface-wave tomography, Geophys. J. Int., 163, 1087–1111, 2005. Finally, in 2006, I was pleased to be able to continue Dahlen, F. A., and Y. Zhou, Surface-wave group-delay and at- my collaboration with Frederik Simons, who just joined the tenuation kernels, Geophys. J. Int., 165, 545–554, 2006. Geosciences Department as our newest assistant professor in Zhou, Y., G. Nolet, F.A. Dahlen, and G. Laske, G., Global upper- September 2006, following two years as a faculty member mantle structure from finite-frequency surface-wave tomog- at University College London. Frederik and I extended our raphy, J. Geophys. Res., 111, doi:10.1029/2005JB003677, spherical generalization of the one-dimensional time-fre- 24 pages & 22 figures, 2006. Simons, F. J., F.A. Dahlen, and M. Wieczorek, Spatiospectral quency multitapers of Slepian and Thomson to the case of a concentration on a sphere, SIAM Review, 48, cover article, double polar cap, for application to the so-called “polar gap” 504–536, 2006. problem in satellite geodesy (Geophysical Journal International Simons, F. J. and F.A. Dahlen, Spherical Slepian functions and 2006), and will shortly submit a new paper to the same the polar gap in geodesy, Geophys. J. Int., 166, 1039–1061, journal, comparing periodogram, maximum likelihood and 2006.
Thomas S. Duffy crystal structures and phase transitions at conditions of the Professor Earth’s deep lower mantle and outer core. Ph.D., 1992, California Institute There has been considerable interest in recent years in of Technology the potential role of hydrogen in the Earth’s interior. Even email: [email protected] if present in small quantities, hydrogen can strongly af- fect phase relations, rheological and transport properties, and even seismic velocities. Wadsleyite (bMg2SiO4) is the high-pressure polymorph of olivine that is expected to be a dominant mineral in the Earth’s transition zone from 410 km to 520 km depth. Wadsleyite can incorporate variable amounts of water up to 3.3 wt %. With graduate student Zhu Mao, we have recently measured the single-crystal elastic constants of hydrous wadsleyite with water contents between 0.4 wt % and 1.7 wt % using Brillouin spectroscopy at ambient conditions. We found that both the bulk and Our research program focuses broadly on the physical and shear modulus of hydrous wadsleyite decrease strongly with chemical properties of minerals relevant for understanding water content. Compared with anhydrous wadsleyite, 1 wt large-scale geophysical properties of the Earth and planets. % of water will lead to 7% decrease in the bulk modulus and Currently, we are emphasizing study of elastic properties to 11% decrease in the shear modulus. The olivine to wadsley- pressures of the Earth’s upper mantle and examination of ite phase transition is believed to be the origin of the major Kiefer, B., S. R. Shieh, T. S. Duffy, and T. Sekine, Strength, elas- seismic discontinuity near 410 km. Using these new results, ticity, and equation of state of nanocrystalline cubic silicon ni- tride (c-Si N ) to 68 GPa, Physical Review B, 014102, 2005. 3 4 we are examining the potential effects of water content on Shieh, S. R., T. S. Duffy, and G. Shen, X-ray diffraction study of the seismic signature at this depth. With post-doctoral fellow phase stability in SiO2 at deep lower mantle conditions, Earth Fuming Jiang, we are also carrying out parallel measurements and Planetary Science Letters, 235, 273-282, 2005. on the elastic properties of hydrous forsterite. The next step Kiefer, B. and T. S. Duffy, Finite element simulations of the laser- for both materials is to measure the elastic properties as a heated diamond anvil cell, Journal of Applied Physics, 97, 114902, 2005. function of pressure to conditions approaching the 410-km Runge, C. E., A. Kubo, B. Kiefer, Y. Meng, V. Prakapenka, G. Shen, discontinuity. This work is being carried out in collaboration R. J. Cava, and T. S. Duffy, Equation of state of MgGeO3 with colleagues from the University of Colorado and North- perovskite to 65 GPa: Comparison with the postperovskite western University. phase, Physics and Chemistry of Minerals, 33, 699-709, Seismological observations of the lowermost mantle (the 2006. D" region) have revealed a region of incredible complexity Majzlan, J., S. Speziale, T. S. Duffy, and P. C. Burns, Single- crystal elastic properties of Alunite, KAl3(SO4)2(OH)6, Physics that includes a seismic discontinuity, strong lateral hetero- and Chemistry of Minerals, 33, 567-573, 2006. geneity and regional seismic anisotropy. We are carrying out Jiang, F., S. Speziale, and T. S. Duffy, Single-crystal elasticity of a number of studies to assess the role of the phase transi- brucite, Mg(OH)2, to 15 GPa by Brillouin scattering, American tion in (Mg,Fe)SiO3 from perovskite to a post-perovskite Mineralogist, 91, 1893-1900, 2006. Kubo, A., B. Kiefer, G. Shen, V. Prakapenka, R. J. Cava, and (CaIrO3-type) phase. The existence of a CaIrO3-type phase T. S. Duffy, Stability and equation of state of the post- under deep lower mantle conditions was a surprising finding perovskite phase in MgGeO3 to 2 Mbar, Geophysical Re- as this is a very rare type of layered structure. Together with search Letters, 33, L12S12, 2006. colleagues from Berkeley and Chicago, we have carried out He, D. W., and T. S. Duffy, X-ray diffraction study of the static deformation experiments to examine development of lattice strength of tungsten to 69 GPa, Physical Review B, 73, 134106, 2006. preferred orientation in (Mg,Fe)SiO3 post-perovskite as well Speziale, S., S. R. Shieh, and T. S. Duffy, High-pressure elastic- as two analog materials (MgGeO3 and CaIrO3). Using our ity of calcium oxide: A comparison between Brillouin scat- observations together with convection and deformation mod- tering and radial x-ray diffraction, Journal of Geophysical eling, it appears that observed slip planes could explain some Research, 111, B02203, 2006. observations of seismic anisotropy in the D" region. Our oth- Shieh, S. R., T. S. Duffy, A. Kubo, G. Shen, V. B. Prakapenka, er studies of post-perovskites are focusing on determination N. Sata, K. Hirose, and Y. Ohishi, Equation of state of the post-perovskite phase synthesized from a natural of equation of state, compressibility, and structural response (Mg,Fe)SiO3 orthopyroxene, Proceedings of the National in different compositions for silicates and germanates at con- Academy of Sciences, 103, 30393043, 2006. ditions exceeding 1 Mbar and 2000 K. Merkel, S., A. Kubo, L. Miyagi, S. Speziale, H.-K. Mao, T. S. Duffy, and H.-R. Wenk, Plastic deformation of MgGeO Two-Year Bibliography 3 post-perovskite at lower mantle pressures, Science, 311, Books: 644-646, 2006. Chen, J., Y. Wang, T. S. Duffy, G. Shen, and L. Dobrzhinetskaya, Shieh, S. R., A. Kubo, T. S. Duffy, V. B. Prakapenka, and G. Advances in High Pressure Technology for Geophysical Ap- Shen, High-pressure phases in SnO to 117 GPa, Physical plications, Elsevier, Amsterdam, pp. 512, 2005. 2 Review B, 73, 014105, 2006. Refereed articles: Other miscellaneous publications: Speziale, S., F. Jiang, and T. S. Duffy, Compositional depen- Liu, H., H.-R. Wenk, and T. S. Duffy, Rheology and elasticity dence of the elastic wave velocities of mantle minerals: studies at ultra-high pressures, preface to special issue, Implications for seismic properties of mantle rocks, Structure, Journal of Physics: Condensed Matter, 18(25), June 28, Composition, and Evolution of Earth’s Mantle, edited by R. 2006. van der Hilst, J. D. Bass, J. Matas, and J. Trampert, AGU, Washington, DC, 303-323, 2005. Articles in press or submitted: Duffy, T. S., Synchrotron facilities and the study of deep plane- Wan, J. T. K., T. S. Duffy, S. Scandolo, and R. Car, First prin- tary interiors, Reports of Progress in Physics, 68, 1811-1859, ciples study of density, viscosity, and diffusion coefficients
2005. of liquid MgSiO3 at conditions of the Earth’s deep mantle, Yin, H., K. D. Hoburt, R. L. Peterson, S. R. Shieh, T. S. Duffy, Journal of Geophysical Research, in press, 2006. J. C. Sturm, Tunable uniaxial vs biaxial in-plain strain in Mao, Z., F. Jiang, and T. S. Duffy, Single-crystal elasticity of
integrated silicon and silicon-germanium thin films using zoisite, Ca2Al3Si3O12(OH) , by Brillouin scattering, American compliant substrates, Applied Physics Letters, 87, 061922, Mineralogist, in press, 2006. 2005.
Lincoln S. Hollister For information on the permitting process, see http:// Professor www.eos.ubc.ca/research/batholiths/. In addition, Ph.D., 1966, California Institute the BATHOLITHS team has been involved in debate in of Technology public forums in Canada. An op-ed I had published in the email: [email protected] Seattle Post-Intelligencer is found at: http://seattlepi. nwsource.com/opinion/279541_seismicrebut01.html. NOTE: The future of controlled source seismic imaging of coastal areas of the world will be affected by how our project fares in the arena of public and governmental policy. Comments by Terry Pavlis on the Hollister and Andronicos (2006) manuscript: From: tpavlis
Gerta Keller The new results from the Texas localities were presented Professor at AGU in Baltimore and GSA in Philadelphia in 2006 and Ph.D., 1978, Stanford University received wide media attention, with press releases by NSF email: [email protected] and GSA of our work, an invitation to give a public evening lecture at GSA to present the results, and two invitations to present talks at special symposia. The results obtained from the Brazos, Texas, provide support for the earlier findings of the pre-KT age of the Chicxulub impact and also revealed that this impact caused no extinctions. A website is main- tained on the research. The Chicxulub Debate: http://geoweb.princeton.edu/people/faculty/ keller/chicxulub.html Our new theory and its supporting evidence has been During the past two years my research project on the Creta- carried by news outlets all over the world and more than ceous-Tertiary boundary impact and mass extinction, done 100 news articles have appeared in international magazines, in collaboration with an international team of scientists, has including top journals like Nature, The Economist (G.B), culminated in spectacular success with the coming together La Recherche (France), Der Spiegel (Germany), Focus (Swit- of empirical evidence from sedimentology, stratigraphy, zerland), Facts (Austria), National Geographic, etc., and the paleontology, mineralogy, geochemistry, and paleomagnetic Geological Society of London sponsored a debate on my stratigraphy. The environmental history revealed by all of team’s work. Our work was included in six documentary these disciplines indicates that the 25-year-old impact mass films, including ABC Australia, the History Channel, Swiss extinction theory can no longer be supported. The Chicxulub TV, and the American Museum of Natural History in New impact, commonly believed to be the cause for the KT mass York. In addition, our work was the main feature in a special extinction, predates this mass extinction by 300,000 years. A BBC Horizon documentary (“What didn’t kill the Dino- second impact together with major Deccan volcanism is the saurs”), and a 45-minute TV interview with Alexander Kluge likely cause for the mass extinction. Our research results have for German Film, TV and Media. caused further controversy and calls for confirmation or refu- tation of our results. As a result, we obtained NSF funding Two-Year Bibliography Refereed articles: to drill new KT sequences in Texas and Brazil, localities at Adatte, T., G. Keller, D. Stueben, M. Harting, U. Kramar, W. 1000 km and 7,800 km from the Chicxulub impact location. Stinnesbeck, S. Abramovich, and C. Benjamini, 2005, Late Drilling was completed between the fall of 2005 and January Maastrichtian and K/T paleoenvironment of the eastern Te- 2006. thys (Israel): mineralogy, trace element and platinum group elements, biostratigraphy and faunal turnovers. Bulletin Keller, G., T. Adatte, Z. Berner, M. Harting, G. Baum, M. Prauss, Société Géologique de France. 176, 1, 35-53, 2005. A.A. Tantawy and D. Stueben, Chicxulub Impact Predates Keller, G., Biotic effects of late Maastrichtian mantle plume K-T Boundary: New Evidence from Texas EPSL, in press. volcanism: implications for impacts and mass extinctions. Keller, G., T. Adatte, A.A. Tantawy, Z. Berner, D. Stueben, H.A. Lithos, 79, 317-341, 2005. Leanza, High Stress Late Cretaceous to early Danian Keller, G., Impacts, volcanism and mass extinctions: random paleoenvironment in the Neuquen Basin, Argentina. Creta- coincidence or cause & effect? Australian Journal of Earth ceous Research, in press. Sciences, 52, 725-757, 2005. Keller, G. and A. Pardo, Guembelitria Blooms – Environmental Stueben, D., M. Harting, U. Kramar, W. Stinnesbeck, G. Keller, Catastrophes Index, Cretaceous Research, in press. and T. Adatte, High resolution geochemical record in Mexico Mort, H.P., T, Adatte, K.B. Föllmi, G. Keller, P. Steinmann, P., V. during the Cretaceous-Tertiary transition. Geochmica et Matera, Z. Berner, D. Stüben, D., Phosphorus and the roles Cosmochimica Acta, 69, (10), 2559-2579, 2005. of productivity and nutrient recycling during Oceanic Anoxic Stinnesbeck, W., C. Ifrim, H. Schmidt, A.Rindfleisch, M-C. Buchy, Event 2, Geology, in press. E. Frey, A.H. González-González, H.J.Vega, L. Cavin, Mort, H.P., T. Adatte, G. Keller, D. Bartels, K.B. Föllmi, P. Stein- G. Keller, and K.T. Smith, A new lithographic limestone mann, P., Z. Berner, E.H., Organic carbon deposition and deposit in the Upper Cretaceous Austin Group at El Rosario, phosphorus accumulation during oceanic anoxic event 2 in County of Muzquiz, Coahuila, Northeastern Mexico. Revista Tarfaya, Morocco, Cretaceous Research, in press. Mexicana Ciencias Geologicas, v. 22 (3), 401-418, 2005. Mort, H.P., Adatte, T., G. Keller, K.B. Föllmi, B. Gertsch, P. Stein- Keller, G. and A. Pardo, Qué mató a los dinosaurios? Muy Inte- mann, Z. Berner, D. Stüben,����������������������������� The���������������������������� Role of Productivity and resante, May 2006. Nutrient Regeneration at the Cenomanian-Turonian Bound- ary (OAE 2), in review. Articles in press or submitted: Keller, G., Impact Stratigraphy: old principle - new reality. GSA Pardo, A. and G. Keller, Biotic Effects of Environmental Catastro- Special Paper, in review. phes at the end of the Cretaceous: Guembelitria and Hetero- Meudt, M., Z. Berner, U. Kramar, G. Keller, and D. Stüben, Trace helix Blooms. Cretaceous Research, ISC7, in press. element content of foraminifera tests: potentialities and limits Keller, G., T. Adatte, Z. Berner, E.H. Chellai, D. Stueben, Oce- to trace hydrothermal influence on past seawater composi- anic Events and Biotic Effects of the Cenomanian-Turonian tion, Geochemical Geology, in review. Anoxic Event, Tarfaya Basin, Morocco. Cretaceous Re- search, ISC7, in press.
