Near-bottom water warming in the Laptev Sea in response to atmospheric and sea-ice conditions in 2007 by Jens A. Hölemann et al., Polar Research 30 (2011); doi:10.3402/polar.v30i0.6425

Polar Research, 30 (12 May 2011) 6425; doi: 10.3402/polar.v30i0.6425

Near-bottom water warming in the Laptev Sea in response to atmospheric and sea-ice conditions in 2007

Jens A. Hölemann,*¹ Sergey Kirillov,² Torben Klagge,³ Andrey Novikhin,² Heidemarie Kassens,³ and Leonid Timokhov²

¹Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, DE-27570 Bremerhaven, Germany
²Arctic and Antarctic Research Institute, 38 Bering Street, RU-199397 St. Petersburg, Russia
³Leibniz Institute of Marine Sciences, Wischhofstrasse 1-3, DE-24148 Kiel, Germany

Abstract

In this paper we present new data from ship-based measurements and two-year observations from moorings in the Laptev Sea along with Russian historical data. The observations from the Laptev Sea in 2007 indicate that the bottom water temperatures on the mid-shelf increased by more than 3 C compared to the long-term mean as a consequence of the unusually high summertime surface water temperatures. Such a distinct increase in near-bottom temperatures has not been observed before. Remnants of the relatively warm bottom water occupied the mid-shelf from September 2007 until April 2008. Strong polynya activity during March to May 2007 caused more summertime open water and therefore warmer sea surface temperatures in the Laptev Sea. During the ice-free period in August and September 2007, the prevailing cyclonic atmospheric circulation deflected the freshwater plume of the River Lena to the east, which increased the salinity on the mid-shelf north of the Lena Delta. The resulting weaker density stratification allowed more vertical mixing of the water column during storms in late September and early October, leading to the observed warming of the near-bottom layer in the still ice-free Laptev Sea. In summer and autumn 2008, when the density stratification was stronger and sea surface temperatures were close to the long-term mean, no near-bottom water warming was observed. Warmer water temperatures near the seabed may also impact the stability of the shelf's submarine permafrost.

*Corresponding author: Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, DE-27570 Bremerhaven, Germany. e-mail: jens.hoelemann@awi.de

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