Observations of supercooling and frazil ice formation in the Laptev Sea coastal polynya

Abstract

[1] This paper examines a hydrographic response to the wind-driven coastal polynya activity over the southeastern Laptev Sea shelf for April-May 2008, using a combination of Environmental Satellite (Envisat) advanced synthetic aperture radar (ASAR) and TerraSAR-X satellite imagery, aerial photography, meteorological data, and SBE-37 salinity-temperature-depth and acoustic Doppler current profiler land-fast ice edgemoored instruments. When ASAR observed the strongest end-of-April polynya event with frazil ice formation, the moored instruments showed maximal acoustical scattering within the surface mixed layer, and the seawater temperatures were either at or 0.02°C below freezing. We also find evidence of the persistent horizontal temperature and salinity gradients across the fast ice edge to have the signature of geostrophic flow adjustment as predicted by polynya models.

Polynya impacts on water properties in a Northeast Greenland fjord

“…(Figure 2a). This range of supercooling is similar to that reported for the Arctic polynyas by Skogseth et al [2009] and Dmitrenko et al [2010b]. In contrast to 77-80 m, the surface layer (2 m depth) tended to be warmer by up to 0.3°C during the period between 25 December, 5 days after the polynya opened, to 4 March, when the polynya closed (moorings m02 and m03, Figure 2e).…”

Study of the Impact of Ice Formation in Leads upon the Sea Ice Pack Mass Balance Using a New Frazil and Grease Ice Parameterization

“…The lack of vertical variation, a constant mixed layer thickness, and a single frazil crystal size are significant simplifications from previous process models of frazil ice formation. These simplifications are made despite observations of the variable vertical structure of the ocean beneath cracks in the sea ice (Dmitrenko et al 2010) and the varying freezing temperature of water with depth and pressure (McDougall et al 2014). In particular variations in the depth of the mixed layer are known to be linked to the layer salinity under sea ice (Petty et al 2014) and horizontal mixing rates vary over the depth of the water beneath the lead during frazil ice formation (Skyllingstad and Denbo 2001).…”

“…There is no explicit consideration of the mechanics of polynya formation within the model, and the frazil formation scheme assumes that the ice-free areas of the grid cells next to land are arranged into leads evenly spaced by the structure length L throughout the grid cell, as it does with every sea ice grid cell. The model does not consider the dynamics of large open polynyas at the sea ice to land or ice shelf interface, as is often observed in the Laptev (Dmitrenko et al 2010) or Weddell Seas (Eicken and Lange 1989). The high rates of frazil ice formation in the coastal areas are mechanical in origin.…”

Supercooling of Seawater Near the Glacier Front in a Fjord

“…Supercooling is frequently observed in polynyas (Skogseth et al, 2009;Dmitrenko et al, 2010). The water can be supercooled by as much as 0.01-0.02°C.…”