Internal variability in projections of twenty-first-century arctic sea ice loss: Role of the large-scale atmospheric circulation

Each member is subject to an identical greenhouse gas emissions scenario and differs only in the atmospheric model component's initial condition. September Arctic sea ice extent trends during 2020-59 range from −2.0 × 10⁶ to -5.7 × 10⁶ km² across the 39 ensemble members, indicating a substantial role for internal variability in future Arctic sea ice loss projections.

A similar nearly threefold range (from -7.0 × 10³ to −19 × 10³ km²) is found for summer sea ice volume trends. Higher rates of summer Arctic sea ice loss in CCSM3 are associated with enhanced transpolar drift and Fram Strait ice export driven by surface wind and sea level pressure patterns. Over the Arctic, the covarying atmospheric circulation patterns resemble the so-called Arctic dipole, with maximum amplitude between April and July.