Oden Southern Ocean 0910 OSO 0910 Cruise Report

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John Anderson, Martin Jakobsson and OSO 0910 Scientiﬁc Party Stockholm 2010

Oden Southern Ocean 0910

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Oden Southern Ocean 0910

Table of contents Summary Participants Introduction and background Marine geology and geophysics Oceanography Ecology Physics Methods Multibeam bathymetry Equipment System settings Sound velocity correction Ship board processing Chirp sonar profiling Equipment System settings Ship board processing Sediment coring and processing Coring Multi Sensor Core Logging Index properties and shear strength Oceanography Moorings CTD/LADCP measurements Salinity calibration Ecology Water sampling for ecological studies Experimental study on marine animals Lake studies Preliminary Results Marine geology and geophysics Multibeam bathymetry Chirp sonar profiling Sediment coring Multi Sensor Core Logging, index properties and shear strength Oceanography Moorings CTD and water sampling CTD/LADCP XBTS/XCTDS Ecology Handling simultaneous UV and predation threats in marine systems Diel changes in the vertical distribution of lake zooplankton Acknowledgements References Appendices I: Sediment core lithologies II: Multi Sensor Core Logging plots III: Chirp sonar profiles and coring locations IV: Samples for radiocarbon dating V: XCTD/XBT/XSV/CTD stations

Oden Southern Ocean 0910

Summary to test the system and coring methods prior to The Oden Southern Ocean cruise began on Feb- reaching our main study area in eastern Pine ruary ( as the Oden departed McMurdo Station Island Bay. The coring went well, except there in route to Little America Trough in the western was minimal recovery in the stiff sediments Ross Sea for the deployment of oceanographic that cover the bottom at this locality. moorings (Figure !). We began collecting swath On February !' our !& nautical mile bathymetry and sub-bottom profiler records as journey from McMurdo Sound to eastern Pine soon as we left the ice dock, which included Island Bay was completed and we began con- mapping some interesting recessional moraines ducting scientific operations. Satellite images in McMurdo Sounds. Calm seas were encoun- had indicated that there was very little sea ice tered during the transit allowing us to set up in the area, which indeed proved to be the coring equipment on the back deck and prepare case. In fact, " ! proved to be a historical the labs. We reached Little American Trough event in terms of the limited sea ice cover in on February ! and conducted a small bathy- Pine Island Bay. This allowed us to conduct a metric survey needed to select the mooring sites. detailed multibeam survey of the bay without The two mooring deployments went smoothly restriction. In addition, we were able to oc- and were completed on schedule. The next sci- cupy ") coring stations and ! CTD stations entific objective was the deployment of another in the eastern part of the bay and in Ferroro oceanographic mooring in the western part of Bay, which is a fjord located in eastern Pine Pine Island Bay for scientist from the University Island Bay (Fig. map of study areas showing of Gothenburg. Again, the mooring went suc- track lines and CTD and core stations). The cessfully but winch problems prevented us from preliminary results of our work in the region completing the CTD cast at this station. After are provided in the following sections. See the oceanographic work was completed, we at- also Appendix ! for brief descriptions of indi- tempted our first Kasten core, intended mainly vidual research projects.

Participants Dr. John Anderson, Co-Chief Scientist, Rice University Mr. Matthias Danninger, Scientist Dr. Martin Jakobsson, Co-Chief Scientist, Stockholm Ms. Christina Wiederwohl, Scientist, Texas A&M University University Dr. Frank Nitsche, PI, Lamont Doherty Geological Ms. Alexandra Kirshner, Scientist, Rice University Observatory Ms. Rebecca Minzoni, Scientist, Rice University Dr. Lars-Anders Hansson, PI, Lund University Mr. Rodgrigo Fernandez, Scientist, Rice University Dr. Samuel Hylander, Scientist, Lund University Mr. Travis Stolldorf, Scientist, Rice University Dr. Nina Kirchner, Scientist, Stockholm University Mr. Thomas Aidehag, Teacher Dr. Richard Gyllencreutz, Scientist, Stockholm University Mr. Ville Lenkkeri, Artist Dr. Rezwan Mohammad, Scientist, Stockholm University Mr. Paul Clark, Oceanographic Technician, Texas A&M Mr. Björn Eriksson, Multibeam Technician, Stockholm University University Mr. Markus Karasti, Coring Technician, Stockholm Dr. Matthew O’Regan, Scientist, Stockholm University University Dr. Wojciech Majewski, Scientist, Polish Academy of Mr. George Aukon, Science Technician, Raytheon Polar Sciences Services Mr. Kyle Jero, Scientist

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Figure 1. b) Map showing the track for the crossing of the Drake Passage.

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Figure 1. a) Map showing the route (white line) of the OSO0910 expedition with icebreaker Oden. Coring, CTD and water sampling stations are shown in separate maps in the result sections of the included projects.

Oden Southern Ocean 0910

Introduction and background Swath bathymetry data acquired during OSO0910 will be integrated into a regional Marine geology and geophysics database that is being used to map and ana- One of the objectives of the " ! Oden lyze the distribution of cross-shelf troughs cruise was to investigate the history of Pine and the related paleo ice flow pattern along Island Ice Stream to see if it has a history the entire continental margin of the Bell- of rapid change and to attempt to identify ingshausen and Amundsen Seas and thus those factors that contributed to ice stream significantly extend previous studies that retreat in the past. Our first task was to focused mainly on two major trough sys- map with Oden’s multibeam system a large tems in front of the Pine Island Glacier and trough on the continental shelf where Pine in the central Bellingshausen Sea. Compar- Island Ice Stream was located during and ing location and shape of these cross-shelf after the Last Glacial Maximum. The inner troughs with present ice flow will lead to portion of the trough had been mapped in new insights into the different processes that previous expeditions and is known to con- created them and may indicate large-scale tain geomorphic features that are indicative differences in ice sheet dynamics of today of subglacial melt water drainage, possibly compared to previous glaciations. Building instantaneous discharge (Lowe and Ander- upon a previous bathymetric compilation son, " "). The multibeam data acquired of the Amundsen Sea (Nitsche et al., " ') during our cruise revealed large lineations data colleted during OSO0910 will be used on the seafloor that are typical of other gla- to generate the first bathymetric compila- cial troughs around Antarctica where ice tion of the entire margin. The new bathym- streams flowed in the past. We also iden- etry compilation will be used to identify tified some large wedges of sediment that cross-shelf troughs, and determine their ge- mark former grounding line positions and ometries, including width, depth, and ori- were successful in collecting cores on these entation. Using information about present features that yielded carbonate material for ice flow, such as balance velocity maps, we radiocarbon dating. These radiocarbon will compare the distribution of the cross- ages will hopefully allow us to study the his- shelf troughs with present ice stream lo- tory of ice stream retreat from the continen- cations and identify troughs that can be tal shelf, which is the first step in determin- linked to present ice streams or to smaller ing the cause of retreat. For example, we outlet glaciers. Cross-shelf troughs that may find that the ice stream retreated from correspond to neither of those, or appear the shelf during times when sea level was too large to be formed by small outlet gla- rising rapidly. Other mechanisms for rapid ciers, will indicate the locations of previous ice stream retreat include under penning ice streams that are different from present of the ice by subglacial melt water and, as ones, and thus indicate major changes in previously mentioned, melting of the ice by ice flow pattern of the WAIS. Comparison warm deep water. We will study the cores with size and geometry of depositional fea- for evidence of both mechanisms, evidence tures on the continental slope will provide such as unique sediment types that might additional indication if a trough drained be generated by melt water discharge or large areas of the ice sheet or just a coastal unique fossil assemblages that might indi- glacier. The results will be integrated into cate periods of warm deep water incursion a new conceptual model that describes the onto the continental shelf. Dr. Wojciech ice flow pattern during previous glaciations. Majewski of the Polish Academy of Sci- ences will conduct analyses of foraminifera Oceanography in the cores for assemblages that have been Oceanographic data collected during linked to Circumpolar deep water. OSO0910 will be used to investigate processes controlling the flow of warm Cir-

