Results from the development and analysis of a novel temperature dataset for the high latitude North-West Atlantic are presented. The new 1° gridded dataset (“ATLAS”) has been produced from about 13,000 Argo and 48,000 marine mammal (hooded seal, harp seal, grey seal and beluga) profiles spanning 2004–8. These data sources are highly complementary as marine mammals greatly enhance shelf region coverage where Argo floats are absent. ATLAS reveals distinctive boundary current related temperature minima in the Labrador Sea (−1.1°C) and at the east Greenland coast (1.8°C), largely absent in the widely-used Levitus'09 and EN3v2a datasets. The ATLAS 0–500 m average temperature is lower than Levitus'09 and EN3v2a by up to 3°C locally. Differences are strongest from 0–300 m and persist at reduced amplitude from 300–500 m. Our results clearly reveal the value of marine mammal-borne sensors for a reliable description of the North-West Atlantic at a time of rapid change.