Pacific Arctic sea ice loss resulting from atmospheric circulation-driven ocean heat transport

Abstract

Arctic sea ice is disappearing rapidly, but the melt comes from two different pathways: direct surface warming and the movement of warm water into the Arctic. This study focuses on the latter, i.e. dynamic melting, defined specifically as sea-ice loss caused by circulation-driven ocean heat transport, not mechanical ice motion or thermodynamic surface heating. Using CESM2 and its slab ocean counterpart, which preserves surface warming but suppresses changes in ocean heat transport, we approximately separate these two pathways and examine how they respond to different climate forcing agents. We find that atmospheric circulation-driven ocean heat transport accounts for roughly 25.2% of the total sea-ice loss on the Pacific side of the Arctic. Aerosols strengthen a North Pacific anticyclone that pushes more warm Pacific water through the Bering Strait, accelerating sea-ice decline even though aerosols themselves cool the surface. Greenhouse gases (GHGs), by contrast, generate atmospheric circulation patterns that partially offset their own thermodynamic warming. These results show that dynamic melting is strongly forcing-dependent and that models lacking realistic ocean-atmosphere circulation may systematically underestimate regional Arctic sea-ice vulnerability. Our framework separates a 12.2% thermodynamic sea-ice loss from a 16.3% coupled loss, implying that circulation-driven ocean heat transport explains about 25.2% of the total western Chukchi response. This dynamic contribution is forcing-dependent: aerosols enhance ocean-driven ice loss, offsetting 26.8% of their thermodynamic cooling effect, whereas GHGs produce an opposite-signed circulation response that partly damps thermodynamic ice loss.