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cumpolar Deep Water onto the Antarctic ics in present and, especially, future aquatic continental shelf in the eastern Ross Sea. ecosystems. Two moorings were deployed to record current, temperature, salinity and pressure in Physics the interior of Little America Troughs. High Data collected during OSO0910 will be used resolution conductivity/temperature/depth to determine a complete set of cosmic ray (CTD) measurements were taken to char- response functions for the ice Cherenkov acterize the summer regional water mass detector used in the surface air shower ar- stratification and circulation, the bounda- ray that is part of the IceCube neutrino ries and spreading of water masses, and to observatory now under construction at the infer mixing histories and interactions with South Pole. This will be accomplished by the sea-ice and continental ice. The moor- means of a latitude survey conducted with ings will be left out for one year, with " ! the detectors mounted in a portable freezer deployment and " !! recovery. on the icebreaker Oden, recording data on the entire " )–" ! voyage from Sweden Ecology to McMurdo and return. The project will This project addresses how organisms in advance understanding of the acceleration freshwater and marine ecosystems handle and transport of solar energetic particles one of the most hostile environments on by enhancing the ability of the IceTop air earth with respect to ultraviolet (UV) radia- shower array to measure details of solar en- tion. The project has a strong basic science ergetic particle spectra. profile by focusing on adaptations among a group of crustacean zooplankton that is Specific objective of solar physics research able to adjust the photoprotective pigmen- with IceTop are to: tation in accordance with the present UV threat. We expect to find the strongest pig- • Enable high resolution observations of mented zooplankton on earth in Antarctic the spectra of solar particles with momen- freshwaters, i.e. will be able to assess the tum above ! GV. potential reaction norm with respect to • Extend the sensitivity for detection of pigmentation. In addition to the basic sci- high energy particles by approximately two ence, the project will provide predictive orders of magnitude to better understand knowledge regarding how organisms han- the circumstances under which the sun can dle elevated UV levels, which are currently accelerate these particles. increasing also in temperate systems. Our • Examine the relationship between so- study includes four parts !) quantification lar particle event size and spectral shape. of different pigments, ") UV effects on com- munity composition, #) assessment of po- The geomagnetic field prevents cosmic tential differences in the ecotoxicological ray particles from hitting the atmosphere fingerprints of marine and freshwater zoo- below a “cut off” rigidity (momentum per plankton, and $) monitoring of Antarctic unit charge) that is a calculable quantity lakes in order to compare with an already for any location on Earth. By observing the existing database on Arctic systems. Stud- change in signal of a detector on the surface ies will be performed both as monitoring of the earth with change in cut off one can of marine and freshwater habitats, as well deduce in some detail the response of the as experimental studies of specific mecha- detector to the primary particles at the top nisms. The general aim with the project is of the atmosphere. Crudely speaking the cut to connect large-scale global changes, bio- off is high at the equator (few particles get diversity and evolutionary ecology, which in) and low near the magnetic poles (many has the potential to reveal intriguing predic- particles get in). tions regarding the functioning and dynam-

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Figure 2. Summary plot of barometric pressure corrected neutron counting rates for the voyage to date plotted together with geographic latitude. The occasional high values of the neutron intensity occur when the ship is docked – the extra neutrons are generated in the environment. This illustrates one important reason for doing a latitude survey on a ship – the water provides an nearly constant environment.

Methods Equipment Icebreaker Oden is equipped with a Kongs- Multibeam bathymetry berg EM122 !° × !° multibeam echo sound- During the cruise the multibeam system er including the capability of logging the was operated continuously, from McMur- acoustic properties of the water column do until we reached the economical zone (Figure #). The system was upgraded in of Chile, " nmi outside of the country’s " ) from an EM120. The EM122 multi- southern tip. In Pine Island Bay and Fer- beam can perform seabed mapping to full rero Bay systematic multibeam mapping ocean depth (!! m). The nominal sonar was carried out along deﬁned survey lines frequency is !" kHz with an angular cov- with " to >% % overlapping swaths (see erage sector of up to !% degrees and $#" Results). The multibeam and subbottom beams per ping. Due to the ice protection of data acquisition was monitored around the transceivers, the useable angular cover- the clock during four hour shifts by one or age is reduced down to less than " × &%°; the two watchmen at each shift (Table !). Post- width of the useable mapping data is typi- processing of both the multibeam and sub- cally three–four times the water depth. The bottom proﬁling data was done during the transmit fan is split in several individual watches (see below). sectors with independent active steering according to vessel roll, pitch and yaw. This

Table 1. Multibeam watch standing.

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places all soundings on a “best ﬁt” to a line A Seatex Seapath 200 motion sensor is perpendicular to the survey line, thus ensur- used for roll, pitch and heave compensation ing a uniform sampling of the bottom and of the Multibeam echo sounder. The Seap- possible ! % coverage. The EM122 trans- ath 200 is also use to provide heading and ducers are linear arrays in a Mills cross con- position information. ﬁguration with separate units for transmit and receive.

System settings The following system settings were usually used for EM122 multibeam surveys during the OSO0910 cruise: (Runtime Parameters – Sounder Main) Max. angle: "× % …"× &%deg, depending on sea state Max coverage: depending on water depth, usually higher than angular limit Angular coverage mode: AUTO (MANUAL results in less beams being used) Beam spacing: EQDIST Ping mode: AUTO Pitch stabilization: On Heading filter: MEDIUM Runtime Parameters – Sound Speed Sound speed profile: .asvp file from CTD or XCTD/XBT/XSV Abs. coeff. files, salinity: Automatically computed from SVP Abs. coeff. files, CTD: D:\sisdata\common\svp_abscoeff\default Sound speed at transducer: Sound velocity probe used. (In the Arctic where we have had more sea ice, we have instead used sound velocity from profile) Runtime Parameters – Filter and Gains Spike Filter Strength: OFF Range Gate: NORMAL Slope, Aeration, Sector Tracking, Interference: All off Absorption Coefficient Source: Salinity, #%ppt Normal incidence sector: &°

Runtime Parameters – Filter and Gains Real Time Data Cleaning: None Javad and Trimble: Off ATH Logging: Off

Sound velocity correction tion of the depth data from multibeam. The During the entire cruise regular XBT (eX- XSV is the only probe that directly provides pendable Bathy Thermograph), XSV (eX- a sound velocity proﬁle of the water col- pendable Sound Velocimeter), and XCTD umn. For all the other probes sound velocity (eXpendable Conductivity Temperature has to be calculated from the water physical Depth) casts were carried out. In total, !#& properties (pressure, temperature and salin- expendable probes were used and the data ity). The sound speed formula used is Cop- from most of them were used to calibrate pens (!)(!, taken from the Simrad EM120 the multibeam echo sounding data in terms Operators Manual). A !" m value of of sound velocity. In addition, ten CTD sta- !&&&.(! (acquired previously from a deep tions were completed which also provided CTD station) was added to the sound ve- information for the sound velocity correc- locity proﬁles (the echo sounder operating

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Figure 3. Schematic illustration of the EM122/SBP120 system installed on the Oden. The drawings are modiﬁed versions of Kongsberg’s original. The system was ﬁnanced by the Knut and Allice Wallenberg foundation, Swedish Research council and Swedish Maritime Administration.

