Environmental Conditions Impacting Northwest Passage Sea Ice

As Arctic sea ice loss increases open water in the Northwest Passage, understanding the drivers of sea ice concentration (SIC) becomes crucial. We investigate the environmental factors leading to extreme September SIC anomalies using composite analysis and linear regression. The composite analysis examines differences in atmospheric and sea ice variables for years with anomalously high and low SIC. The results show that differences in sea ice thickness and temperature emerge as early as January in years with high and low SIC. Dynamic variables, such as 10-m zonal wind, become important later, in May. A multiple regression model further reveals that sea ice thickness is the most influential predictor of September SIC from January to May. After May, thermodynamic variables (surface fluxes, cloud forcing, water vapor, and 2-meter air temperature) and dynamic processes that transport sea ice become more important. This work highlights that strongly anomalous September SIC in the Northwest Passage is the result of a sustained interplay between thermodynamic and dynamic processes.