The main goal is to describe and analyze the seasonal processes occurring in the zooplankton associations of the Laptev Sea on the basis of long-term seasonal samples. The database comprises the following: 200 stations were established, 600 samples of zooplankton were collected and processed, particularly, the research results of the Russian-German expeditions TRANSDRIFT IV, V, VI, VII and VIII and the Russian-American expedition MERA-9" in different regions of the Laptev Sea shelf within the period of 1989-2000. Regular seasonal and yearly observations were carried out only in the southeastern Laptev Sea (Tiksi Bay, Buor-Khaya Gulf). The preliminary results are:
- it was found that the zooplankton composition on the Laptev Sea shelf includes 107 taxa of 10 various types. Copepoda (51 species), among which 16 species were found for the first time in this region, are the dominant taxa in species variety
- the distribution of the plankton fauna on the Laptev Sea shelf is connected with the type of hydrological regime and can vary significantly from year to year
- the summer zooplankton complex in the Olenek, Yana, and Tumat bays of the Laptev Sea comprises freshwater and brackish-water species, the brackish-water fauna dominating in winter. The pelagic fauna in the Anabar Gulf, and in the western, central, and northeastern regions is represented by marine and brackish-water species. The former prevail in the western and northeastern areas, the latter in the central part. The brackish-water fauna dominates in the eastern and southeastern regions
- in the southeastern Laptev Sea, two maxima of total zooplankton density are usually observed in one year: at the end of winter (March-May) and in summer (July-September). The first maximum is connected with the beginning of the reproduction period of some Copepoda species and slightly pronounced. At the end of May-June the density of plankton organisms decreases due to the influence of river discharge within the period of the spring flood. In July-September the maximum amount of zooplankton is observed
- the seasonal variations of average abundance in the zooplankton populations in the southeastern Laptev Sea are well pronounced. The abundance of individuals within the most intensive reproduction period can exceed the abundance of overwintered organisms at the beginning of the year by 50 times. The interannual variations of average abundance in this sea region exceed the ones within the summer period by 2 times and within the winter period by 7 times. The correlation between the abundance of zooplankton populations at the beginning of the year and that observed at the end of summer is well pronounced
- the amplitude of seasonal and interannual variations of average zooplankton abundance in each concrete sea region is significantly specified by the behavior of the populations of 1-3 mass species, the intensity of their reproduction, and their degree of biotic potential under winter conditions
- our analysis of the vertical distribution of the pelagic fauna at the end of winter and in summer showed that the abundance of organisms within both observation periods during daylight is greater in the surface level due to the concentration of nauplii and young stages of Copepoda; the rate of adult stages increases when depth increases as well
D. Bolshiyanov, G. Fedorov, L. Savelieva
For climate reconstruction a variety of methods have been in use but the spore-pollen analysis is considered to be the most informative one. It is important that only the pollen data on those sections which have been dated by radiocarbon are used. The paleotemperature curves have been plotted. They qualitatively, not quantitatively describe climate changes. These curves have been transformed into arbitrary (conventional) units and based on that, a statistical spectral analysis was carried out. As a result, long-term trends and climate cyclicity for the different parts of the Arctic were identified. In addition, by analyzing the curves for 12 sectors of the Arctic, they were grouped into 3 climatic provinces. Based on the same principles, the Laptev Sea was divided into paleoclimatic areas. As a result of this work, a number of paleoclimatic curves for the Laptev Sea region and a series of maps showing the distribution of vegetation in the continental circumference of the sea will be obtained. These maps can be made only for three periods of the Holocene, as only for the we have enough and correct 14C data. It was planned and already started to try to create a digital computer model for the reconstruction of vegetation distribution, but this work has to be continued. Of course the reconstruction of the sea level position in the Holocene is not the only possible method. This is just one of the used approaches. The Holocene sea level is reconstructed by estuarine deposits of the large rivers and the character of lamination in these deposits.