Adam Maloof Island, Bahamas. The purpose of this study is two-fold. First, Assistant Professor I hoped to document the source of magnetization in modern Ph.D., 2004, Harvard University carbonate muds as an analogue for ancient carbonate rocks email: [email protected] that we use for paleomagnetic study. This project has already led to one publication (Kopp et al. 2006), and I am currently preparing a comprehensive manuscript on the topic. Second, I conducted a digital topographic, and stratigraphic survey of the tidal flat to determine the nature and origin of facies variation in carbonate parasequences (in other words, is it sea level variation or tidal channel migration that controls the architecture of ancient carbonate rocks?). In fact, students in my new course, GEO 450, will conduct a 10-day research project on this topic during Spring break. I expect to submit these results for publication before the summer. My research continues to involve using sedimentary and During the summer of 2006, my new graduate stu- volcanic rocks to extract information about Earth’s ancient dent (Swanson-Hysell) and I spent two months in Australia magnetic field and the relative motion of continents, per- testing the true polar wander hypothesis for global change turbations to the global carbon cycle, climate change, and 800 million years ago. The hypothesis was first published in processes related to small meteorite impacts. GSA Bulletin in September 2006, and has generated a small During January 2006, I completed the second and final amount of public interest (News Item 1: http://geoweb. field season at Lonar Crater in India. Lonar Crater is young princeton.edu/people/maloof/). Currently, Swanson- (~40 kyr old) and formed in layered basalts, and therefore Hysell, a team of three Princeton freshman and I are prepar- represents a fairly pristine terrestrial analogue to craters on ing Australia samples for isotopic, trace element and paleo- Mars. Currently, I am writing the paper that presents the magnetic analysis. We will return to Australia this summer digital topography and the geology of the crater and ejecta for at least two months, to continue the true polar wander blanket. I am also a contributing author to papers currently project and to begin a new project in 2.7 Ga basalts with my in preparation at Harvard and MIT on shock remagnetiza- prospective graduate student, Catherine Rose. tion of basalt and remanence acquisition in impact generated For his first year project, graduate student Swanson- glass, respectively. Hysell is conducting a paleomagnetic and geochronologi- In the winter of 2006, I completed a third field season cal study of 1.1 Ga basalts from Ontario. These rocks were on the Holocene carbonate platform of Northwestern Andros thought to contain some of the only evidence in Earth history for non-dipole contributions to the geomagnetic Maloof, A.C., D.P. Schrag, J.L. Crowley, and S.A. Bowring, An field. Swanson-Hysell presented our findings at the annual expanded record of Early Cambrian carbon cycling from the Anti-Atlas Margin, Morocco; Canadian Journal of Earth Sci- Geological Society of America Meeting this fall and will be ences, 42 pp. 2195-2216, 2005. preparing the results for publication this spring. Kopp, R.E., B.P. Weiss, A.C. Maloof, H. Vali, C.Z. Nash, and J.L. In collaboration with Prof. Sam Bowring (MIT) and Kirschvink. Chains, clumps, and strings: Magnetofossil ta- graduate student David Fike (MIT/Caltech), I have expand- phonomy with ferromagnetic resonance spectroscopy; Earth ed on work published in 2005 in the Canadian Journal of and Planetary Science Letters, 247 pp. 10-25, 2006. Maloof, A.C., G.P. Halverson, J.L. Kirschvink, D.P. Schrag, B.P. Earth Sciences on the Early Cambrian of Morocco. We have Weiss, P.F. and Hoffman, Combined paleomagnetic, isotopic, added strontium and sulfur isotopic analyses and new ura- and stratigraphic evidence for true polar wander from the nium-lead geochronology to the published record of physical Neoproterozoic Akademikerbreen Group, Svalbard; Geologi- stratigraphy and carbon isotopes to better constrain models cal Society of America Bulletin, 118 pp. 1099-1124, 2006. for the evolutionary radiation of macroscopic animals. I have Articles in press or submitted: compiled this data in a proposal to NSF to (1) support David Halverson, G.P., F.O. Dudas, A.C. Maloof, and S.A. Bowring, Fike as a postdoctoral fellow at Princeton, (2) contribute to Evolution of the 87Sr/86 Sr composition of Neoproterozoic analysis costs at the geochronology laboratory at MIT, and seawater; Palaeogeography, Palaeoclimatology, Palaeoecol- (3) fund a new field season in Morocco. ogy, in review. During the next month, I will be concentrating on Halverson, G.P., A.C. Maloof, M. and Hurtgen, Stratigraphy and geochemistry of an 800 Ma negative carbon isotope stage in preparing lecture notes and problem sets for GEO 450, Earth northeast Svalbard; Chemical Geology, in press. Surface Processes. Two-Year Bibliography Refereed articles: Halverson, G.P., P.F. Hoffman, D.P. Schrag, A.C. Maloof, and A.H.N. Rice, Toward a Neoproterozoic composite carbon-iso- tope record; Geological Society of America Bulletin, 117 pp. 1181-1207, 2005.
Nadine McQuarrie plate boundaries. Research projects start with structurally Assistant Professor based field studies, the goal of which is to produce new geo- Ph.D., 2001, Arizona University logic maps at finer scales and higher resolutions than previ- email: [email protected] ously available. New geologic mapping is essential because the intersection of 3-dimensional topography and geologic structures on a 2-dimensional geologic map provides one of the few ways we can understand the geometry of structures at depth. Using the geological mapping as a foundation, the projects expand to include the creation and sequential restoration of geologic cross sections as well as new mineral cooling ages to determine the distribution, magnitude and rate of deformation. The overarching questions that drive my research include: 1) When and why is deformation plate like or diffuse? A specific question that illustrates this is: The 1960’s and 1970’s heralded in a revolution in earth-sci- “Can motion along the boundary between the North Ameri- ence thinking. Scientists realized that the outer shell of the can plate and Pacific plate (the San Andreas fault, California) earth is composed of a mosaic of 15 irregular sections or cause motion along faults 1000 km to the east (Wasatch plates. Initial tenants of plate tectonics assume that these front fault, Utah)?” 2) How and why do rates of deforma- tion along faults vary depending on the window of observa- plates are rigid and deform along narrow zones at plate 1 4 7 boundaries. In the 40 years following, we have learned that tion (10 , 10 or 10 years)? 3) Does focused precipitation or when the boundary of a plate is a continent, the resulting erosion change the way in which mountain ranges deform? deformation, or “orogen,” can be very broad and diffuse. The physiographic expression of mountain ranges is a func- The interaction of plates, at plate boundaries, generates large tion of plate interactions as well as climate, which redistrib- (magnitude 6-9) earthquakes that have recurrence intervals utes material through erosion. Thus, 4) what are the primary of 50 years to 500,000 years depending on the width of the controls on the topographic evolution of mountain ranges? deforming boundary. These earthquakes along narrow plate My research addresses these big questions as described in the boundaries (Sumatra) or diffuse (Iran) emphasize the impor- following section. tance in understanding how plates are currently deforming Integrating Rates of Deformation Across an Orogen as well as how plate boundaries have evolved through time. With the advent of global positioning systems (GPS), precise My research focuses on the kinematic evolution of mountain displacement fields of continental deformation are becom- belts, which are the continental expression of fundamental ing increasingly more exact and available across continents. These displacement fields provide an unprecedented view of eruptive centers through the Basin and Range, 3) comparing modern (the last 10 years) deformation occurring at plate robust features of the reconstruction velocity field with the boundaries, but provide only a geologically instantaneous latest GPS velocity field such as the counterclockwise rota- snapshot of plate behavior. Displacement histories over tion of the Sierra Nevada Mountains, California. 5 7 much longer scales (10 -10 years) are required for addressing Evaluating the Primary Controls on the Topographic questions of how the lithosphere responds to major changes Evolution of Mountain Ranges in plate geometry and kinematics, or to understand what The topographic expression of modern mountain ranges is portion of the modern strain recorded by GPS networks will the combination of a prior deformational history, active de- result in permanent deformation. For many regions on earth formation, which is currently raising the mountain range and the detailed geologic history necessary for long-term displace- erosional processes, which remove material and act to lower ment fields is just not available. In the last few years, I have the elevation of mountain ranges. Quantifying the feed- focused on acquiring and compiling displacement informa- backs between lithology, tectonics, and climate on multi- tion in Bolivia and western North America. scale morphologies of mountain ranges is at the forefront In Bolivia my collaborators and I have determined cool- of current geological research. One of the main objectives ing ages on minerals and collected structural data that have to this research is to understand the magnitude of control been combined in a preliminary kinematic model depict- climate and the associated erosion rates have on the forma- ing how the fold-thrust belt has developed through time tion and development of orogens. The Andes Mountains http://ge- (Barnes et al, 2006, McQuarrie et al., in rev.) ( extend over 8000 km along the western side of the South oweb.princeton.edu/pub/mcquarrie/Bolivia_NFTB. American continent and are the result of a common tectonic mov ). We have used new mapping to construct a balanced process—subduction of the Nazca plate under the South cross section across the Andean plateau from the volcanic American plate. This shared tectonic regime, combined with arc to the undeformed foreland. The restored cross section significant along strike changes in morphology, structure, and was imported into 2D MOVE (a cross-section restoration zonal climate regimes, make the South American Andes an program), and the displacement along folds and faults was ideal location to look at the factors that control topographic forward modeled providing a quantitative description of the expression of deformation. One of the first order changes kinematics (displacement, velocity, velocity change) of fold- in the morphology of the Andes Mountains along strike is thrust belt deformation. Cooling ages of minerals sampled variation in width of high elevations. Interestingly, the widest throughout the region provide age constraints for long- portion of the high elevation Andes, between 12° and 27° S, term rates of deformation and erosion. The cooling ages, is also the driest, suggesting limited erosion is an important combined with the simulated velocity field, will be used to factor in the construction of broad (350-550 km) high (4-5 link uplift and erosion to an evolving thermal field through km) continental plateaus. We are looking at the topographic 2D and 3D thermo-mechanical models. This will allow us evolution of the Andes in 3 locations: 1) the Central Andean to test the range of permissible deformation rates that can plateau in Bolivia where an impressive high elevation plateau produce the cooling history recorded in apatite fission track spans a pronounced switch in hemisphere–scale Hadley pre- and apatite and zircon (U-Th)/He sample ages. cipitation regimes at ~17°-18° S (Barnes et al, 2006, Mc- In western North America more is known about tim- Quarrie et al., in rev.), 2) the northern edge of the plateau in ing, amount, and spatial variations of deformation than any Peru where a wide zone (~350 km) of high topography with other comparable region. Compiling all of the available data minimal vertical relief transitions abruptly into a significantly on the timing and magnitude and direction of fault displace- narrower (150 km) mountain range with a narrow drainage ment into an Arc GIS (global information systems) format, divide, and 3) the Ecuadorian Andes, which is one of the we can sequentially restore deformation through western most narrow zones of high elevation topography along the North America with time, creating a series of palinspastic 8000 km long mountain chain. maps from 36 million years ago to present. The data from these maps are displayed in a variety of ways, including Active Projects computer animations, that highlight not only the areas where COCA: Climate-Orogenic Coupling in the Andes. One of the reconstructions are accurate, but more importantly where the most abrupt along strike changes in morphology of the the reconstructions are inaccurate (implying problems with Andean Mountains is in Peru. Along the northern edge of existing models and signaling where more field-based data are the Andean plateau in Peru a west-stepping, right-angle bend needed) (http://geoweb.princeton.edu/pub/mcquar- in topography is mimicked in the structural elevation (i.e. rie/WestUS_GES016.mov). The maps can also be displayed stratigraphic erosion level) of lower Paleozoic rocks. Nicole as velocity fields over 2-5-10 m.y. increments that can be Gotberg (Princeton graduate student) has initiated mapping compared to the modern GPS strain field (McQuarrie and as part of a multidisciplinary project (geophysics, structural Wernicke, 2005). The power of these sequential reconstruc- geology, sedimentology, stable isotope geochemistry, ther- tions come from: 1) highlighting areas that are not strain mochronology, climate, and geodynamical modeling) and is compatible and require additional field research on the tim- constructing balanced cross sections to quantify the mini- ing, magnitude and style of deformation (Lease et al., in rev.), mum and maximum shortening estimate across the pro- 2) restoring other data sets of interest, such as the volcanic nounced change in mountain width.
10 Structural Architecture and Kinematics of the Himalayan in time from the elevation history. We have two projects Orogen in Bhutan. The Tibetan-Himalayan orogenic system is determining the deformation and elevation history of the the archetype of continent-continent collision, and tectonic Andes in Bolivia and Ecuador. In these regions, much of models born in the Himalaya are invoked to explain orogen- the deformation occurred between 40-30 Mya, implying esis all around the world. Yet, encompassing a region greater long-lived elevations, however youthful topography and low than 2.5x106 km2, and only accessible to geologic field re- temperature thermochronometers suggest young (10-5 Ma) search in the last 20-30 years, the Tibetan-Himalayan orogen uplift and exhumation. This discrepancy needs to be rec- may be one of the more incompletely mapped and thus least onciled or understood, which will likely involve new plate understood orogens. The Bhutan Himalaya has traditionally tectonic-deformation paradigms. Postdoctoral researcher An- been an area of limited access. However, through formal col- drew Leier is combining sedimentology, U-Pb ages of detrital laborations with the Department of Geology and Mines of zircons, and O18/O16 isotope ratios to compare the timing of the Kingdom of Bhutan, specifically with the help of Tobgay isotopic changes in areas of unknown elevation (the Boliv- Tobgay, a geologist in the Department of Geology and Mines ian Altiplano today) to timing of isotopic changes in areas who is pursuing his Ph.D. at Princeton University, we can of known elevation (the Amazon Basin). Graduate student gain access to previously restricted areas. To determine the Sarah Johnston is combining detailed structural mapping first-order framework of the eastern Himalaya in Bhutan, of the Ecuadorian Andes with cooling ages from multiple and to constrain the kinematic history of deformation, we thermochronometers to document the history of deforma- plan on: 1) mapping the frontal, unexplored portion of the tion (when faults moved) and exhumation (when minerals Bhutan Himalayas; 2) integrating new mapping with existing cooled) and to model the elevation history of the mountain maps of the hinterland regions; 3) creating balanced crustal- range through time. scale structural cross sections along two transects; and 4) re- 40 39 Two-Year Bibliography storing these sections sequentially using new Ar/ Ar ages to Refereed articles: elucidate regional cooling patterns and ages of synkinematic McQuarrie, N., B. K. Horton, G. Zandt, S. Beck, and mineral growth to date fault motion. Graduate students P. G. DeCelles, The lithospheric evolution of the central Tobgay Tobgay and Sean Long are compiling preliminary Andean Plateau: Tectonophysics, v. 399, pp. 15-37, 2005. McQuarrie, N. and B. P. Wernicke, An Animated Tectonic Recon- and existing mapping, determining U-Pb ages and εNd con- struction of Southwestern North America since 36 MA: Geo- centrations in our initial rock samples and analyzing white sphere, v. 1, pp 147-172. doi: 10.1130/GES00016.1, 2005. mica in fault rocks to ascertain 40Ar/39Ar ages of synkinematic Barnes, J., T. A. Ehlers, N. McQuarrie, P. B. O’ Sullivan, minerals. J. D. Pelletier, Eocene to recent variations in erosion across the central Andean fold-thrust belt, northern Bolivia: impli- Elevation Versus Deformation. Traditionally the topographic cations for plateau evolution: Earth and Planetary Science history of mountain ranges has been thought to mimic the Letters, v. 248, pp. 118-133, (2006). deformational history. Thus, as compressive forces shorten Articles in press or submitted: and thicken the continental crust, the buoyancy forces associ- McQuarrie, N., J. Barnes, T.A. Ehlers, Geometric, kinematic and ated with a thicker, lighter crust raises the surface elevation of erosional history of the Central Andean Plateau, Bolivia: mountain ranges. Recent analytical advances that capitalize Tectonics, in review. on systematic changes in the ratios of stable isotopes with Lease, R.O., N. McQuarrie, M. Oskin, Dextral shear on the 18 16 Bristol-Granite Mountains Fault zone: Successful geologic elevation, particularly the ratio of O /O , suggest that the prediction from kinematic compatibility of the Eastern Califor- deformation history of a mountain range may be decoupled nia Shear zone: Journal of Geology, in review.
