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Abstract:
Located between Greenland and Iceland, the Denmark Strait is a key gateway for the transport of dense waters formed in the Nordic Seas to the Subpolar North Atlantic. There, the Denmark Strait Overflow Water (DSOW) spills over the shallow sill of the Strait into the Irminger Basin, feeding the lower limb of the Atlantic Meridional Overturning Circulation (AMOC). DSOW has high oxygen content, reflecting its recent ventilation by buoyancy loss in the Nordic Seas. As it spills over the sill and spreads southward, DSOW is thought to entrain Arctic-origin, Atlantic-origin, and Labrador Sea Waters (LSW). However, the proportions of water masses that become entrained into the overflow plume further downstream in the Irminger Basin and their variability over seasonal and interannual timescales remain unclear. Additionally, oxygen variability in DSOW and its relationship with oxygen content of the LSW in the Irminger Basin is poorly understood. Here we use data from BGC-Argo floats and an optimum multiparameter (OMP) framework for water-mass decomposition to address the question: How does the oxygen content of DSOW vary in the Irminger Basin and how is this observed variability connected to changes in the relative contributions of water masses (e.g., LSW, Atlantic-origin Water) that become entrained in the overflow plume? This study will have broad implications for assessing the role of overflow waters in the oxygenation of the North Atlantic Basin.
