4. Large-scale atmospheric circulation over the Arctic: impact on thermal regime of the continental shelf of the Laptev and East Siberian Seas through the onshelf Atlantic water penetration
S. Kirillov, M. Makhotin, N. Koldunov
10. The response of the arctic terrestrial biota to the Last Glacial Maximum: regional versus global (the dated environmental transect from the Laptev Sea area through Chukotka to Alaska)
A. Sher , E. Yan , N. Zhavoronkina
The Laptev Sea is the main source area of ice for the Arctic Basin (Transpolar Drift). Dynamic factors strongly affect the distribution and variability of the ice cover in this area. Remote sensing data are the most important source of information about Arctic sea ice, obtained daily and covering all Arctic regions. However, the interpretation of satellite images requires calibration by synchronous data of visual observations. Two observational data sets are used in the present research: unique visual data from six high-latitude cruises (research vessel "Akademik Fedorov", icebreaker "Kapitan Dranitsyn") and passive microwave (AMSR) data. A comparative analysis of ice concentration from visual observations and satellite images shows significant differences near the ice edge, while the two datasets agree well in the open water and ice-covered regions. The interannual variabilities of sea-ice concentration and thickness were analyzed for summer periods of 2000-2005. During the last five years the most difficult ice situation was observed in the Laptev Sea in 2004, and 2005 was marked as the year of smallest sea-ice extent in relation to the mean annual values. A detailed research of interannual variability of summer sea-ice characteristics in the Laptev Sea in 2000-2005 is presented in the report.
G.N. Belozersky, O. Preobrazhenskaya, A. Moshkina
During our activity at the OSL and the Institute for Polar Ecology (Kiel, Germany) we intend to investigate a number of Arctic pack-ice samples for biotic (Chlorophyll a, sympagic meiofauna) and abiotic parameters. The main goal is to interpret the obtained results in order to understand the potential impact of global changes on the Arctic ecosystem. Our plan includes analyses of ice samples and comparison of samples from the Laptev and Greenland seas. We also intend to compare first-year ice and multi-year ice samples. The practical result of our work will be the creation of a common database according to our and literature data.
I. Fedorova, Yu.G. Strelchenko, D.A. Nikels
Hydrological and geochemical investigations in the Lena Delta, grounding field observations and perennial runoff records allow obtaining some features of the processes of liquid and solid matter accumulation and outflow. According to previous studies the runoff and suspended matter redistribution near Sardah Island is changing. Thus, the Sardahskaya Channel becomes more important (deeper and more abounding) than the Trofimovskaya. In the high-water period secondary channels in the delta can provide nontrivial liquid and suspended runoff, which indicates the erosion rate.The Lena River shows an increasind trend with respect to annual runoff. The seawater fetch to the river channel in the offshore line influences external sedimentation and accumulation. According to the AMS data the strong river influence on the sediment beds of the lakes of the 1st terrace (closee to the junction of the Olenekskaya and Bulkurskaya branches) decreased 4.3 kyr BP.
S. Kirillov, M. Makhotin, N. Koldunov
The thermal regime of the bottom layer on the Siberian shelves is a significant factor influencing the evolution of the submarine cryolithozone. This impact results in intensive thermal degradation of the coastline and shallow areas of the shelf in recent times. The warm Atlantic water (AW) following along the continental slope of the Arctic Basin is one of the most pronounced thermal factors affecting the Siberian Arctic. Wind forcing can further drive this water onto the shelf, thus increasing the temperature of the bottom layer at the shallows. Bottom-water temperatures and salinities of the Laptev and East Siberian seas were examined to find out the response to atmospherical forcing. Evidence for episodically occurring warm and salty water inflow was found in the Lena River submarine palleovalley as far as 300 km south of the continental slope up to 40 m depth. This inflow is thought to be associated with the warm AW penetration onto the outer and mid-shelf. These expansion events mostly correspond to eastern winds or the general anticyclonic wind pattern over the Siberian Arctic.