François M. M. Morel chemical factors control the growth and activity of phyto- Albert G. Blanke, Jr., Professor of plankton in the sea is the overarching question addressed in Geosciences; my research group. Ongoing projects include: the acquisition Director, Center in Environmental of carbon and iron by diatoms, the storage of iron by nitro- BioInorganic Chemistry gen fixing cyanobacteria, the acquisition of phosphorus from Ph.D., 1971, California Institute of organic compounds by coccolithophores, and the biological Technology role of cadmium in the sea. A separate long-term project email: [email protected] addresses the biogeochemical cycling of mercury. All theses projects involve some aspects of the chemistry, biochemistry, and geochemistry of trace metals in aquatic systems. Iron Uptake by Diatoms. Iron is known to limit the growth of phytoplankton, particularly diatoms, in large regions of the oceans. Old laboratory data from our group have shown Marine phytoplankton are responsible for about half of the that diatoms take up the free iron (i.e., the iron that is not global primary production and, by exporting organic matter bound to strong chelating agents) from solution. But, ac- cording to field data, the free iron in surface seawater is too to the deep sea, they maintain a low concentration of CO2 in surface waters and in the atmosphere. What physical and low to support the growth of these dominant primary pro- 11 ducers. Both new and old laboratory data show that diatoms carbon acquisition system may be in part responsible for the can obtain their iron by reducing Fe(III) in some chelates. ecological success of diatoms in the oceans. We have established that Fe(III) reduction at the diatom Use of Organic Phosphorus Sources by Coccolithophores. surface is an essential step in the uptake of iron in all cases Coccolithophores are calcite precipitating phytoplankton and developed a model for uptake kinetics that reconciles all that are dominant in many oligotrophic gyres of the oceans available data (Shaked et al. 2005). This model provides a and they can form massive blooms visible from space. They chemical framework to quantify the bioavailability of Fe in owe part of their ecological success to their ability to obtain seawater. In the course of this study, we have also shown that phosphorus from organic compounds when inorganic P diatoms produce an abundant quantity of superoxide (O -), 2 concentrations are vanishingly low. This is achieved through by extracellular reduction of oxygen (Kustka et al. 2005). the activity of the zinc enzyme alkaline phosphatase which Superoxide is an extremely reactive radical able to reduce and cleaves phosphate from various organic substrates. We have oxidize many solutes, including Fe, in seawater. To obtain a studied the activity of this enzyme in the ubiquitous species more mechanistic understanding of the iron uptake system Emiliana huxleyi and demonstrated that very small enzyme of diatoms, we have now studied the effect of Fe availability (and thus zinc) concentrations are necessary to provide the on the expression of genes coding for the proteins that are phosphate necessary for growth (Shaked et al. 2006). We thought to be responsible for the reduction of Fe(III) and the have now isolated and partially characterized this enzyme, transport of Fe in the two diatoms whose full genomes have which has no homology to other known alkaline phosphatas- been sequenced (Kustka et al. in press). Recently, we have es (Xu et al. 2006). This work provides the basis for studying established that diatoms and other marine phytoplankters are the expression of alkaline phosphatase, and, hence, the extent able to acquire Fe from iron storage proteins such as ferritins of P limitation, in the field. and Dps proteins (Castruita et al. submitted). These proteins may thus play an important role in the biological cycling of The Biological Role of Cadmium. Cadmium, an element iron in surface seawater (see below). which has been thought to be only toxic to organisms, behaves exactly like a nutrient in the sea. Because of its Iron Storage in Cyanobacteria. In addition to directly excellent correlation with phosphate, cadmium is used as a limiting primary production in some oceanic regions, iron is paleotracer for nutrients. Over the past several years, we have thought to limit it indirectly in many other regions by con- demonstrated that cadmium is an important micronutrient trolling the input of fixed nitrogen. This is because the nitro- for marine phytoplankton. In particular, we have discovered genase enzyme, which is responsible for dinitrogen (N ) fixa- 2 that diatoms possess a Cd-carbonic anhydrase, which is tion, requires a lot of Fe. The most important nitrogen fixer involved in the acquisition of inorganic carbon for photo- in the sea is the cyanobacterium Trichodesmium which thrives synthesis. We have obtained the full DNA sequence for this in tropical and subtropical regions where iron inputs from at- enzyme, characterized its active center by X-ray spectroscopy mospheric dust are highly episodic. We have thus been study- and shown its induction upon Cd addition (Lane et al. ing the mechanism of Fe storage in Trichodesmium. As a first 2005). We have also now shown that many diatom species step, we have identified, isolated, over-expressed and partially possess closely homologous versions of this Cd enzyme and characterized a Dps protein (DNA-binding protein from that it is induced under CO2 and Zn limitation (Park et al. starved cells) from this organism (Castruita et al. 2006). This 2006). Recently, we have been able to over-express an active protein, the first Fe storage protein isolated from a marine form of the enzyme (the first known Cd enzyme) and, in col- microbe, is able to store vast quantities of Fe; it is also able to laboration with Yigong Shi’s group in MOLBIO, obtain its bind to DNA and protect it from degradation. This second crystal structure (Xu et al. in prep). attribute may be important to protect the genetic material of the organism during periods of dormancy when nutrient Mercury Methylation. Our continuing work on the bio- concentrations are low or other environmental conditions are geochemistry of mercury is presently focused on mercury unfavorable. methylation. Since methyl-mercury is the species accumu- lated in fish via the food chain, this is a key transformation in Inorganic Carbon Acquisition by Diatoms. A few years determining human exposure to mercury. Yet it has received ago, we reported that diatoms growing under present-day surprisingly little attention over the past 20 years. The two atmospheric conditions function as unicellular C plants, i.e., 4 questions we are trying to answer are: 1) where is methyla- that they concentrate carbon by accumulating an interme- tion occurring in the ocean and by what mechanism? and diate C organic compound before CO fixation in their 4 2 2) what controls the rate of methylation by sulfate reducing chloroplast. This work, which implies that CO may limit the 2 bacteria in freshwater systems? On the basis of previous productivity of diatoms, has been controversial. Our ongo- field data, we have proposed that methyl mercury in the ing work shows that, in accord with our previous findings, open ocean may originate from the deep sea, perhaps from specific inhibitors of the two enzymes involved in the forma- hydrothermal vents. We have indeed measured significant tion of the C intermediates and the release of CO from 4 2 concentrations of methylmercury in some hydrothermal them (PEPC and PEPCK) inhibit photosynthesis in diatoms samples and shown that mercury methylation can be effected but not in well-characterized C microalgae (McGinn et al. in 3 chemically at high pressure and temperature by reaction with prep.). This project, in concert with our work on cadmium- yet unidentified trace organic compounds (Eileen Ekstrom’s carbonic anhydrase, indicates that a particularly effective 12 doctoral thesis, 2006). In terrestrial systems, we know that Tang, D. and F.M.M. Morel, Distinguishing between cellular and mercury methylation is effected by sulfate reducing bacteria. Fe-oxide associated trace elements in phytoplankton, Marine Chemistry 98 p. 18-30, 2006. Using cobalt limitation as a means to modulate the activity Shaked, Y., Y. Xu, K. Leblanc and F. M. M. Morel, Zinc avail- of vitamin B12, we have shown that the acetylCoA pathway ability and alkaline phosphatase activity in Emiliania huxleyi: is responsible for Hg methylation in sulfate reducing bacteria Implications for Zn-P co-limitation in the ocean, Limnology and Oceanography, 51: 299-309, 2006. that oxidize their substrate to CO2 (as commonly believed), but not in others (Ekstrom et al. submitted). Castruita, M., M. Saito, P.C. Schottel, L.A.Elmegreen, S. Myneni, E.I. Stiefel, and F.M.M. Morel, Overexpression and charac- Two-Year Bibliography terization of an iron storage and DNA-binding Dps protein Refereed articles: from Trichodesmium erythraeum., Applied Env. Microbiology Morel, F.M.M. and E.G. Malcolm., “The Biogeochemistry of Vol.72(4); 2918-2924, 2006. Cadmium” in Biogeochemical Cycles of Elements, Vol. 43 Xu, Y, T.M. Wahlund, L. Feng, Y. Shaked, and F.M.M.Morel, A of Metal Ions Biological Systems; (A. Sigel, H. Sigel, and novel alkaline phosphatase in the coccolithophore emiliania R.K.O. Sigel, eds), M. Dekker, New York, pp. 301, 2005. huxleyi (prymnesiophyceae) and its regulation by phospho- Sunda, W., N.M. Price, F.M.M. Morel, “Trace Metal ion buffers rus. Journal of Phycology, Vol.42(4); 835-844, 2006. and their use in culture studies” in Algal Culturing Tech- Park, H., B. Song, and F.M.M. Morel, Diversity of the cadmium niques, R. Anderson, Editor, Academic Press, Burlington, MA containing carbonic anhydrase (DDCA) in marine diatoms p. 35-63, 2005. and seawater., Environmental Microbiology, (13 Oct-2006 Lane, T.W, M.A. Saito, G.N. George, I.J. Pickering, R.C. Prince, doi: 10.1111/j.1462-2920.2006.01151.x). F.M.M. Morel, A., cadmium enzyme from a marine diatom, Articles in press or submitted: Nature, Vol. 435 p. 42, 2005. Xu, Y., D. Tang, Y.Shaked and F.M.M. Morel, Zinc, cadmium and Amyot, M., F.M.M. Morel and P. A. Ariya, Dark oxidation of cobalt interreplacement and relative use efficiencies in the dissolved and liquid elemental mercury in aquatic environ- coccolithophore Emiliania huxleyi., Limnology and Oceanog- ments, Environ. Sci. Technol., 39(1) p. 110, 2005. raphy, submitted. Sternberg, E., D. Tang, T.-Y. Ho, C. Jeandel and F.M.M. Morel, Ekstrom, E. and F.M.M Morel, Cobalt Limitation of Growth and Barium Uptake and Adsorption in Diatoms, Geochemica et Mercury Methylation in Sulfate Reducing Bacteria, submit- Cosmochimica Acta , Vol. 69(11) 2745-2752, 2005. ted. Kustka, A. B., Y. Shaked, A.J. Milligan, D. W. King, F.M.M. Morel, Kustka, A.B., A.E. Allen and F.M.M. Morel, Sequence analysis Extracellular production of superoxide by marine diatoms: and transcriptional regulation of Fe acquisition genes in two Contrasting effects on iron redox chemistry and bioavailabil- marine diatoms. Journal of Psychology, in press. ity. Limnol. and Oceanogr., 50(4) 1172-1180, 2005. Shaked, Y., A.B. Kustka and F.M.M. Morel, A general kinetic model for iron acquisition by eukaryotic phytoplankton. Lim- nol. And Oceanogr., 50(3) 872-882, 2005.
Satish Myneni the environment. This area of research is gaining importance, Associate Professor and researchers from different disciplines began conducting Ph.D., 1995, Ohio State studies to explore these interactions in greater detail. I am inter- University ested in exploring one of these fundamental interactions, which email: [email protected] include the evaluation of the chemical state of water in different geologic media and how this modifies the biogeochemical be- havior of different inorganic and organic moieties in the natural systems. I am also interested in evaluating the chemical state(s) of important geochemical species to develop predictive patterns for explaining their macroscale behavior. A summary of my current research projects, and accom- plishments in the last one-year are provided below. Speciation of Aluminum and Iron in Aqueous Solutions and in Solid Phases Water is essential for the origin and survival of life on our planet Aluminum and iron are among the most abundant elements and perhaps plays an important role on the existence of life on in the Earth’s crust and form common minerals of all soils and other planetary bodies as well. In several different forms, water sediments. The oxides and oxyhydroxides of these elements are mediates the physical and chemical interactions between various highly reactive towards aqueous contaminants and nutrients components of the Earth’s surface environment, which includes and play an important role in the geochemical cycling of several mineral oxides, biota and their byproducts, and the atmosphere. elements. However, several oxides and oxyhydroxides of Al3+ One of the challenges in environmental sciences is to gain a bet- and Fe3+ exist in the form of amorphous and poorly crystalline ter understanding of interactions between these different com- precipitates and aqueous polymers, whose genesis, structure, ponents in nature, and to use it to predict a variety of biogeo- composition, and reactivity are poorly understood. These chemical processes such as elemental cycling, biological chem- metastable phases occur as nanosize particulates, and convert istry of elements, and the fate and transport of contaminants in to crystalline phases if given enough time. The rates of trans-
13 formation depend on several physicochemical variables in the of C, N, and S in organic molecules to evaluate the associa- environment, and vary from a few hours to several months. My tion of these elemental cycles with the halogen-cycle. We research focuses on the structural chemistry of these metastable found several interesting results on these systems, and some phases, and on the influence of different environmental vari- of the highlights are as follows. ables that modify their transformation. My group members, Chemistry of natural organohalogens. While manmade organo- Laura Harrington and Michael Hay, are participating in this halogens are widely distributed throughout the biosphere investigation. and are characterized by varying degrees of persistence and We use different x-ray scattering and spectroscopy toxicity, natural production of organohalogen compounds techniques to evaluate the coordination environment of Al3+ 3+ is gaining recognition as a significant contributor to the and Fe in the stable and metastable phases, and vibrational organohalogen burden in the environment. With the help spectroscopy to understand the coordination environment of of my research group members, I made significant progress bridging and terminal hydroxyls. We also use x-ray spectro- in understanding the chemistry of natural organohalogens microscopy to evaluate the heterogeneity in size and compo- in the past 3-4 years. Using x-ray spectroscopy, I directly sition of these phases. In collaboration with Dr. Ann Chaka showed that the formation of organochlorines and their spe- at the National Institute of Standards and Technology, we are ciation variations in soils are directly related to the weather- conducting quantum chemical calculations to complement ing of plant material. Dr. Deshmukh (postdoctoral scholar) the experimental investigations. conducted a detailed speciation of organochlorines in the The formation of different oxyhydroxides of Al3+ and 3+ O-horizons of soils, and his studies indicated that a majority Fe in the environment is influenced by the speciation of of chlorinated organic molecules in weathering plant material these ions in aqueous solutions. It is well understood that are associated with the soluble polyphenol fraction, but not these ions exist as hexa-aqua complexes (e.g. Al(H O) 3+) 2 6 with stable lignins, as thought by several previous investiga- in highly acidic solutions and hydroxylated species (e.g. tors. Specific molecules identified in our investigation are Al(OH) (H O) l+/-) at all other pH values, and exhibit least m 2 n chlorinated xanthones (probably associated with lichens), solubility at near neutral pH. The chemical behavior of these and several other aliphatic and aromatic chlorinated mol- two ions in aqueous solutions is significantly altered by their ecules (sources uncertain at this stage). The X-ray microscopy hydroxylation; however, the changes in the electronic state studies conducted by Ms. Leri (graduate student) indicated a of these ions responsible for this enhanced reactivity is not heterogeneous distribution of organochlorines in weathering well understood. We built a new synchrotron experimental leaves, which we are attributing to the differences in organic chamber to evaluate the electronic states of the hydrated, and molecule halogenation processes. Senior, Ms. Jevon Hard- hydroxylated species of these ions in aqueous solutions. ing, and Leri are currently evaluating the dynamics of natural Chemistry of Natural Organic Molecules organochlorines in soil systems. Organic molecules are found everywhere on the surface of Researches conducted by Ms. Hakala (senior) and Leri the Earth, and their composition, molecular structure and have shown that organobromines, like organochlorines, are concentration modifies the biogeochemical processes in the common in terrestrial and marine environments. Since they environment. One of the bottlenecks in our understanding of are present at high concentrations in marine systems, we are the elemental cycles is related to the speciation of C, N, and planning detailed studies on their formation in the photic S associated with the organic molecules, and their variation zone of ocean water, and their accumulation and dehalogena- in the environment. For the past several years, my research tion in sediments. Although iodine is present at trace concen- group has been developing and using X-ray spectroscopy and trations, we are finding that iodide and iodate present in soils spectromicroscopy methods for studying the chemistry of react with naturally occurring organic molecules and form natural organic molecules in their pristine state (Rev. Min- organoiodines in short time. The presence of Ca is signifi- eral., 2002). Using these methods, I am investigating the: cantly affecting the sensitivity of X-ray spectroscopy methods • Functional group composition and macromolecular in detecting organoiodines in all natural samples. However, structure of natural organic molecules in soils and we found that the reactions of inorganic iodine with organic sediments, molecules are slow, and take about a week to reach equilib- • Role of minerals in the retention and fractionation of rium in laboratory microcosms. Rachel Zwillinger, a senior in organic molecules in the environment, my research group, conducted these investigations. • Chemistry of natural organohalogens in the environ- Reactive Carboxylic Acids in Natural Organic Molecules. Car- ment: coordination chemistry, rates of formation in boxylic acid groups are one of the most important reactive the environment and their role in various biogeo- groups in naturally occurring organic molecules. It has been chemical reactions, and widely assumed that a majority of these carboxylic acids are • Reactions at the microorganism-water interfaces. present as aromatic carboxylic acids (such as in salicylic acid). To investigate the biogeochemical processes involved in However, a combination of multidimensional nuclear mag- organic molecule halogenation in terrestrial systems and their netic resonance and infrared spectroscopy studies indicated rates in detail, we built a field station in the Princeton Uni- that a majority of carboxylic groups in natural organics are versity campus. In addition, we are monitoring the speciation associated with the aliphatic fraction, and have an electron withdrawing group on the adjacent C-atom (in the a- and 14 b-positions). The presence of such groups makes the carboxyl E. Kneedler, J.R. Lawrence, G.G. Leppard, J. Majzlan, group much more reactive and promotes the formation of B.S. Mun, S.C.B. Myneni, A. Nilsson, H. Ogasawara, D.F. Ogletree, K. Pecher, M. Salmeron, D.K. Shuh, B. Tonner, T. strong complexes (chelation) with aqueous metals and min- Tyliszczak, T. Warwick, T.H. Yoon, 2005, Soft x-ray microsco- eral surfaces. This information is important in understanding py and spectroscopy at the molecular environmental science the reactivity of common stable biomacromolecules and their beamline at the Advanced Light Source: 86-104, 2005. origin in aquatic systems. Edwards D.C., S.C.B. Myneni, Near Edge X-ray Absorption Fine In summary, my research group is developing into a Structure Spectroscopy of bacterial hydroxamate sidero- phores in aqueous solutions, 11809-11818, 2006. diverse and interdisciplinary research group to address the Cavalleri M., L.A. Naslund, D.C. Edwards., P. Wernet, H. Ogas- fundamental biogeochemical processes in the environment. awara, S.C.B. Myneni, L. Ojamae, M. Odelius, A. Nilsson, Two-Year Bibliography L.G.M. Pettersson, The local structure of protonated water Refereed articles: from x-ray absorption and density functional theory. (19) Edwards, D.C., S.B. Nielsen, A.A. Jarzecki, T.G. Spiro, S.C.B. 194508, 2006. Myneni, Experimental and theoretical vibrational spectros- Leri A.C., M.B. Hay, A. Lanzirotti, W. Rao, S.C.B. Myneni, Quan- copy studies of acetohydroxamic acid and desferrioxamine titative speciation of absolute organohalogens concentra- B in aqueous solutions: Effects of pH and iron complexation. tions in environmental samples by x-ray absorption spectros- Geochim. Cosmochim. Acta, 69: 3237-3248, 2005. copy: 5711-5718, 2006. Edwards D.C., S.C.B. Myneni, Hard and soft x-ray absorption Poussart P.M., S.C.B. Myneni, A. Lanzirotti, Tropical dendro- spectroscopic investigation of aqueous Fe(III)-hydroxamate chemistry: A novel approach to estimate age and growth siderophore complexes J. Phys. Chem. A 109: 10249-10256, from ringless trees. Geophys. Res. Let. 33 (17) L17711, 2005. 2006. Strathmann T.J., S.C.B. Myneni, Effect of soil fulvic acid on Castruita M., M. Saito, P.C. Schottel, L.A. Elmegren, S.C.B. nickel (II) sorption and bonding at the aqueous-boehmite Myneni, E.I. Stiefel, F.M.M. Morel, Overexpression and char- acterization of an iron storage and DNA-binding Dps protein (g-AlOOH) interface. Environ. Sci. Technol. 39: 4027-4034, 2005. from Trichodesmium erythraeum.: 2918-2914, 2006. Majzlan J., S.C.B. Myneni, Speciation of iron and sulfate in acid Bellenger J., F. Arnaud-Neu, Z. Asfari, S.C.B. Myneni, E.I. Stiefel, waters: Aqueous clusters to mineral precipitates. Environ. A. Kraepiel, Complexation of oxoanions and cationic metals Sci. Technol. 39: 188-194, 2005. by the biscatecholate siderophore azotochelin. DOI 10.1007/ Naslund L., D.C. Edwards, P. Wernet, U. Bergmann, H. Ogas- s00775-006-0194-6. awara, L.G.M. Pettersson, S.C.B. Myneni, A. Nilsson, X-ray Articles in press or submitted: absorption spectroscopy study of the hydrogen bond network Deshmukh A.P., C. Pachec, M.B. Hay, S.C.B. Myneni, Structural in the bulk water of aqueous solutions. J. Phys. Chem. A environments of carboxyl groups in natural organic mol- 109: 5995-6002, 2005. ecules from terrestrial systems. Part 1: 2D NMR Spectros- Li W., S. Seal, C. Rivero, C. Lopez, K. Richardson, A. Pope, A. copy. Geochim. Cosmochim. Act, in review. Schulte, S.C.B. Myneni, H. Jain, K. Antoine, A.C. Miller, Role Hay M. B., S.C.B. Myneni, Structural environments of carboxyl of S/Se ratio in chemical bonding of As-S-Se glasses inves- groups in natural organic molecules from terrestrial systems. tigated by Raman, X-ray photoelectron, and extended x-ray Part 1: Infrared Spectroscopy. Geochim. Cosmochim. Acta, absorption fine structure spectroscopies. J. App. Physics 98: in review. 053503, 2005. Komlos J., B. Mishra B., S.C.B. Myneni, P. Jaffe, Quantification Bluhm H., K. Andersson, T. Araki, K. Benzerara, G.E. Brown, of in-situ bioreduced uranium and of real time U(IV) reoxida- J.J. Dynes, S. Ghosal, M.K. Gilles, H. –Ch Hansed, J.C. tion in carbonate-rich sediments. Environ. Sci. Technol, in Heminger, A.P. Hitchcock, G. Ketteler, A.L.D. Kilcoyne, review.
