Variability of the Arctic freshwater export west of Greenland: a proxy from 67 years of hydrographic observations on the Labrador Shelf
The Arctic Ocean is a major source of freshwater to the subpolar North Atlantic. A large export of Arctic freshwater has the potential to alter the salinity budget of the North Atlantic, freshen regions of deep-water formation, disrupt the meridional overturning circulation and impact on the European (and global) climate. However, the mechanisms controlling the storage and the export of low-salinity Arctic waters are not yet fully understood. The harsh conditions of this remote ocean hinder the hydrographic measurements in the region. Long-term observational programs in the Arctic are not available and the multidecadal variability of the export fluxes remain unclear. Our current knowledge is only from models and relatively recent observations.
In this talk I will present the first measurements of the multidecadal (1950 to 2016) variability of the Arctic freshwater export on its route west of Greenland, from observations. To do so, we analysed a dataset of repeated hydrographic observations at the Seal Island section, on the Labrador Shelf. These observations started in 1928 and have been repeated almost yearly in the summer since 1950. They lie downstream of the western route of the freshwater export (through the Candian Arctic Archipelago and Davis Strait) and thus capture the signal of the Arctic export water. First, I will introduce this dataset and its potential to inform about Artic freshwater export variability. I will continue presenting new understanding of the circulation on the Labrador Shelf. Using the 1/12º NEMO model (a coupled ice-ocean general circulation model) we are able to describe the details of the shelf circulation and to put the observations in context (i.e. how the observations capture and inform about the Arctic freshwater export variability). The model study also covers the fate of the Hudson Bay outflow and the role it plays in the Labrador shelf system. Finally, I will show how the observations serve as a proxy for the Arctic freshwater export and how it has varied from 1950 to present.
The results that will be discussed in this talk will focus on the role of this export as a major link between the freshwater budgets of the Arctic and the North Atlantic. The accumulated export has been quantified and compared to contemporary changes observed in the freshwater budgets of both basins. Here I will show how their variability is comparable throughout the time series and how the advection of freshwater west of Greenland is a key component of the balance of these freshwater budgets. The discussion will underline the relevance of the freshwater export west of Greenland to the total magnitude of the export (west and east of Greenland). Finally I will introduce the most recent changes in the export and how this is showing in the North Atlantic salinity budget.