T. Kuznetsova, A. Bryantseva, I. Chursina
Recent multidisciplinary studies of the permafrost deposits in Northern Yakutia have greatly improved our knowledge about the Late Pleistocene and Holocene environmental history of the region. The goal of the project is a detailed reconstruction of the sub-latitude alterations of terrestrial ecosystems of the Laptev Sea region. It is based on complex analyses of diatom, pollen assemblages and mammal distribution combined with geological, geochronological and various analytical data. The research is focused on:•analyzing the resemblances and distinctions of the terrestrial ecosystems from different locations of the Laptev Sea region;•compiling and synthesizing all the obtained paleoecological information and factors, which influence terrestrial ecosystems.All the data on the variations of the terrestrial ecosystems of this region in the Late Pleistocene and Holocene are new.
L. Mazurenko, V. Kaulio, E. Logvina
The methane hydrate occurrences related to active gas vents northeast of Sakhalin Island in the Sea of Okhotsk are a very interesting phenomenon, which was discovered in 1991. The gas-seepage sites are found on the continental slope northeast of Sakhalin Island within a 20-km-wide zone that extends about 130 km from north to south. Their occurrence as well as coring results suggest that this region is one of the most favorable regions for gas-hydrate formation. Recent expeditions have shown that gas-hydrate formation within gas-vent sites requires intensive multidisciplinary investigations. Repeated studies of the gas-vent area have created the basis for a comparative study of subsurface gas-hydrate accumulations in the NE part of the Sea of Okhotsk.The hydrogeochemical studies of gas-hydrate-associated venting structures off NE Sakhalin were conducted within the framework of the OSL Fellowship Program 2003 (OSL-03-14, Principal Investigator T.V. Matveeva). Gas sources for gas-hydrate formation were to be revealed and the role of gas-hydrate formation (exemplified by the Deriugin Basin) in the global climate changes was to be determined during the OSL Fellowship Program 2005/06. The study of hydrate dissociation is of particular importance in the context of global climate change. Undoubtedly a zone of submarine gas-hydrate formation provides also a geochemical barrier to emission of hydrocarbon gas from the lithosphere. However, not only does gas stabilization occur but gas is also emitted into the hydrosphere in considerable amounts. Investigations of gas-hydrate formation and dissociation are necessary for defining the role the hydrates play in the ecosystem of the Sea of Okhotsk. Therefore, the main tasks of this project were to clarify the origin of the methane involved in the gas-hydrate formation, to estimate the amount of methane stabilized in gas hydrates and to reveal the role of gas-hydrate formation as a barrier for methane venting into the hydrosphere and atmosphere.The results mentioned above significantly improve our knowledge of submarine gas-hydrate formation and are useful for quantitative estimations of the gas amount in the subsurface hydrate occurrences. Moreover, the results can form the basis for related ecological investigations aimed at revealing the influence of natural hydrates on the climate changes in the region of the Sea of Okhotsk.
The project is aimed at the study of the environmental changes of the White Sea during the last three centuries (on the basis of fossil algae assemblages) in order to provide information about different climatic fluctuations in the Arctic region. The results of the palynomorph study of White Sea sediments reveal the following main features of their composition: (i) predominance of dinoflagellate cysts in the surface sediments (in total concentration and relative abundances in palynomorph assemblages); (ii) relatively low concentration of chlorococcalean algae, which are mainly related to the freshened bays; (iii) high total concentration and percentages of gonyaulacoid species of Atlantic Ocean origin indicating the extensive influence of Atlantic waters on the White Sea hydrology, and the favorable conditions for their habitat; (iv) distribution patterns of dinocyst assemblages in core sediments provide evidence for hydrographic changes during the past 250 years, which are caused by climatic fluctuations in the Arctic; (v) modern aquatic palynomorph data from the White Sea sediments prove an excellent proxy for paleoenvironmental reconstructions.
V.I. Petrova, P.B. Semenov, A.V. Kursheva
Lithological and mineralogical data of the sediment samples, taken from the Mendeleev Rise during the "Akademik Fedorov" cruises (2004, 2005), are indicative of a relatively stable accumulation of pelites in depressions mostly owing to sedimentation of slurry. Ccarb content values are relatively high while Corg concentrations, not exceeding 0.2% in the uppermost sediment layer, begin to decrease within the first centimeters of the section and continue to decrease to almost trace concentrations. Norg in the sediment section of the sublatitudinal profile averaged 0.05%. Such low values are characteristic of abyssal Pacific and Atlantic sediments indicative of a high level of initial OM transformation. The low concentrations of chlorophyll a in the water samples (about 0.1 mkg/l ) make the assumption of hydrobionthic origination of OM questionable. Our investigations, therefore, reveal the uniqueness of the compositional content of the loose sediments from the Mendeleev Rise, which is probably caused by the dominant role strongly transformed material plays in sediment formation.