Guust Nolet Tony’s own efforts at keeping research going as usual, helped George J. Magee Professor of much to keep a positive spirit among the geophysicists. Geophysics and Geological With Mark I have started to investigate how his ap- Engineering; proach to seismic tomography can be incorporated in the Associate Chair “Princeton” vision; the data he uses are complementary to Ph.D., 1976, University of Utrecht ours. With him I have also started to revamp the Powerpoint (The Netherlands) lectures of GEO210 (Earthquakes and Volcanoes) and intro- email: [email protected] duced quiz-like questions for use with clickers. 140 clickers have been acquired by the department and will have their maiden voyage in GEO210 during the Spring of 2007. Huub is part of the research group in wavelets that Tony and I run together with Ingrid Daubechies in the math- ematics department. Since his arrival he has finished some loose ends from his Ph.D. research at CSM, also involving The past year was characterized by the arrival of two new wavelets, but we hope to enlist him in the more tomography- postdocs that I supervise together with Tony Dahlen: Mark oriented projects by next year. With Ignace Loris, a postdoc Panning and Huub Douma. With Tony’s illness casting a in the math department, I have been working at the testing shadow over the researchers on the third floor of Guyot, both of wavelet-based regularization algorithms for application I Mark and Huub’s considerable enthusiasm, together with seismic tomography.
15 My two students, Yue Tian and Karin Sigloch, are close and G. Nolet (eds.), Seismic Earth: Analysis of broadband to finishing a major effort at remeasuring seismic data from seismograms, AGU Monograph Series, 37-48, 2005. Levander, A., and G. Nolet, Perspectives on array seismology the digital networks in the past twenty years. Existing mea- and US Array, in A. Levander and G. Nolet (eds.), Seismic surements of delay times and amplitudes were not suitable Earth: Analysis of broadband seismograms, AGU Mono- for application in finite-frequency tomography. I expect this graph Series, 157, 1-6, 2005. to lead to a whole new suite of tomographic models of the Dahlen, F.A., and G. Nolet, Comment on the paper “On sensitiv- Earth in the next two or three years, starting with a P-wave ity kernels for wave-equation transmission tomography” by de Hoop and van der Hilst, Geophys. J. Int., 163, 949-951, model that should make up the major part of Karin’s the- 2005. sis next year. With Yue, I have also been working at mak- Zhou, Y., F.A. Dahlen, G. Nolet and G. Laske, Finite-frequency ing finite-frequency software sufficiently user-friendly for effects in global surface-wave tomography, Geophys. J. Int., distribution, thereby eliminating one of the major obstacles 163, 1087-1111, 2005. for this theory – developed at Princeton and first applied Lebedev, S., G. Nolet, T. Meier and R.D. van der Hilst, Auto- mated multimode inversion of surface and S waveforms, here – to become accepted widely. The success of this effort Geophys. J. Int., 162, 951-964, 2005. is confirmed by the fact that one of the articles that resulted Zhou Y., G. Nolet, F. A. Dahlen, G. Laske, Global upper-mantle from this, Montelli et al., Science, 2004, reached the number structure from finite-frequency surface-wave tomography, two spot in ScienceWatch’s list of ten most cited papers in J. Geophys. Res., 111, B04304, doi:10.1029/2005JB003677, the geosciences over the past two years, a rare distinction for 2006. a paper in the field of solid earth geophysics. Simons, F.J., G. Nolet, J.M. Babcock, R.E. Davis and J.A. Orcutt, A future for drifting seismic networks, EOS Trans. AGU, 31, Much of my own efforts in the past year have gone to the 305-307, 2006. writing of a new book on seismic tomography. In the Fall of Montelli, R., G. Nolet, F.A. Dahlen and G. Masters, A catalogue this year, I have taught most of the chapters in GEO558 and of deep mantle plumes: new results from finite-frequency I hope to finish the book by September 2007. On the basis of tomography, Geochem. Geophys. Geosys. (G3), Q11007, a first draft, Cambridge University Press has already accepted doi:10.1029/2006GC001248, 2006. Nolet, G., S.-I. Karato and R. Montelli, Plume fluxes from seismic it for publication. During the writing I have obtained some tomography, Earth Plan. Sc. Lett., 248, 685-699 , 2006. new results, but lack of time has so far prevented me from Sigloch, K., and G. Nolet, Measuring finite-frequency body wave writing these up in separate publications, and if that situation amplitudes and travel times, Geophys. J. Int., 167, 271-287, does not improve I may end up leaving them simply in the 2006. book. Montelli, R., G. Nolet and F.A. Dahlen, Comment on ‘Banana- doughnut kernels and mantle tomography’ by van der Hilst Two-Year Bibliography and de Hoop, Geophys. J. Int., 167, 1204-1210, 2006. Refereed Articles: Nolet, G. and R. Montelli, Optimum parameterization of tomo- Books: graphic models, Geophys. J. Int., 161, 365-372, 2005. Levander, A., and G. Nolet (eds.), Seismic Earth: Analysis of Nolet, G., F.A. Dahlen and R. Montelli, Traveltimes and ampli- broadband seismograms, AGU Monograph Series 157, tudes of seismic waves: a re-assessment, in A. Levander 2005.
Tullis C. Onstott NAI for coring into deep permafrost in the Canadian Arctic Professor was funded in June, and I had six weeks to get a field team Ph.D., 1980, Princeton University on site. Despite transport difficulties, I did manage to get 4 email: [email protected] investigators, including myself, to High Lake for 3 weeks, dur- ing which we successfully captured 200 meters of permafrost and subpermafrost core from Archean metavolcanic strata. We were able to utilize core liners, fluorescent microspheres and perfluorocarbon compounds added to the drilling water with an HPLC pump during the coring. These protocols assured us of being able to obtain high-quality cores for microbial analyses and of being able to assess the level of contamination. We were also able to obtain some moderately contaminated samples of the subpermafrost saline water before the borehole froze. Cores were processed on site in a cleaned, anaerobic Deep Permafrost Environments and the Mars Exploration glove bag, and samples were sealed in vacuum canisters for Program pore gas analyses, frozen in a -20oC freezer for DNA and lipid Given the recent reports published in Science of modern fluvi- analyses, and were sealed in Mason jars and kept in ice coolers al-like gully deposits in Martian craters that appear to emanate for activity measurements and enrichments. We were able to from beneath the permafrost, it is imperative that we examine obtain dry ice through shipments from Calgary, which permit- the permafrost/subpermafrost regions on Earth to understand ted us to transport samples back to the USA. Unfortunately, what forms of microbial life exist therein. Our proposal to the new regulations from the Dept. of Homeland Security exacer-
16 bated our transport efforts, and many samples arrived unfrozen ment of the near-IR CRDS and to support a mid-IR CRDS or exposed to air. From Princeton, the salvaged core samples using a Quantum Cascade Laser in collaboration with Prof. were shipped out to five other investigators for characterization Clair Gmachl at PRISM, who is the Director of the MIRTHE of their geophysical, microbial, and geochemical properties. Facility. NASA also eliminated support for their ASTID and 35 At Princeton, SO4 microautoradiography experiments are ASTEP programs, which meant that the proposals we sub- being performed to locate regions within the rock core that mitted this year concerning Planetary Protection of Martian harbor sulfate reducing bacteria. These experiments are being Rovers are in limbo. Nevertheless, thanks to support from performed at 4oC as opposed to the -6 to 2oC in situ tempera- Princeton University and our IPTAI grant we were able to tures. support an undergraduate, David Smith, to go to Kennedy Another good development for this research is the pub- Space Center this summer, where he tested the survivability lication of a new amplification procedure last year known as of psychrotolerant aerobic bacteria on Mars by utilizing a Multiple Displacement Amplification (aka MDA). This has Mars Simulation Chamber with the assistance of Dr. Andrew the potential of being much more sensitive than the PCR Schuerger of the University of Florida. technique that is commonly utilized. Daniel McGown has The South African Deep Microbiology Project and been testing this procedure in our lab, and it appears to be suc- NELSAM cessfully amplifying DNA from Lupin Mine filters for where The discovery by my former graduate student, LiHung Lin, of no PCR product had been formerly derived. This was an an environment in the deep subsurface of South Africa, which important step forward for Daniel’s thesis research, which is to is dominated by one sulfate reducing bacterial species that perform environmental genomic analyses of the Lupin Mine has been sustained for millions of years by radiolysis of water subpermafrost saline water. With the ability to clone this am- and sulfide was published inScience this year. It was quite an plified product, we can now use PCR to amplify specific genes, achievement because it not only required DNA and S isotopic such as functional genes, to identify the metabolic capabilities analyses of the fracture water, but also S isotopic analyses of of the subpermafrost community and, with our colleagues at the fracture mineralogy, the latter of which he performed as a LBL, obtain complete sequence data, perhaps yielding almost postdoctoral research associate at the Carnegie Institute. This complete genome sequences for our low diversity and extreme- publication is timely as a recent review paper published in ly low biodensity environments. The MDA procedure will Nature citing LiHung’s earlier papers on radiolytic reactions be essential for analyses of the core samples collected at High is proposing the same mechanism may be supporting deep Lake, which, based upon prior experiences, typically yield no subseafloor microbial life. PCR product except from the contaminated portions. The use The DNA obtained from this same site was completely of this procedure requires extreme care in maintaining a DNA- sequenced by the Joint Genomics Institute and the annota- free laboratory environment. tion that was completed this year indicates that it appears to Our group has continued to focus upon methane as a represent the complete genome of one microbial species. This potential biomarker for Martian life since the discovery of organism, which hasn’t been successfully cultured and is the methane in the Martian atmosphere in 2004 by several inves- dominant species below a depth of 2 km in South Africa, tigators. This discovery led to a plethora of papers speculat- represents a new genus of Firmicutes with genetic capabilities ing on its abiogenic or biotic origin, including my own paper that are surprising when compared to what we thought were published this year in Astrobiology Journal. One thing that is the characteristics of deep subsurface organisms. It is capable certain is that the methane is emanating from the subsurface of both autotrophic and heterotrophic metabolisms, of N2 of Mars today, but whether it is related to the modern gully fixation, and of chemotactic motility. In a manuscript that is deposits is not known. No instruments are currently flight almost ready for submission to Science, we are proposing to ready that are capable of performing C and H isotopic analyses name this organism, Desulforudis audaxviator. It is the first of methane, which is critical to determining the origin of the complete genome assembled from environmental DNA and methane. John Kessler, a postdoctoral research fellow in our exhibits an incredibly low number of small nucleotide poly- laboratory, however, has succeeded in constructing a near-IR morphisms, which implies either a surprisingly low number Cavity Ringdown Spectrometer (CRDS), which currently has of doublings in this ancient environment or a remarkably low a reproducibility of 0.03%, better than has ever been published mutation rate compared to ocean planktonic species. It also for CRDS devices to date, and he has been measuring trace contains evidence of multiple lateral gene transfers including gases in the lab air. Now that he has obtained sufficient preci- from Archaea and from viruses. sion for Martian methane gas concentrations, he is modifying This year we completed coring and installing a packer in the instrument to measure the C and H isotopic composition what has been named the DAFBIO borehole hole located at of methane in the lab air, at which point he’ll be ready to pub- 3.7 km depth in Tau Tona mine as part of an NSF funded lish his first paper on the instrument. project to monitor earthquake seismicity. This borehole will The bad news is that NASA has cut funding for the NASA enable us to relate ongoing mining-induced seismicity activity Astrobiology Institute, which means that our fourth and fifth to geochemical and microbial fluctuations and now represents year funding will be reduced from what was promised. As a the deepest site in the world for long term observation of result, John Kessler submitted two proposals to NSF equip- subsurface phenomena. This was truly an international effort ment programs to acquire support to complete the develop- as the ICDP has paid for the acquisition of pristine cores from 17 the site, the German government is supporting a group from Two-Year Bibliography Univ. of Potsdam to investigate changes in gas chemistry and Refereed articles: the South African NRF is supporting our colleagues from Lin, L-H, J.A.Hall, J. Lippmann, J.A. Ward, B. Sherwood-Lollar, and the Univ. of Free State to run the site. Having the capability T.C. Onstott, Radiolytic H2 in the continental crust: Nuclear for long term in situ studies will hopefully lead to an under- power for deep subsurface microbial communities, Geochem. standing of some of the mysterious relationships we’ve been Geophys. Geosys, 6: 10.1029/2004GC000907, 2005. Kieft, T.L., S.M. McCuddy, T.C. Onstott, M. Davidson, L-H Lin, observing with spot samples over the past six years. In the B. Mislowack, L.M. Pratt, E. Boice, B. Sherwood Lollar, J. coming year, we may have to modify the packer system be- Lippmann-Pipke, S.M. Pfiffner, T.J. Phelps, T. Gihring, cause of the deformation that occurred in the borehole during D. Moser, and A. van Heerden, Geochemically Generated, En- the interval of time separating the completion of coring and ergy-Rich Substrates and Indigenous Microorganisms in Deep, installation of the packer. We will also be analyzing the cores Ancient Groundwater, Geomicrobiology Journal, 22:325-355, for sulfate reducing activity and extracting and sequencing 2005. Moser, D. P., T. M. Gihring, F. J. Brockman, J. K. Fredrickson, the DNA (again using the MDA methodology). In a related D. L. Balkwill, M. E. Dollhopf, B. Sherwood Lollar, L. M. Pratt, laboratory activity, Mark Davidson, my graduate student, has E. Boice, G. Southam, G. Wanger, B. J., Baker, S. M. Pfiffner, for the first time, successfully completed a retentostat experi- L.-H. Lin, and T. C. Onstott. Desulfotomaculum spp. and ment under thermophilic, anaerobic conditions using a model Methanobacterium spp. Dominate 4-5 km Deep Fault. Appl. sulfate reducing bacterium that is phylogenetically similar to Environ. Microbiol. 