OCEAN SCIENCES
The University of Alaska (UA) requests renewed funding for shipboard technician activities associated with the 133-foot research vessel Alpha Helix. The Alpha Helix is owned by the NSF and operated by UA. In calendar year 1994, the Alpha Helix will support 145 days of NSF-funded research projects in the Gulf of Alaska and the Bering Sea. UA technicians will be responsible for operating and repairing instruments while at sea, maintaining instruments ashore and assisting with scientific operations necessary before and after cruises. Budgets for years two and three of this award will be negotiated when ship schedules are finalized.
This project will provide shipboard scientific support equipment for the research vessel Alpha Helix, an NSF-owned ship operated by the University of Alaska, Institute of Marine Science, and dedicated to use in support of ocean science research. The Shipboard Scientific Support Equipment Program provides funds for ship equipment deemed essential to the proper and safe conduct of ocean science research. This Program provides support for such items as deck equipment including winch systems for the deployment and retrieval of scientific instruments, navigational equipment such as radars, gyroscopes and earth satellite receivers to pinpoint the location of research sites, communication equipment including radio transceivers and satellite transceivers for voice and scientific data communications and other equipment such as motorized workboats for transporting scientists to and from data retrieval sites. The Project Director, Thomas D. Smith, is fully qualified to direct this project, having had considerable experience in overseeing the acquisition and installation of shipboard equipment. This project will allow the institution to replace the ship's obsolete SSB radio with one that meets current requirements, replace fire fighting nozzles with modern ones and install uninterruptable power supplies to protect equipment.
The University of Alaska will operate the 133-foot general oceanographic research vessel (R/V) Alpha Helix during 1996 in support of NSF-funded projects. The ship is scheduled for 174 operating days in 1996, of which 123 days are in support of NSF-sponsored projects. The cruises will be primarily in the north Pacific Ocean but include significant research cruise legs to the Aleutian, Bering and Chukchi Seas regions during minimum ice conditions in late summer. This vessel is part of a fleet used by the NSF and other research agencies to support oceanographic research. Most oceanographic research requires specialized equipment that must be permanently installed on the research vessel. Trained crew members are also required to support the equipment systems and research operations. This is the first year of a planned three-year award.
This work is to develop an improved geophysical instrument package for use on U.S. Navy nuclear-powered submarines during science cruises to the Arctic Ocean. The PIs plan an integrated data acquisition system that would expand the current instrument suite to include a swath-bathymetric imaging system, a "chirp"-type low-frequency bottom penetrating sonar and an integrated data logging and quality control computer system. With specifically adapted instrumentation the submarine is the only platform for underway marine geophysical surveys in the High Arctic. The proposed 12 kHz bathymetric imaging system will acquire co-registered bathymetry and backscatter from the sea floor across a swath up to 20 km wide. Data from the "chirp" sonar will, under favorable conditions, define the acoustic stratigraphy of at least the upper 100 m sediment below the sea floor. Transducers for both sonars will be housed in a single pod secured beneath the submarine. The combined backscatter, bathymetry, "chirp" profiles and gravity anomaly data collected over the entire deep Arctic Ocean will provide not only the basis for solving some of the vexing problems of Arctic tectonics, but it also will provide an essential database for planning future coring, dredging or deep sea drilling. This instrument package will make the most of the opportunity generously offered by the U.S. Navy to provide operational support for annual submarine cruises through 1999. Critical design goals include: collection of high quality data, dockside installation (i.e., without dry-docking), boat-to-boat transfer with modest effort and cost; and minimization of returns from the ice canopy. The proposed development, integration and testing effort is a complex undertaking, requiring coordination between participating organizations, user community and the submarine fleet. These submarine cruises will be the only opportunity to systematically collect this data with a set of optimized instruments over the entire ocean basin. The combined suite of swath bathymetry and backscatter imagery, gravity anomaly data, bottom-penetrating chirp sonar, and possibly magnetometer data, will provide a complete geophysical characterization of the morphology, recent sedimentology, shallow stratigraphy and deep structure of the major Arctic Ocean basins.
