Neil T Lewis, William Seviour, Hannah Roberts-Straw, James Screen

We investigate the response of surface temperature persistence, quantified using a lagged autocorrelation, to imposed Arctic sea-ice loss in coupled model experiments. Sea-ice loss causes increases in persistence over ocean in midlatitudes and the low-Arctic, which are of a similar magnitude to the total response to climate change in these regions. Using an idealised model, we show that sea-ice loss induces a slowing of meridional wind anomalies, which can drive the midlatitude persistence increase obtained in coupled models. Sea-ice loss should induce persistence increases in the Arctic, through its effect on the surface heat capacity. However, in coupled models with imposed sea-ice loss, persistence increase in the Arctic is essentially absent. We suggest that methods used to constrain sea-ice in coupled models may spuriously reduce the effects of sea-ice loss on persistence.