Sea ice in the Barents and Kara Seas: models versus reanalyses

Abstract. Satellite measurements indicate that the Barents and Kara Seas have experienced some of the most significant declines in sea ice concentration and an increase in sea surface temperature in the Arctic. Understanding the processes driving these changes is of utmost importance to assess the implications of climate change in the Arctic and globally. Given the observational limitations in these high-latitude areas, coupled models and reanalysis products play a key role. However, it is essential to better understand the strengths and limitations of such data products. Models are often evaluated on a pan-Arctic scale, but results might differ when considering sub-regions. This study examines two regional coupled ocean-atmosphere models (HIRHAM-NAOSIM 2.2 and RASM), two coupled model intercomparison project, phase 6 (CMIP6) models (CNRM-ESM2_1, NorESM2-MM), two regional ocean reanalyses (RARE 1.15.2 and TOPAZ 4B), one global reanalysis (ORAS5) and OSI-SAF satellite observations over the period 1991–2020. We focus on spring (March–April–May) and autumn (August–September–October) sea ice area and sea ice concentration, the edge of the sea ice, and the temperature of the mixed layer. The results show a statistically significant decrease in sea ice area and sea ice concentration in the satellite measurements and in all reanalyses. However, only one of the coupled models, HIRHAM–NAOSIM, exhibits a statistically significant sea ice decline in the Barents Sea, albeit weaker than in the reanalyses, and no coupled model shows a significant trend in the Kara Sea. Additionally, the reanalyses show a more pronounced warming of the mixed layer than the coupled models, particularly in autumn and in the Kara Sea.