This proposal seeks support for a design study of a submarine-mounted Swath Bathymetric Imaging System (SWABS) to be used on U.S. Navy nuclear-powered submarines during future unclassified science cruises to the Arctic Ocean. The system would be an adaptation of a demonstrated design, the SeaMARCTM towed side-looking sonar system. Towed platforms can be readily adapted for hull mounting on a submarine. The proposed 12-kHz side-looking sonar will acquire co-registered bathymetry and backscatter of the sea floor across a swath up to 20 km wide. If the (SWABS) is installed for the 1997 cruise, the remaining three cruises in the Submarine Science program (SUBSCI) could collect more than 800,000 km2 of data, covering a large fraction of the deep Arctic Basin operational area for these cruises. The final result of this study will be a set of documents that demonstrate the feasibility of installing a swath bathymetric imaging system on the submarine assigned to the 1997 SUBSCI cruise.
The PIs will investigate the record of the catastrophic floods, known as joekulhlaups, generated by subglacial eruptions or drainage of ice-dammed lakes on Iceland that cause the introduction of volcaniclastic material into the ocean, where it is deposited as turbidites on the submarine fan. Samples of land-based joekulhlaup events, as well as those from deep sea cores, will be examined. Oxygen isotopic stratigraphy will provide chronology. The findings will help resolve the history of flood events and contribute to the modeling of sedimentation around a volcanic hotspot such as Iceland that is strongly influenced by glacial cycles.
This project is a U.S.Danish study of the Southeast Greenland margin to provide a better understanding of the volcanic rifted continental margins which contain great thicknesses of mafic igneous material emplaced during continental breakup. This is an ideal setting to study volcanic rifted margins, because of a known hotspot and well-defined hot-spot track, a relatively simple tectonic and geologic history and a thin postrift sediment cover. The NSF's recent Ocean Drilling Program (ODP) drilling and numerous existing field studies provide additional background data. A multichannel and wide-angle seismic study is planned with the objectives to determine the influence of a mantle plume on the rifted margin magmatism, the detailed structure of the continentocean transition, and to compare the crustal structure of conjugate volcanic margin segments. The data will provide a framework for interpreting geological and drilling results on the margin, and for constraining thermomechanical models of volcanic rifted margin evolution.
A high-resolution stratigraphic study will be undertaken to ascertain the timing of the onset of global conditions on Siberia and Alaska and the timing of the massive late Pliocene volcanism on the North Pacific rim on orbital and millennial time scales, based on fluxes and tephrochronology of cores from the North Pacific, respectively. The temporal relationship between the two phenomena will determine if the massive volcanic activity was responsible for the onset of large-scale glaciation in the Northern Hemisphere at the end of Pliocene.
Fast-paced cycles of 2,0003,000 years recorded in the North Atlantic cores show apparently synchronous discharge of icebergs from at least two sources on Iceland and the Gulf of St. Lawrence, and may be related to mechanisms originating in the ocean/atmosphere system. Each cycle also correlates with cold pulses in Greenland ice cores and linked to Heinrich events. The PI's research will investigate further the role of ice sheets in forcing rapid climate shifts. If the 2,0003,000 year cycles persist through different glacial/interglacial periods, then they would imply that the oscillations operate independently of large glaciers and originate in the atmosphere/ocean system.
