The duration of ice-free periods in different parts of the Arctic Ocean plays a great role in processes in the climate system and defines the most comfortable sea ice conditions for economic activity. Based on satellite-derived sea ice concentration data acquired by passive microwave instruments, we identified the spatial distribution of the dates of sea ice retreat (DOR), dates of sea ice advance (DOA), and the resulting ice-free period duration (IFP) between these days for the Kara and Laptev seas during 1979–2022. The monthly decline in sea ice extent was detected from June to October in both seas, i.e., during the whole ice-free period. The annual mean sea ice extent during 2011–2021 decreased by 19.0% and 12.8% relative to the long-term average during 1981–2010 in the Kara and Laptev seas, respectively. The statistically significant (95% confidence level) positive IFP trends were detected for the majority of areas of the Kara and Laptev seas. Averaged IFP trends were estimated equal to +20.2 day/decade and +16.2 day/decade, respectively. The observed DOR tendency to earlier sea ice melting plays a greater role in the total IFP extension, as compared to later sea ice formation related to the DOA tendency. We reveal that regions of inflow of warm Atlantic waters to the Kara Sea demonstrate the largest long-term trends in DOA, DOR, and IFP associated with the decrease in ice coverage, that highlights the process of atlantification. Also, the Great Siberian Polynya in the Laptev Sea is the area of the largest long-term decreasing trend in DOR.

HYDROMETEOROLOGICAL FORCING OF WESTERN RUSSIAN ARCTIC COASTAL DYNAMICS: XX-CENTURY HISTORY AND CURRENT STATE

In recent decades, acceleration of coastal erosion has been observed at many key sites of the Arctic region. Coastal dynamics of both erosional and accretional stretches at Kharasavey, Kara Sea, was studied using multi-temporal remote sensing data covering the period from 1964 to 2022. Cross-proxy analyses of the interplay between coastal dynamics and regional (wave and thermal action) and local (geomorphic and lithological features; technogenic impact) drivers were supported by cluster analysis and wind–wave modelling via the Popov–Sovershaev method and WaveWatch III. Ice-rich permafrost bluffs and accretional sandy beaches exhibited a tendency towards persistent erosion (−1.03 m/yr and −0.42 m/yr, respectively). Shoreline progradation occurred locally near Cape Burunniy (6% of the accretional stretch) and may be due to sediment flux reversals responding to sea-ice decline. Although the mean rates of erosion were decreasing at a decadal scale, cluster analysis captured a slight increase in the retreat for 71% of the erosional stretch, which is apparently related to the forcing of wind–wave and thermal energy. Erosional hotspots (up to −7.9 m/yr) occurred mainly in the alignment of Cape Kharasavey and were predominantly caused by direct human impact. The presented study highlights the non-linear interaction of the Arctic coastal change and environmental drivers that require further upscaling of the applied models and remote sensing data.

The rapid Arctic Sea ice shrinkage in the 21st century leads to an increase in the duration of the ice-free period in the Arctic Ocean seas. The ice-free period duration is an important indicator of climate processes for coastal dynamics monitoring in the Russian Arctic zone. The considerable changes in the ice-free period duration significantly affect the functioning of coastal infrastructure, navigation, and coastal ecosystems. Recent satellite microwave sensing data covering the period of more than 40 years of observations make it possible to analyze the state and dynamics of the sea ice cover in the coastal zone of the Russian Arctic. Based on the gradient-threshold method, which was adapted for coastal data, the annual estimates of the ice-free period characteristics for the Kara Sea coastal zone over the period of 1979–2019 are obtained using satellite sea ice concentration data available from different scientific centers (JAXA, OSI SAF, and NSIDC). According to the analyzed satellite data sources, the ice-free period duration in the Kara Sea coastal zone has increased statistically significantly almost everywhere over the past decades. The ice-free period duration has increased due to both earlier melt onset (the average rate of changes is –8 days/decade), and later freeze-up (the average rate of changes is +4 days/decade). The average rates of changes in the total ice-free period duration are +12 days/decade for the period of 1979–2019. The main contribution to the formation of the total ice-free period duration is made by the dynamics of the starting dates of the period, which has high inter-annual variability and a large spatial diversity. The estimates of the ice-free period duration trends allowed for the detection of the most intensely changing areas within the Kara Sea coastal zone: the Yugorsky Peninsula, the western and northern coasts of the Yamal Peninsula. The study specifies the regional features of manifestation of sea ice climate changes within the framework of monitoring of the Russian Arctic coastal dynamics.