Linking Duration of Open Water with the date of Open Water Onset in the Kara Sea

Abstract:

Sea ice coverage (C_R) less than 30% is considered as open water. The duration between onset and end dates, i.e., T_open and T_close, is defined as the open water period. The date of sea ice melt onset (change in sea ice volume (SIV) begins to less than zero) to T_open is the melt period. Satellite based sea ice concentration (SIC) from 1989 to 2019 shows a negative correlation between T_open and T_close (r = -0.77, p < 0.01) in the Kara Sea. This phenomenon is also captured by a coupled ocean and sea-ice model (NAPA1/4). The model results reveal that thermodynamics dominates the sea ice variations and ice basal melt is greater than the ice surface melt. Influenced by the sea ice conditions, the net heat flux has larger interannual variations during melt period than open water period. More net heat flux into the sea during melt period leads to an earlier formation of open water. T_close is also significantly correlated with net heat flux during melt period, but without obvious relation with that during open water period. This is the physical basis of the negative correlation between T_open and T_close. Therefore, the duration of open water (DOW) can be predicted by linking to T_open (DOW = -1.72T_open + 177.15, T_open is the number of days relative to the end of May) and thence support earlier planning of marine activities.