This project is to participate in a cruise on the Research Vessel Jan Mayen (University of Tromsø, Norway) which was planned as a U.S.Norwegian research cruise between investigators at the University of Colorado and the University of Tromsø. The Co-Chief Scientists on the cruise will be Hald (Tromsø) and Jennings (Colorado). The research plan was developed jointly during a sabbatical of Hald in Colorado and built upon the reconnaissance marine cruises that had been undertaken with the Institute for Arctic and Alpine Research (INSTAAR) leadership in 1991 and 1993. The cruise will take place between Sept. 21 and Oct. 10, 1996 (Tromsø-to-Tromsø), and will undertake a transect from NW Iceland, across Denmark Strait to the East Greenland margin at ca. 68°N. The major goal of the cruise is to extract sediment cores which will provide information on the extent of the Greenland Ice Sheet in the Denmark Strait, and the late Quaternary paleoceanography and on ice-sheet/ocean interactions across this critical "gateway" between the Arctic and mid-latitude North Atlantic. Based on existing core data (mainly 12 m long gravity cores) and on a detailed analysis of 1655 km of seismic tracklines on the East Greenland shelf, key coring sites have been selected to: (1) test potential late Quaternary ice-sheet grounding positions on the shelf and (2) extend our paleoceanographic time-frame on the shelf well beyond the 814 ka basal age limit that we encountered previously. The ability to obtain 10 m cores will potentially allow the team to obtain records into Marine Isotope Stage 2/3, depending on the glacial history. The Jan Mayen will be equipped with a piston corer that will allow the scientists to obtain 10 m cores, which will revolutionize their ability to extract the information needed to obtain data on glacial ice extent and icesheet ocean interactions. Preliminary analyses of the East Greenland cores also will be undertaken, including visual and x-radiograph core descriptions, laser color logging, bulk density measurements, volume and mass magnetic susceptibility, accelerator maps spectrometry 14C dating of foraminifera and potentially molluscs, and coarse resolution foraminiferal biostratigraphy.
Joint Oceanographic Institutions Incorporated (JOI) proposes to provide the U.S. oceanographic community the opportunity to participate in the future planning of the Nansen Arctic Drilling Program ((NAD)). NAD is a potentially significant international research effort designed to understand the geological and oceanographic evolution of the Arctic, as well as elucidate the contribution of the Arctic region to global change and its forcing functions. This knowledge will help characterize the Arctic basin and its impact on global processes. (NAD) is planning a workshop to produce a ten-year "Implementation Plan" for scientific ocean drilling in the Arctic. The (NAD) Implementation Plan will outline the strategy and steps necessary to achieve NAD's scientific goals. Because of the difficult and costly nature of scientific ocean drilling in the Arctic, the endeavor will require close multinational cooperation and funding. The workshop's planning and organization will be guided by the (NAD) Secretariat, which is funded by the eight NAD member countries and housed at JOI. Specifically, this proposal seeks full support for the travel of U.S. scientists and two JOI staff to attend the workshop, as well as partial funding to cover the cost for the JOI/(NAD) Secretariat to organize the workshop, and also to produce and print the resulting (NAD) Implementation Plan. The travel expenses of the participating non-U.S. scientists (about 30) will be covered by individual (NAD) member and observer countries. Funding for the rest of the cost of the workshop will be sought from participating countries, and the balance will be covered by the (NAD) Secretariat.
Funds are requested to cover the costs of gravity and bathymetry data acquisition in the Arctic Ocean for a study of the Arctic Mid-Ocean Ridge (AMOR) and the adjacent sliver of continental crust, the Lomonosov Ridge. In concert with the physical oceanographic program, we would like to collect additional long bathymetric and gravity anomaly profiles across the combined Lomonosov Ridge and AMOR. This data, combined with that collected on previous submarine science cruises, will permit the construction of regional scale maps across much of the basin within the operational area. The advance of plate tectonics into the Arctic Ocean basin has reached only to the Lomonosov Ridge. The AMOR is the northern extension of the Mid-Atlantic Ridge. It is perhaps the slowest spreading ridge on Earth. Propagation of the AMOR into the Arctic Ocean separated the Lomonosov Ridge from the northern edge of Eurasia beginning at about 58 Ma. This separation has continued up until the present time. Maps produced during this study will be used to define transverse structures in the ridge (the geometry of half graben bounding faults and transfer zones) and the morphology of the AMOR. The regional lines also will be useful for studies of isostatic compensation of both the Lomonosov Ridge and the AMOR, as well as defining he transition from the Lomonosov Ridge to the adjacent enigmatic Alpha-Mendeleev Ridge.
