Field measurements from Storfjorden on Svalbard in April 2006 are presented. A cold atmosphere and strong winds produced effective cooling (about 400 W/m²) of open water near Edgeøya. Such open water surrounded by ice during freezing conditions is called a polynya. The cooling produced frazil ice, small singular crystals whirling around in turbulent water. This frazil ice was advected away from the island driven by the winds. The supercooling lasted for three days until the wind direction turned to east, bringing warmer air and pushing warmer water into Storfjorden from the south.
Measurements of ocean temperature and salinity were calibrated by accompanying water samples, and reveal a supercooling event. The maximum supercooling measured was 0.037ºC below the in-situ freezing point. This is the strongest supercooling observed with modern and accurate instrumentation. This is also the first observations from an active Arctic polynya with concurrent sampling of hydrography and frazil ice.
These measurements are consistent with results from a one-dimensional frazil ice model, confirming that such supercooling levels can be expected. The vertical gradient in temperature, with near bottom supercooling of 0.016 ºC was also reproduced. Concentration of frazil ice in the water was modelled to be lower than 1% due to advection in the surface layer. Surface salinity reached 35.9 psu from the salt released from this ice growth.
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| The picture shows Frank Nilsen from UNIS right after measuring the new Arctic record of cold water in Storfjorden (photo: Lars H. Smedsrud/BCCR). |