I. Dmitrenko, S. Berezovskaya, S. Kirillov
Annual observations, performed in the Laptev Sea in 1998-1999 within the framework of the Russian-German project „Laptev Sea System", for the first time revealed a strong vertical non-uniformity of currents caused by the presence of a density stratification of the water column. The unstability of these currents is accompanied by turbulization of the density interface. This causes an increase in vertical exchange intensity across the density interface by several orders of magnitude. It should be noted that this increase has not been taken into account up to now. Moreover, the sea currents, regulating the vertical fluxes of heat, salt, and admixtures, exert control over a number of important environmental processs, in particular, freezing, fast-ice propagation, quasi-stationary location of the fast-ice edge and the fast-ice margin of the polynya, upper-layer salinization and desalinization of the near-bottom layer in winter, and redistribution of suspended sediments in the water column. This project aims to study the influence of the current regime on the formation of the Laptev Sea environmental system. The study focuses on the eastern Laptev Sea as a critical region subjected to freshwater input via river runoff and exhibiting significant fluxes of dissolved and particulate matter across the coastal zone. Based on the analysis of the unique acoustic Doppler Current Profiler records by statistical and turbulent structure methods, the vertical fluxes of heat, salt, and admixtures through the density interface will be calculated for the annual cycle. For further understanding the dependence of these fluxes on the Laptev Sea environment, these data will be analyzed in conjunction with mean multi-annual hydrological, climatological and ice data, current, temperature and depth profilers and regional meteorological records as well. Owing to the importance of the current regime for a wide variety of coastal processes, the study could provide important basic information for the Laptev Sea System project and at the same time help extend our understanding of the impact of mesoscale hydrology on the environmental interaction in the Laptev Sea.
S. Drachev, D. Chizhov, A. Rudoy
The Laptev Sea represents a unique occurrence of a continental margin/spreading axis intersection in the Arctic, which is important for addressing the processes of active rifting and its influence on some components of the natural environment. Since 1993 this region has been under consideration of the Russian-German interdisciplinary project "Laptev Sea System"/"Laptev Sea System 2000". Despite the explicit achievements in Laptev Sea geology, the recent and modern tectonics of this active extensional structural assemblage is still far from being defined. To investigate the recent tectonic development of the Laptev Sea continental margin and its possible influence on the processes occurring in the marine paleoenvironment, such as sedimentation and permafrost formation/degradation, constitutes the main goal of the project. The basic dataset on which the research team will base their investigation consists of various geophysical and geological data among which there are processed offshore CDP profiles with a recording length of up to 6 s TWT and PARASOUND echograms obtained during the RV POLARSTERN cruise in 1998. These data provide a representative basis to consider the recent and modern tectonic processes in the eastern, currently active part of the rift sytem and their impact on the Laptev Sea environmental system.
M. Grigoriev, E. Pavlova, P. Rekant
For a detailed reconstruction of the sediment transport in the land-ocean system of the Laptev Sea during the Late Pleistocene-Holocene, a comparison of marine geophysical and geological data with terrestrial geological, geomorphological and geocryological information along the transect Lena Delta–Laptev Sea shelf and the adjoining deep Arctic Ocean is proposed. The study will be based on the comprehensive analysis of new and published data on the history of the Lena Delta, solid river discharge, shore dynamics, data on natural outcrops and drill cores, as well as on a seismic-facies analysis. The main development stages of the region in respect of its geomorphology, sedimentology and geocryology will be specified and the character of changes of paleogeographical, paleooceanic and hydro-lithodynamical conditions for the last 60-70 kyr will be evaluated in detail. This will allow us to consider the land/shelf/continental-slope interaction as one sysstem of sedimentary material transformation and transport and trace the main stages of its history.
The main results will be a set of geological, geomorphological maps and paleogeographical-paleoecological schemes for individual time intervals of the Late Pleistocene-Holocene.
S. Pivovarov, E. Kirillova, M. Nitishinsky
The proposed research constitutes a study of nutrients distribution and variability in an arctic coastal system. Phosphate, nitrate, ammonia, and silicate are mineral basis of primary production in seawater. An accurate assessment of conditions and fluxes of nutrients in the Laptev Sea, and in particular of their variability, is essential to assessing and understanding the state, functioning and health of marine ecosystems, as well as the changing contribution of the region to the Arctic Ocean. As the Laptev Sea part systems are inherently interconnected and complex, we must use an observation-oriented, multi-disciplinary, and multi-environmental approach. Chemical changes are often inextricably modified by or coupled to other processes: physical, biological, and geological. These processes at the Arctic Shelf define critical pathways for nutrients.
The aim of our investigation is to determine the dominant mechanisms of exchange between the nutrient rich river waters and the slope and shelf waters where nutrients are limited, and how these vary on interannual time scales.
The proposed studies will be based upon the high quality data set obtained during the unique TRANSDRIFT expeditions and AARI's archive data set. The activities proposed include nutrient measurements during four cruises planned in the Arctic Seas in summer 2000.
