Fig. 5: Atmospheric lower boundary response to historical sea-ice loss.

a Regression map of early-winter (November–December) BKS SIC against early-winter SIC during 1979–2019, scaled by the early-winter BKS SIC difference between BKS low- and high-SIC years (1). b Differences of the prescribed early-winter SIC between the atmosphere-only BKS historical low- and high-SIC simulations (atm_lo and atm_hi). c 200-year simulated differences of early-winter SIC between the coupled BKS historical low- and high-SIC simulations (cpl_lo and cpl_hi). d Differences between c and b. e–h are the same as (a–d), but for early-winter SST (°C). i Regression map of early-winter BKS SIC against early-winter surface upward THF during 1979–2019, scaled by the early-winter BKS SIC difference between BKS low- and high-SIC years (W/m²). j 200-year simulated differences of early-winter surface upward THF between the atmosphere-only BKS historical low- and high-SIC simulations (atm_lo minus atm_hi). k The same as (j), but for the coupled BKS historical low- and high-SIC simulations (cpl_lo minus cpl_hi). l The differences between k and j (k minus j). Cross-hatching denotes the statistical significance at the 95% confidence level according to bootstrap resampling.