1. Historical-Faunistic, ecological, population, and production analysis of zooplankton from Lakes of different regions and geomorphological levels in the Lena Delta
E. Abramova , I. Akhmetshina , E. Vinogradova
E. Abramova, I. Akhmetshina, E. Vinogradova
The project is aimed at investigating zooplankton in the lakes from different regions and geomorphological levels of the Lena Delta for understanding peculiar features of the modern pelagic fauna of this big region and the history of its formation. The main results are:
•in the lakes of the Lena Delta, 128 taxa of zooplankton belonging to 2 types (Rotatoria and Arthropoda) were determined.
• the species composition is very similar in polygonal ponds situated in different parts of the delta. A remarkable difference in the species composition is typical for large thermokarst lakes as well as for alas lakes.
• the highest abundance, biomass and production of zooplankton were observed in the polygonal and flood-plain lakes of the first terrace, which are regularly influenced by river water. The seasonal dynamics of quantitative characteristics shows a well-pronounced conformity connected with environment conditions and the life cycle of the common species.
• the pelagic fauna of the lakes is of heterogeneous origin and consists mainly of both recent and modern freshwater elements with amphibiotic brackish-waters organisms of neolimnic assemblage.
Our current knowledge on the Siberian Arctic is incomplete. Our understanding of the changes observed in Arctic hydrological system, therefore, are limited. This project was aimed at determining and quantifying the change in the hydrological regime of the second largest arctic river. The water balance of the Lena River was studied in order to assess the role of climatic and anthropogenic factors in runoff variations. Historical data analyses show that the Lena River and its major tributaries experienced an extended low-water period from 1936-1957 and high-water periods from 1974-1983 and 1988-2001. Since the late 1960s the increase in river discharge and annual precipitation has been particularly pronounced due to large-scale changes in atmospheric circulation patterns. Runoff in the Lena River basin increased by 10% from 1936 to 2001 due to extended wet periods during the second part of the past century. The trend is weaker for the Vilui River basin because it is subject to reservoir regulations that cause additional water losses through reservoir filling and increased evaporation. Runoff regulation strongly affects the winter runoff regime of both the Vilui River and the lower reaches of the Lena River causing an increased winter discharge at the Lena river outlet station of approximately 33%. The results of this project improve our understanding of current changes in the Siberian Arctic as they prove that increased precipitation produces additional runoff to the Laptev Sea. This also directs our attention to the importance of human impact within the Vilui sub-basin, which should not be neglected while analyzing the runoff changes on a regional scale.
S. Drachev, M. Kasymskaya, V. Kaulio
This project was funded in 2003 with the main goal of revealing the structure of the uppermost part of the permafrost developed on the eastern Laptev Sea shelf, on the New Siberian Islands and adjacent mainland, with particular emphasis on their comparative analysis. This study was based on numerous scientific data collected within the scope of the Russian-German program "Laptev Sea System 2000" as well as on PARASOUND data obtained during RV "Polarstern" 1998 cruise and drill cores recovered from several shallow wells in the course of RV "Kimberlit" 2000 cruise. PARASOUND transects obtained during 1993 and 1995 cruises of RV "Polarstern" were also used, as well as published results of upper sedimentary layer sampling with piston corers. The results previously obtained within the framework of the OSL project OSL-01-07 (Principal Investigator S.S. Drachev), in particular the Map of Submarine Permafrost Roof in the eastern Laptev Sea and its basis and the digital grid of depths, and of the OSL project OSL-01-19 (Principal investigator N.N. Romanovskii) were widely involved. The results of many years of permafrost research obtained by the scientific team led by N.N. Romanovskii (Geological Department of Moscow State University) were used as a basis when determining the major forms of permafrost-generated landscapes of the New Siberian Islands and Primorskaya Lowland.
Within the framework of this project it was intended to prepare and defend a PhD thesis, which is the outcome of 8 years of activity within the framework of the Russian-German research in the Laptev Sea region. An attempt was made to analyze all the obtained data and knowledge on lakes and their evolution gained throughout the years of research.The aim of the project was to investigate the modern structure and evolution of the lacustrine geosystems of Taimyr Peninsula. To achieve this goal the following fundamental tasks were to be solved:
1. to reveal the main factors responsible for lacustrine geosystems formation on Taimyr Peninsula;
2. to reveal the primary stages of lacustrine geosystems evolution on Taimyr Peninsula;
3. to carry out palaeolimnological zoning and classification of lacustrine geosystems of Taimyr Peninsula.
In general the main factors influencing the formation and evolution of the lacustrine systems are climate (general moisture fluctuation), connected in the Arctic in the Late Pleistocene mainly with glacier formation and degradation, basic levels of erosion fluctuations, associated on Taimyr Peninsula with oscillations of the Kara and Laptev sea levels, and also tectonic movements resulting in the rearrangement of the hydrological system.Other tasks were to investigate several important inferences concerning the evolution of sea-level oscillations, the development and main features of glaciers and the neotectonic structure on Taimyr Peninsula, to classify Taimyr lacustrine systems, and to describe in detail the evolution history of Taimyr Lake since its formation until the present day.