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software requires all profiles to extend to !" spection and editing using tools available in m depth). Icebreaker Oden is equipped Fledermaus. The final edited cube surfaces with a real-time sound velocity probe by were used for analysis of the seafloor mor- Applied Micro System LDT for providing phology. However, in some cases the actual up-to-date sound speed values near the “clean” soundings were exported to allow transducers needed for beam forming. This higher resolution surfaces to be created real time probe is situated within the sea- than the preset PFM surfaces. The process- water intake in the ship’s hull. Depending ing continued until we arrived at Punta Ar- on re-circulation of water in the sea-wa- renas when all of the data had gone through ter intake and probably other factors, the a first cleaning. sound velocity reading can fluctuate within a range of up to several meters per second Chirp sonar profiling (usually some ± .#m/s). However, during Equipment the OSO0910 cruise the values provided by Icebreaker Oden is equipped with a Kongs- the real time probe were stable and usually berg SBP120 #° subbottom profiler. The in good agreement with the surface values SBP120 subbottom profiler is an extension from the expendable probes or CTD sta- to the EM122 multibeam echo sounder. tions. Therefore, the real time probe data The primary application of the SBP120 is were used. During previous Arctic Ocean the imaging of the topmost sediment lay- expeditions, the real time probe values have ers under the sea floor. The SBP120 uses been of varying quality and not always pos- an extra transmit transducer unit, whereas sible to use. The sea ice free conditions in one broadband receiver transducer of the Pine Island Bay likely made this probe more EM122 multibeam echo sounder is used for reliable during the OSO0910 expedition. both the EM122 and the SBP120 systems. A frequency splitter directly after the re- Ship board processing ceiver staves divides the !" kHz multibeam The acquired multibeam data were imme- signal from the lower frequency (".% to ' diately processed onboard using the soft- kHz) chirp sonar signal. ware Fledermaus, version '. .!d. The sur- The normal transmit waveform is a chirp veyed areas were divided into several PFM signal (which is an FM pulse where the fre- projects (Figure $). PFM, Pure File Magic, is quency is swept linearly or hyperbolically). the multibeam file structure of Fledermaus. The outer limits for the start and stop fre- The raw multibeam data (.all is Kongs- quencies of the chirp are ".% k Hz and ' k Hz, berg’s raw file format produced with the providing a maximum vertical resolution of EM122 system) within a survey area are approximately .# milliseconds. In addition merged into a PFM with a defined grid size to linear chirps, the system offers CW puls- resolution. The grid resolution was set de- es, hyperbolic chirps and Ricker pulses. The pending on the water depth in the survey system is capable of providing beam open- area. In general, a grid cell size of " × " ing angles down to #°, and up to !! beams m was used for all the surveys on the ca in a transect across the ship’s keel direction # –! m deep continental shelf during with a spacing of usually #°. The system is the OSO0910 expedition. The deepest sur- fully compensated for roll, pitch and heave vey lines located in ># m water depth movements of the ship by means of the Sea- were merged into PFMs with ( × ( m sized tex Seapath 200 motion sensor used for the grid cells. The projection was set to Polar Multibeam echo sounder. Stereographic with a true scale at '!°S and the horizontal datum to WGS ($. In gen- System settings eral, the processing consisted of a first ap- The initial system settings used for SBP120 plication of the “Cube” algorithm (Calder chirp sonar were adopted from the Lo- and Mayer, " #) followed by manual in- monosov Ridge off Greenland (LOMROG)

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Figure 4. Maps showing the extents of the PFM multibeam processing projects. The ﬁlename of each processing project is shown with letters in a black box. expeditions (Jakobsson et al., " (). How- of the acquisition delay. The most com- ever, since there was very little sea ice dur- monly applied settings are listed below and ing the OSO0910 expedition, some different a screen dump of the acquisition window is settings were applied. In particular, it was shown in Figure %. possible to use the automatic adjustment

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Transmit mode: Normal Synchronization: Fixed rate Ping interval: % ms Acquisition delay: Calculate delay from depth Acquisition window: " –"% ms. In steep terrain when it is hard to follow the seaﬂoor reﬂection a larger window was sometimes used Pulse form: Linear chirp down Sweep frequencies: "% –' Hz Pulse shape: %% (Simrad recommendation, % actually will not result in a non-tapered signal, but in an almost-not-documented slight tapering due to physical and electronics restrictions). Pulse length: generally around #%ms (seems to be a good trade-off between energy/ penetration and resolution). Source power: –1 dB Beam width Tx/Rx: #° (“focused” is not narrower than #°, which is the physical limit of the transducers) Number of beams: % beams Beam spacing: #° Automatic slope correction: Off Slope along/across: Usually . ° but can be changed when going along/across steep slopes (> #°) constantly. Slope quality: Parameter read from Multibeam data stream, do not set or change

Ship board processing tables of the core locations and sediment Since the main part of the work during the recovery. One attempt at collection of a OSO0910 expedition was carried out in Pine gravity core loaded with a weight of ! " Island Bay along pre-defined survey lines kg was unsuccessful due to a winch failure. proper line breaks for the subbottom pro- The gravity corer was lost as the wire had files were made. This greatly facilitated the to be cut. The main hydraulic coring winch data processing. The profiles were named was found to be un-repairable and heavy according to the convention OSO0910- coring operations with the piston/gravity PI-##, where ## simply represent a line corer had to be terminated. A smaller elec- number that was incremented. Raster im- trical winch capable of pulling ca !.% ton ages of the chirp sonar profiles were created had instead to be used for all coring opera- using the Kongsberg SBP120 software. The tions. Thus, all "' sediment cores collected post-processing consisted of match filtering during the cruise were collected with the # and in some cases Time Varied Gain (TVG) meter Kasten corer. Actually, the original was applied. Some examples of chirp sonar plan for the cruise called for use of the Kas- profiles and a map of the named profiles in ten corer as this method allows quick ac- Pine Island Bay are shown in the result sec- cess to the core for onboard sampling. The tion. main objective of the coring was to acquire suitable material for radiocarbon age dat- Sediment coring and processing ing and previous coring in the region had Coring shown that carbonates are rare. Thus, our A piston/gravity corer, which in piston core strategy was to collect and wash onboard mode can be rigged up to !" m, and a # me- large volumes of material, which in some ter long Kasten corer were brought to take cases involved collecting more than one sediment cores during the OSO0910 expe- core from the same location. The Kasten dition. The result section provides further corer has a # meter long !%× !% cm barrel information on sediment cores collected made out of stainless steel. The core head during the expedition, including maps and can be loaded with a maximum of !( led

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Figure 5. Screen dump of Kongsberg’s acquisition software for the SB120 chirp sonar profiler were the system settings listed above can be seen. This software was also used for post-processing of the multibeam data. weights of #" kg/weight. Until coring sta- on sediment color (Munsell Color Chart), tion ten !$ weights were used while after texture, and structures. Samples were also this station the amount of weights were in- taken from the freshly opened cores for creased to !'. foraminiferal analysis. Next, two archive Core locations were selected using a cores were taken from each Kasten core by combination of swath bathymetry and sub- inserting liner halves with inner diameter of bottom profiler data. In general, Pine Is- ( mm into the Kasten core and removing land trough was found to contain relatively the smaller core halves using a piano wire little post-LGM sediment, so most cores and spatulas. The archive cores were deliv- penetrated only a meter or two before ter- ered to the sedimentology lab where they minating in stiff till or gravelly glacimarine were logged and later described in detail sediments. No thick post-glacial sediments (Appendix I). The remaining sample in the were identified within the trough. Kasten core was sieved in a " mm and .% As soon as the core was on deck it was mm sieve and examined for carbonate shell transported into a tent that had been erected material. A separate sample was washed on the back deck with a large sink for wash- and examined for foraminifera. This ap- ing samples (see photo of tent). The cores proach proved highly successful and a total were described, photographed, and physi- of 31 carbonate samples were recovered at cal properties (shear strength) were meas- 14 core locations, including a number of ured. Lithological descriptions were based samples at the contact between subglacial

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The 3 m long Kasten corer lowered into the water using the A-frame of the Oden.

Core processing in the tent setup on Oden’s aft deck.