During the summer of 1995, a U.S.NorwegianRussian expedition in the NorwegianGreenland and Barents Sea discovered a warm gas vent located on an ancient fracture zone known as the Hornsund Fault, at great distance from known present-day plate boundaries in the region. The vent was characterized by high heat flow, clathrates, H2S and an unknown species of Pogonophore worm. This award is to return rapidly back to the site, to map, in detail, the extent of the vent domain using a Russian vessel equipped with side-looking sonar and a remotely operated vehicle (ROV). In addition, it is to investigate likely sites along the Knipovich Ridge for recent hydrothermal activity. It is believed that the examination of the warm gas vents along the margin of the Barents Sea may shed new light on the degree of thermal rejuvenation of ancient plate boundaries in the region, and the possible role that warn vents in the Arctic region may play on deglaciation events, either in modern settings on land (such as Spitsbergen) or in ancient glaciated regions, such as the Bear Island Fan.
Several lines of paleolimnological and lake water chemistry research suggest that: (1) selenium (Se) in lake sediments is linearly related to the percentage of organic matter for individual lakes and (2) normalized to organic matter concentration for lake districts, Se concentration is related to distance from the open ocean. The linkage is through the delivery of Se in marine aerosols from the open ocean to lake basin catchments, and the subsequent incorporation of Se (a chemical analog for S) into organic matter. Marine aerosols are the only significant sources of Se to most aquatic ecosystems. This Small Grant for Exploratory Research (SGER) award supports the investigation of stratigraphic variations in Se concentration in coastal lakes as a record of changing distance to open ocean and as a proxy for sea-ice cover. Methods will involve chemical palynological and radiometric analyses (the later to establish absolute age) of existing cores spanning the Holocene and core spanning the Little Age to the present. This will enable calibration of the method against known climate variation and historically-documented variation in sea-ice cover.
In this project, the PI will participate, with Scripps Ocean Data Facility (ODF) personnel, in oceanographic sections crossing from the Siberian continental shelves into the Nansen, Amundsen and Makarov Basins of the Arctic Ocean, and a transect of the Siberian ends of the three basins from JulySeptember 1996, as part of the ACSYS (Arctic System Sciences) program on both Swedish and German icebreakers. The PI proposes to augment the full-depth current and temperature (CT) measurements by providing 36-place rosettes, and carrying out top-quality measurements of salinity, dissolved oxygen and nutrients at about 120 locations along the tracks. These data are crucial to understanding the interactions of the Arctic Ocean circulation on the global climate system. The ODF capability will add a very important element of quality control to this set of measurements.
An inert and safe chemical tracer will be released in the center of the Greenland Sea gyre during the summer of 1996 to study mixing, convection and circulation within the gyre, as well as exchange with the surrounding waters, and flow into the North Atlantic through the Denmark Strait. The tracer will be sampled in November 1996, prior to winter convection, in March 1997, during or just after winter convection, and again in May 1997. Samples also will be taken in the surrounding waters and across the Denmark Strait on cruises through 1998 to study the paths and rates of water mass exchange. This work is in collaboration with European scientists (European Subpolar Ocean Programme Phase 2) and contributes to the World Ocean Circulation Experiment (WOCE).
Dissolved organic carbon (DOC) is the major reservoir of organic carbon in the Arctic Ocean, and as such this reservoir may also serve as an important sink for atmospheric carbon dioxide. Characterization of the processes controlling the concentrations and fates of DOC is therefore critical for gaining a quantitative understanding of the Arctic Ocean carbon cycle. During a U.S. Navy submarine cruise from MarchMay 1995 along the shelf breaks of the Beaufort, Chukchi, East Siberian and Laptev Seas, approximately 1,000 samples will be collected and analyzed for concentrations of nutrients, DOC and dissolved inorganic carbon (DIC). Approximately 100 water samples will be analyzed for dissolved oxygen, alkalinity and chlorophyll pigments during the cruise track. These data will be used to determine the sources of DOC to the various regions, the rates of microbial remineralization processes and the coupling between nitrogen and carbon cycling.
