09:30 〜 09:45
[ACG52-03] Transition from pack ice zone to marginal ice zone in the Arctic Ocean and its impact on the changes in the atmosphere-sea ice-ocean system
キーワード：Arctic sea ice loss, Marginal ice zone, Arctic amplification
With the rapid loss of Arctic sea ice during the recent decades, the pack ice zone (PIZ) is gradually transiting to the marginal ice zone (MIZ), but its impacts on the atmosphere-sea ice-ocean system are still unclear, especially for the Arctic Amplification. This study identifies the transition region from PIZ to MIZ in the Arctic during 1979–2021, and compares changes in the atmosphere-sea ice-ocean system over the transition region to those over the pan Arctic Ocean. The transition from PIZ to MIZ provides amplifications of changes in ice thickness and ice-wind speed ratio against those over the pan Arctic Ocean in late summer and autumn. Such transition in summer increases the absorption of shortwave radiation by the ice-ocean surface (0.5 W m–2 yr–1, P<0.001), contributing more than 60% to the pan Arctic Ocean, further increasing upper ocean heat content (0.04×108 J m–2 yr–1, P<0.001); while that in winter enhance the releases of surface turbulent heat fluxes, increasing 2-m air temperature by nearly 8 K in October–March in 1979–2021, about twice that over the pan Arctic Ocean, though the extent of transition region only occupies about 15%. Since 2001, the June–August MIZ area fraction and sea ice concentration in the region from PIZ to MIZ provide better forecast skill for September Arctic sea ice extent than sea ice concentration and extent over the pan Arctic Ocean. Results highlight the importance of MIZ changes to the Arctic climate system.