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and glacimarine sediments that will allow Multi Sensor Core Logging us to determine the timing of retreat of the The Geotek Multi-Sensor Core logger Pine Island ice stream. (MSCL) from Stockholm University was Of the two archive core halves, one will set-up in the main lab on the foredeck of be shipped to the Antarctic Marine Geology the Oden. Sensors were oriented in the ver- Research Facility in Tallahassee, Florida for tical direction to allow for split-core log- permanent storage and the other will be ging. Measurements of the gamma ray de- transported to the Stockholm University. rived density, compressional wave velocity (p-wave), magnetic susceptibility, sediment

Tent setup on the aft-deck for sampling and processing of the Kasten cores.

Washing and sieving of sediment samples taken from the Kasten corer.

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thickness and temperature were acquired at found to be ""."& s. A $ s gate and # s a down core resolution of ! cm. Each logged delay was used for calibration and logging. section was digitally scanned and the RGB Magnetic susceptibility was acquired values extracted from the image by averag- with a Bartington point sensor. Magnetic ing over a !-cm moving window. susceptibility of whole cores is often col- Gamma-ray attenuation was measured lected using a loop sensor, which provides using a 137Cs source with a % mm collimator a spatially integrated susceptibility signal and a ! second count time. Calibration of that encompasses the entire diameter of the the system was performed using a machined core, with effective sensor lengths of gener- piece of aluminum that fits within a split ally $–& cm. The point sensor differs in that core liner. There are ( different thicknesses the area influencing the magnetic suscepti- of aluminum on the calibration piece. Once bility measurement is much smaller, gener- filled with distilled water, the calibration ally being constrained to the diameter of the piece and liner were placed under the 137Cs sensor face (~" cm), and a depth of only a source, and the number of gamma rays pass- few mm into the sediment. No mass or vol- ing through each section over a course of ume corrections were made to the Magnetic # s was logged. The relationship between susceptibility measurements. the measured counts per second [ln(cps)] The ambient room temperature was and the known density of the aluminum/ recorded during logging of each section water mixture at each step is defined by ei- using a standard platinum resistance ther- ther a "nd order polynomial or a linear re- mometer, placed on the bench beside the lationship. The difference between the two MSCL. All cores were allowed to equilibrate best-fit approaches is often minimal, and in with room temperature overnight prior to this instance R2 values for the polynomial logging. fit and linear fit were .)))'# and .)))&" Sediment thickness is a key parameter for respectively. The simpler linear fit was used calculating the density and p-wave velocity to convert cps to density where; of sediments. The measurement of sediment thickness is achieved using two displacement transducers attached to the p-wave For p-wave velocity measurements, a pair velocity housings. At the start of logging a of automated transducers sends a compres- reference height is set by manually lower- sional wave through the sediment. The up- ing the p-wave transducers so that they are per transducer is automatically lowered to in contact with the sediment surface. This a prescribed height, so that it is in contact reference height becomes the maximum with the sediment surface, and the travel distance the transducers will travel in the time of the p-wave between the send and vertical direction, and by default, the mini- receive transducer is logged. Conversion mum sediment thickness recognized by the of the travel time into a p-wave veloc- MSCL. In theory, intervals where the sedi- ity requires calibration to account for de- ment thickness is larger than the reference lays introduced by the electronic circuitry height are recognized and recorded as the and those associated with the passage of sediment surface stops the downward mo- the p-wave through the liner. Calibration tion of the p-wave velocity transducers. is performed by measuring the travel time However, in soft and easily deformable through a section of split liner filled with sediments, the resistance of the spring- distilled water at a known temperature. The loaded transducers is often higher than the temperature and thickness of the water is sediment strength. In these instances, small used to calculate a theoretical travel time, deviations in down core thickness (i.e. !–% with the difference between the logged and mm) are not recorded. theoretical travel time used to define a p- A reference height was set for each core wave travel time offset (PTO). This was and/or section at the beginning of logging.

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The location of the reference height meas- the linear relationship derived between the urement was selected where the sediment ln(cps) and the set of variable density stand- thickness was minimal. The actual sediment ards used to calibrate the system. thickness at this location was measured and recorded using a set of calipers, and subse- The equation for calculating the p-wave ve- quently used to process the data. Because of locity (Vp in m/s) was, the uncertainty in the true sediment thickness (see below), processing was not done using the MSCL utilities program, but rather manually in Excel. Sediment thickness where TOT is the logged total travel time of was calculated from, the p-wave passing through the sediments, and PTO the travel-time offset that accounts for delays in the electronic circuitry and the where ThicknessX (cm) is the sediment delay associated with the liner thickness. thickness (excluding the liner) at position No temperature or salinity corrections were

‘X’; ThicknessR (cm) is the caliper-meas- applied to the processed p-wave data. ured thickness of the sediment where the Errors associated with the sediment p-wave velocity transducers were used to thickness measurement impact the density set the reference height; CTD (mm) is the and p-wave calculations oppositely, and logged ‘core thickness deviation’. Once the both are sensitive to small (±! mm) errors. downcore sediment thickness was calcu- For example, a ! mm underestimate of the lated, the bulk density and p-wave velocity sediment thickness will cause the density of the sediments could be determined using to be ~ . % g too high and the p-wave ve- - the calibration data. Bulk density ( B) was locity ~$! m/s too low (Figure &). In many calculated from, instances, the derived sediment thickness was adjusted by a few mm to get reasonable agreement between the calculated density and velocity data (Table "). For exam- where cps were the logged counts per second ple, cores displaying very high bulk density for gamma rays passing through the sedi- (>". g/cc) in intervals where the p-wave ment. Constants in this equation are from velocity was consistently below !$ m/s

Figure 6. Inﬂuence of core thickness deviations on the calculated bulk density and p-wave velocity. Error introduced into the calculated density is slightly non-linear, with larger errors associated with higher density (lower cps) sediments.

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Table 2. Adjustment of derived sediment thickness in order to get reasonable agreement between the calculated density and velocity data.

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25 Cruise Report

(the velocity of water) were rectified by in- ple weights ranged between ") and $ g for creasing the sediment thickness by a few the wet samples, indicating a ±".%–#.%% er- millimeters. Adjustments to the reference ror. Additional errors can arise from incom- sediment thickness were facilitated by complete filling of the constant volume sampler paring downcore variations in density and or overfilling the ring by compressing the p-wave between archived halves taken from sediment during sampling. the same Kasten core. Where necessary, fur- Shorebased analysis of the dried samples ther improvements to the adjusted sediment using a helium displacement pycnometer thickness can be achieved by directly meas- will provide accurate data on the grain den- uring the sediment thickness every !–" cm. sity of sediments from different lithologic The processed data files include all the units, and is independent of sampling and raw data required to calculate the sedi- shipboard measurement errors for the bulk ment thickness, density and p-wave veloc- density measurement. The grain density is ity. For presentation purposes, the data used in conjunction with either direct or was cleaned, providing two additional col- MSCL derived measurements of sediment umns in the data files. Bulk density values bulk density to determine sediment poros- of !$% m/s - and with a signal amplitude of >$ % were where is the fractional porosity, G is the - - retained. grain density, B the bulk density and F the Results from core logging (showing only pore fluid density. the cleaned data) are presented for each archived half in Appendix II. The lithologic Shear strength plots in I also contain MSCL data (magnetic The undrained shear strength (Su) and un- susceptibility and bulk density). Where two confined compressive strength (UCS) were archived halves exist from a single Kasten measured on the scraped surface of each Core, the measurements are overlain. Large Kasten core using a hand-held shear vane variations between the two archived halves and pocket penetrometer respectively. from the same core sometimes exist. Differ- Measurements were made prior to sampling ences in magnetic susceptibility generally of the archived halves, and approximately arise from non-uniform distribution of peb- every ! –" cm downcore. Measurements bles/rock fragments, or significant anoma- near the base of the Kasten core and in the lies in sediment thickness (holes/dropstones) core catcher material were sometimes omit- while differences in bulk density give a related due to clear sample disturbance. tive indication of sample disturbance and/ The hand held vane shear is equipped or core thickness logging errors. with three different diameter blades. The largest was used for the majority of meas- Index properties urements, as it is most sensitive for low Index property samples, commonly used to strength sediments. The force required to directly determine the bulk density, poros- reach failure is read directly from the instru- ity, water content and grain density of sediment face, and is given in kg/cm2. One full ments, were taken using two ).( cm3 stain- rotation of the standard (medium) blade is less steel rings. The sample bulk density equal to ! kg/cm2, while a full rotation of was calculated shipboard by measuring the the large blade is equal to ." kg/cm2 (where wet mass of the sample and dividing this by ! kg/cm2 = )(. &' kPa). the volume. However, motion of the ship, The pocket penetrometer measures the even during coring operations, resulted in unconfined compressive strength, which is a digital balance accuracy that was, at best, equal to twice the undrained shear strength. within ±!g of the true sample weight. Sam- A "% mm diameter (!."# cm2) foot was

