The Beaufort Gyre (BG), the largest freshwater reservoir in the Arctic Ocean, periodically releases freshwater into the Atlantic Ocean. This freshwater, comprising meltwater and meteoric water, may significantly influence the Atlantic Meridional Overturning Circulation (AMOC), a critical component of the global climate system. Over the past 20 years, multi-year ice (MYI) melting has strongly increased in the BG, and this increase could also impact the AMOC. However, quantifying the loss of MYI volume is challenging due to the difficulties in estimating sea ice thickness. Here, we estimate the meltwater thickness (MWT) in the Beaufort Sea by integrating historical data of ocean temperature and salinity, supplemented by oxygen isotope (δ^18 O) data. Results show that the average MWT in the BG was ~8.31 m from 1990 to 2020. Following a regime shift in the Arctic sea ice in 2007, the average MWT increased from 7.80 m (from 1990 to 2007) to 9.21 m (from 2008 to 2020), with a MWT trend of 57 cm/decade. Lastly, the 3-year smoothed (from 1993 to 2020) time series of MWT and Arctic summer sea ice volume (from the PIOMAS reanalysis) are strongly correlated (r=-0.96), indicating MYI meltwater accumulation in the BG over the past two decades.

The Labrador Sea plays an important role in the Atlantic Meridional Ocean Circulation (AMOC) as one of the formation regions of the North Atlantic Deep Water, a major component of the AMOC. The Labrador Sea is connected to the Arctic Ocean via (1) Nares Strait and Baffin Bay, and (2) Fram Strait and the East Greenland Sea. The freshwater budget of the Labrador shelf and Baffin Bay is strongly influenced by the production-drift-melt cycle of sea ice and the melting of local glaciers. These freshwater inputs have a strong seasonal signature and have likely been affected by global warming. Besides, the region is at the receiving end of outflow coming from the Beaufort Sea (the largest freshwater reservoir in the Arctic Ocean). These freshwater flows can be defined as remote and have no seasonal signature. While mean Freshwater fluxes have been estimated in the region, their temporal variability and the contribution of local vs. remote anomalies are not well known yet. In this presentation, I will introduce you to a new methodology to estimate the freshwater (FW) input in Baffin Bay and the Labrador shelf. We use all available historical salinity data between 1950 and 2023 to produce a weekly climatology of FW input. I will show you the typical patterns of freshwater input in this region before analyzing the interannual anomaly. This climatology allows us to separate the anomaly into a seasonal cycle contribution (e.g., seasonal glaciers and sea ice melt) and a residual contribution (e.g. the export of freshwater from the Arctic). In the seasonal cycle contribution, we will see how the decrease in sea ice melt and increase in glacier melt cancel each other, and how a negative anomaly is advected from the east of Greenland to both the Labrador shelf and Baffin Bay. Lastly, we will see how this negative seasonal cycle contribution partly offsets the positive residual contribution which spreads from a freshening Arctic Ocean. As a result, the freshening of the subpolar Atlantic Ocean is, so far, less dramatic than expected.