Warming of the Intermediate Atlantic Water of the Arctic Ocean in the 2000s

This analysis evaluates the thermal state of the intermediate (depth range of 150–900 m) Atlantic Water (AW) of the Arctic Ocean, beginning in the 1950s and with particular focus on the transition from the 1990s to the 2000s and on changes during the 2000s. Using an extensive array of observations, the authors document AW warming trends across various time scales and demonstrate that the 2000s were exceptionally warm, with no analogy since the 1950s or probably in the history of instrumental observations in the Arctic Ocean. Warming in the recent decade was dominated by a warm AW pulse in addition to the underlying trend. Since 1997, the Canadian Basin experienced a faster warming rate compared with the Eurasian Basin. The relative role of the AW warmth in setting the net energy flux and mass balance of the Arctic sea ice is still under debate. Additional carefully orchestrated field experiments are required in order to address this question of ongoing Arctic climate change.