Guyot Science 2003 Department of Geosciences, Princeton University 1 2 Guyot Science 2003 A Summary of the Research Progress and Accomplishments Made by the Faculty Members of the Department of Geosciences During the Year 2003 Last year, January-December 2003, was another good year for the Princeton Department of Geosciences. As usual, a number of individual faculty members received outside honors and awards in recognition of the overall excellence of their research. Jason Morgan was awarded a 2002 National Medal of Science, the nation’s highest honor for scientists and engineers, presented annually by the President of the United States. This is a fitting end to Jason’s remarkable 44-year career as a geoscientist at Princeton. In October 2003, the department hosted a two-day MorganFest symposium, in honor of Jason’s retirement. Isaac Held of the Program in Atmospheric and Oceanic Sciences was elected a Member of the National Academy of Sciences, and George Philander was elected a Fellow of the American Academy of Arts and Sciences. Tony Dahlen was awarded the 2003 Inge Lehmann Medal of the American Geophysical Union; this medal is presented biennially for outstanding contributions to the understanding of the structure, composition and dynamics of the earth. Danny Sigman will be one of the recipients of the 2004 AGU Macelwane Medal; this medal recognizes signifi- cant contributions to the geophysical sciences by an outstanding young scientist (less than 36 years of age). Danny is the first member of the geosciences department to receive this coveted award. Jorge Sarmiento was inducted as a 2003 Fellow, and Allan Rubin was elected as a 2004 Fellow of the American Geophysical Union; this is a prestigious honor restricted to no more than 0.1 percent of the membership each year. More than half of the faculty members in the Department of Geosciences are now Fellows of the AGU. Maia Schweizer, a departmental concentrator who will receive her B.A. Degree in 2004, has been awarded a Marshall Fellowship, to pursue graduate studies in biogeosciences at Oxford Univer- sity. 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, 2002-2003, is appended to each narrative report. Back Row: Rob Hargraves (deceased), Satish Myneni, Greg van der Vink, Guust Nolet, Tony Dahlen, Jorge Sarmiento, John Suppe. Middle Row: Bob Phinney, Lincoln Hollister, Peter Bunge, Ken Deffeyes (emeritus), François Morel, Michael Bender, Bess Ward, Tullis Onstott. Front Row: Jason Morgan, Tom Duffy, Franklyn van Houten (emeritus), Gerta Keller, George Philander, Bill Bonini (emeritus), Allan Rubin. Photo by Pryde Brown, with additions by Laurie Wanat. 3 Michael Bender ingassing due to temperature-driven solubility changes, and Professor also to atmospheric mixing. Ph.D., 1970, Columbia University email: [email protected] Highlights of our research of last year include: 1. Assembling and analyzing our atmospheric O2/N2 records of the past 5 years. The results show that oceans have been responsible for about 70% of fossil CO2 sequestration, and the land biosphere 30%. They also confirm that the most interannual variability in CO2 uptake is associated with the diminution of land biosphere sequestration during El Nino events. 2. Assembling about 8 years of O2/N2 data in air over the equatorial Pacific, collected intermittently using automated samplers installed on ships. These results show a maximum The activities of my laboratory focus on studies of the in O2/N2 ratios, but it is considerably smaller than predicted by a variety of ocean circulation/biogeochemistry models. geochemistry of O2, with applications to understanding the global carbon cycle and glacial-interglacial climate change. The results call into question aspects of these models. The geochemical properties we study are the concentration 3. Matt Reuer’s rapid progress with the analysis of Southern Ocean samples for the isotopic composition and concentra- of O2 in air (which we measure to very high precision), and 16 the relative abundance of the three stable O isotopes ( O, tion of O2, to constrain rates of net and gross production. 17 18 The results show that ocean productivity is highest in the O, and O) in O2. There are two subjects for the isotopic northern end of the Southern Ocean and decreases to the studies: O2 in fossil air extracted from ice cores, and dis- south. This result agrees with satellite studies of chlorophyll solved O2 in seawater. Three processes affect the concentra- distribution but contradicts inversion studies of the produc- tion and isotopic composition of O2: photosynthesis, tivity distribution, as well as hypotheses that net production respiration, and isotope exchange between O2 and CO2 in the stratosphere. in the Southern Ocean is limited by the availability of nutrients, or favored by cold temperature. Studies of the O2 concentration (or ratio of O2/N2) in 4. There were three significant analytical advances during the air