26 Oden Southern Ocean 0910

used on the penetrometer, and the dial "$-position SBE-32 Carousel sampler trig- reading (in kg) after the foot was pressed gered through the Sea-Bird 11+ deck unit. into the core surface was used to calculate To guide the approach to the ocean floor a UCS (kg/cm2). In many instances, the Teledyne Benthos 200 kHz sonar altimeter presence of pebbles in the sediment made was mounted on the lower frame of the ro- acquiring reliable vane shear measurement sette. Most profiles reached to within ! m difficult. In such instances the smaller area of the bottom. of influence exerted by the penetrometer CTD data were acquired and processed provided more accurate strength readings. using Sea-Bird Seasave software, version Where both penetrometer and vane shear '.!(c on a laptop computer running Win- measurements are taken on the same core, dows XP Professional. Immediately after there is generally good overall agreement each cast all CTD/LADCP raw data outputs between the measured and derived shear were copied over to the ships network. strengths, but generally, the penetrometer Processed CTD data files were made avail- readings provide a slightly higher strength able to all science staff generally within an estimate. Shear strength measurements are hour of each cast completion. displayed alongside the lithologic columns The surface pressure readings from CTD in Appendix I. sensor was recorded on the log sheet before each deployment. The rosette was initially Oceanography lowered to ! meters for approximately " Moorings minutes to soak the CTD sensors, and af- Two moorings were deployed in the Lit- ter the pumps turned on and the oxygen tle America Trough of the eastern Ross sensor signal stabilized, it was returned to Sea. The moorings are identical in design the surface before starting the actual cast. and each consists of dual Benthos acous- To best accommodate LADCP and CTD de- tic release, # Sea-Bird SBE-37 Microcats, scent rates, the winch payout and hauling and 2 Nortek Aquadopps 3000 (Figure rate was & m/min for most of the down '). The acoustic releases were tested and cast. On approaching within ~"% m off the armed using a Benthos Universal Deck Box bottom, as determined from altimeter, the UDB-9000M provided by the University of winch was slowed to # m/min. On the way Gothenburg. up, the rosette was stopped to close the Ni- skin bottles at depths selected during the CTD/LADCP measurements down-cast to resolved main water column Profiles of temperature, conductivity, dis- features. E.g. target levels included extreme solved oxygen, and currents were meas- values in T and S, regions with homogene- ured using equipment property of Texas ous layers for salt control, and layers near A&M University. The basic CTD package the sea surface and sea floor. Once on deck, consisted of a Sea-Bird Electronics SBE911+ water samples were collected from the Ni- CTD body and deck unit system fitted with skin bottles for salinity and oxygen-!( iso- dual ducted conductivity-temperature sen- topes measurements. Salinity analysis was sors paired with pumps, and a single SBE- done primarily to standardize conductivity 43 dissolved oxygen sensor. A downward- measurements derived from the CTD sen- looking Teledyne RD Instruments 300 kHz sors. Analysis of oxygen-!( samples will be Workhorse Sentinel Lowered ADCP was carried out at TAMU. used to profile currents. This instrument comes with its own internal compass and Salinity calibration: tilt sensors and was calibrated in McMur- !!( water samples were drawn from the do with the same battery pack used dur- rosette for onboard analyses of salinity. ing the cruise. Water samples were drawn Autosal Model 8400B provided by the Uni- from !" ! -liter Niskin bottles using a versity of Gothenburg located in highly a

27 Cruise Report

Figure 7. Schematic of mooring design.

stable air-conditioned lab, was used for sa- salinity minus CTD salinity. Mean Delta S linity measurements. Calibration was per- was ~ . )) with a standard deviation of formed at the beginning of each run with . &&. For the estimation of this error, !!" batch P149 of IAPSO Standard Seawater points out of !!( ()%%) were used. Points from October " '. excluded were greater than " times the Error in salinity remained constant standard deviation of the mean error. throughout the cruise (Figure (). Salinity error, denoted as DeltaS, is reported as rosette Ecology

28 Oden Southern Ocean 0910

Water sampling for ecological studies site with a light meter (Biospherical Instru- We sampled ! sites along the East Ant- ments, San Diego, USA). arctic coast from McMurdo (S''o$%."´; E!&#o (.() to Ferrero Bay (S'#o"#.$; Experimental study on marine animals W! "o$(.)´). Sampling was performed In order to test if the animals change strategy with a " L Niskin sampler at ", ! , " , $ , when not allowed to migrate and when ( and !" m depth. From each level the released from predator cues, we performed water was analyzed for nutrient and chlo- a mechanistic experiment onboard Oden rophyll levels, as well as zooplankton and using copepods gathered in Pine Island Bay. algal taxonomy and numbers. A light and The experiment consisted of !" aquaria temperature proﬁle was also taken at each with seawater and copepods put under UV

Table 3. Details of the CTD 911+ sensor set.

Figure 8. Salinity diﬀerence, DeltaS (Rosette-CTD), vs. Sample number for conductivity sensor.

29 Cruise Report

lamps. Each aquarium was covered with took sub-samples for phytoplankton enu- Plexiglas allowing, or not allowing UV to meration (preserved in Lugol´s solution), penetrate. The experiment was run for ten conductivity and temperature (Ecoscan Con days and each treatment was replicated &, Eutech Instruments, Vernon Hills, USA). six times. Then the " L sample was filtered through a % μm net and zooplankton larger than Lake studies that size were retrieved on the net. These Our freshwater study was performed !–" were rinsed into a % ml centrifuge tubes February " ! in Lakes Fryxell and Hoare and preserved in Lugol´s solution for later and we used a Jiffy drill to enlarge holes pre- enumeration using a dissecting microscope. viously drilled by the LTER project above From the % μm filtered water, sub-samples the deep site of the lakes positioned at S''o for seston nutrient composition (carbon, #&,&" ´; E!&# o (,'%%’ and S'' o #',&&!’; nitrogen and phosphorus) were taken out E!&" o %$.%'$’, in Lakes Fryxell and Hoare with a syringe and filtered through a GF/F respectively. All sampling equipment were filter ("% mm, Whatman). Prior to the sam- kept dry for at least a month and rinsed in pling syringes, filter holders and filters for alcohol (' %) prior to sampling and also P analysis were acid washed and all filters between lakes, in order to reduce the risk were combusted at %% °C. The sample siz- of spreading organisms to these pristine sys- es for N, P and C analyses ranged between tems. From the hole in the ice we sampled ( and !% ml. Sub-samples for analysis of along a depth profiles at !, $, ) and !% m chlorophyll a (range ."–!.% L) were then depths. In Lake Hoare the profile was taken taken out and filtered through GF/F filters. once, whereas in Lake Fryxell we performed Filters were stored at –" °C until analysis a diurnal study (at the times: !&, "", $ and onboard Oden. Light and temperature pro- ! ). With a water sampler (Limnos TM) " files were taken from surface to !( m depth L of water were taken up from each depth, with a light meter (Biospherical Instruments, put into buckets. From the " L sample we San Diego, USA), measuring at wavelengths

