Variability of Labrador Sea Water in the central subpolar North Atlantic from the late 1990s to the late 2010s

Available hydrographic data of the past two decades have revealed substantial variations in the hydrographic properties of North Atlantic Deep Water (NADW) components in their respective source regions. Here, we report on a hydrographic data obtained from ship surveys and profiling Argo floats that all have been collected outside the formation regions in the central subpolar North Atlantic. There, a repeat hydrography line following the western flank of the Mid-Atlantic Ridge (MAR) from about 47°N to 52°30’N was sampled almost annually since 2008 with the most recent survey having been made in 2019, and less frequently in earlier years. We investigate hydrographic changes observed in the NADW components along this line over the past two decades and focus on the upper part of NADW, the Labrador Sea Water (LSW). The location of the least diluted LSW at the MAR often coincides with the location of the Subarctic Front separating the fresh subpolar waters from the saline waters imported by the North Atlantic Current. We thus connect changes in the water mass properties observed next to the MAR to the changing formation history of LSW as well as to spatial shifts in the location of the frontal system and variability in the circulation patterns.