Effect of sea ice loss on Earth's energy budget depends on its spatial pattern

Abstract The global mean sea ice concentration (SIC) is decreasing under global warming, but the effect of SIC reduction on Earth’s energy budget remains uncertain. Here we show that SIC-induced radiation anomalies at the top of the atmosphere are sensitive to the location of SIC reduction in each season, and therefore the impact of SIC reductions on Earth’s energy balance depends on their spatial pattern. SIC-induced radiation anomalies warm the Earth system under CO2-induced long-term global warming, but the SIC-induced radiation anomalies during specific historical periods could counterintuitively even cool the Earth system if the SIC reduction occurs with certain spatial patterns. Idealized experiments indicate that SIC-induced surface warming is greater in the Arctic regions, resulting in a more negative Planck feedback. Global low cloud fraction responses to Arctic and Antarctic SIC reduction are also distinct, leading to more negative SIC-cloud feedback in some Arctic regions. As a result, SIC reduction in some Arctic regions induces negative Planck and cloud feedbacks that overwhelm the positive sea ice albedo feedback, resulting in a net cooling radiative effect on the planet, while the radiative effect of SIC reduction over most Antarctic regions warms the earth.