Linkages Between the Arctic and the Earth System: What Should We Be Watching?

Increasingly prominent changes in the Arctic environment can interact with changes elsewhere in the earth system through a two-way coupling, enabling the Arctic to shape changes in other regions as well as be shaped by them. Five examples of ongoing changes illustrate these interactions. First, there are indications that the retreat of sea ice during the summer and autumn seasons may be impacting the weather and climate of regions beyond the Arctic. To the extent that enhanced open water warms the overlying air column and alters air pressure aloft, the loss of sea ice can impact the Arctic Oscillation and hence weather patterns affecting Europe, northern Asia and eastern North America. Second, methane releases from the seafloor of arctic shelves as well as arctic lakes has been documented in recent years, with suggested links to thawing permafrost. An acceleration of these releases may impact global atmospheric methane concentrations and hence radiative warming of the surface. Third, global sea level is already being impacted by freshwater losses from Greenland, mountain glaciers and smaller ice caps in the Arctic. The actual rates of these releases, and their relative contributions to sea level rise, are subject to considerable (factor-of-two) uncertainties, but they are associated with some of the more immediate and consequential global impacts of changes in the Arctic. Fourth, the Arctic interacts with the global ocean through exchanges inflows and outflows in the North Pacific and the North Atlantic. Measurements show increasingly warm inflows to the Arctic from both the Atlantic and the Pacific, although the inflowing warmth appears to occur in pulses. There are indications that the Pacific inflows have contributed to the recent sea ice reduction in the Chukchi-Beaufort sector, while the impact of circulating Atlantic water on the overlying sea ice is a topic of active investigation. Finally, a freshening of the subpolar North Atlantic seas as a result of ice melt, excess precipitation and river discharge has been detected in recent years. A role of the arctic’s freshwater variations in oceanic deep convection has long been suspected but has not been conclusively determined, although the potential implications for the climate of the North Atlantic and western Europe are substantial.