| Summary: | The densest waters in the deep limb of the Atlantic meridional overturning circulation (AMOC) consist of overflow waters from the Nordic Seas: Denmark Strait Overflow Water (DSOW) and Iceland-Scotland Overflow Water (ISOW). These overflow waters are then substantially modified along their pathways by the entrainment of overlying intermediate waters and are eventually exported from the sub-polar gyre as Lower North Atlantic Deep Water. Since 2014, the OSNAP array has provided new insights into the sub-polar overturning circulation, including key boundary current arrays deployed across the Reykjanes Ridge, off East and West Greenland, and along the western side of the Labrador Sea. Here, using the OSNAP array data between 2014 and 2020, we quantify the mean transports of overflow waters along the deep boundary pathways, as well as recirculation within the Labrador Sea and Irminger Basin. Changes in the water properties of ISOW and DSOW as they advect around the deep subpolar gyre are also assessed. We further examine the traditional use of potential density of 27.88 kg/m 3 as the interface between ISOW and DSOW, and assess whether water mass boundary definitions need to change with increasing distance and entrainment along the deep circulation pathways.
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