constrain the fate of fossil fuel CO2 that does not remain in the atmosphere: these measurements allow us to partition past year: (a) Jan Kaiser developed the basis of a method for the “missing” CO2 between the oceans and the land bio- sphere. They also constrain rates of seasonal biological making continuous measurements of O2/Ar ratios of production by the oceans. Finally, they provide a test of dissolved gases in surface waters, along ships’ cruise models describing the global interaction of ocean circulation tracks. He recently participated in an oceanographic and biogeochemistry: These models predict that there should cruise in the eastern equatorial Pacific, and made his first measurements. Jan’s technique will give rates of net be a relatively large maximum in the atmospheric O2/N2 ratio in air over the tropical Pacific. biological production in the upper ocean at far greater resolution than any previous experimental approach. The isotopic measurements of O2 in ice core trapped gases reflect the relative fertility of Earth’s biosphere, aver- The method is a significant advance in constraining the aged over about 1,000 years. The triple isotope composition fertility of ocean ecosystems and addressing other problems of interest concerning the ocean carbon cycle. of O2 in seawater reflects the fraction of dissolved O2 from (b) We have continued to build and install auto- photosynthesis. O2 supersaturation reflects net production (photosynthesis in excess of respiration); by combining mated air samplers. We now have a record from Cape Grim (Tasmania) that is over 1 year long. It shows that measurements of O2 concentrations and isotopes, we can determine rates of photosynthesis, respiration, and net samples are collected with much better integrity, yield- production in aquatic ecosystems. Of course rate determina- ing cleaner records of atmospheric variations. This tions of these processes in seawater have been made for many improvement is particularly important for Ar/N2 years; what makes our work new is that our approach does measurements, whose amplitude of annual variability is not require labor-intensive bottle incubations at sea, and our only 10-25 parts per million. measurements can be made on large numbers of samples (c) Makoto Suwa and Bruce Barnett have built an collected by colleagues on cruises of opportunity, and automated extraction line for Makoto’s ice core samples, returned to the lab. and he has begun his thesis measurements. We have also begun planning or doing 3 new projects. Supplementing the O2 studies are studies of Ar. In seawater samples, Ar gives a measure of physical supersatura- The first is a collaboration with Chuck Dismukes, tion due to warming of waters and bubble entrainment. In Department of Chemistry, to investigate the source of O produced during photosynthesis (it is primarily from air samples, the Ar/N2 ratio reflects seasonal outgassing and 2 water but there is reason to think that some comes from 4 bicarbonate). The second, and potentially most interest- Bender, M. L., Climate-biosphere interactions on glacial-interglacial ing, is a study with Larry Edwards of the possibility of timescales, Global Biogeochemical Cycles, in press, 2003. helium/uranium dating of speleothems, which have Battle, M., M. Bender, M. Hendricks, D. T. Ho, R. Mika, G. McKinley, S. Fan, T. Blaine, and R. Keeling, Measurements terrific high-resolution climate records. The third, with and models of the atmospheric Ar/N2 ratio, Geophysical Lonnie Thompson, is an attempt to use gas stratigraphy Research Letters, 30 (15), 1786, doi:10.1029/2003GL017411, to data a critical portion of one of his tropical ice cores. 2003. Bender, M. L. (Chair) and 14 co-authors, A large Scale CO Two-Year Bibliography 2 Observing System: Oceans and Atmosphere, National Keller, K. R. D. Slater, M. Bender and R. M. Key, Possible biological Oceanic and Atmospheric Administration, 214 pp + 9 or physical explanations for decadal scale trends in North Appendices, 2002. Pacific nutrient concentrations and oxygen utilization, Deep- (Note: this document presents a 5-10 years implementation plan, Sea Research Part II - Topical Studies in Oceanography, 49, commissioned by the NOAA Office of Global Program, for 345-362, 2002. systematic observation of CO and related properties in the Blunier, T., B. Barnett, M. L. Bender and M. B. Hendricks, Biological 2 oceans and atmosphere). oxygen productivity during the last 60,000 years from triple Hendricks, M. B., M. L. Bender, and B. Barnett, Net and gross O oxygen isotope measurements, Global Biogeochemical 2 production in the Southern Ocean from measurements of Cycles, 16 (3), art. No. 1029, July-August, 2002. biological O saturation and its triple isotope composition, Bender, M. L., Orbital tuning chronology for the Vostok climate 2 submitted to Deep Sea Research. record supported by trapped gas composition, Earth and Planetary Science Letters, 204, 275-289, 2002.