71:8773-8783, 2005. Lin, L.H.,P-L Wang, D. Rumble, J. Lippmann-Pipke, E. Boice, L.M. Desulforudis audaxviator. The retentostat enables him to test Pratt, B. Sherwood Lollar, Brodie, Eoin, T. Hazen, G. Andersen, the metabolic physiology of the organism under zero growth T. DeSantis, D.P. Moser, D. Kershaw, and T.C. Onstott, Long conditions, and thus represents a more accurate laboratory term biosustainability in a high energy, low diversity crustal simulation of subsurface conditions than a chemostat experi- biome. Science 314:479-482, 2006. ment where growth is continuous. Once the packer system Onstott, T. C., L-H Lin, M. Davidson, B. Mislowack, M. Borcsik, J. Hall, G. Slater, J. Ward, B. Sherwood Lollar, J. Lippmann- has been tested in South Africa, the plan is to set up an in situ Pipke, E. Boice, L.M. Pratt, S.M. Pfiffner, D.P. Moser, T.M. retentostat experiment and monitor changes in the biodensity Gihring, T. Kieft, T.J. Phelps, E. van Heerden, D. Litthaur, and microbial community structure. M. DeFlaun, R. Rothmel, G. Wanger, and G. Southam, The This year, in a trip to a Pt mine in South Africa, I was origin and age of biogeochemical trends in deep fracture water successful in recovering biofilm samples containing the star- of the Witwatersrand Basin, South Africa. Geomicrobiol. Jour. 23:369-414, 2006. shaped microbe that had been seen in samples collected four Pfiffner, S. M., J.M. Cantu, A., Smithgall, A. Peacock, D.C., White, years ago. In January ’07 we’ll try to determine the phylog- D. P. Moser, T. C. Onstott, and E. van Heerden, Phospholipid eny of this organism. I also collected samples of some of the Fatty Acid Profiles and Biodensity Estimates for Water, Rock most bizarre biofilms I’ve ever seen from dripping boreholes. and Air Samples Recovered from Witwatersrand Basin Mines. I have been working with Bianca Mislowack to complete Geomicrobiol. Jour. 23:431-442, 2006. her Ph.D. thesis during several visits she made to my office Slater, G. F., J. Lippmann-Pipke, C. M. Reddy, G. Lacrampe-Cou- loume, T.C. Onstott, B. Sherwood Lollar, 14C distribution in over the past year. She has completed a manuscript that methane and DIC in South African gold mines: Implications is ready for submission to Environmental Microbiology and to timing of methanogenesis. Geomicrobiol. Jour. 23:453-462, which represents the first chapter of her thesis. We plan to 2006. submit this in early January ’07. Her goal is to complete two Wanger, G., T.C. Onstott, and G. Southam, Structural and Chemi- more chapters during ’07 and submit her thesis. cal Characterization of a Natural Fracture Surface from 2.8 Kilometers Below Land Surface: Biofilms in the Deep Subsur- Deep Underground Science and Engineering Laboratory face. Geomicrobiol. Jour. 23:443-452, 2006. (DUSEL) Gihring, T. M., D.P. Moser, L.-H. Lin, M. Davidson, T.C. Onstott, This year we completed the “glossy” report on DUSEL L. Morgan, M. Milleson, T. Kieft, E. Trimarco, D. L. Balkwill, and M. Dollhopf, The distribution of microbial taxa in the subsur- entitled DEEP SCIENCE: A Deep Underground Science face water of the Kalahari Shield, South Africa. Geomicrobiol. and Engineering Initiative, which will be released in January Jour. 23:415-430, 2006. ‘07. The two candidate sites for DUSEL are submitting their Lin, L-H., T.M. Gihring, B. Sherwood Lollar, E. Boice, L.M. Pratt, S3 proposals to NSF in January ’07 along with a competing J. Lippmann-Pipke, R.E.S. Bellamy, J. Hall, and T.C.Onstott, proposal from the University of Washington for a site located Planktonic microbial communities associated with fracture- derived groundwater in a deep gold mine of South Africa. in the Cascades. One site will be awarded funds for further Geomicrobiol. Jour. 23:474-497, 2006. characterization and the development of a plan for construc- Trimarco, E., D.L. Balkwill, M.M. Davidson, and T.C. Onstott, In tion, which will then be submitted to Congress for FY09. Situ Enrichment of a Diverse Community of Bacteria from a 4-5 km Deep Fault Zone in South Africa. Geomicrobiol. Jour. The As Remediation Project (SERDP) 23:463-473, 2006. My laboratory technician, Eric Chan, successfully completed Onstott, T. C., D. McGown, J. Kessler, B. Sherwood Lollar, K.K. the laboratory phase of this investigation which demonstrat- Lehmann, S. and Clifford, S. Martian CH4: sources, flux and ed that As could be successfully removed from groundwater detection. Astrobiology Journal 6:377-395, 2006. under sulfate reducing conditions and that the solid phase As Sherwood Lollar, B., G. Lacrampe-Couloume, G.F. Slater, J. Ward, D.P. Moser, L.-H Lin, and T.C. Onstott, Abiogenic gases sup- was stable under aerobic conditions. This is being prepared port H2-based autotrophy and methanogenesis in the deep for publication as we await the decision of SERDP to fund a subsurface. Chem. Geol. 226:328-339, 2006. field demonstration of our process in Florida this year. 18 Michael Oppenheimer Of particular importance will be the development of new ap- (Woodrow Wilson School and proaches to scientific assessment that minimize the impact of Department of Geosciences) negative learning on societal decisions. The relation between Albert G. Millbank Professor of negative learning and precautionary approaches to decisions Geosciences and International will be explored within a formal framework, and particular Affairs case studies of learning will also be investigated. Ph.D., 1970, University of Chicago Two-Year Bibliography email: [email protected] Unrefereed Articles, Reports, Meeting Abstracts The Latest Myths and Facts on Global Warming (with James D. Wang), Environmental Defense, 2005. Future of Sea Level Rise and the New Jersey Coast: Assessing Potential Impacts and Opportunities (with M.J.P. Cooper and M. Beevers) November 16, 2005. Naik, V., D. L. Mauzerall, L. W. Horowitz, D. Schwarzkopf, V. Ramaswamy, and M. Oppenheimer, Sensitivity of global tro-
pospheric O3 distribution and its radiative forcing to regional The overarching theme of my research is the question of biomass burning emissions (abstract), 2005 Joint Assembly, what constitutes a dangerous level of climate change. More May 23-27, New Orleans, LA, 2005. specifically, I have explored particular outcomes or impacts Naik, V., D. L. Mauzerall, L. W. Horowitz, D. Schwarzkopf, V. of climate change that might have important consequences Ramaswamy, and M. Oppenheimer, Regional attribution of for people and societies, and therefore could produce useful ozone production and associated radiative forcing: a step to crediting ozone reductions (abstract), 8th International benchmarks for policy makers on an appropriate approach Global Atmospheric Chemistry Conference, September 4-9, for limiting the greenhouse gas emissions that are caus- Christchurch, New Zealand, 2005. ing warming. Specific studies have focused on the effect of Development of a New Global Coupled Terrestrial Carbon-Nitro- warming on 1) Antarctic and Greenland ice sheets, 2) coral gen Model (abstract with S. Gerber, L. Hedin, S. Pacala), reef ecosystems, and 3) the nitrogen biogeochemical cycle. American Geophysical Union, December, 2005. In each case, attempts are being made to use modeling, ob- Donner, S.D., C. J. Kuchark, J.A. Foley, J.A, M. Oppenheimer, The impact of changing land use practices and climate vari- servations, and paleoclimatic data to provide bounds on the ability on nitrate export by the Mississippi River (abstract). probability of various outcomes for given levels of warming. EPA Mississippi River Nutrient Science Workshop, St Louis, The most important outcome has been recognition that a MO, 2005. warming in excess of two degrees Celsius is likely to lead to Donner, S.D., T.E. Twine, C.J. Kucharik, M. Oppenheimer, M. outcomes that would be widely recognized as dangerous. Can the climate be used to predict annual nitrogen flux by the Mississippi River and the extent of Gulf Hypoxia? (ab- More recently, I have begun to focus on the issue of deci- stract) AGU Fall Meeting, San Francisco, CA, 2005. sion making under uncertainty under expectations of future Naik, V., D. L. Mauzerall, L. W. Horowitz, D. Schwarzkopf, learning. I have developed the concept of “negative learning” V. Ramaswamy, and M. Oppenheimer, The Sensitivity which involves flows of errant information from scientists of Radiative Forcing from Biomass Burning Aerosols and to policy makers resulting from a mismatch of decision and Ozone to Emission Location, AGU Fall Meeting, San Fran- cisco, CA, 2006. learning timeframes. We have employed a Bayesian decision Linked Regimes to Solve the Timing Problem for Global Warming model to explore the economic consequences of negative (with A. Petsonk), Prepared for the conference on Nesting learning, which are substantial. and Overlapping Institutions, Woodrow Wilson School, Princ- eton University, 24 February 2006. Major Research Themes, 2007 and 2008 M. Oppenheimer, Invited Presentation: Communicating Broadly: My research will continue to focus on the West Antarctic Perspectives and Tools for Ocean, Earth and Atmospheric and Greenland ice sheets, a global assessment of coral reef Scientists, Fall meeting, AGU, December, 2006. ecosystems, and construction of a nitrogen sub-model within Published books, chapters in books the Geophysical Fluid Dynamics Laboratory’s Earth System Emissions Pathways to Avoid Dangerous Climate Change: A Mode. In cooperation with GFDL, I am also catalyzing the Transatlantic View (with C. Jaeger) in Options for Future development of a state-of-the-art ice sheet model. An area Climate Policy: Transatlantic Perspectives, German Institute of expanding interest will be the development of new deci- for International and Security Affairs, Berlin, 2005. Guest Editor, Climatic Change vol. 77, Nos.1-2 Special Issue: sion making models appropriate to global change problems, Global Warming: The Psychology of Long Term Risk, 2006. including the detailed exploration of “negative learning.”
19 S. George H. Two sets of processes determine the climate variations described above. One associated with the drifting of continents Philander (which affects the frequency of volcanic eruptions and hence Knox Taylor Professor of the composition of the atmosphere) is mainly responsible for Geosciences the long-term global cooling. The other is associated with the Ph.D., 1970, Harvard University Milankovitch cycles, the periodic variations in sunlight. The email: [email protected] global cooling affected the response to relatively constant Mila- nkovitch forcing by introducing feedbacks at certain times. For example, the global cooling led to the appearance of north- ern glaciers around 3 Ma, bringing into play the ice-albedo feedback. (White glaciers reflect sunlight, thus promoting the growth of glaciers by depriving the Earth of heat.) This mecha- nism has been studied extensively in connection with ice ages, but many puzzles remain. One concerns the recent discovery that fluctuations in equatorial sea surface temperatures are highly correlated with, and lead by a few thousand years, those in global ice volume. Our research explores how changes in the oceanic circulation, and in interactions between the ocean and atmosphere, contribute to the tropical signature of the Ice Ages. Equatorial sea surface temperature patterns depend on the winds and in turn influence the winds. This implies that inter- actions between the ocean and atmosphere amount to positive feedbacks. Their impact on the global climate is evident during El Niño episodes when the atmospheric concentration of the powerful greenhouse gas water vapor increases significantly. Sea surface temperature patterns depend critically on the subsur- face thermal structure of the ocean, especially the depth of the thermocline, the interface between the shallow layer of warm surface waters and the much colder water at depth. El Niño corresponds to changes in the slope of the equatorial ther- mocline as in the sketch on the left (below). Changes in the spatially averaged depth of the thermocline, as in the sketch on the right, also alter sea surface temperatures, by means of These geological records show that the present is an unusual entirely different (diabatic) processes that involve changes in moment in the recent history of our planet. Superimposed the heat budget of the ocean. on the global cooling that started some 50 million years (Ma) ago when polar temperatures were close to 10ºC are periodic oscillations that were modest in amplitude up to ~3 million years but then started to amplify, culminating in dramatic fluctuations between prolonged ice ages that persisted for some 100,000 years, and brief temperate interglacials. (Varia- tions in 18O in seafloor cores, the top panel, are a measure of polar temperatures.) Our species took advantage of the current A balanced heat budget implies that a decrease in the interglacial – it started 10,000 years ago – to advance rapidly, heat loss in high latitudes is accompanied by a decrease in the from the invention of farming to industrial activities that heat gain in low latitudes. The latter depends on the degree are causing a rapid rise in the atmospheric concentration of to which the depth of the thermocline allows cold water to greenhouse gases. This rise, the vertical upper bar in the lower rise to the surface. Hence a decrease in heat gain means a panel which shows measurements from Antarctic glaciers, is deeper tropical thermocline. A warming of the extra-tropical occurring at a time when those concentrations are at a natural atmosphere does this directly. Alternatively, a freshening of the maximum. That it is also occurring in an era, the past 1 Ma, of surface waters that decreases surface salinities and makes the great climate sensitivity, follows from the cause of the recurrent water buoyant does this indirectly by inhibiting the meridi- ice ages: very modest, periodic variations in the distribution onal overturning of both the deep, slow thermohaline, and the of sunlight because of periodic variations in orbital parameters shallow, swift wind-driven components of the oceanic circula- such as the tilt of the Earth’s axis. To anticipate what will hap- tion. The two components respond very differently: in one case pen next, it will be helpful to understand what had happened surface waters cool in high latitudes; in the other case equato- in the past. rial waters warm. A climate model can favor either response depending on its treatment of turbulent, diffusive, oceanic 20 processes, and of ocean-atmosphere interactions. Simulations Two-Year Bibliography of the Earth’s current climate are insufficient to determine Refereed articles or book chapters: Boccaletti G., R. Pacanowski, and S.G. Philander, A diabatic which models are realistic so that studies of past climates are mechanism for decadal variability in the tropics, Dynamics of of central importance for the understanding and prediction of Atmospheres and Oceans, 39, 3-19, 2005. future global warming. Philander, S.G., Sextant to Satellite; the Education of a Land- The climate records in the first figure provide several strin- based Oceanographer in History of Physical Oceanography gent tests for climate models. One is related to conditions up – Developments since 1960. Editors M. Jochum and R. to 3 million years ago when the equatorial Pacific was as warm Martugudde. Publisher Springer/New York, 2006. Barreiro M., S.G. Philander, R. Pacanowski, A. Fedorov, Simula- in the east as in the west. El Niño was in effect a permanent tions of warm tropical conditions with application to middle rather than intermittent phenomenon. Another is the climate Pliocene atmospheres, Climate Dynamics, 26, 349-365, 2006. response to periodic variations in sunlight (the Milankovitch Fedorov A., P. Dekens, M. McCarthy, C. Ravelo, P.B. de Menocal, forcing) especially those associated with the tilt (obliquity) of M. Barreiro, R. Pacanowski, S.G. Philander, The Pliocene the Earth’s axis. Discrepancies between the observations and Paradox, Science, 312, 1485-1489, 2006. Fedorov A., G. Boccaletti, R. Pacanowski and S.G. Philander, the simulations with climate models indicate a need for reduc- The Freshening of Surface Waters in High Latitudes; Effects ing uncertainties and eliminating inconsistencies in measure- on the Thermohaline and Wind-driven Circulations, J. Physi- ments, and a need to improve models. cal Oceanography, 36, 2006.
