Arctic Sea Ice and Eurasian Climate:A Review

The Arctic plays a fundamental role in the climate system and has shown significant climate change in recent decades,including the Arctic warming and decline of Arctic sea-ice extent and thickness. In contrast to the Arctic warming and reduction of Arctic sea ice, Europe, East Asia and North America have experienced anomalously cold conditions, with record snowfall during recent years. In this paper, we review current understanding of the sea-ice impacts on the Eurasian climate.Paleo, observational and modelling studies are covered to summarize several major themes, including： the variability of Arctic sea ice and its controls; the likely causes and apparent impacts of the Arctic sea-ice decline during the satellite era,as well as past and projected future impacts and trends; the links and feedback mechanisms between the Arctic sea ice and the Arctic Oscillation/North Atlantic Oscillation, the recent Eurasian cooling, winter atmospheric circulation, summer precipitation in East Asia, spring snowfall over Eurasia, East Asian winter monsoon, and midlatitude extreme weather; and the remote climate response（e.g., atmospheric circulation, air temperature） to changes in Arctic sea ice. We conclude with a brief summary and suggestions for future research.

Ice bottom evolution derived from thermistor string-based ice mass balance buoy observations

Digital information on sea ice extent,thickness,volume,and distribution is crucial for understanding Earth's climate system.The Snow and Ice Mass Balance Apparatus(SIMBA)is used to determine snow and ice temperatures in Arctic,Antarctic,ice-covered seas,and boreal lakes.Snow depth and ice thickness are derived from SIMBA temperature regimes(SIMBA_ET and SIMBA_HT).In warm conditions,SiMBA_ET temperature-based ice thickness may have errors due to the isothermal vertical profile.SIMBA_HT provides a visible ice-bottom interface for manual quantification.We propose an unmanned approach,combining neural networks,wavelet analysis,and Kalman filtering(NWK),to mathematically establish NwK and retrieve ice bottoms from various SIMBA_HT datasets.In the Arctic,NWK-derived total thickness showed a bias range of-5.64 cm to 4.01 cm and a correlation coefficient of 95%-99%.For Baltic Sea ice,values ranged from 1.31 cm to 2.41 cm(88%-98%correlation),and for boreal lake ice,-0.7 cm to 2.6 cm(75%-83%correlation).During ice growth,thermal equilibrium,and melting,the bias varied from-3.93 cm to 2.37 cm,-1.92 cm to 0.04 cm,and-4.90 cm to 3.96 cm,with correlation coefficients of 76%-99%.These results demonstrate NWK's robustness in retrieving ice bottom evolution in different water environments.

Observations and geophysical value-added datasets for cold high mountain and polar regions

The Earth’s cold regions,in particular,the Arctic,Antarctic,and High-Mountain Asia(HMA),are dominated by the changing cryosphere and have inherently fragile environ-ments(Guo,2018;Kulmala,2018;Guo et al.,2020;Li et al.,2020;Yao et al.,2022;Group on Earth Observations(GEO),2022).Warming has reshaped the regions where the cryo-sphere is located;it has also been affecting water availability in lowland downstream areas,opening up northern sea routes,and affecting the stability of roads and infrastruc-ture in permafrost rich areas(Pulliainen et al.,2019).Changes in the phase of water and its consequences have thus had a major impact on the environment and the lives of billions of people.