Oden Southern Ocean 0910 OSO 0910 Cruise Report
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] Oden Southern Ocean 0910 OSO 0910 Cruise Report John Anderson, Martin Jakobsson and OSO 0910 Scientific Party Stockholm 2010 Oden Southern Ocean 0910 *++*,!+* ] -$./$, 012* 1-*- 1 -1-0-1$ 3*$,$31 .!2*-* .!(* ! " #$ $%&% 3( ) 3 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 5 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 7 Cruise Report Figure 1. b) Map showing the track for the crossing of the Drake Passage. 8 Oden Southern Ocean 0910 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. 9 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 proc- esses controlling the flow of warm Cir- 11 Cruise Report 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 cur- rent, temperature, salinity and pressure in Physics the interior of Little America Troughs.