Heat over the Pacific Arctic Continental Shelves: Recent Changes in Content, Surface Fluxes and Throughput

The thermal state of the Pacific Arctic coupled ocean and sea ice system attained previously unobserved conditions in recent years, suggesting fundamental alterations to the regional storage, modification, and throughput of heat. We examine the manifestation of these changes on the Bering and Chukchi Sea continental shelves using a combination of in situ moored and ship profile temperature and salinity data, atmospheric reanalysis data, and remotely sensed sea ice data. Analyses reveal a system responding strongly to the positive feedbacks of the well-known ice-albedo system superimposed upon long-term trends of oceanic warming. Mid-winter observations of ocean heat fluxed into the Arctic help explain the historically low sea ice concentrations observed in 2017, 2018 and 2019. Using integrations of a Pan-Arctic (PA) Regional Ocean Modeling System (ROMS) ice and ocean circulation hindcast model that does not use data assimilation, we assess the skill of this hindcast model in reproducing the basic nature of the recent changes. Such changes in the thermal environment have some known and many unknown but likely important consequences for the regional ecosystem and for the earth climate system.