The Laptev Sea flaw polynya, Russian Arctic: effects on the mesoscale hydrography

Abstract

A detailed analysis of hydrographic data from a period of 20 years (1980−99) has shown that the persistent presence of a flaw polynya influences mesoscale hydrography of the Laptev Sea, Russian Arctic. Based on these data, the interannual variability of surface water salinity within the polynya has been estimated. As the salinity increase in the surface water layer is mainly caused by the formation of new ice within the polynya, the average ice-production rate of the polynya was calculated. The results indicate an ice production of 3−4 m per season. A further aim of this study was to calculate the probability that the convective mixing in the polynya penetrates to the sea-floor. It is demonstrated that the probability is maximal in the flaw-polynya area, but does not exceed 20% in the eastern and 70% in the western part of the polynya as a result of strong vertical density stratification from river runoff, especially in the eastern Laptev Sea. Additional studies of water circulation in the marginal zone of the flaw polynya were carried out during field observations in April-May 1999. On the basis of conductivity-temperature-depth and current measurements we deduce that high current velocities (62 cm s-1) recorded in surface waters near the fast-ice edge are caused by a convectively driven circulation system under the polynya. Our measurements indicate that these high-velocity currents are part of a cellular circulation, which results from the rejection of brine during intensive ice formation in the polynya. The observed azimuthal alignment of the crystalline structure of sea ice is also, most probably, the consequence of this quasi-stationary cellular circulation.

Spatial and temporal variability of sea ice in the Laptev Sea: Analyses and review of satellite passive-microwave data and model results, 1979 to 2002

“…In addition, openings in the pack ice that form during winter are sites of brine formation, affecting the local convection and water mass stratification (Dmitrenko et al, 2001). The wind-driven polynyas result in intense heat loss from the ocean to the atmosphere, controlling the formation of fog banks and low-level clouds (Arctic stratus).…”

Seasonal variations in Arctic sediment dynamics—evidence from 1-year records in the Laptev Sea (Siberian Arctic)

“…The flaw polynyas in the Russian Arctic are caused by continuous southerly winds, which keep large areas off the fastice edge open (Zakharov, 1997). The polynya in the Laptev Sea is an important factor for the hydrography during winter (Dmitrenko et al, 2001a). It causes the formation of a cellular circulation with stable underice surface currents directed to the open water and counter currents below the pycnocline in the bottom layer because of brine rejection during ice formation (Dmitrenko et al, 2001a).…”

Russian-German Collaboration in the Arctic Environmental Research

“…The rate of salinity adjustment in response to ice formation was evaluated statistically from time series of winter salinity observations. These results evidence that, for instance, in the eastern Laptev Sea polynya, the mean salinity increase of the surface layer can reach up to 4 units, corresponding to an ice production of 3 to 4 m [Dmitrenko et al, 2001]. Therefore, it was confirmed that the Laptev Sea polynya is an important ice source for the Transpolar Drift system.…”

“…The increased winddriven advection of ice away from the Laptev Sea coast when the Arctic Oscillation (AO) is positive implies enhanced coastal polynya production and brine release into the shelf water. When the AO is negative, the ice production and seasonal salinity amplitude tends to weaken [Dmitrenko et al, 2001]. …”