Allan Rubin earthquakes themselves. For studies of earthquake interac- Professor tion, which can be conducted sensibly only in a statistical Ph.D., 1988, Stanford University sense, such large numbers are essential and cannot be ob- email: [email protected] tained from standard catalogs. For the past year most of my research has been devoted to developing a theoretical understanding of earthquake nu- cleation, a spin-off of one of our ongoing projects designed to study the very asymmetric distribution of earthquake aftershocks in our central San Andreas fault catalog. The modern view of fault friction is that it depends upon both the fault sliding velocity and the evolving physical or chemi- cal state of the fault surface, which together comprise the “rate” and “state” aspects of “rate-and-state” friction. Despite the fact that the standard rate-and-state equations have been For the past few years I have been studying earthquake phys- around for over 20 years, their implications for earthquake ics observationally, theoretically, and most recently experi- nucleation on elastically-deformable faults (meaning any mentally. The primary impetus for this work has been the fault in the Earth, as opposed to small laboratory versions) advent of waveform cross-correlation as a tool for obtaining have remained elusive. The interest in this topic stems from precise relative locations of microearthquakes. Because the the fact that if nucleation occurred on large enough tempo- number of earthquakes increases exponentially with decreas- ral and spatial scales, precursory signals could be detected ing magnitude, earthquakes near the detection threshold and interpreted prior to damaging earthquakes. While the of existing seismic networks represent a potential wealth observational record in this regard has not been promising, of data for both structural geologists and seismologists. A there have been numerous suggestions of “nucleation events,” major impediment to exploiting these datasets has been that occurring on timescales of fractions of a second to hours location errors are typically ~1 km, a value that exceeds both before the main dynamic earthquake phase, that scale with the earthquake dimensions (tens of meters for magnitude 1 the ultimate size of the earthquake. events) and the length scales of significant structures within It is sad but accurate to say that the constitutive laws for fault zones. By cross-correlating the seismograms of “similar” the evolution of the fault “state” are essentially empirical. earthquakes (those with similar locations and focal mecha- Two versions are in common use. In one, termed the “ag- nisms), it is possible to determine relative arrival times with ing” law, the fault state increases linearly with time when the errors that are less than one-tenth the sampling rate. From surfaces are in stationary contact, but in the other, termed such measurements I and students and postdocs working the “slip” law, the state does not evolve unless the surfaces are with me have relocated many thousands of microearthquakes sliding. In the last decade the aging law has become the clear recorded by seismic networks in California and Hawaii. In favorite of numerical modelers. We have, for the first time, most of our study regions we have reduced errors in rela- succeeded in obtaining analytic expressions for the size and tive location to meters to tens of meters for events separated temporal evolution of the earthquake nucleation zone under by tens to hundreds of meters. This increased resolution this law. This has led to two significant realizations. First, allows us to image fault-zone structures that previously were nucleation near the base of the seismogenic zone should take invisible, and to obtain catalogs of many thousands of events the form of an expanding crack that under some conditions in which relative location errors are much smaller than the would be detectable using surface instruments. Second, the 21 aspect of this law that leads to such large nucleation zones earthquakes in terms of area, that reach slip speeds of only (possibly hundreds of meters across) is an aspect that is not 10–100 times the background plate tectonic rate. The sec- supported by existing laboratory friction experiments. Under ond is the close association of these events with “subduction the “slip” law, in contrast, nucleation takes the form of much tremor,” which apparently consists of large numbers of small smaller “pulses” that migrate in one direction only and that earthquakes deficient in high-frequency radiation (and which would be much less likely to be detected from the surface. plausibly represent just much faster, but still slow, earth- Our analytic results allow this difference in behavior to be quakes). Both the slow slip events and the tremor migrate at ascribed to the different responses of the fault surface to rates of 1–10 km/day. Our analytic results for the aging law large, abrupt increases in sliding velocity as the edge of the provide a possible explanation for these periodic events, and nucleation zone sweeps by. our more general results represent the only existing model In fact, such “velocity-stepping” experiments have been for interpreting the observed migration velocities. While this a staple of the experimental community for decades, but does not mean that our models are “correct” in any microme- these typically have been limited to jumps of a single order of chanical sense, the increased understanding that comes with magnitude, both because larger jumps are difficult to stabilize analytical results often transcends the precise form of the and because it was unclear that such large jumps would be equations studied, and can be immensely useful in pointing geologically relevant. With Chris Marone at Penn State we out what sorts of studies (observational, experimental, and have succeeded in stabilizing velocity jumps of 2 to 3 orders theoretical) are needed to get at the heart of the matter. of magnitude, and find them to be clearly consistent with Two-Year Bibliography the slip law and inconsistent with the aging law. In addition, Refereed articles: our work has shown that the “slide-hold-slide” experiments Rubin, A. M.and J.-P. Ampuero, Earthquake nucleation on (ag- that captured the imagination of the modeling community ing) rate and state faults, J. Geophys. Res., 110, B11312, as favoring the aging law really point to a failure of both doi:10.1029/2005JB003686, 2005. Peng, Z., J.E. Vidale, C. Marone, and A. Rubin, Systematic laws. Future work with Chris Marone and Nick Beeler at the variations in recurrence interval and moment of repeating USGS will be designed to sort this out. The good news is aftershocks, Geophys. Res. Lett., 32 (15): Art. No. L15301 that the failure of the slip law appears to be restricted to very AUG 2, 2005. low sliding speeds, so low that they might be only marginally Articles in press: relevant to nucleation. Rubin, A. M., and J.-P. Ampuero, Aftershock asymmetry on a Several recent discoveries of “new” kinds of earthquakes bimaterial interface, J. Geophys. Res, in press. make this an exciting time to study nucleation. The first of Pritchard, M.E., A.M. Rubin, and C.J. Wolfe, Do flexural stresses these are quasi-periodic “slow” earthquakes in many subduc- explain the mantle fault zone beneath Kilauea volcano?, in press. tion zones around the world, comparable to magnitude 7
Jorge L. Sarmiento ted. The new journal articles published and in press during Professor 2006 can be categorized into three broad areas: Ph.D., 1978, Columbia University Ocean Biogeochemical Processes and Modeling (published email: [email protected] references 1 and 3 and in press references 1, 2, and 7): I am particularly excited by the Deutsch et al. (in press) paper (ref- erence 2), which describes a new global estimate of nitrogen fixation at the ocean surface. We demonstrate in this paper that fixation occurs in close association with areas of denitri- fication, which implies that negative feedbacks on the fixed nitrogen cycle occur on century rather than multi-millennial time scales. We conclude that major excursions of the ocean fixed nitrogen pool, such as have been suggested by some authors, are unlikely. Modeling and Observational Constraints on Carbon The most important research accomplishment of the past Sinks (published references 2, 6, and 7, and in press refer- year was the publication of my book Ocean Biogeochemical ences 3, 4, and 5): These papers represent the culmination of Dynamics by Princeton University Press, which I authored to- several long-term projects, aimed at understanding the global gether with Nicolas Gruber. One of the nicest compliments carbon cycle. Crevoisier et al. (2006; published reference I have received on the book so far was from Wally Broecker 6) describes a new method we developed to estimate highly who said: “A superb book. Goodbye Tracers in the Sea.” resolved terrestrial CO fluxes over North America using new This has been a productive year for other research as well, 2 data being obtained as part of the North American Car- with seven articles published as of the time of this writing, bon Project (NACP). Mikaloff –Fletcher et al. (published three of them in Nature; seven papers in press, one of them reference 6 and in press reference 5) and Jacobson et al. (in in Science and another in Nature; and three articles submit- 22 press references 3 and 4) describe our newest estimates of the Research Board for a multimillion dollar project to develop a air-sea CO2 flux and our detailed examination of the implica- model for the eastern Bering Sea fisheries. Our letter of in- tions of these air-sea fluxes for our understanding of terres- tent was well received and we are one of two teams who have trial CO2 fluxes. We demonstrate in these papers that there been invited to prepare a full proposal. I am very excited by does not appear to be a CO2 sink in the tropics, which was this project, as I suspect the impacts of global warming on one of the few remaining places where it was still thought fisheries will be very large and I believe we are in a position that there might be a CO2 fertilization sink. The implica- to make substantial contributions to our understanding of tions for the future growth of atmospheric CO2 are huge, as what these might be. all carbon models up to now have assumed that such a fer- tilization sink would make a major contribution to reducing Two-Year Bibliography the rate of atmospheric CO growth in the future. Books: 2 Sarmiento, J. L., and N. Gruber, Ocean Biogeochemical Dynam- Southern Ocean Circulation and Biogeochemistry (pub- ics, Princeton University Press (a textbook/research mono- lished references 4 and 5, and in press reference 6): Under- graph), 2006. standing the critical role of the Southern Ocean in control- Refereed articles or book chapters: ling ocean biogeochemistry and its carbon cycle is an ever- Orr, J. C., V. J. Fabry, O. Aumont, L. Bopp, S. C. Doney, R. deepening interest to which I am planning to dedicate greater M. Feely, A. Gnanadesikan, N. Gruber, A. Ishida, F. Joos, R. effort over the next few years, particularly as it looks like the M. Key, K. Lindsay, E. Maier-Reimer, R. Matear, P. Mon- fray, A. Mouchet, R. G. Najjar, G.-K.Plattner, K. B. Rodgers, US oceanography community may finally be returning their C. L. Sabine, J. L. Sarmiento, R. Schlitzer, R. D. Slater, with major field research. Published reference 4 (Marinov I. J. Totterdell, M.-F. Weirig, Y. Yamanaka, and A. Yool, et al., 2006) demonstrates that there is a clear separation in Anthropogenic ocean acidification over the 21st century and the Southern Ocean between regions that control the air-sea its impact on marine calcifying organisms, Nature, 437: 681- balance of CO (confined primarily to high latitude regions 686, 2005. 2 Dunne, J. P., R. A. Armstrong, A. Gnanadesikan, and J. L. of deep-water formation), and regions that control the Sarmiento, Empirical and mechanistic models for the par- return of nutrients from the deep ocean to the surface (lower ticle export ratio, Global Biogeochem. Cycles, 19, GB4026, latitude areas where Subantarctic Mode Water forms). In doi:10.1029/2004GB002390, 2005. Mignone et al., (2006, published reference 5), we show that Behrenfeld , M. J., R. T. O’Malley , D. A. Siegel, C. R. McClain, major differences in the representation of Southern Ocean J. L. Sarmiento , G. C. Feldman , A. J. Milligan , P. G. circulation can be explained as resulting from differences in Falkowski , R. M. Letelier , E. S. Boss, Climate-driven trends in contemporary ocean productivity, Nature, 444: 752-755, the representation of wind forcing and mixing in the ocean 2006. models. These differences have major consequences for the Crevoisier, C., M. Gloor, E. Gloaguen, L. W. Horowitz, J. L. rate of CO2 uptake estimated by these models. In Sarmiento Sarmiento, C. Sweeney and P. P. Tans, A direct carbon bud- et al. (in press reference 6), we examine how the Southern geting approach to infer carbon sources and sinks. Design Ocean cycling of silicic acid and nitrate determines the deep and synthetic application to complement the NACP observa- tion network, Tellus B, 58 (5), 366-375, doi: 10.1111/j.1600- distribution of these two nutrients. 0889.2006.00214, 2006. As regards the future, many of the papers that were Jin, X., N. Gruber, J. P. Dunne, J. L. Sarmiento, and R. A. published this year, particularly those on ocean biogeochem- Armstrong, Diagnosing the contribution of phytoplankton istry and the global carbon cycle, represent the culmination functional groups to the production and export of particu- late organic carbon, CaCO , and opal from global nutrient of many years of research that has begun to reach closure. I 3 and alkalinity distributions, Global Biogeochem. Cycles, 20, have spent much of my time this fall planning and trying to GB2015, doi10.1029/2005GB002532, 2006. obtain funding for the next years of research, which I hope Marinov, I. A. Gnanadesikan, J. R. Toggweiler, and J. L. Sarmien- to continue during my sabbatical next year. I recently heard to, The Southern Ocean biogeochemical divide. Nature, from NSF that our latest proposal on Southern Ocean pro- 441: 964-967, 2006. cesses received high ratings and will be funded depending on Mignone, B. K., A. Gnanadesikan, J. L. Sarmiento, R. D. what their budget finally turns out to be. Another proposal I Slater, Central role of southern hemisphere winds and eddies in modulating the oceanic uptake of anthropogenic submitted to NOAA to form a Climate Process Team (CPT) carbon, Geophys. Res. Lett., 33, L01604, doi:10.1029/ on Southern Ocean biogeochemical processes also reviewed 2005GL024464, 2006. well and will be funded if the budget permits. I am hop- Mikaloff-Fletcher, S. E., N. Gruber, A. R. Jacobson, S. C. Doney, ing to leverage the CPT project into a larger one with DOE S. Dutkiewicz, M. Follows, K. Lindsay, D. Menemenlis, A. support. As regards the global carbon cycle, my group is Mouchet, and J. Sarmiento, Inverse estimates of anthropo- genic carbon uptake, transport, and storage by the ocean, focusing now on the tropical carbon balance using satellite Global Biogeochem. Cycles, 20, GB2002, doi:10.1029/ and other observations of CO2, CO and CH4. We have new 2005GB002530, 2006. support from DOE for our work in North America, but are Patra, P. K., K. R. Gurney, D. A. S., S. Maksyutov, T. Nakazawa, trying to obtain support for our research on the tropics. D. Baker, P. Bousquet, L. Bruhwiler, C. Y.-H., P. Ciais, S.-M. Finally, I have been exploring how we could develop a Fan, I. Fung, M. Gloor, M. Heimann, K. Higuchi, J. J., R. M. Law, T. Maki, B. C. Pak, P. Peylin, M. Prather, P. J. Rayner, new set of models to predict the effect of global warming on J. Sarmiento, S. Taguchi, T. Takahashi, and C.-W. Yuen, fisheries. I am one of the leaders of a consortium of investi- Sensitivity of inverse estimation of annual mean CO2 sources gators who submitted a letter of intent to the North Pacific and sinks to ocean-only sites versus all-sites observational 23 networks, Geophysical Research Letters, 33, L05814, Sarmiento, Inverse estimates of the oceanic sources and
doi:05810.01029/02005GL025403, 2006. sinks of natural CO2 and their implied oceanic transport, Global Biogeochem. Cycles in press. Articles in press: Sarmiento, J. L., J. Simeon, A. Gnanadesikan, N. Gruber, R. M. Boyd, P.W., T. Jickells, C. S. Law, S. Blain, E. A. Boyle, K. O. Key, and R. Schlitzer, Deep ocean biogeochemistry of silicic Buesseler, K. H. Coale, J. J. Cullen, H. J. W. de Baar, M. acid and nitrate, Global Biogeochem. Cycles in press. Follows, M. Harvey, C. Lancelot, M. Levasseur, R. Pollard, Sweeney, C., E. Gloor, A. J. Jacobson, R. M. Key, G. McKinley, R. B. Rivkin, J. Sarmiento, V. Schoemann, V. Smetacek, J. L. Sarmiento, and R. Wanninkhof, A new global air-sea S. Takeda, A. Tsuda, S. Turner, A. J. Watson, A synthesis gas exchange for CO implied by recent estimates of oceanic of mesoscale iron-enrichment experiments 1993-2005: key 2 bomb radiocarbon and ocean models, Global Biogeochem. findings and implications for ocean biogeochemistry,Science Cycles, in press. in press. Deutsch, C., J. L. Sarmiento, D. M. Sigman, N. Gruber, and J. P. Articles submitted: Dunne, Spatial coupling of nitrogen inputs and losses in the Najjar, R. G., X. Jin, F. Louanchi, O. Aumont, K. Caldeira, S. C. ocean, Nature in press. Doney, J.-C. Dutay, M. Follows, G. M. Kay, E. Maier-Reimer, Jacobson, A. R., S. E. Mikaloff-Fletcher, N. Gruber, J. L. R. J. Matear, K. Matsumoto, A. Mouchet, J. C. Orr, G. K. Sarmiento, M. Gloor, and TransCom Modelers, A joint atmo- Plattner, J. L. Sarmiento, M. F. Weirig, Y. Yamanaka, and sphere-ocean inversion for surface fluxes of carbon dioxide: A. Yool, Impact of circulation on export production, dissolved I. Methods and global-scale fluxes, Global Biogeochem. organic matter and dissolved oxygen in the ocean: Results Cycles in press. from OCMIP-2. (Global Biogeochemical Cycles) Jacobson, A. R., S. E. Mikaloff-Fletcher, N. Gruber, J. L. Dunne, J. P., J. L. Sarmiento, and A. Gnanadesikan, submitted. Sarmiento, M. Gloor, and TransCom Modelers, A joint atmo- A synthesis of global particle export from the surface ocean sphere-ocean inversion for surface fluxes of carbon dioxide: and cycling through the ocean interior and on the sea floor, II. Regional results, Global Biogeochem. Cycles, in press. Global Biogeochem. Cycles, submitted. Mikaloff Fletcher, S. E., N. Gruber, A. R. Jacobson, M. Gloor, S. Mignone, B. K., R. H. Socolow, J. L. Sarmiento, and M. Oppen- C. Doney, S. Dutkiewicz, M. Gerber, M. Follows, F. Joos, K. heimer, Atmospheric stabilization and the timing of carbon Lindsay, D. Menemenlis, A. Mouchet, S. A. Müller, and J. L. mitigation, Climatic Change, submitted.
Daniel Sigman not completely consumed by algal growth. What factors Professor control the physical conditions and nutrient status of the Ph.D., 1997, MIT and Woods Hole polar surface ocean? Over the ice age/interglacial cycles of the Oceanographic Institution last three million years, how have the characteristics of the email: [email protected] polar ocean affected other regions of the ocean, atmospheric carbon dioxide, and climate? What terms and rates compose the budgets of “fixed” (biologically available) N in the modern ocean, on land, and in the atmosphere? What are the sensitivities of the differ- ent inputs and outputs? How have the N budgets in these systems changed over climate cycles, and how have these changes affected the fertility of ocean and land? What has been the role of such changes in the global carbon cycle? My research activities over the past year are summarized My group members and I are focused on two distinct but below under the following headings: (1) isotope method de- complementary research goals. First, we use the isotopic velopment, (2) laboratory studies of isotope discrimination, composition of dissolved nitrogen species (such as nitrate (3) studies in the modern ocean, (4) studies in the terrestrial - biosphere, the atmosphere, and ice cores, (5) paleoceano- (NO3 ) and dissolved organic nitrogen) to provide integrative constraints on nitrogen cycle processes in modern environ- graphic studies, and (6) model studies of past ocean changes. ments, mostly in the ocean but also in terrestrial systems My group’s body of work in these areas represents our effort and the atmosphere. Second, we treat the past, as recorded to progress from the introduction of new measurements, in marine sediments and glacial ice, as an archive of natural to the development of the background information needed experiments from which the underlying controls on the phys- to make those measurements useful, to their application to ical and biogeochemical fluxes of the environment can be important questions, and finally to a quantitative consider- determined; we study the past N cycle both in its own right ation of the findings in a broader environmental context. The and as an indicator of broader environmental change. citations below refer to manuscripts listed in the publications A unifying goal of this work is to understand the role of section of the annual review form. plant nutrients in the interaction between life and the envi- Isotope Method Development ronment. Two sets of questions, focused on the ocean, have In 2006, we published a manuscript on our method for the - most centrally motivated our studies: removal of nitrite (NO2 ) from aqueous samples [Granger et The polar oceans are special domains in the ocean where al., 2006]. Our goal for this method is to prevent this species - the “major nutrients” nitrogen (N) and phosphorus (P) are from contaminating the isotopic analysis of nitrate (NO3 ).