N. Romanovskii, A. Kholodov, V. Tumskoy
Within the framework of previous project, radically new concepts were developed concerning the ice-bonded permafrost distribution up to the shelf edge, the occurrence of continuous offshore permafrost starting from the isobaths of 30-40 m, and the absence of open taliks under thermokarst lakes. These statements are supported by the results, though not numerous, of field studies and mathematical simulation. For this reason, the corresponding inferences are of a preliminary character.
The research project is aimed at the continued investigation of the offshore and onshore permafrost evolution and the dynamics of the gas-hydrate stability zone (HGSZ). Such studies will include processing of new field data, refinement of the paleogeographic scenario and computations based on new mathematical models. Additional data will be derived on:
- the actual temperature state and the evolution of the offshore and onshore permafrost an the HGSZ on the shelf and coastal lowlands during the past four climatic and glacioeustatic cycles under the conditions of rift structures with different values of geothermal heat flows
- the effect of neotectonic movements and compensational sediment accumulation on permafrost thickness
- the influence of lake thermokarst on the thickness of lake taliks and the character of ice-bonded permafrost distribution as a function of sea depth and permafrost zonation
A. Sher, S. Kuzmina, T. Kuznetsova
Very few is known about the environment of the Laptev Sea shelf land during the deep regression stages in the Pleistocene, when the general climatic pattern and environment were dramatically different from the modern ones. However, terestrial sediments along the Laptev Sea coast contain rich and various archives of the past life. They include fossil mammals and insects (a very sensitive indicator of the past environment), plant macrofossils, etc. Some of these materials were collected earlier, but not dated properly. Interesting materials have been recently obtained in the course of the "Laptev Sea System 2000" program. The proposed project is aimed at the recognition of the basic features of the Laptev shelf land environment and climate during the Pleistocene from the paleontological and geochronological evidence available. The first step to achieve this aim is to summarize different kinds of paleoecological information under the dating control and to provide the backround for its adequate interpretation through the better knowledge of modern ecology and distribution of organisms. The main task of the project is to create a group of three linked databases (insect, mammal, and geochronological). These databases will serve as a necessary framework for the current analysis of the shelf land environment, its properties and dynamics, and for the interpretation of paleoecological evidence to be obtained in future from the Laptev Sea area, both from the coastal sites and from the drilling cores in the sea.
V. Shevchenko, A. Klyuvitkin, M. Kozachenko
In close cooperation with our German colleagues, we plan to study the atmospheric input of natural and anthropogenic tracers in the Laptev Sea and adjacent Arctic Ocean and to compare it with other pathways of these tracers (river discharge, sea ice etc.). We will use our data and samples of aerosols, snow, water from melt ponds, ice-rafted sediments, sedimentary matter collected by sediment traps from the Laptev Sea and adjacent Arctic Ocean as well as soils, moss and lichens from the Laptev Sea hinterland. All material was collected during the SPASIBA-91 expedition and during the ARK-XI/1 and ARK-XIV/1a expeditions of RV POLARSTERN. Furthermore, relevant material, provided by Russian colleagues and literature data, will be included in the proposed study. The work will be carried out in laboratories in Moscow, St. Petersburg and Bremerhaven, including optical and scanning electronic microscopy, X-ray diffractometry, instrumental neutron activation analysis, granulometric analyses, inductively coupled plasma mass spectrometry (ICP-MS), and calculation of back trajectories of air masses. It will be a contribution to the research program „Laptev Sea System 2000".
E. Taldenkova, S. Demyankov, A. Ovsipyan
The project is aimed at the paleoenvironmental reconstruction of the eastern Laptev Sea shelf area under the conditions of the postglacial sea-level rise and water-mass changes. The proposed research will primarily focus on a detailed study of macro- (molluscs) and microfossils (foraminifers and ostracodes) in the gravity sediment core (PS-51/138) recovered in the eastern Laptev Sea in 1998 during the TRANSDRIFT V expedition aboard RV POLARSTERN. The core is located at the position where the oceanographic bottom station YANA was deployed, which provided a unique year-round record of temperature and salinity. The combination of detailed paleontological evidence compared with the distribution of recent bivalves, ostracodes and forams in surface samples, AMS-C14 datings, oxygen-isotopic determination of calcareous microfossils and oceanographic information will make it possible to reconstruct paleoenvironmental changes in the region with high precision. Based on the present chronology the expected time span covered by the core is about 11 ka.