This proposal requests funds for collection, measurement and interpretation of about 200 tracer element (Tritium, Helium, Oxygen and CFC's) samples in the framework of the planned 1996 Arctic Ocean submarine cruise. The work will be focused on a broad survey of the upper waters in the Canadian Basin. Results from a previous submarine cruise (USS Pargo, 1993) demonstrated the feasibility of obtaining high-quality transient tracer samples from surface stations. The measurements will be used, together with hydrographic data, to: (1) study the transport of shelf waters into the Arctic halocline; (2) derive evolution, circulation patterns and mean residence times of the upper waters in the Canadian Basin; (3) delineate pathways and storage times of river runoff and sea-ice meltwater in the upper layers of the Canadian Basin; and (4) validate Arctic Ocean circulation models.
The major scientific objective of this proposed four-year study is to understand the coupled ocean mixed layer-ice system response to the passage of atmospheric storms. The most intense surface cooling and wind stresses in the Arctic are associated with these storms, and their long-term cumulative effects on the heat and water budgets for the Arctic Ocean cannot be predicted without including realistic mixed layer physics, ice thermodynamics and three-dimensional wind-driven ocean circulation. The PI has shown in previous work that oceanic instabilities may lead to significant deep oceanic convection and possible formation of bottom water. The initial energy source to trigger these instabilities may be provided by transient atmospheric forcing. Numerical models will be developed, including a three-dimensional simulation of the upper ocean (temperature, salinity, circulation and ice) response to passage of atmospheric storms. This numerical model will consist of an existing ocean primitive equation model with embedded turbulence-closure mixed layer and an ice model with realistic thermodynamics and mechanical properties. The embedded mixed layer will include previously neglected physics to predict the onset of conditional instabilities and possible formation of deep water. The realistic prediction of deep convection is necessary to understand the start of the global conveyor belt and the role of the oceans in climate change. A major deficiency in earlier ocean models has been the lack of adequate convection physics to realistically predict the correct temperature and salinity properties for the convectively produced deeper water masses. The proposed modeling program, including realistic storm forcing and realistic ocean convection, will directly tie atmospheric forcing and ice thermodynamics to mixed layer dynamics and the start of the global conveyor belt in the GreenlandIceland Seas. The results will lead to more realistic parameterization of subgrid scale convection of heat, mass, momentum, nutrients and tracers in basin and global oceanic models.
This proposal requests funds to continue analysis of data collected in the Northwest Passage near Resolute, Northwest Territories, Canada, in April and May of 1995. The data that was collected consisted of nearly 1,200 vertical profiles of microstructure temperature (T), conductivity (C) and turbulent dissipation rate, continuous measurements of the vertical profile of currents with a 300-kHz acoustic doppler current profiler (ADCP); and continuous measurement of T (10 depths) and C (3 depths) from sensors mounted on a mooring. All measurements span the approximate depth range from 2 to 125 m below the ice base, in 150 m of water. The three-dimensional structure and horizontal phase propagation of the large-amplitude internal gravity waves that are responsible for most of the mixing in this region were determined. A separate study by Cota (University of Tennessee) investigates the relative importance of light and nutrient fluxes on the spring growth of ice algal communities. The two-year period covered by this renewal will allow the study of generation, evolution and dissipation of large-amplitude, non-linear waves (with Ingram and Marsden); surface mixing under the smooth, land-fast sea ice (with McPhee); and the role of tide-related vertical mixing on the provision of nutrients to the ice algal communities (with Cota).