Niskin sampler deployed from the starboard side of Oden

30 Oden Southern Ocean 0910

ing a passage to McMurdo and escorted the US cargo ship American Tern into relatively safe waters beyond the worst pack ice, we began our journey towards Pine Island Bay. The multibeam was operated continuously along this transit with an opening angle set between &% and & °. The reason for narrowing the swath is that the outer beams are noisy and generally suffer from an offset making the outer parts of the swath appear like a “railroad track”. It is clearly seen in figure !! how the noisy outer part is excluded when narrowing the beam, however, on the cost of narrower swath width. The route towards Little America Trough, where two moorings were going to be deployed before we could go to Pine Island Bay, took us along the front of the Ross Ice Shelf, where catabatic winds had cleared the sea ice. The weather was calm implying that high quality swath bathymetry could be collected. In fact, the swath bathymetry from this transect required a minimum of post-processing. The routine of throwing XBTs for sound velocity correction of the Drilling a hole through several meters of ice is chal- lenging. With logistical support from NSF we were multibeam data had begun already in Mc- able to sample two lakes in the Dry Valleys. Murdo Sound (see the oceanographic section for a map with XBT/XSV/XCTD/CTD locations). Glaciogenic features dominates $ –' (PAR) and #$ nm (UV-A) and #" the seafloor morphology in front of the Ross nm (at the border between UV-A and UV-B). Ice Shelf, in particular Mega Scale Glacial Lineations (MSGL) (Figure !!). In the area Preliminary Results of Little America trough we mapped regular undulating features with relief of about Marine geology and geophysics ! m and constrained to some MSGL (Figure Multibeam bathymetry !!). These undulating features make the The first area that was multibeam surveyed seafloor appear with a corrugated pattern. was McMurdo Sound since Oden was go- Identical features have been mapped previ- ing back and forth clearing the passage ously in the western Ross Sea (Anderson, from ice to the US base located on Ross Is- !)))) and they will be the subject for our land. Several passes over the same track al- further analysis. lowed gridding at a resolution of !%× !% m Pine Island Bay was reached February grid cells in water depths even deeper than !'. The wind was calm and there were prac- % m (Figure )a and b). The data revealed tically no sea ice at all in the bay allowing so-called recessional moraines, a sign of us to map along pre-defined survey lines. that the ice sheet retreated. These moraines Some multibeam swaths had previously are developed perpendicular to the ice flow been collected in our area of interest. These direction (Figure ! ). provided a general idea of the extension of the Pine Island Trough. The inner part of After Oden finished the mission of clear- the trough is rather well mapped while the

31 Cruise Report

Figure 9a. Swath bathymetry of McMurdo Sound collected while Oden was clearing the passage from ice to Mc- Murdo Station.

outer seaward part, which was our main first three were defined in between the cross- area of interest, is poorly mapped. Our sur- ing overview tracks and the last along the vey began with some overview lines cross- trough axis since we realized that we not ing the trough. This was necessary in order were going to be able to fill the all the areas to gather information to begin the coring between the trough crossing lines (Figure program which aimed to identify ice stream !"). The final result is shown in figure !# in grounding line wedges in the trough and the form of shaded relief derived from a % core in front, on, and behind them to derive × % m resolution grid. The data is, howev- a chronology of the deglaciation. After the er, processed to a higher resolution (mostly overview lines we completed a full survey " × " m) allowing more detailed maps to could begin where mapping was done with be generated. " –% % overlapping swaths. The area of MSGL are prominent in the mapped interest was divided into four subareas, the

32 Oden Southern Ocean 0910

Figure 9b. Detailed map of the mapped area closest to McMurdo ice pier.

Figure 10. 3D view of the swath bathymetry collected in McMurdo Sound. The image shows recessional moraines.

33 Cruise Report

Figure 11. Swath bathymetry from the area of Little America Trough. The shown part is from processing tile ROSS- AMUND-II shown in ﬁgure 2. The upper swath is acquired with an opening of 60° while the lower is acquired with 65°. Note the somewhat rougher appearance of the outermost part of both the port and starboard side of the swath when an opening of 65° is used. This problem is vastly accentuated in bad weather conditions. Up is south and thus towards the Ross Ice Shelf.

area at water depths below approximately the bay in the past and possibly joined up &' –' m. There is a pronounced ground- with the large Pine Island ice stream. There ing line wedge at about '"°% ’S that rises is also a possibility that the inner part of more than % m in the topography. The sur- the fjord could contain sediment records for face of the wedge located shallower than higher resolution climate studies. There ex- &' m is completely obliterated by iceberg ist, to our knowledge, one multibeam track scours (Figure !#). Similar features to those leading in and out of Ferraro Bay. Mapping mapped in the eastern Ross Sea that gives was carried out along this existing track for the seafloor a corrugated appearance are two reasons: !) To successively build upon also mapped here. the existing bathymetric database, and ") The wind picked up very rapidly the "$th by following the outer edge of the exist- of February and waves built up almost in- ing multibeam swath into Ferraro Bay un- stantly. We decided to head for Burke Island known potential hazardous shallow areas located in Pine Island Bay to map and po- could be avoided. Figure !$ shows a map tentially core some areas of interest. How- compiled from the multibeam data col- ever, the area off the southwestern shores lected in Ferrero Bay. These data have only of Burke Island did not provide enough been subjected to a first rough cleaning and protection for the swell so we decided to will be further processed. However, since instead go to another target area; Ferrero there were practically no sea ice or wave Bay. This bay forms an over-deepened fjord motion in Ferraro Bay, the collected data and there are traces in the sea floor suggest- was of high quality. ing that an ice stream extended out from Chirp sonar profiling 34 Oden Southern Ocean 0910

Figure 13. Swath bathymetric image derived from the Pine Island Bay survey. The most prominent morphological provinces are labeled. The red stars are core locations (see coring results below).

Figure 12. Survey of the outer part of the Pine Island Bay Trough. The survey was divided into four sub-surveys rep- resented by the labeled boxes in red. Box number 2 was surveyed in bad weather with heavy seas why several lines had to be run twice.

The SBP120 chirp sonar system was run along with the multibeam continuously dur- profiles are shown in Figure !'. As soon as ing the entire cruise. The transit from Mc- we left the continental shelf the chirp so- Murdo to Pine Island Bay took mainly place nar provided sometimes more than ! ms over the continental shelf, which generally TWT penetration in the sediment stratigra- is characterized by a thin drape, sometimes phy. Figure !( shows a profile acquired at less than ! m thick, of unconsolidated sedi- about !")°W off the continental slope. Ap- ment overlying diamicton. Typical profiles pendix III contains subbottom profiles near of the Pine Island Bay Trough are shown all the coring sites. in Figures !% and !&. The locations of the

35 Cruise Report

Figure 14. Mulitbeam bathymetry collected in Ferrero Bay. The red stars are coring locations.

36 Oden Southern Ocean 0910

Figure 15. Proﬁles OSO0910-PI4 A and B spliced together. The proﬁle location is shown in Figure 17.

37 Cruise Report

Figure 16. Proﬁle OSO0910-PI-06 across the entire Pine Island Trough. The proﬁle location is shown in Figure 18.

38 Oden Southern Ocean 0910

Figure 17. Locations of the chirp sonar proﬁles shown in Figures 16 and 17.

39 Cruise Report

Figure 17. Locations of the chirp sonar proﬁles shown in Figures 16 and 17.

