The interannual variability of potential temperature in the central Labrador Sea

The interannual variability of potential temperature in the central Labrador Sea is studied with a suite of numerical simulations with an eddy-resolving regional ocean model and compared with available observations. The model successfully reproduces the observed variations in potential temperature at depths comprised between 150 and 2000 m over the period 1980-2009, capturing also the warming trend of the last decade and the deep water formation event in 2008. The suite of experiments allows for quantifying the contribution from the physical forcings responsible for the interannual variability of potential temperature in the region. The local atmospheric forcing drives the interannual signal by driving convection, while the incoming current system along the east coast of Greenland is responsible for about half of the warming trend (similar to 0.3-0.4 degrees C) during the last decade through restratification process. The lateral transport of Irminger water in the convective region into the central Labrador Sea is further analyzed integrating a passive tracer. It is found that the overall amount of Irminger water transported in the convective region of the Labrador Sea is directly correlated with the amount of vertical convective mixing. In the last decade, following the decrease in convective activity, the model reveals a substantial decrease in concentration of Irminger Current water below 500 m in the Labrador Sea interior: by 2010 the overall amount is less than half than in the previous 20 years.