Rapid Export of Waters Formed by Convection Near the Irminger Sea's Western Boundary

The standard view of the overturning circulation emphasizes the role of convection, yet for waters to contribute to overturning, they must not only be transformed to higher densities but also exported equatorward. From novel mooring observations in the Irminger Sea (2014–2016), we describe two water masses that are formed by convection and show that they have different rates of export in the western boundary current. Upper Irminger Sea Intermediate Water appears to form near the boundary current and is exported rapidly within 3 months of its formation. Deep Irminger Sea Intermediate Water forms in the basin interior and is exported on longer time scales. The subduction of these waters into the boundary current is consistent with an eddy transport mechanism. Our results suggest that light intermediate waters can contribute to overturning as much as waters formed by deeper convection and that the export time scales of both project onto overturning variability.

Global Irminger