Tracing overflow water from the origin in the Nordic Seas to the Greenland-Scotland Ridge

Ailin Brakstad, Geophysical Institute, University of Bergen, Bergen, Norway; Bjerknes Centre for Climate Research, Bergen, Norway, Kjetil VĂ¥ge, University of Bergen, Bergen, Norway, Geoffrey Gebbie, Woods Hole Oceanographic Institute, Woods Hole, United States and Emil Jeansson, NORCE Norwegian Research Centre, Bjerknes Centre for Climate Research, Bergen, Norway
Dense water formed in the Nordic Seas spill across gaps in the Greenland-Scotland Ridge as overflow plumes that feed the lower limb of the Atlantic Meridional Overturning Circulation. Open questions remain regarding where and how these dense overflow waters are formed and transported to the ridge. In this study we employ a recently developed inverse method called Total Matrix Intercomparison (TMI), which combines hydrographic and geochemical observations between 1980 and 2019 to investigate the origin, pathways, and final composition of the overflows from the Nordic Seas. One major advantage of the TMI method is that pre-defined source water masses are not required. Instead every surface grid point is considered a potential source, and the inversion resolves the pathways that connect each interior grid point to the surface. These pathways are then used to trace the water masses constituting the overflows back to their origins. In particular, we use the inversion to estimate the relative contribution from the Iceland and Greenland Seas to the overflows both east and west of Iceland.