Zahn, M., Fournier, S., Fenty, I.G., Steele, M., Wood, M., and Gaube, P. (2025)
Presented at:
AGU Annual Meeting 2025Salinity controls upper ocean stratification in the Arctic and plays a critical role in sea ice formation by modulating vertical heat exchange and surface cooling. While freshwater discharge from large Arctic rivers is an important component of the Arctic Ocean’s freshwater budget, its influence on sea ice formation remains poorly understood. Here, we use satellite observations and a high-resolution coupled ocean-sea ice model to investigate how freshwater anomalies impact the timing and spatial distribution of fall sea ice formation in the Beaufort Sea, a region that has seen some of the most significant sea ice loss and freshwater accumulation in the Arctic. We find that both satellite and model data consistently show early formation of an ice bridge across the Mackenzie River freshwater plume, extending from the coastline to the offshore ice edge. The timing and extent of this ice bridge vary interannually in association with freshwater distribution patterns. Enhanced salinity stratification from Mackenzie River discharge is associated with reduced upper ocean heat content and earlier sea ice onset by three weeks on average relative to nearby saltier waters. These findings highlight the important role of terrestrial freshwater discharge in shaping regional sea ice processes and suggest that future changes in Arctic runoff may influence sea ice seasonality and extent.
