Fig. 1

Schematic diagram of the currents that supply dense water to Denmark Strait. The colours indicate warm (red) to cold (green) transformation. Fresh, low-density water also flows along the Greenland continental slope (not shown). Hydrographic profiles from the western Iceland Sea region, outlined in black, document the seasonal cycle of the fresh surface layer (Fig. 4). The red line represents a hydrographic section obtained from a research ship in August 2012. The grey lines are glider trajectories and the orange and yellow lines indicate transects from the two gliders that were operating in the western Iceland Sea in February and April 2016, respectively. The dashed lines along the Greenland shelf represent the mean 50% sea ice concentration³⁸ contours from winter (Jan–Mar) 2016 (white) and decadal means from 1980–1989 (red), 1990–1999 (orange), and 2000–2009 (yellow). The acronyms are: EGC = East Greenland Current; NIJ = North Icelandic Jet; NIIC = North Icelandic Irminger Current; NAC = Norwegian Atlantic Current. The inset shows the winter mean sea ice concentration within the western Iceland Sea region outlined in black. The red lines are decadal means, and the dashed red line represents the mean from 2010 to 2016