Ye.I. Polyakova, T.S. Klyuvitkina, V.V. Razina
The main goal of our study was to correlate major changes in the Late Pleistocene and Holocene Laptev Sea hydrology and sea-ice regime under the conditions of postglacial sea-level rise and climate warming, with the past environments on the surrounding hinterland and the Laptev Sea shelf, exposed during the Late Pleistocene sea-level low stand, on the basis of microfossil assemblages from sediment cores. The following results were achieved: (i) on the basis of a detailed study of aquatic palynomorph assemblages and re-examination of dinocyst assemblages along with previously obtained diatom records, the major phases of the development of sedimentation processes, sea-ice, hydrological conditions, riverine discharge and Atlantic water advection were determined for the past approximately 17 cal. ka.; (ii) three major phases of the postglacial vegetation development on the Laptev Sea shelf and in the surrounding hinterland were reconstructed.
A. Sher, E. Yan, N. Zhavoronkina
The processing of the large volume of data on fossil insects from several regions of the Siberian and Alaskan Arctic has been completed. This makes possible the comparison of faunas, environmental and climatic conditions of the Last Glacial Maximum along the transect from the Lena Delta through the Indigirka-Kolyma Lowland and Chukotka to Alaska. The preliminary results show some common features and trends, but also some important differences in the composition of synchronous faunas. We hope that the further analysis under this project will demonstrate the significance of regional variations in climatic and environmental factors during the time of global cooling. These variations are related to different latitudinal and longitudinal positions of the sites, in particular, to their distance from the Pacific Ocean. However, biological factors should not be ignored (e.g., historical differences between the Asian and American faunas).
E. Taldenkova, A. Stepanova, S. Dem'yankov
The project is aimed at summarizing the results of recent and fossil benthic assemblage studies carried out by our group during the last five years. The tasks of the project are i) to reconstruct paleoenvironmental changes in the Laptev and Kara seas based on the distributional pattern of recent species and downcore succession of fossils and ii) to prepare for publication 2 papers and one monograph discussing the obtained results.The major postglacial to Holocene environmental changes at the Laptev Sea continental margin have been reconstructed based on the results of fossil benthic assemblage studies in four AMS14C-dated cores. Species composition of ostracods and foraminifers suggests that the Atlantic-derived waters reached the western Laptev Sea continental slope already 15.8 cal.ka, i.e., prior to the establishment of the pathway through the Barents Sea shelf further west, and were then constantly present in the studied area. Cold and low-nutrient benthic marine environments with recurrent coastal open-water polynyas are reconstructed for the period 15.8-14.1 cal.ka. The gradually increasing freshwater influence during the subsequent period reached its maximum between 12.7-11.2 cal.ka, when the outer shelf was flooded, and pioneer brackish-water assemblages of bivalves and ostracods inhabited the estuarine parts of the river paleovalleys. Following the pattern of sea-level rise, these strongly fluvially-affected assemblages rapidly transformed into shallow-water marine ones. After 3.5-3 cal.ka, when the sea level was at its modern position, the well-pronounced changes in the composition of benthic assemblages from both the outer shelf and the upper continental slope indicate climate cooling combined with an intensification of surface and bottom-water circulation. The distribution of recent ostracods over the river-affected eastern Laptev and Kara sea shelves was studied in relation to salinity changes. Four assemblages were established, which could be linked to the average summer bottom-water salinities, from freshwater assemblages of river estuaries to taxonomically diverse normal marine assemblages of the outer shelf and upper continental slope.
V.E. Tumskoy, A.V. Bortsov, A.G. Pronina
Within the framework of several grants (RFBR, INTAS, OSL), the geological structure and geocryological conditions of deposits in "thermokarst lagoons" on Bykovsky Peninsula were studied. The core samples, obtained during drilling of the bottom beds of thermokarst lagoons from the ice, were analyzed. Particle-size distribution, chemical composition, micropaleontological remains and thermophysical properties of the sediments in thawed and frozen states were determined. We further developed the existing mathematical model of the development of thermokarst lakes for modeling the conditions of freezing-thawing processes in thermokarst depressions taking into account their marine salinization.