LAUSR

Warm water of subtropical origin flows northward in the Atlantic Ocean and transports heat to high latitudes. This poleward heat transport has been implicated as one possible cause of the declining sea-ice extent and increasing ocean temperatures across the Nordic Seas and the Arctic Ocean, but robust estimates are still lacking. Here, we use a box inverse model and more than 20 years of volume transport measurements to show that the mean ocean heat transport was 305 ± 26 TW for 1993–2016. A significant increase of 21 TW occurred after 2001, which is sufficient to account for the recent accumulation of heat in the northern seas. Ocean heat transport may therefore have been a major contributor to climate change since the late 1990s. This increased heat transport contrasts with the Atlantic Meridional Overturning Circulation (AMOC) slowdown at mid-latitudes and indicates a discontinuity of the overturning circulation measured at different latitudes in the Atlantic Ocean. An increase in ocean transport from the North Atlantic into the Nordic Seas and Arctic Ocean is warming the region. Observations from 1993 to 2016 show a significant increase in heat transport after 2001, with the heat being transported over the Greenland–Scotland Ridge.