Thickness and production of sea ice in the Okhotsk Sea coastal polynyas from AMSR‐E

Abstract

From comparisons with thickness of sea ice from Advanced Very High Resolution Radiometer (AVHRR) and ice‐profiling sonar data we have developed an Advanced Microwave Scanning Radiometer‐EOS (AMSR‐E) thin ice thickness algorithm for the Sea of Okhotsk. This algorithm can estimate ice thickness of ≤0.2 m without snow using the polarization ratio of AMSR‐E brightness temperature at a 36.5 GHz channel from a linear relationship with AVHRR ice thickness. When a snow cover exists on the thin ice surface, as occurred a few times in each winter, it is shown that the algorithm cannot detect the thin ice. Sea ice and dense shelf water (DSW) production in coastal polynya are estimated on the basis of heat flux calculation with the daily AMSR‐E ice thickness for three winters (December–March) of 2002–2003 to 2004–2005. The ice production is largest in the northwest shelf (NWS) polynya which accounts for ∼45% of the sum of ice production in major coastal polynyas. The ice production in major coastal polynyas would cover the maximum ice area of the Okhotsk Sea if the average ice thickness is assumed to be 1 m. Variability of the ice production is mainly modulated by air temperature. In the NWS polynya, which is the main DSW production area, the annual DSW formation rate is estimated to be ∼0.36 Sv.