High-resolution reconstruction of sea-ice and hydrological conditions in the south-eastern Laptev Sea during the Holocene deduced from microalgae assemblages.

Polyakova, Yelena, Klyuvitkina, Tatiana, Bauch, Henning and Kassens, Heidemarie (2011) High-resolution reconstruction of sea-ice and hydrological conditions in the south-eastern Laptev Sea during the Holocene deduced from microalgae assemblages. [Talk] In: 5. APEX International Conference and Workshop: Quaternary Glacial and Climate Extremes. , 01.06.-04.06. 2011, Longyearbyen, Svalbard, Norway . APEX Fifth International Conference and Workshop: Quaternary Glacial and Climate Extremes / hosted by The University Centre in Svalbard (UNIS), Longyearbyen, Svalbard, June 1st - 4th 2011. ; p. 41 .

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Abstract

The Laptev Sea constitutes the central part of the wide Siberian shelf and is regarded as a key area for the freshwater and sea-ice balances of the Arctic Ocean. More than a quarter of the total continental freshwater runoff to the Arctic Ocean is discharged into the Laptev Sea, mainly via the Lena River (Gordeev, 2000). Furthermore, the Laptev Sea polynya is a major source area for sea ice, which is transported to the Siberian branch of the Transpolar Drift (e.g., Zakharov, 1996). Therefore, knowledge of the Holocene variability of the Laptev Sea hydrology is essential for understanding Arctic Ocean water circulation in the past.

Our paleoenvironmental reconstructions based on a detailed study on diatom and aquatic palynomorph assemblages and a detailed radiocarbon (AMS 14 C) chronology of sediment cores obtained from the south-eastern Laptev Sea adjacent to the Lena River Delta. Established linkages between hydrographical parameters (e.g., summer surface-water salinity, sea-ice conditions, Polyakova, 2003; Klyuvitkina, Bauch, 2006) and the composition of surface-sediment diatom and aquatic palynomorph assemblages were used to reconstruct environmental conditions under postglacial sea-level rise and climatic changes. Our records give evidences for inundation of the outer Laptev Sea shelf (> 51 m water depth) approximately 11.3 cal. ka. River-proximal environment characterized by avalanche-like precipitation of river-loaded matter (“marginal filter”) under water salinity <9. The time interval 10.7-9.2 cal. ka was marked by enhanced influence of Atlantic Water on the Laptev Sea hydrology. Because a continuously rising sea level resulted in the southward retreating coastline, surface-water salinities on the outer shelf approached modern values of about 15-16 around 8.6 cal. ka. Approximately 8.9-8.5 cal. ka, when the sea-level reached the position of the present-day isobaths of about 32-30 m, the inner-shelf was flooded. On the inner Laptev Sea shelf, modern-like environmental conditions were reached about 1 to 1.5 ky later, around 7.4 cal. ka. During the last 6 cal.ka in the area adjacent to the Lena Delta variations in surface water salinities, reconstructed using freshwater diatoms as a proxy (Polyakova, 2003) indicate the changes in the volume of the Lena River runoff through the major riverine channels Trofimovskaya, Bykovskaya and Tumatskaya. It was shown, that the Lena River outflow increased in north-eastward direction via Trofimovskaya and Bykovskaya channels 4.2-2.7 cal. ka. A general increasing trend in riverine discharge is observed between 2.7 and 1.2 cal. ka, and a steep decrease in outflow recorded for the last 1.2 cal. ka.

References
Gordeev V.V., 2000. River input of water, sediment, major ions, nutrients and trace metals from Russian territory to the Arctic Ocean. In: E.L.Lewis et al. (eds.) The freshwater budget of the Arctic Ocean, Kluwer, Amsterdam, 297-322.

Klyuvitkina T.S., Bauch H.A., 2006. Holocene changes in paleohydrological conditions in the Laptev Sea based on aquatic palynomorph assemblages. Oceanology, 6, 911-921.

Polyakova, Ye.I., 2003. Diatom assemblages in the surface sediments of the Kara Sea (Siberian Arctic) and their relationship to oceanological conditions. In: Stein, R., Fahl, K, Fütterer, D. K., Galimov, E. M., Stepanets, O. V. (Eds.), Siberian River Run-off in the Kara Sea: Characterization, Quantification, Variability, and Environmental Significance, Proceedings in Marine Sciences, Elsevier, Amsterdam, 375-399.

Zakharov, V. F., 1996. Sea Ice in the Climatic system, St.-Petersburg, Gidrometeoizdat, 213 pp. (In Russian).

Document Type: Conference or Workshop Item (Talk)
Keywords: Paleoceanography; Laptev Sea; Holocene; sea-ice
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-P-OZ Paleo-Oceanography
Projects: Polynya, Laptev Sea System
Date Deposited: 22 Dec 2011 11:30
Last Modified: 19 Dec 2014 08:53
URI: http://oceanrep.geomar.de/id/eprint/13131

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