Variability of Atlantic Water on shelf of Northeast Greenland: Patterns and Drivers

During the last two decades, rising ocean temperatures have significantly contributed to accelerated mass loss of the Greenland Ice Sheet. The melting of the ice sheet is now the single largest contributor to global mean sea level rise. Warming subsurface Atlantic Intermediate Water (AIW) found on the wide continental shelf of Northeast Greenland and in the fjords interacts with marine-terminating glaciers, which until recently were considered stable, and causes their rapid melting and retreat. The main source of these waters is the westward recirculation of subducted Atlantic Water (AW) in Fram Strait, which has shown a warming of up to 1°C over the past few decades.

The variability of the AIW on the Northeast Greenland (NEG) shelf is investigated using historical hydrographic observations and high-resolution numerical simulations with the Finite-Element-Sea ice-Model (FESOM2). There is excellent agreement of both the mean and long-term distribution of AIW on the shelf between the model and observations. The two main circulation regimes of AW in Fram Strait are also well-replicated by the numerical simulations.

The dominant variability of the AIW temperature occurs at interannual timescales. A shelf-wide process drives this variability of AIW temperatures. EOF analysis shows that over 81% of the variance of maximum AIW temperatures is explained by the first mode, which features a monopol-like pattern across the whole NEG shelf. There is a strong co-variability between the maximum AIW temperature and the volume transport of AIW towards the glaciers, which moves through the deep trough system as a bottom intensified jet and recirculates on the shelf. A connection between the AIW temperatures on the shelf and the AW boundary current along the shelf edge suggests the East Greenland Current influences AIW properties. An increase in strength of the current corresponds to greater AIW volume transport through the trough system, and also warmer AIW and AW temperatures on both the shelf and off the continental slope. This suggests that the drivers of variability of AIW temperatures on the NEG shelf may be found further offshore, with a connection to AW circulation in Fram Strait.