M.N. Grigoriev, I. Shapovalova, D. Streletskiy
Published data concerning the dynamics and composition of coasts, their lithology, morphology, hydrodynamic and geocryological conditions within a coastal zone were collected and along with our own data analyzed for a detailed assessment of basic parameters and the effect of coastal erosion. Based on current material a database was developed involving parameters of coastal erosion and assessment of sediments and organic carbon fluxes. Database development is based on detailed segmentation of coasts by the parameters indicated above as well as classification of erosional, stable and accumulative coast types of the Laptev and East-Siberian Seas. The basic results of works are reflected in a digital map. Our research made it possible to generalize all collected data on a set problem concerning the coast of these seas, where the influence of permafrost peculiarities on the character and intensity of relief-forming and sedimentological processes is extremely strong.
This project was aimed at studying the interior ocean dynamics in the eastern Laptev Sea shelf area. Short and long-term ADCP measurements were analyzed in order to recognize the spatial distribution of heat transport by internal-wave overturning in the Laptev Sea and its role in the formation of freeze-up pattern anomalies. It was found that the mixing intensity due to the breaking of internal waves varies from molecular up to 5-30 x 10-5 m2/s within the pycnocline layer. This could result in ice-formation onset being delayed by up to 5-6 days over the eastern part of the Laptev Sea during freeze-up period. It was also found that an energy increase by the factor of 2-3 is possible during strong atmospheric forcing. These forcings might significantly delay ice formation onset due to the fact that the heat exchange is increased by internal-wave action.
T. Kuznetsova, N. Noskova, A. Bryantseva
The project is aimed at the reconstruction of the basic futures of the Laptev shelf environment during the Late Pleistocene and Holocene. The research was focused on the investigation and analysis of favourable and unfavourable periods of environmental conditions for different species of mammals and plants. We reconstruct the animal population and traced their change. All the data are new. Another focus is the study of oxygen isotope ratios in bone's phosphate as indicator of climate variations.A combination of paleozoological and paleobotanical (diatoms) data under strictly defined stratigraphic and chronological (14C) control allows us to reconstruct the Late Pleistocene and Holocene paleoenvironmental history of the Laptev Sea surroundings.
Ye.I. Polyakova, T. Novichkova, E. GolovninaMoscow State University, Moscow, Russia
The main goal of our study within the scope of this project was to reconstruct the short-term variability in the Lena River discharge onto the Laptev Sea shelf during the late Holocene. The study was based on detailed investigations of the downcore distribution of aquatic microalgae in the sediment cores obtained from the regions adjacent to the Lena Delta during the TRANSDRIFT expeditions. Using diatom and aquatic palynomorph assemblages as a proxy, the following major paleoenvironmental results were achieved:
(i) spatial and temporal variations in the surface water salinity in the Laptev Sea shelf area adjacent to the Lena Delta were reconstructed for the last 6 cal. ka;
(ii) the impact of the Atlantic waters on the inner Laptev Sea hydrology during the Holocene was revealed;
(iii) the major stages of the changes in the direction of the Lena River discharge were revealed: generally eastward outflow via the Bykovskaya channel approximately between 6 and 4.2 cal. ka, and after 2.8 cal. ka, and increase in riverine outflow in the northward direction via the Trofimovskaya channel between 4.2 and 2.8 cal. ca.
A. Sher, S. Kuzmina, A. Sokolov
The Mutual Climatic Range (MCR) method based on fossil insect assemblages is a powerful tool for reconstructing climatic conditions of the past. A very large volume of information on the distribution of many insect species and the climatic parameters of their ranges was collected in the course of this project. The usage of this information has already allowed us to build comparative climatic characteristics of certain periods in the Late Pleistocene and early Holocene.
E.E. Taldenkova, A. Stepanova, S. Dem'yankov
The project is aimed at investigating recent and fossil benthic assemblages from the eastern Kara and western Laptev seas in order to reconstruct paleoenvironmental changes under postglacial sea-level rise with particular interest lying in the traces of Atlantic water influence on the studied regions.
The main results are:
• first recent ostracods from the eastern Kara Sea were studied in detail (species identification, description, SEM photos);
• the recent distribution of ostracod and mollusc assemblages were established from coretop samples from the eastern Kara Sea in relation to salinity and water depth changes;
• the paleoenvironmental changes in the eastern Kara Sea mid-shelf since 8.1 cal.ka were reconstructed; a considerable influence of marine (Atlantic-derived?) waters from ca. 6-5 cal.ka was revealed;
• the continuous influence of Atlantic water on the western Laptev Sea continental slope is recorded in the species composition of microfossils since ca. 15.8 cal.ka with its maximum between ca. 11 and 4 cal.ka.