Arctic spin-up under melting sea ice

The Arctic sea ice has been rapidly declining due to climate change, with significant impacts on subpolar ocean dynamics and mid-latitude regional weather patterns. However, climate models (e.g., CMIP5 and CMIP6) show a large inter-model spread in projected sea ice changes, often underestimating the observed decline. This discrepancy may result from the poor representation of key ocean heat transport processes in the Arctic Ocean. Using a high-resolution global ocean-sea ice model (NEMO-SI3) with a 1/12° grid, forced at the surface by the Earth System Model UKESM1.1, we explored how atmospheric forcings, boundary currents, energetics, and horizontal/vertical mixing change with the declining Arctic sea ice from 1990 to 2100 under the SSP3-7.0 scenario. We investigated how these changes in the Arctic Ocean drive upward heat fluxes from Atlantic Water (AW) beneath the halocline to the ocean surface, and quantified their contribution to the ocean surface heat budget in an increasingly energetic Arctic. Finally, we demonstrated the critical role of enhanced upward AW heat flux in accelerating sea ice decline under a warming climate. Our study underscores the potential importance of processes linked to Arctic spin-up in the facilitation of heat transfer from the warm, sub-surface Atlantic Water to the cold, fresh Arctic Ocean surface, accelerating sea ice melt and influencing the global climate system.