In recent years, a pressing environmental issue has come to the forefront: the Arctic is warming at an accelerated rate compared to the rest of the Earth. This phenomenon, known as Arctic Amplification, is estimated to be causing the region to warm 2-4 times faster than the global average. The implications of this accelerated warming have been immediate and severe, contributing to the loss of sea ice and impacting fragile regional ecosystems.  However, little is known regarding the spatial and temporal variability in the onset of this accelerated warming across the region.  Here, we use in-situ observations as well as the ERA5 reanalysis, covering the period from the 1940s to the present, to show that there is considerable variability in the onset of Arctic Amplification across the region.  We show that the onset occurred earlier over the Arctic Ocean, during the 1950s and 1960s, as compared to the land, where it happened in the 1970s or later. In addition, the onset occurred earlier in the western Arctic but that the magnitude is warming is larger in the eastern Arctic where it is associated with the loss of sea ice. In addition, we identify evidence that the onset of Arctic Amplification was preceded by a cooling period most likely related to the end of the so-called Early 20^th Century Warming that was also the largest in the Arctic.  This cooling was most pronounced over the Canadian Arctic Archipelago and suggests that there was also regional variability in this period of warming as well.  This research highlights the complex nature of Arctic Amplification, and the timing of its onset as well as its connection with the Early 20^th Century Warming. As will be discussed, it provides insight into potential mechanisms responsible for the amplified warming in the region.

Arctic amplification, sea ice loss