40 Oden Southern Ocean 0910

Sediment coring In total "' coring stations were occupied cores exhibit alternation between the upper and of these "# were successful in retrieving two units, but all cores have surface brown sediments (Figure !)). In general, post-LGM clay units. This stratigraphic progression sediments are quite thin in the central and clearly reﬂects increasing distance from the outer Pine Island trough. Previous coring grounding line as the ice sheet retreated operations have revealed thicker sediments from the continental shelf. Contacts tend in the inner trough, but these are conﬁned to be relatively sharp, which implies that to deep basins and are mainly composed of the grounding line of the ice sheet may have a single sediment facies consisting of brown back-stepped across the trough. Future clay with rare dropstones (Lowe and An- work will focus on the nature and timing of derson, " #). The generalized stratigra- ice stream retreat in the bay. phy of the central and outer trough consists Samples for foraminifera were taken of, from bottom to top, dark gray till and/ every ! cm from all cores except KC-5, or proximal glacimarine sediments, brown where they were taken every " cm. Surface glacimarine sediments with an ice-rafted samples were taken at all sampling sites. In component that decreases upwards in the general, the core tops are rich in foraminif- unit, and an upper unit consisting of brown era, with benthic agglutinated forms domi- clay with minor ice-rafted material. A few nating at sites from greater water depth. In

Figure 19. Coring stations. Only the number of each coring station is shown. The full names follow the convention OSO0910-KC-##, where ## is the unique number plotted on the map for each station beginning with 1 for the ﬁrst. KC means Kasten Corer. Note that even the stations were we did not recovered any sediments are plotted.

41 Cruise Report

the shallowest-water samples calcareous Multi Sensor Core Logging, index properties benthic and planktonic species are present. and shear strength Foraminiferal diversity and abundances The results from the sediment physical decrease sharply down core. From ~# cm property measurement are plotted in Ap- down, many samples are barren or contain pendix II and the shear strength measure- few specimens only. However, in several ho- ments are displayed alongside the lithologic rizons rich foraminiferal assemblages were columns in Appendix I. The index samples encountered. They are strongly dominated are listed in Table $. by calcareous forms, especially the only planktonic Neogloboquadrina pachyder- Oceanography ma. Environmental and stratigraphic signif- Moorings icance of those events will be investigated. During this cruise we deployed " moorings in the Little America Trough of the east- Appendix IV contains relevant information ern Ross Sea (Figure " ). The ﬁnal loca- on samples taken for radiocarbon age dat- tion of each mooring was established at the ing. ship GPS position when the anchor weight was slipped at the end of the deployment. XCTDs were launched within a mile of each

Table 4. Index samples taken using two 9.8 cm3 stainless steel rings.

Table 5. Mooring locations and details.

42 Oden Southern Ocean 0910

Figure 20. Locations of the two moorings in the Little America Trough. mooring site. The moorings are to be re- occurred throughout the cruise. This result- trieved in February " !!. ed in multiple missed opportunities to collect key hydrographic (CTD/LADCP) data, CTD and water sampling in particular a broken winch prevented us CTD/LADCP from taking CTD stations at the mooring A total ! CTD cast were occupied (Table locations. Other missed opportunities were &, Figure "!) during this cruise in the main due to regular servicing of the CTD winch trough leading to Pine Island Glacier. CTD and the breaking of the hydraulics on the data from these casts confirm the inflow A-frame. of relative warm and saline bottom water along this trough, as well as in Ferrero Bay. XBTs/XCTDs While the rosette was at the sea surface XBTs/XCTDs were launched at sites where during the first # casts, the pressure sensor CTD stations were originally planned, or on the CTD was reading –) m. Because of unobtainable due to weather, winch prob- this, the pressure offset in the configuration lems, and time constraints. In total, !"' settings was increased by +) m after station XBT and % XCTD probes were launched s003c1 to force the pressure at the sea sur- (Appendix V). XBTs were provided by face to be approximately m. The pressure TAMU, Stockholm University, and Lamont sensor will be sent off for calibration upon Doherty Earth Observatory and XCTDs immediate arrival at TAMU to investigate provided by Stockholm University. this offset. Serious problems with the CTD winch re- Ecology

43 Cruise Report

Table 6. CTD stations.

Figure 21. Locations of the CTD stations.

44 Oden Southern Ocean 0910

The ozone hole above Antarctica has dur- on earth. Copepods at high latitudes are of- ing the last decades increased considerably ten pigmented bright red as a result of the allowing higher doses of ultraviolet (UV) carotenoid astaxanthin that is effective in radiation to reach the biota. Also aquatic protecting the animal against harmful UV- organisms in the sea and in freshwater sys- radiation, but also makes the animals more tems are strongly affected by UV and some, visible and thereby vulnerable to predation. such as zooplankton, have evolved photo- In addition to red carotenoids, many crusta- protective pigmentation that can be adjust- ceans are able to incorporate mycosporine- ed to the present UV environment. The very like amino acids (MAAs) that are invisible, high UV radiation and the long summer day UV protective compounds. Preliminary re- lengths at the high latitudes of polar regions sults from temperate regions indicate that if put a strong pressure on these organisms, predation is high, the animals prefer using probably the strongest on earth. Hence, MAAs instead of carotenoids, i.e. there is studies in Antarctic systems offer a rare op- an inverse relation between the amount of portunity to study photoprotective adapta- these photoprotective pigments. A third op- tions when they are at their maximum and portunity to avoid high UV exposure dur- to address how these extreme levels of UV ing day is to migrate to deeper waters and radiation may affect induction of different then return to the surface during night, a pigments, and shape communities in fresh- phenomenon known as diel vertical migra- water and marine systems. A main aim with tion (DVM). our project has also been to compare re- We expected that Antarctic marine sys- sponses among organisms in temperate and tems, where UV penetration is high, the Antarctic systems. Such comparisons has amount of red photoprotective pigmenta- the potential to improve our understand- tion would be very low, since predation ing of how ecosystem function and commu- from visually hunting predators, such as nity composition may change as UV radia- fish, is also high. Our studies along the East tion increases also in temperate regions, as Antarctic coast confirmed this hypothesis is currently the case in e.g. northern Scan- showing almost undetectable amounts of dinavia. visible photoprotective carotenoids (astax- anthins). However, the amounts of invisible Handling simultaneous UV and predation photoprotective MAA´s were high (Figure threats in marine systems "#) and the copepods performed consid- As specific study organism we have chosen erable diel vertical migration (Figure "$). crustacean copepods (Figure ""), which are Hence, these small animals made the best common in most fresh and marine waters of a bad situation: avoided the strongest UV

Figure 22. Copepods display large diﬀerences in pigmentation. The copepod to the left is from a system with low predation pressure and high UV exposure. The right one resembles the transparent, marine copepods in Antarctica.

45 Cruise Report

Figure 23. Contents of MAAs (mycosporine-like amino Figure 24. An example of copepod vertical distribu- acids) were generally high compared with carote- tion at day and night, showing that a main part of noids, and individuals at the surface generally had the population occur at the surface during night, but higher MAA content than individuals dwelling deeper migrates to below 40 m during day. down where UV is less of a problem.

radiation at the surface and were transpar- mm precipitation per year and has a mean ent in order to reduce the risk of being seen temperature of –!(o °C, making them one by predators, such as fish. of the driest, coldest and harshest aquatic We expected the copepods in the UV environments on Earth. The lakes are treatment to increase their carotenoid and ice-covered year around, although in late MAA concentration as protection against summer a fringe of water opens up close UV, whereas the copepods receiving only to the shore. Due to the low precipitation visible light were expected to reduce their the only inflow to the lakes is from glacier photoprotective pigmentation. Interesting- melt water and they lack surface outflow. ly, this hypothesis was corroborated by the The surface areas of the lakes are about '.! data and already after ! days the copepods and !.) km2, and maximum depths " and in the UV treatment had about &&% higher #$ m in L. Fryxell and Hoare, respectively. MAA and "&% higher carotenoid concen- The ice thickness in summer has been esti- trations than the ones receiving only visible mated to between #.' and %.% m, although light. Hence this experiment showed that we could only confirm a thickness of !–" m, copepods rapidly adjust their level of pig- not including the about ! m thick porous, mentation to the current threat situation, partly melted snow/ice cover on top of the i.e. pigmentation is a plastic trait. regular ice. We also performed a diel study on the Diel changes in the vertical distribution of vertical distribution of zooplankton in one lake zooplankton of he lakes (L. Fryxell). Since very little UV Our original plan included studies also in is penetrating through the permanent ice- freshwater systems, which turned out to cover of the lakes and no predators exist, be impossible at a later stage of the cruise we expected that the zooplankton should planning. However, we were offered an op- be positioned where the food is, i.e. have portunity to visit two lakes of the Dry Val- the same vertical distribution as the algae. leys near McMurdo prior to entering Oden. Interestingly, we found no such pattern, but The two lakes studied were Lakes Fryxell instead the dominant taxa of rotifers (Phi- and Hoare which are situated in Taylor lodinia sp.) generally showed a maximum Valley. The Dry Valley´s receive less than % close to the surface, whereas algal maxima

