09:15 〜 09:30
[ACG52-02] A new look at the Baffin Bay and Labrador Shelf freshwater content: estimation of a weekly climatology and interannual anomalies
キーワード：Baffin Bay and Labrador Sea, Subarctic Atlantic, Freshwater budget, Salinity, Sea Ice melt, Glacier melt
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. An example of such remote freshwater signal is the Great Salinity Anomaly of the early 1970s, which lowered the upper ocean salinity in the Labrador Sea by nearly 0.4. 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 study, we developed 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. The climatology allows us to highlight the typical patterns of freshwater fluxes in this region such as sea ice melting near the North Water Polynya in May-June, or glacier melting off the coast of Greenland and Baffin island from July to September. Importantly, 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, the decrease in sea ice melt and increase in glacier melt cancel each other in the northern Baffin Bay, whereas a negative anomaly, which we interpret as the reduction in sea ice melt east of Greenland, is advected from the east of Greenland to both the Labrador shelf and the central Baffin Bay. Lastly, the analysis of the residual contribution reveals a large increasing trend in remote FW input, which started around the mid-2000s. We attribute this signal to the melting of the multi-year ice in the Arctic Ocean, whose signal propagates along the coast of Greenland before reaching our study region. This dramatic increase in remote freshwater input is set to lower the upper ocean salinity in the Labrador Shelf to levels even below those witnessed during the Great Salinity Anomaly.
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. An example of such remote freshwater signal is the Great Salinity Anomaly of the early 1970s, which lowered the upper ocean salinity in the Labrador Sea by nearly 0.4. 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 study, we developed 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. The climatology allows us to highlight the typical patterns of freshwater fluxes in this region such as sea ice melting near the North Water Polynya in May-June, or glacier melting off the coast of Greenland and Baffin island from July to September. Importantly, 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, the decrease in sea ice melt and increase in glacier melt cancel each other in the northern Baffin Bay, whereas a negative anomaly, which we interpret as the reduction in sea ice melt east of Greenland, is advected from the east of Greenland to both the Labrador shelf and the central Baffin Bay. Lastly, the analysis of the residual contribution reveals a large increasing trend in remote FW input, which started around the mid-2000s. We attribute this signal to the melting of the multi-year ice in the Arctic Ocean, whose signal propagates along the coast of Greenland before reaching our study region. This dramatic increase in remote freshwater input is set to lower the upper ocean salinity in the Labrador Shelf to levels even below those witnessed during the Great Salinity Anomaly.