Among the outstanding issues regarding Arctic Ocean circulation are the fate of its riverine inputs and the nature of the processes ventilating sub-surface waters of its interior. Circulation and material transport and transformation in the Arctic needs to be more completely characterized because of the potentially critical role the Arctic plays in global themohaline circulation and on a more immediate timescale, because of the need to predict the fate of pollutants, including radioactive and industrial wastes and pesticides, in this sensitive environment. It is proposed to develop and apply new means to address these issues by adapting methodologies for mapping geochemical tracer fields in real time using the submarine platform, in combination with more conventional chemical hydrography conducted from the ice upon surfacing with the sub. Specifically, a sea-going fiber optic UV spectrometer will be mounted on the hull of the submarine. This instrument will continuously monitor the humic fraction of dissolved organic matter along track during the SCICEX-96 field season (August 1996) and monitor multiple parameters during the SCICEX-97 field season. In addition discreet samples will be taken via ice-based hydrocasts from the ice for calibration purposes and continuation of a related study to track Arctic river waters by geochemical means. This dataset will allow an unprecedented examination of the carbon cycle and circulation questions in the Arctic.
The recent use of the U.S. Navy's atomic submarine Pargo for non-military scientific exploration in the Arctic has opened a new dimension in the oceanography of the least-sampled ocean basin. Based on samples brought back from the 1996 science cruise of the Pargo, the proposed project will make additional measurements of dissolved inorganic carbon (DIC) and add new and critical measurements of dissolved organic carbon (DOC) and particulate carbon (PC). These measurements will qualify the inorganic and organic carbon pools associated with waters in the Canada, Makarov, Amundsen and Nansen Basins, as well as shelf and upper slope waters of the Chukchi region that appear to be the site of entry for a huge amount of carbon to the upper halocline of adjacent waters. Spatial changes in the carbon pools will be analyzed with respect to geochemical tracer data such as tritium and 3He collected from the Pargo and other Arctic cruises to estimate the rates of change associated with each pool. Such rates are critical for understanding the Arctic's role in the carbon cycle at the world ocean and global scale. As one of the atmospheric constituents that is prominent in the heat budget of the lower atmosphere, carbon dioxide has received increasing scrutiny to assess the non-human induced factors that influence its abundance. The Arctic Ocean is currently poorly characterized in this respect but is a potentially important link in the dynamics of the ocean's carbon cycle. First order questions include the size of the carbon reservoirs associated with the unique water masses of the Arctic, the water mass formation rates and the changes, if any, that can be expected in these cold reservoirs if climate change brings about a warning in this region.
This proposal requests funding to investigate the magnitude and variability of bacteria and phytoplankton mortality due to viral attack in the Arctic Ocean. Viral distribution, abundance and variations in composition and diversity of viruses in the study area also will be investigated. In addition to the examination of natural viral communities, samples will be screened for the presence of sewage-derived bacterial viruses as an indicator of the penetration of terrestrial biological pollutants into the Arctic Ocean. Collection, fixation and concentration of sea water samples will be accomplished at sampling sites by deployment from a U.S. Navy submarine. Subsequent analyses will be conducted in the laboratory. Total counts of viruses and the frequency of viral infection in phytoplankton and bacteria will be determined by electron microscopy on fixed samples. To examine natural community diversity, concentrates of viruses will be purified and subjected to pulsed-field gel electrophoresis to separate viral DNA based on genome size. From the number, positions and staining intensity of different bands, the diversity, genome sizes and abundance of viruses in each sample will be estimated. Sewage-derived viruses will be detected by amplification of target DNA sequences using the polymerase chain reaction and by plaque assay. Through coordination with other researchers, viral abundance, frequency of viral infections and viral community diversity will be related to hydrographic and biological variables in order to determine those which may be important in regulating viral propagation.
