Wind-forced currents as a linkage between the Laptev Sea (Siberia) and the Arctic Ocean

Water circulation is of significant importance for the Arctic environment. Both thermohaline and wind-forced circulation give rise to sea currents. In the Laptev Sea (Russian Siberia) wind-forced deformations of the sea level are as high as 220 cm. However, in most publications dealing with the Laptev Sea circulation they are usually neglected because of their non-periodic nature and short duration compared to the relatively stable thermohaline structure. The wind-forced circulation results in intensive bottom currents that are opposite in direction to the wind. In the Arctic such currents have previously been recorded in the Barrow Canyon, Chukchi Sea. The presence of south-oriented reversal currents has previously been postulated for the Laptev Sea though no reliable observational data have been available.

To investigate the water circulation in the Laptev Sea, we analyzed 3D-current and echo intensity records from the two Broadband Acoustic Doppler Current Profilers (ADCP) Workhorse 300 kHz, sea-level and bottom temperature recorded from a bottom CTD, wind and sea level from the nearest polar stations and satellite RADARSAT ScanSAR images of the Laptev Sea. All the data mentioned above were obtained from August 1998 to September 1999.

The ADCP records provide evidence of the strong non-periodic southeasterly currents in the layer underlying the pycnocline. Their duration varies from 3 to 7 days, the average current velocity is 20-22 cm/s, with a maximum of 59 cm/s. These currents were recorded 28 times during the year. They are definitely seasonal being absent during winter when the sea ice cover was compacted. We found that these reversal currents result from the wind-forced deformations of the sea level down to 84 cm produced by southeasterly winds. They are directed opposite to the wind and act to reduce the wind-forced deformations of sea level. Thus, the wind-forced barotropic deformations of the sea level seem to be one of the main factor determining the water circulation in the eastern Laptev Sea.

The reversal currents are responsible for the advection of relatively warm waters from the north that occurs in the lower water level at depths between 30 and 40 meters. This induces a vertical heat exchange between the Atlantic and surface waters in the northern Laptev Sea. During winter the reversal currents correspond well with flaw polynya openings in the eastern Laptev Sea, caused entirely by southeasterly winds. Wind-forced sea-level deformation of ice-free flaw polynyas form reversal currents hampering the advection of the shelf high–salinity waters from polynyas to the Arctic Ocean.

The reversal currents seem to adhere to the submarine relic river valleys in the eastern Laptev Sea. These regions can hence be considered as zones of strong interaction between the Arctic Ocean and the Laptev Sea under the influence of wind-forced currents.