Exploring Rapid Climate Change in the Arctic with the Arctic System Reanalysis

The Arctic System Reanalysis version 2 (ASRv2) is a multi-agency, university-led retrospective analysis (reanalysis) of the Arctic. ASRv2 blends atmospheric observations, satellite data, and output from the polar-optimized version of the Weather Research and Forecasting (WRF) model using the WRF 3-D variational data assimilation system. With the Arctic’s vital link to global climate change, this physically-consistent comprehensive integration of the regional climate and synoptic meteorology of the Greater Arctic for 2000-2017 provides a high resolution depiction in space (15 km horizontal resolution with 71-vertical levels) and time (3h) of the atmosphere-sea ice-land surface system. ASRv2 reproduces the near-surface and tropospheric variables well, and a broad-scale analysis of precipitation and radiative fluxes demonstrates improvement over courser reanalysis products. ASRv2’s high-resolution depiction of topography and detailed land surface, including weekly-updated vegetation and realistic sea-ice characteristics (fractional sea-ice, thickness, and snow cover), allows fine-scale coupled processes between the surface and atmosphere to be well captured. Using ASRv2, two case studies of rapid change in the Arctic are presented. Near-surface March air temperatures have increased by more than 20°C north of Novaya Zemlya in the Kara Sea and Barents Sea during since the early 2000s. Concomitantly, winter sea-ice around Novaya Zemlya has declined approximately 40% decline since 2000, enhancing sensible and latent fluxes from the ocean to the atmosphere, increasing atmospheric moisture, enhancing downward longwave radiation at the surface, leading to a large positive linear trend in downwind precipitation. Thus, ASRv2 permits a reconstruction of the Arctic system's rapid change since the beginning of the 21^st century.