Variations in the volume of ice in the sea of Okhotsk and the Tatar Strait at the phase of maximum ice extent development for 2000–2020

Abstract

Based on satellite images in the visible range, the boundaries of ice zones of various ages in the Sea of Okhotsk and the Tatar Strait for mid-February and mid-March in the period from 2000 to 2020 were delineated. Zone's areas were calculated using microwave range satellite imagery considering ice concentration. Average ice thickness was calculated based on the hummocking coefficient of ice extent. Based on these data, ice volume at the phase of maximum development of ice extent in the studied water areas was calculated using the “ICE” software package as average value for February and March. From the analysis of inter-seasonal variations, it was concluded that for the studied period the volume of ice in the Sea of Okhotsk decreased by ∼56%, or 292 km³. The average rate of ice decrease in the Sea of Okhotsk was ∼27%/10 years, in region I ∼18%/10 years, in region II ∼34%/10 years and in region III ∼29%/10 years. The ice volume change was ∼42% due to decrease in ice cover and ∼58% due to decrease in ice thickness. In the Tatar Strait, the volume of ice decreased by ∼30% (∼3.4 km³). Since the ice cover of the strait remained constant during the period under study, the ice volume declined solely due to decrease of the ice thickness.