The Impact of Ocean Margin Processes in the Labrador Sea on the Atlantic Meridional Overturning Circulation
Final Report Abstract
The overarching hypothesis was: Processes near the ocean margin in Labrador Sea are instrumental for both fast export of newly transformed LSW and for Eulerian downwelling. The main goals were to assess the seasonality in both the export of newly formed LSW at the western boundary of LS (goal 1) and the downwelling along the boundary of LS (goal 2). The proposed work could unfortunately not be conducted in the way it was intended because of the lack of sufficient recoveries of bottom pressure recorders. This meant that the analyses required to perform in order to accomplish goal 2 were not possible. The main results are: We found a strong seasonality of LSW properties exported in the DWBC in terms of salinity, with the freshest conditions found around May and the strongest seasonal salinity amplitudes found at the inshore flank of the DWBC. We interpreted this such, that the injection of newly transformed, fresh LSW into DWBC to occur far upstream of the 53°N array. The second finding is that superimposed on the pronounced but gradual (decadal-scale) transition to more saline and warm conditions in the LSW, a strong year-to-year change in the arrival time and intensity of newly transformed LSW in the DWBC is observed. The can in part be related to the intensity of convection (i.e. intensity of heat loss to the atmosphere) in the respective years. Strong convection seems to be connected to a much earlier arrival of newly transformed LSW (as early as February) and larger amplitudes of the freshwater anomalies. Whether this is mainly due to the fact, that the center of convection was located closer to the 53°N array or whether the DWBC circulation was spun-up as a result of the anomalous atmospheric forcing (or both), still needs to be resolved, and represents a very relevant future research topic for the understanding of the coupling of LSW formation in Labrador Sea and the strength of the meridional overturning circulation.
