The spatio-temporal variability, trends, and drivers of winter Arctic polynyas

Carmen Hau Man Wong , Céline Heuzé , Luisa Ickes, Lu Zhou

Polynyas, thin-ice or open water regions within the sea ice, have regularly been observed in the Arctic since satellite observations began in the 1970s. Their opening, in response to complex interactions between several drivers, significantly influences the regional weather and climate, ecosystem, and the global ocean. Yet their monitoring at the pan-Arctic scale is rare since their detection is not trivial. Here, we use three sea ice satellite data products to detect and investigate all Arctic polynya events since 1978, focusing on their winter locations and total area. We compute the polynyas’ recurrence percentage, total number and area, varying the sea ice concentration (30 – 60\%) and thickness (10 – 30 cm) thresholds to enhance our analysis robustness. We find that the most active polynya regions are along the coasts of the Laptev Sea, Kara Sea, Franz-Josef Land, northwestern Greenland, Beaufort Sea and Chukchi Sea. Both total and cumulative polynya areas have significant increasing trends in these regions and at the pan-Arctic scale between 1978-2024. In these regions, we find consistent positive correlations for atmospheric drivers (air temperature and wind speeds) with polynya openings and area, along with a strong increase in air temperature and a weak increase in extreme wind events. Temperature is correlated with polynya area extent and wind variables with polynya opening in most regions. Under rising temperatures and stronger extreme winds, our results suggest an increase in Arctic polynya activity, although polynyas might then extend into the open ocean, where different processes would drive their opening.