Data Analysis:

Numerical Modeling:



Meteorological and Ice Data Analysis

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Frazil ice formation in winter polynyas: h – ice thickness (cm), Q – total heat flux at the ice free surface; ρi is the frazil ice density (920 kg/m3), and L is the specific heat of fusion (3.35 x 105 J/kg). (Martin and Cavalieri, 1989)

eq0b Columnar ice growth below the existing ice: h0 – initial ice thickness (cm), θ is cumulative number of days below freezing, Tf is the freezing temperature of sea water (°C), and Ta is the surface air temperature (°C). (Zubov, 1945)
eq0c Salt flux at the surface due to ice formation: S – water salinity, r ratio of ice salinity to water salinity (Martin and Cavalieri, 1989)


Fig. 9

Calculations were carried out for the grid points of the oceanographic polygon with a one-day time step from October 1 1984 to April 15 1985. Polynya events (opening and closing) were evaluated on the basis of meteorological data and aerial ice charts (Fig. 9). Calculations were checked and corrected every 10 days using information from the ice charts.


Fig. 10

Total duration of polynya events is only 25 days out of 180. However, average salt flux during these events (10x10-5 kg/m2/s) is more than an order of magnitude larger than average salt flux caused by columnar ice growth on the shelf (0.6x10-5 kg/m2/s). The latter is in turn about 3 times larger than the salt flux in the deep water (0.2x10-5 kg/m2/s).

According to our calculations, in the winter of 1984-85 the relative contribution of polynya events to the total salinity increase on the northwestern Laptev Sea shelf was about 70%, while 30% was attributed to columnar ice growth. This yields average winter salt flux on shelf equal to 1.9x10-5 kg/m2/s.


Only 20% of the salt released over the shelf during the winter of 1985 stayed there, while 80% was transported away.