24 This method is particularly relevant to Granger’s culture stud- remarkable similarity to nitrate assimilators with respect to ies of denitrifying bacteria (see below), in which there were N-to-O isotope coupling, with the exception of a strain that large accumulations of nitrite. However, it has also proven possesses only the auxiliary periplasmic nitrate reductase critical in the analysis of low-nitrate water samples from Nap. The ~1:1 N-to-O isotope coupling of normal respirato- some regions of the surface ocean. Nitrite is unstable and ry denitirification provides a critical constraint for interpret- converts partially to nitrate during its degradation. For this ing isotope distributions in the environment. While the ex- reason, this method is becoming an integral part of the water pression of Nap is likely minimal in most environments, the collection process at sea. finding of its unique isotopic behavior indicates the potential An on-line method for the coupled analysis of 17O/16O for computational chemists to test enzyme mechanism using and 18O/16O of nitrate in natural waters, developed by Jan coupled N-to-O isotope constraints. Finally, the results also Kaiser and Meredith Hastings, is in press [Kaiser et al., in offer mechanistic insight into the controls on the amplitude press]. This method couples our previously described method of the coupled N and O isotope effects of denitrification. 15 14 18 16 for nitrate N/ N and / O analysis, which converts nitrate Studies in the Modern Ocean to N O gas, with pyrolysis of the N O to N and O , allow- 2 2 2 2 The isotopes of nitrate represent a potentially powerful con- ing for 18O/17O/16O determination of the O . 17O/16O is a 2 straint on the internal cycling of fixed N in the ocean, with useful fingerprint for atmospheric nitrate, and Kaiser’s tech- implications for ocean circulation and the carbon cycle. My nique is orders of magnitude more sensitive than previous strongest interest in this regard is in the supply, transport, methods, allowing for extension of this analysis to a diversity and consumption of nitrate in regions of the polar ocean, the of sample types and environments. An application of the Southern Ocean in particular. Combined nitrate concentra- method is described in a manuscript in review on the origin tion and isotope data, interpreted with a numerical model, of atmospheric nitrate in Antarctica, first-authored by Joel allowed Peter DiFiore to quantify the different physical Savarino of CNRS, France [Savarino et al., in review]. mechanisms of nitrate supply, the rate of biological export On the basis of previous work on dissolved organic N by production, and the isotope effect of nitrate assimilation in Angie Knapp in our lab, collaboration among Moritz Lehm- the Subantarctic Zone of the Southern Ocean [DiFiore et al., ann, Ben Houlton, and Masha Prokopenko has resulted in 2006]. Among other observations, DiFiore found that the the development of a high-sensitivity method for measuring isotope effect of nitrate assimilation is greater in the Subant- the 15N/14N of dissolved ammonium (NH +). Data using 4 arctic than in the seasonal sea ice zone of the Antarctic. Based this method are described in a manuscript in review first-au- on our previous culture work, we suggest that this is due to thored by Houlton [Houlton et al., in review]. the limited availability of light in the Subantarctic, where Also building upon Knapp’s dissolved organic N method, summer mixed layers are deeper than in the Antarctic. These Becky Robinson and Brigitte Brunelle have previously estab- 15 14 studies of the modern polar ocean provide needed constraints lished, improved, and tested a new technique for the N/ N for our paleoceanographic studies [Robinson et al., 2005; of diatom microfossil-bound N, for paleoclimate studies Robinson and Sigman, in review]. [Robinson et al., 2004, 2005]. In 2006, Brigitte’s first-au- Nitrate N and O isotope data are also contributing to thored manuscript, which includes a description of impor- our understanding of fixed N loss from the ocean. In 2006, tant improvements and an informative set of method tests, Moritz Lehmann submitted his first-authored manuscript was accepted for publication [Brunelle et al., in press]. With describing porewater nitrate N isotope analyses from Bering Brunelle’s updated protocol, we are producing more precise Sea basin and margin. This large data set and its analysis are measurements than previously, reducing the amplitude of the a major part of our long-term goal to develop a mechanistic signal that can be recovered from the sedimentary record. understanding of the expression (and under-expression) of Laboratory Studies of Isotope Discrimination isotopically fractionating N reactions in sediments and other The utility of isotopic distributions in the environment is media. This goal is central to the use of the N isotopes to premised on knowledge of the magnitudes of isotope dis- constrain N budgets, in the ocean (e.g., [Sigman et al., 2005; crimination by individual biogeochemical reactions, which is Lehmann et al., 2005]) and on land (e.g., [Houlton et al., most often gained through lab studies of cultured organisms. 2006]). The focus of Julie Granger’s thesis was on the isotope effects Studies in the Terrestrial Biosphere, the Atmosphere, and of nitrate-consuming processes, in particular, nitrate as- Ice Cores similation by algae (central to studies of nutrient supply and Recent Ecology and Evolutionary Biology graduate stu- uptake in the surface ocean) and denitrification by heterotro- dent Ben Houlton has measured the isotopic composition phic bacteria (central to studies of the global ocean’s input/ of nitrate, dissolved organic N, and ammonium in cloud output budget of fixed N). In 2004, we published the first water, rainfall, soil extracts, soil water, and streams across laboratory data on the relationship between N and O isotope a well-constrained rainfall gradient on the island of Maui. fractionation during nitrate assimilation; we found that the 15 14 18 16 The resulting N isotope budgets for these forests indicate N/ N and O/ O ratios of nitrate increase in equivalent an important and rainfall-dependent role for denitrification proportions as the nitrate is consumed. In 2006, we submit- in tropical systems [Houlton et al., 2006]. Associated with ted a manuscript describing our first results with denitrifiers changes in the forest N budget across the rainfall gradient, we [Granger et al., in review]. In brief, the denitrifiers show found a remarkably abrupt transition in the form of N fuel- 25 ing plant growth, from nitrate to ammonium with increasing in which deep ocean overturning is weak and focused in the rainfall [Houlton et al., in review]. The Maui gradient sug- North Atlantic, and a “thermal” state, in which overturning gests that the plants in these forests are not so much driving is strong and distributed among the different polar ocean the N fluxes as finding a solution for their N demand that is regions. The inter-basin interactions that she has described, consistent with the redox-driven activity of soil microbes. when combined with other processes, have led us toward a Paleoceanographic Studies more complete hypothesis for the role of polar ocean stratifi- cation in the Pleistocene cycles in CO and climate [Sigman My collaborators and I continue to pursue the evidence for 2 reduced vertical exchange (i.e. “stratification”) in the halo- et al., in review]. cline-bearing polar ocean regions under colder climates of the Two-Year Bibliography past 3 million years. A major motivation for this focus is that Refereed articles: Hastings, M. G., D. M. Sigman, and E. J. Steig, Glacial/intergla- the reconstructed polar ocean changes have the capacity to cial changes in the isotopes of nitrate from the Greenland affect atmospheric CO2 in the observed sense of its glacial/ Ice Sheet Project 2 (GISP2) ice core, Global Biogeochemical interglacial oscillation. In 2006, graduate student Brigitte Cycles, 19, GB4024, doi:10.1029/2005GB002502, 2005. Brunelle’s first-authored manuscript on ice age conditions Sigman, D. M., J. Granger, P. DiFiore, M. F. Lehmann, A. V. in the Bering Sea of the Subarctic North Pacific, mentioned Geen, R. Ho, and G. Cane, Coupled nitrogen and oxygen above with regards to its methodological advances, was ac- isotope measurements of nitrate along the eastern North Pacific margin, Global Biogeochemical Cycles, 19, GB4022, cepted for publication [Brunelle et al., in press]. This paper doi:10.1029/2005GB002458, 2005. reports diatom-bound N isotope and export flux proxy data Lehmann, M. F., D. M. Sigman, D. C. McCorkle, B. G. Brunelle, indicating reduced nutrient supply from below during the S. Hoffmann, M. Kienast, G. Cane, and J. Clement, The ori- last ice age, strengthening the case for a bipolar (Antarctic gin of the deep Bering Sea nitrate deficit -- Constraints from and North Pacific) increase in stratification during ice ages. the nitrogen and oxygen isotopic composition of water col- umn nitrate and benthic nitrate fluxes, Global Biogeochemi- These data constrain the cause for this change, which is cal Cycles, 19, GB4005, 10.1029/2005GB002508, 2005. under investigation, to a mechanism that applies to both of Jaccard, S. L., G. H. Haug, D. M. Sigman, T. F. Pedersen, H. R. these regions. Thierstein, U. Röhl, Glacial/interglacial changes in Subarctic North Pacific stratification, Science, 308,1003-1006, 2005. Model Studies of Past Ocean Changes Robinson, R. S., D. M. Sigman, P. J. DiFiore, M. M. Rohde, We have recently begun to consider a physical mechanism T. A. Mashiotta, and D. W. Lea, Diatom-bound 15N/14N: for the apparent climate/polar stratification link mentioned New support for enhanced nutrient consumption in the above. This mechanism involves the reduced sensitivity of ice age Subantarctic, Paleoceanography, 20, PA3003, seawater density to temperature at low temperatures: in the 10.1029/2004PA001114, 2005. Haug, G. H., A. Ganopolski, D. M. Sigman, A. Rosell-Mele, �����G. E. case of a globally colder ocean, temperature gradients become A. Swann, R.����������������������������������������������� Tiedemann, S. L. Jaccard, J. Bollmann�������, M. A. less important in polar ocean density structure, reducing Maslin, M. J. Leng������������������������������������������, and G. Eglinton, North Pacific seasonal- their opposition to the stratifying effect of the net atmo- ity and the glaciation of North America 2.7 million years ago, spheric deposition of fresh water on polar ocean regions. Nature, 433, 821-825, 2005. Recent AOS postdoctoral researcher Agatha de Boer has used Knapp, A. N., D. M. Sigman, and F. Lipschultz, N isotopic compo- sition of dissolved organic nitrogen and nitrate at the Ber- a general ocean circulation model to investigate this effect muda Atlantic time-series study site, Global Biogeochemical [de Boer et al., in press]. The results provide proof of concept Cycles, 19, GB1018, 10.1029/2004GB002320, 2005. for a direct effect of whole ocean temperature change on the Granger, J., D. M. Sigman, M. Prokopenko, M. F. Lehmann, and rate polar ocean overturning. They also point to interactions P. D. Tortell, A method for nitrite removal in nitrate N and O among the polar regions of the different ocean basins. In a isotope analysis, Limnology and Oceanography: Methods, 4, 205-212, 2006. second manuscript, de Boer has demonstrated that the den- DiFiore, P. J., D. M. Sigman, T. W. Trull, A. J. Lourey, and K. L. sity/temperature effect described above fits into a common Karsh, Nitrogen isotope constraints on Subantarctic biogeo- theoretical framework with the ocean’s response to changes in chemistry, Journal of Geophysical Research – Oceans, 111, southern hemisphere winds and in low-to-high latitude water C8, C08016, doi:10.1029/2005JC003216, 2006. vapor transport [de Boer et al., in review]. She describes a Houlton, B. Z., D. M. Sigman, and L. O. Hedin, Isotopic evidence “haline” end member state (where salinity has a dominant for large gaseous nitrogen losses from tropical rainforests, Proceedings of the National Academy of Sciences, 103, 23, effect on the relative densities of the polar ocean regions), 8745-8750, 2006.
26 Frederik Simons speeds). A technique developed by Richard Allen (a Princeton Assistant Professor alum, now at Berkeley) measures the so-called predominant Ph.D., 2002, MIT period of the P wave, which is empirically correlated with the email: [email protected] earthquake magnitude. One of the undergraduate students I advised at University College before joining Princeton, Ben Dando (now a Ph.D. student at Leeds), spent a semester try- ing to refine this method, with very mixed results. But when I tried my canned wavelet algorithms, the results jumped out onto the screen. With Dando and Allen, I published a paper, “Automatic detection and rapid determination of earthquake magnitude by wavelet multiscale analysis of the primary ar- rival,” in which the details of the method are spelled out. An implication important for earthquake source physics is that it seems that the earthquake magnitude can be predicted from In the past year I have made research progress on a few differ- the observations of very short sections of the seismogram, of ent fronts. even shorter duration than the time it takes for the earthquake First, I have continued the development of algorithms fault to completely rupture. How and whether an incipient for the automatic detection and discrimination of teleseismic earthquake “knows” from the very beginning of rupture where earthquake phases onboard autonomous oceanic divers, and the endpoint shall be, i.e. how big it will get, is a possibility applied these to data collected by our prototype MERMAID confirmed by our study, one which I am hoping to take up float. My Princeton colleague Guust Nolet and myself pub- further. lished a paper with coauthors from the Scripps Institution of A third line of research consisted of my continued interest Oceanography on this topic in the Transactions of the Ameri- in the mechanically anisotropic properties of the continental can Geophysical Union (EOS). The main news to report was lithosphere. The lithosphere is the rigid outer layer of the the discovery of a relatively small (magnitude 6) earthquake Earth – just how rigid is often the question. In my Ph.D. detected at a relatively large (about 5,000 km) distance by our work, working on the Australian lithosphere, I raised the pos- hydrophone on one of its experimental runs. “Seismologists sibility that this elastic rigidity could be a directionally aniso- detect earthquake” could have been our title, but for obvious tropic quantity (and I showed that, in Australia, this was the reasons we chose to focus on the more weighty consequences case). The possible causes (is it reflecting fossil deformation of this first very promising step. In “A future for drifting due to past mountain-building activity that involves the entire seismic networks” we describe how we believe that the next crust as well as portions of the mantle?) as well as the possible generation of seismic networks will be autonomous, and consequences (will zones of anisotropy channel future conti- floating. Our technology has the potential to definitively -ad nental deformation?) of such mechanically anisotropic behav- dress the coverage gap in whole-Earth seismic tomography by ior have continued to intrigue me, and I worked with another putting intelligent earthquake recorders afloat the two thirds undergraduate, Jonathan Watson, at Birkbeck College in of the Earth’s surface that are covered by oceans. Much of our London, to detect evidence for it in the South African litho- progress in the coming years will depend on the continued in- sphere. The short answer is Yes, the South African lithosphere volvement of the engineers at Scripps in what is at this point is also mechanically anisotropic, and we have some results of still only a small pilot study. seismic anisotropy to argue that it is indeed consistent with Even if we can’t get all of Scripps’s engineers’ attention an origin in past wholesale deformation. But the long answer all the time, I have shown that the development of intelligent will take some more work, which I expect to continue in the algorithms to analyze earthquake time series fits right into a next year. One of the reasons to be cautious about our results, much wider scheme: that of earthquake early warning. My which are derived from an analysis of the so-called coherence algorithms are based on the discrete wavelet transform, and function between gravity and topography, is that the statistics on a particularly efficient implementation thereof. Proces- of spatially varying, directionally varying, bivariate stochastic sor time and memory restrictions are crucial bottlenecks on fields is poorly understood. In simple terms: If it looks like free-floating oceanic systems that depend on batteries that gravity anomalies and topography are related to each other via must last them a lifetime, but as it turns out, the solutions an anisotropic transfer functions, does that really mean that I developed to address these proved particularly suitable to the lithosphere is mechanically anisotropic, or could this be detect earthquakes in terrestrial contexts, and to analyze them, caused by any anisotropy in the gravity and the topography as well. The goal in earthquake early warning is to know as itself, or due to noise? I have teamed up with a mathematical little as possible about what’s coming into the seismometer, statistician, Sofia Olhede from Imperial College in London, to and to extract as much information as quickly as possible. address this question. After spending two-and-a-half months If an earthquake magnitude, and thus likely damage, can be of her sabbatical with me in Princeton, she and I have now estimated form the harmless first arrival (theP wave), warn- rigorously formulated our research questions and commenced ings can be issued before the arrival of the main ground the development of various detailed solution methods, much shaking (the S and surface waves, which travel at slower of this to be continued in the next year.
