Seasonal contrasts in recent Arctic warming processes: surface air temperature versus surface temperatureOA

Arctic warming has been widely documented, yet the relative contributions of processes controlling surface air temperature(SAT) and surface temperature(ST) warming remain insufficiently quantified, particularly between warm and cold seasons. Here, we use multiple reanalysis datasets to quantify Arctic SAT and ST warming from 1979 to 2021 through thermodynamic and surface energy budget analyses, with a focus on the seasonal contrast between warm season and cold season. We show that SAT warming in both seasons is primarily linked to an increase in the diabatic heating residual associated with surface warming, whereas cold season SAT warming is additionally enhanced by strengthened warm advection, which accounts for 33% of the total SAT increase. ST warming exhibits a stronger seasonal contrast. In the warm season, ST warming is driven jointly by enhanced downward longwave radiation, mainly associated with increased atmospheric water vapor, and sea ice albedo feedback, contributing 27% and 33% of the ST increase, respectively. In the cold season, ST warming is dominated by enhanced downward longwave radiation, with atmospheric water vapor, mid-level cloud cover, and a residual term mainly related to external greenhouse gas forcing contributing 36%, 16%, and 10%, respectively. The Arctic Ocean further modulates this seasonality by absorbing heat in the warm season and releasing it in the cold season, contributing 21% to cold season ST warming and providing an additional heat source for the lower atmosphere. These results demonstrate that recent Arctic warming cannot be interpreted from SAT or ST alone, but reflects seasonally distinct coupling among atmospheric heat transport, radiative feedbacks, sea ice loss, and ocean heat storage and release.