A regime change in Arctic sea ice growth

The decline in Arctic sea ice thickness (SIT) is a key indicator response of the cryosphere to anthropogenic climate change. While the drivers of this decline are debated, they involve a competition between the ice-albedo positive feedback that enhances ocean heat content and the thin-ice negative feedback enhancing ice speed and alters dynamic-thermodynamic interactions. To date, pan-Arctic assessments of the dynamic and thermodynamic responses have been limited to the CryoSat-2 era (2010–Present Day).Here we apply recently developed thickness products to produce novel 30-year records of Arctic sea ice volume (SIV) budget, resolving dynamic and thermodynamic terms. Our residual growth is validated on IMB buoy data and has a slight positive bias of +0.14 m-1 and a strong seasonal cycle. We identify a step change increase of 1,300 km-3 in thermodynamic growth, coincident with the pause in volume decline of the winter of 2007/08, representing a regime change in system behaviour where 76\% of seasonal growth is explained by the mean thickness of the surviving sea ice (p