27 In all of this, somehow the bulk of my research has still Flight Center) and Chris Jekeli from the Ohio State Uni- been concerned with the problem of studying “processes” versity, and myself, have submitted a manuscript entitled (like topography, or the gravity or magnetic fields) that live “Spatiospectral localization of global geopotential fields from on spherical surfaces, my fourth main area of interest. Much GRACE reveals the coseismic gravity change due to the 2004 of the above involved “signal processing” – one-dimen- Sumatra-Andaman earthquake.” The title probably reveals it sional wavelet analysis, two-dimensional coherence analysis all, except my great enthusiasm for the direction our “esoteric – a dirty word to some, but absolutely vital to answer the form of signal processing” seems to have entered. GRACE is geophysical questions (listening to distant earthquakes in a pair of satellites that collects global data on Earth’s time- the oceans, measuring an earthquake’s magnitude before the variable gravity field. GRACE data are noisy, and spherical, main shaking comes in, studying the mechanical properties and collected at an altitude, over incomplete portions of the of the lithosphere) I have continued to be interested in. It globe, and expressed in spherical harmonics… and from this is only logical, then, that I have wanted to get ready for the we want to extract local information – about Earth’s chang- study of any such questions on the surface of the sphere, such ing mass balance due to the hydrological cycle, ocean cur- as will be vital in the analysis of any data where the curvature rents, the melting of ice caps, anthropogenic factors, … and of the Earth’s surface cannot be safely neglected, or, more now also large earthquakes. That we are able to do this at all generally, of observations made on other planets in the solar is in no small way dependent on spherical data analysis, and system (the latter mostly of global extent and made by satel- I expect that myself and my collaborators will continue to lites). “Spatiospectral localization on the sphere” is the name develop methods to do this ever better, in the next year and of this game, and, ever since Mark Wieczorek (of IPG Paris) beyond. and I started getting interested in this in 2003, I haven’t been Two-Year Bibliography able to quit playing it. My Princeton colleague Tony Dahlen Refereed articles: (who is now rivalling me in not being able to get this out of Mark A. Wieczorek and Frederik J. Simons, Localized spectral his mind, I suspect) and I spent much of 2004 on a general- analysis on the sphere, Geoph. J. Int, 162 (3), 655-675, ization of this so-called concentration (or Slepian’s) problem 2005. Saskia Goes, Frederik J. Simons and Kazunori Yoshizawa, (the eponymous paper came out this year in SIAM Review, Seismic constraints on the temperature of the Australian whose cover was graced by one of our figures), and much of uppermost mantle, Earth & Planetary Science Letters, 236 2005 and part of 2006 on one very particular special case. In (1-2), 227-237, 2005. this year’s paper “Spherical Slepian functions and the polar Frederik J. Simons, Ben D. E. Dando and Richard M. Allen, gap in geodesy” Tony and I “localize” spherical harmonic Automatic detection and rapid determination of earthquake magnitude by wavelet multiscale analysis of the primary ar- functions to the equatorial area between two equal-size polar rival, Earth & Planetary Science Letters, 250 (1-2), 214-223, caps. We thereby construct a natural basis for the analysis of 2006. global potential fields that have been measured at an altitude Frederik J. Simons, Guust Nolet, Jeff M. Babcock, Russ E. Davis by satellites, in the presence of noise, but, more importantly, & John A. Orcutt, A future for drifting seismic networks, Eos that are, as is commonly the case, suffering from “polar gaps” Trans. Am. Geophys. Un., 87 (31), 305&307, 2006. Frederik J. Simons and F. A. Dahlen Spherical Slepian functions – small areas on the North and South pole without tracks and the polar gap in geodesy, Geoph. J. Int., 166 (3), 1039- and where no data has been collected. In a submitted paper 1061, 2006. called “Minimum variance multitaper spectral estimation on Frederik J. Simons, F. A. Dahlen and M. A. Wieczorek, Spatio- the sphere,” Mark and I use spherical Slepian functions to spectral localization on a sphere , SIAM Review, 48, (3), derive power spectral estimates and their error bars… and for 504-536, 2206 the last few months Tony and I have been working on what Other miscellaneous publications we’ve provisionally called “Spectral estimation on a sphere.” Frederik J. Simons, Thorsten W. Becker, James B. Kellogg and The short title suggests that we think we’re “covering” this 5 others, MYRES: A Program to Unite Young Solid Earth Researchers, Eos Trans. Am. Geophys. Union, 86 (5), 48-49, problem from all possible angles: I will report on this next 2005. year, when it should have been submitted for publication. Laurent G. J. Montési, Giulio di Toro, Frederik J. Simons and 5 All of our work on this fourth subject has been theoretical others, Young scientists focus on the dynamics of the litho- (paired with numerics and the attendant extensive develop- sphere, Eos Trans. Am. Geophys. Union, 87 (44), 482, 2006 ment of computer code, all of which I am making freely Malcolm Sambridge, Caroline Beghein, Frederik J. Simons and Roel Snieder, How do we understand and visualize uncer- available on the Web), except for a first application about tainty?, The Leading Edge, 25 (2), 542-546, 2006. which Shin-Chan Han (now at NASA’s Goddard Space
28 Seismic Interpretation of Contractional Fault-Related Folds, John Suppe American Association of Petroleum Geologists, p. 110-113, Blair Professor of Geosciences 2005. Ph.D., 1969, Yale University (with J. H. Shaw and S. C. Hook) Pitas Point anticline, California, email: [email protected] USA. In J. Shaw, C. Connors, J. Suppe, editors, Seismic Interpretation of Contractional Fault-Related Folds, American Association of Petroleum Geologists, p. 60-62, 2005. (with J. H. Shaw and C. D. Connors) Part 1: Structural Interpreta- tion Methods. In J. Shaw, C. Connors, J. Suppe, editors, Seismic Interpretation of Contractional Fault-Related Folds, American Association of Petroleum Geologists, p. 1-58, 2005. (with F. Corredor and J. H. Shaw) Shear fault-bend fold, deep wa- ter Niger Delta. In J. Shaw, C. Connors, J. Suppe, editors, Seismic Interpretation of Contractional Fault-Related Folds, American Association of Petroleum Geologists, p. 87-92, 2005. I was on a one-year sabbatical AY2005-2006, spending six (with A. Hubert-Ferrari and Jerome Van Der Woerd) Irregular months as a Visiting Professor of Tectonics at Caltech and six earthquake cycle along the southern Tianshan, China (Aksu area), Journal of Geophysical Research, v. 110, B06402, months at the Ludwig Maximillians University in Munich. doi:10.1029/2003JB002603, 2005. The stay in Germany was the first part of a total of one year (with Li-Fan Yue and Jih-Hao Hung) Structural geology of a of sojourn supported by an honorific award from the Alexan- classic thrust belt earthquake: the 1999 Chi-Chi earthquake der von Humboldt Foundation. Taiwan (Mw7.6), Journal of Structural Geology, v. 27, 2058- I have spent much effort on conference volumes associ- 2083, 2005. ated with a July 2005 “International Conference on Theory (with Kauan-Yin Lai, Yue-Gau Chen, Jih-Hao Hung and Ya-Wen Chen) Fault geometry related surface deformation of an ac- and Application of Fault-Related Folding in Foreland Basins” tive fault: evidence from geomorphic features and coseismic that I organized. This 10-day conference included a logisti- slip, Quaternary International, v. 147, 44-54, 2006. cally ambitious field trip for ~70 international experts to (with Ramon Gonzalez-Mieres) Relief and shortening in detach- remote areas of far western China to observe many examples ment folds, Journal of Structural Geology, v. 28, 1785-1807, of actively growing anticlines, which was the phenomenon of 2006. interest to this conference. Two major collections of papers Other miscellaneous publications: are in process: one is a Memoir of the American Association (with Dengfa He) Guidebook for field trip in south and north of Petroleum Geologists and the other a special section of Tianshan foreland basin, Xinjiang Uygur Autonimous Region, China: International Conference on Theory and Application the Journal of Geophysical Research. I am involved in many of Fault-Related Folding in Foreland Basins, 78 pp, 2005. papers and with the editing. So many of my former students Articles in press or submitted: and friends are contributing that it could be considered a (with A. Hubert-Ferrari, Ramon Gonzalez-Mieres, X. Wang) festschrift. Mechanisms of active folding of the landscape (Southern However, my main current focus is completing a major Tianshan, China), Journal of Geophysical Research, ac- monograph on fault-related fold theory to be published by cepted, 2006. Princeton University Press. In addition, I have obtained a Mass balance and thrusting in detachment folds. (In K. McClay, J. H. Shaw and J. Suppe, editors) Thrust-Related Folding, surprising result in critical-taper wedge theory which allows American Association of Petroleum Geologists Memoir, one to determine absolute fault strength from wedge taper submitted, 2006. data, independent of significant assumptions about material (with Yue-Gau Chen, Kuang-Yin Lai, Yuan-Hsi Lee, John Suppe, properties. This is an important contribution to the long- Wen-Shan Chen, Yu-Nung N. Lin, Yu Wang, Jih-Hao Hung) standing controversy over the strength of major plate-bound- Coseismic fold scarps and their kinematic behavior in the ary faults. Results using this new theory indicate very weak 1999 Chi-Chi earthquake Taiwan, Journal of Geophysical Research, submitted, 2006. faults in Taiwan, Japan, and the Niger Delta. Furthermore, (with Ramon Gonzalez-Mieres) Shortening histories of active this work shows that the upper crust is relatively strong, detachment folds. (In K. McClay, J. H. Shaw and J. Suppe, which raises the fundamental question of how a crust con- editors) Thrust-Related Folding, American Association of taining weak faults is able to be strong. Petroleum Geologists Memoir, submitted, 2006. (with Li-Fan Yue and Jih-Hao Hung) Two contrasting kinematic Two-Year Bibliography styoes of active folding above thrust ramps, western Taiwan. Books: (In K. McClay, J. H. Shaw and J. Suppe, editors) Thrust-Re- (with J. Shaw, C. Connors, editors) Seismic Interpretation of lated Folding, American Association of Petroleum Geologists Contractional Fault-Related Folds: an AAPG Seismic Atlas, Memoir, submitted, 2006. American Association of Petroleum Geologists, 156pp, 2005. (with K. McClay and J. H. Shaw), editors, Thrust-Related Fold- ing, American Association of Petroleum Geologists Memoir, Refereed articles or book chapters: chapter manuscripts in review, 2006. (with A. Ferrari, X. Wang and C. Jia) The Yakeng detachment fold, China. In J. Shaw, C. Connors, J. Suppe, editors,
29 Bess B. Ward availability in OMZs might be quite low, low enough in fact Chair; to limit denitrification at the nitrous oxide reduction step, William J. Sinclair Professor of thus leading to accumulation of nitrous oxide. We have now Geosciences completed three major cruises in the last three years, one Ph.D., 1982 University of each to the three major oxygen minimum zones of the world Washington ocean. Using chelators and various carbon and nutrient ad- email: [email protected] ditions to manipulate the natural communities in trace metal clean incubations, we have shows that carbon is probably the most important limitation in these systems, that denitrifica- tion is very episodic (probably dependent upon C supply), and that Cu(I) rather than Cu(II), as had been supposed, is the Cu species available to microbes. The most interest- ing finding is the denitrifying bacterial assemblages appear to exhibit bloom dynamics, analogous to those observed in My research concerns the marine and global nitrogen cycle, surface phytoplankton communities. In the early stages of using molecular and immunological probes for marine denitrification, the assemblage is quite diverse, but is gradu- bacteria and bacterial processes (especially nitrification and ally dominated by a small number of phylotypes as denitrifi- denitrification), and measuring the rates of N transformation cation intensifies. The implication is that most of the actual processes. We have ongoing research on 1) denitrification work of denitrification is performed by a small number of in several suboxic zones of the world ocean (Arabian Sea, different types of microbes, depending on initial conditions Eastern Tropical North and South Pacific) and in Chesapeake and episodic carbon supply. Variable conditions probably Bay; 2) the genes involved in nitrogen assimilation by phy- ensure continued diversity in the background community. toplankton and the diversity of functional guilds of bacteria These observations provide an explanation both for observed involved in the nitrogen cycle of aquatic systems; 3) genomic patterns in oceanic denitrification and for the maintenance of studies of nitrifying and denitrifying bacteria. diversity in functional groups. Microbes control many of the important biogeochemical Anammox (anaerobic ammonium oxidation) is a recently processes that occur in the oceans as well as on land. They discovered step in the N cycle, that performs essentially the contribute to the trace gas cycles that influence climate; they same role as denitrification. We have made some of the utilize and produce nutrients that are involved in eutrophica- first measurements of this process in Chesapeake Bay, and tion; and they are even capable of cleansing the environment in the OMZ regions of the ocean (Jeremy Rich). Contrary by degrading a vast variety of chemical compounds, both to the first reports by Danish and German investigators, we naturally occurring and anthropogenically produced. My find the anammox occurs in both sediments and the water research focuses on the nitrogen cycle and the microorgan- column, but is not the dominant process. We hypothesize isms involved in transformations of inorganic and organic that our methods, which were designed to minimize artifacts nitrogen in the ocean and in sediment environments. This we perceived in the original methods, may be responsible for research makes use of technical approaches that range from the different conclusions. This is a very controversial area in molecular biology to stable isotope biogeochemistry. The which we are keenly involved and plan to continue work- two main bacterial groups we study are the nitrifiers, auto- ing; a new NSF proposal was recently funded to allow us trophs that oxidize ammonium to nitrite and nitrate, and to investigate the relative importance of denitrification and the denitifiers, heterotrophs that can respire nitrate in the anammox in the Arabian Sea, avoiding some of the artifacts absence of oxygen. The linked activities of these two groups common in the methods used by others for the measure- can be crucial in determining the chemical form and supply ments. of nitrogen to planktonic communities and in determin- 2. Diversity of Functional Guilds: Molecular biological ing the net nitrogen budget of ecosystems. A new project methods have revealed a truly incredible range of diversity in on phytoplankton nitrogen dynamics now makes the link natural microbial assemblages, which now begs the ques- between the carbon and nitrogen cycles explicit, by investi- tion of whether this diversity matters to ecosystem function. gating the potential for N assimilation to control the compo- We approached the problem first by assessing the diversity sition of photosynthetic planktonic assemblages. of important functional groups (e.g., denitrifying bacteria, Ward lab has a web page where all of this is described. nitrifying bacteria) and using the sequence database that we http://geoweb.princeton.edu/research/ecomicro- obtained to design DNA microarrays. The microarrays pro- bio/ecomicrobio.html vide a high throughput method for community composition and activity (gene expression) analysis. Several array projects 1. Denitrification and Anammox: In previous work are moving forward, but publication has been slower than (Granger and Ward, 2003), we showed that denitrification we had hoped. Array projects nearing completion include by cultured bacteria in the lab could be limited by copper the study of nitrifying assemblages in Chesapeake Bay on the availability, leading to the accumulation of denitrification basis of amoA genes, seasonal and composition patterns in intermediates in the medium. We hypothesized that copper phytoplankton in the English Channel on the basis of nitrate 30 reductase and rubisco genes, and denitrifiers in Chesapeake permanently ice-covered Lake Bonney, Antarctica, Aquatic Bay on the basis of nitrite reductase genes. We have recently Microbial Ecology, 52: 197-205, 2005. Casciotti, K. L. and B. B. Ward Nitric oxide reductase (norB) succeeded in analyzing messenger RNA from sediments, genes identified in ammonia-oxidizing bacteria, FEMS Micro- not a trivial problem, and have therefore been able for the bial Ecology, 52: 197-205, 2005. first time to evaluate differential gene expression by different Allen, A. E., B. Song and B. B. Ward, Characterization of diatom members of the assemblage, using the microarray. (Bacillariophyceae) nitrate reductase genes and detection of eukaryotic nitrate reductase genes from marine waters, 3. Economic Studies: We’ve been involved at a low level Journal of Phycology, 41: 95-104, 2005. in the analysis of several nitrifier genomes and have had the O’Mullan, G. D. and B. B. Ward, Comparison of temporal and genomes of two marine denitrifying isolates completed to spatial variability of ammonia-oxidizing bacteria to nitrifica- draft stage. Although fascinating, this work is underfunded tion rates in Monterey Bay, CA, Applied and Environmental Microbiology, 71: 697-705, 2005. (agencies tend to support the actual sequencing, but not the analysis of the data!). Articles in press: Ward, B. B., Nitrification. In:Encyclopedia of Ecology, Ed. S. E. Two-Year Bibliography Jorgensen, Elsevier, Oxford. Refereed articles: Song, B. K. and B. B. Ward., Molecular cloning and characteriza- Taroncher-Oldenburg, G. and B.B. Ward, Oligonucletide microar- tion of high affinity nitrate transporters in marine phytoplank- rays for the study of microbial communities. In: DNA Analysis ton, Journal of Phycology. by Nonradioactive Probes (Ed.) Hilario, E. and Mackay, J.F., Adhitya, A., F. I. M. Thomas and B. B. Ward, Diversity of nitrate Humana Press, Totowa, NY, USA, 2006. reductase genes from planktonic and epiphytic environments Klotz, M. G., D. J. Arp, P. S. G. Chain, A. R. El-Sheikh, L. J. in a seagrass community, Microbial Ecology. Hauser, N. G. Hommes, F. W. Larimer, S. A. Malfatti, J. M. Ward, B. B., Nitrogen cycling in aquatic environments, In: Manual Norton, A. T. Poret-Peterson, L. M. Vergez and B. B. Ward, of Environmental Microbiology, Eds. M. Hullar, American Complete genome sequence of the marine, chemolithoau- Society for Microbiology, New York. totrophic ammonia-oxidizing bacterium Nitrosococus oceani Articles submitted: ATCC 19707, Applied and Environmental Microbiology, 72: Moisander, P. H., A. E. Morrison, B. B. Ward, B. D. Jenkins, J. P. 6299-6315, 2006. Zehr, Spatial-temporal variability in diazotroph assemblages Glatz, R. E., P. W. Lepp, B. B. Ward and C. A. Francis, Microbial in Chesapeake Bay using an oligonucleotide nifH microarray, diversity in the water column of permanently ice-covered Environmental Microbiology. Lake Bonney, Antarctica, Geobiology, 4: 53-67, 2006. Song, B. K., E. Chyun, P. Jaffe and B. B. Ward, Molecular detec- Bronk, D. A. and B. B. Ward, Inorganic and organic nitrogen cy- tion and quantification of uncultured dissimilatory arsenate cling in the Southern California Bight, Deep-Sea Research, respiring bacteria (DARB) in Chesapeake Bay sediments, 52: 2285-2300, 2005. Microbial Ecology. Ward, B. B. and G. D. O’Mullan, Community level analysis: Ge- Rich, J. J., O. R. Dale, B. K. Song and B. B. Ward, Anaerobic netic and biogeochemcial approaches to investigate commu- ammonium oxidation (anammox) in Chesapeake Bay sedi- nity composition and function in aerobic ammonia oxidation, ments, Microbial Ecology. In: Methods in Enzymology, 397:395-413, 2005. Jackson, G. A., B. B. Ward, G. D. O’Mullan, C. A. Francis, M. A. Ward, B. B., Temporal variability in nitrification rates and related Voytek and D. Eveillard, Size and composition of functional biogeochemical factors in Monterey Bay, California, Marine groups in the microbial nitrogen cycle estimated from opera- Ecology-Progress Series, 292: 97-109, 2005. tional taxonomic unit (OTU) analysis of DNA sequence data, Ward, B. B., Molecular approaches to marine microbial ecology Applied and Environmental Microbiology. and the marine nitrogen Cycle, In: Annual Review of Earth Ward, B. B., Nitrification. In:Nitrogen in the Marine Environment, and Planetary Science, 33:092203.122514, 2005. Eds. D. Capone, D. A. Bronk, M. Mulholland. Song, B., and B. B. Ward, Diversity of benzoyl-CoA reductase Ward, B. B., D. Eveillard, J. D. Kirshtein, J. D. Nelson, M. A. genes in aromatic compound degrading denitrifying bacteria Voytek and G. A. Jackson. Ammonia-oxidizing bacterial com- and in environmental samples, Applied and Environmental munity composition in estuarine and oceanic environments Microbiology, 71: 2036-2045, 2005. assessed using a functional gene microarray, Environmental Ward, B. B., J. Granger, M. T. Maldonado, K. L. Casciotti, S. Microbiology. Harris and M. L. Wells, Denitrification in the hypolimnion of
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