46 Oden Southern Ocean 0910

Figure 25.Depth distribution of the rotifer genus Phi- lodinia and the concentration of chlorophyll a in Lake Fryxell showing that the rotifers are most abundant at the surface, while their algal food gather at the bottom of the lake.

for making the Dry Valley sampling possible. The newly upgraded multibeam system on the Oden was financed by the Knut and Alice Wallenberg Foundation, VR and the were generally close to the bottom of the Swedish Maritime Administration. lake (Figure "%). Explanations to this in- verted distribution may be either that Phi- References lodinia feeds on other organisms than algae or that rotifers at the surface has actually Anderson, J.B., 1999. Antarctic Marine eaten the alga there. Geology. Cambridge University Press, Prior to our visit to the Dry Valley lakes Cambridge. we were informed that the biodiversity of Calder, B.R., Mayer, L.A., 2003. Automatic the lakes should be extremely low and we processing of high-rate, high-density should be prepared to find only a few spe- multibeam echosounder data. Geochem- cies of rotifers and no crustacean zooplank- istry Geophysics Geosystems 4, 1-22. ton. Although the diversity was low, we Jakobsson, M., Marcussen, C., LOMROG, found several species of rotifers that have S.P., 2008. Lomonosov Ridge Off Green- never been recorded in this region (J. Lay- land 2007 (LOMROG) - Cruise Report, bourn-Parry, pers. comm), including Felinia Special Publication Geological Survey sp., Kellicottia sp., Keratella quadrata and of Denmark and Greenland. Geological Brachionus sp. Moreover, we found three Survey of Denmark and Greenland, Co- (#!) individuals of copepods in a total vol- penhagen, p. 122. ume of $ L water, suggesting that large Lowe, A.L., Anderson, J.B., 2002. Recon- crustacean are indeed rare. The reasons we struction of the West Antarctic ice sheet were the first to recognize these organisms in Pine Island Bay during the Last Gla- were our large sampling volumes and that cial Maximum and its subsequent retreat the lakes are rarely sampled. history. Quaternary Science Reviews 21, 1879-1897. Acknowledgements Lowe, A.L., Anderson, J.B., 2003. Evidence for abundant subglacial meltwater be- We thank the Captain and crew of icebreak- neath the paleo-ice sheet in Pine Island er Oden for their great work. The Swedish Bay, Antarctica. Journal of Glaciology Polar Research Secretariat, the National 49, 125-138. Science Foundation (NSF) and the Swedish Nitsche, F.O., Jacobs, S.S., Larter, R.D., Research Council (VR) organized and fi- Gohl, K., 2007. Bathymetry of the nanced the expedition through a collabora- Amundsen Sea continental shelf: Impli- tion program. The ecology team from Lund cations for geology, oceanography, and University would like to express a specific glaciology. Gechemistry Geophysics Ge- thanks to Sven Lidström and Addie Coyac osystems 8, Q10009.

47 Cruise Report

48 Oden Southern Ocean 0910

113 N 880 ms

KC04,05 (20100226055956) 920 ms BREAK 960 ms KC19 0S00910-PI-114A (20100226024806) 1000 ms

0S00910-PI-114C 1040 ms

1080 ms KC06 (20100218211005)

820 ms

860 ms

900 ms

940 ms OSO0910-PI-17A 820 ms Line 15-A

860 ms

900 ms KC07, KC08

940 ms

KC07, KC08 (20100218161214)

940 ms

980 ms

1010 ms KC10 (20100218133847) 860 ms

700 ms KC09

900 ms 740 ms

780 ms

940 ms 820 ms

KC09 (20100218133847) 720 ms KC10 860 ms

900 ms

760 ms

960 ms

1000 ms OSO0910-PI-13A 800 ms

1040 ms 880 ms

920 ms

KC11 (20100221113147 to 20100221115019)

960 ms

OSO0910-PI-57-A

1000 ms

1040 ms KC13

980 ms

1020 ms

1060 ms OSO0910-PI-59-A

KC13 (20100221141143) 980 ms

1000 ms

1020 ms

1040 ms KC14(20100222112349)

860 ms

900 ms

940 ms OSO0910-PI-69A

980 ms

1020 ms 1100 ms 800 ms

1340 ms 980 ms

1460 ms Line 98A-(section 2) Line 98A-(section 1)

1160 ms KC15 (20100224204217) 1580 ms

1280 ms

1400 ms 950 ms

1000 ms

1050 ms

1100 ms

OSO0910-PI-01 KC18

1150 ms

1200 ms

1250 ms

1300 ms KC18 (20100216165105)

1150 ms

1200 ms

1250 ms KC23

N KC22

Line 116-A

KC24 KC22 (20100226170133)

960 ms KC23 (20100226162514)

880 ms 1000 ms KC24 (20100226135025)

920 ms 1200 ms

1240 ms N

KC25,26 1100 ms

1140 ms BREAK

Line 124-A Line 123-A KC27 880 ms N 900 ms

920 ms

940 ms

980 ms 980 ms Line 125-A 1000 ms

1040 ms KC27 (20100228053823/20100228055938) 1080 ms 880 ms

1120 ms

1160 ms 920 ms

1200 ms

1240 ms N 960 ms

127

131

MEDDELANDEN från STOCKHOLMS UNIVERSITETS INSTITUTION för GEOLOGISKA VETENSKAPER No 341

Rapportserie ISBN 978-633-7440-1

No. 331. IVARSSON, M. Fossilized microorganisms in volcanic rocks from sub-sea ﬂoor environments. Stockholm 2008.

No. 332. BJÖRKVALD, L. Landscape hydrogeochemistry of Fe, Mn, S and trace ele- ments (As, Co, Pb) in a boreal stream network. Stockholm 2008.

No. 333. BÄCKSTRAND, K. Carbon gas biochemistry of a northern peatland – in a dynamic permafrost landscape. Stockholm 2008.

No. 334. BLAJ, T. Late Eocene through Oligocene calcareous nannofossil from the paleoequatorial Paciﬁc Ocean – taxonomy, preservation history, biochro- nology and evolution. Stockholm 2009.

No. 335. COLLEONI, F. On the Late Saalian glaciations (160–140 ka): a climate mo- deling study. Stockholm 2009.

No. 336. KONN, C. Origin of organic compounds in ﬂuids from ultramaﬁc-hosted hydrothermal vents of the Mid-Atlantic Ridge. Stockholm 2009.

No.337. SELLÈN, E. Quaternary paleoceanography of the Arctic Ocean: A study of sediment stratigraphy and physical properties. Stockholm 2009.

No. 338. SUNDVALL, R. Water as a trace component in mantle pyroxene: Quantify- ing diﬀusion, storage capacity and variation with geological environment. Stockholm 2010.

No 339. PETTERSSON, C-H. The tectonic evolution of northwest Svalbard. Stock- holm 2010.

No. 340. SVAHNBERG, H. Deformation behaviour and chemical signatures of anorthosites: Examples from southern West Greenland and south-central Sweden. Stockholm 2010.

Formerly/1990–2009: MEDDELANDEN från STOCKHOLMS UNIVERSITETS INSTITU- TION för Geologi och Geokemi (ISSN 1101-1599)

Stockholms universitet SE-106 91 Stockholm www.su.se