The proposed study is to investigate the distribution of key properties-abundance, community composition and community metabolic capabilities-of bacterioplankton communities in the Arctic Ocean. In conjunction with data collected during April on the SCICEX-95 cruise, the seasonal and spatial variation of these properties will be studied. The patterns of spatial and temporal variation of these properties will be examined and related to sources of organic matter fueling heterotrophic production. The investigation will be conducted using samples collected from a submarine dedicated to Arctic oceanography and analyzed in the laboratory after the cruise. Community composition will be analyzed using a method developed in the PI's laboratory based on separating partial sequences of the 16S rRNA gene. Community metabolic capabilities will be assessed by the ability of bacteria to grow heterotrophically on a battery of 95 different sole C sources. Bacterioplankton abundance will be determined by epifluorescence microscopy. We will analyze water samples chemically to determine the concentrations of amino acids, carbohydrates and dissolved organic carbon, and conduct bioassays using native bacteria to determine directly the proportion of dissolved organic carbon that they can metabolize.
A number of gaps exist in the understanding of biogeochemical processes associated with the transport of material across the landsea boundary. Among these gaps are lack of data on: (1) small watersheds of different morphoclimatic zones and their ability/efficiency, relative to larger watersheds, to transport materials to the oceans; (2) transport of material through lagoonal estuarine systems, the mixing rates of which are slow and the mixing zones large; and (3) inputs of material to coastal waters in groundwater. Research is proposed to address these gaps through investigations on three types of under-studied systems with the following objectives: (1) To obtain a better understanding of products resulting from arctic-subarctic weathering, the fate of these materials (primary trace elements) in the freshwater-seawater mixing zone and relative contribution of fluxes to the ocean from smaller rivers of this morphoclimatic zone. These studies will be carried out in the Anadyr RiverEstuary system in northeastern Russia. (2) To identify the major biogeochemical interactions that control trace element fluxes through a lagoonal estuary, taking advantage of the slow mixing rate/long residence times of materials in such systems to obtain better resolution of solute-master variable relationships during mixing in the low salinity region. The Patos Lagoons, in Southern Brazil will provide the field site for these investigators. (3) To determine the composition and concentrations of subterranean weathering products associated with the Floridian Aquifer and to investigate biogeochemical processes that influence the fate of trace elements upon entering the marine environment. Freshwater springs, which discharge directly into coastal waters of the West Florida shelf, and the adjacent coastal waters will provide the site for these studies.
Little is known about the environmental change in the Eurasian Arctic, a major site for the formation and passage of sea-ice and water masses in the Arctic Ocean. The knowledge of climatic and oceanographic fluctuations in this region on a millenial and submillenial scale is especially important in view of the special role of the Arctic in the modern global change. This project is aimed at the first time-constrained reconstruction of Holocene paleoenvironments in the Kara Sea, which is strongly influenced by both the extensive continental runoff and the Atlantic water advection. The Kara Sea sediments contain a unique record of variations in the discharge of Siberian rivers, Atlantic water flow, and the formation of bottom waters. A number of sediment cores and surface sediment samples were collected recently in the Kara Sea. Cores from key sites located in a corridor between the estuaries of Ob' and Yenisey Rivers and the marginal Saint Anna Trough, are chosen for a study of the Holocene environmental change on a millenial-to-centennial time scale. Core stratigraphy will be time-constrained by AMS 14C dating of in situ calcareous faunal remnants. Mineralogical, geochemical and grain-size analyses will be used to assess sediment dispersal sources and depositional environments. Stable isotopes will be measured on planktonic foraminifers from the northern Kara Sea to understand the relation between the Siberian river discharge and oceanographic change in the eastern Arctic Ocean. Modern distributional patterns of foraminifers and ostracodes, with respect to the Kara Sea hydrology, will be established to provide reliable paleoenvironmental reconstructions for the Holocene. Results of this collaborative research will significantly improve our knowledge of environmental change in the Eurasian Arctic. Reconstruction of amplitude and timing of riverine and Atlantic water pulses throughout the Holocene will reveal new insights into mechanisms of heat and water vapor transfer from the North Atlantic to the Arctic, and their controls on the extent of sea ice and formation of water masses in the Arctic Ocean.
