Topography-albedo feedback reinforces the transition to a younger Arctic ice pack

Over the past few decades, the Arctic sea ice cover has rapidly shifted from consisting largely of thicker multiyear ice to predominantly thinner first-year ice. While ice-albedo feedback and reductions in overall ice extent have received a great deal of attention, here we explore this critical transition in ice type and the implications of a younger ice pack. We quantify a distinct, overlooked mechanism: the topography-albedo feedback. It provides fundamental context to recent losses of multiyear ice and shows how a younger, smoother ice pack amplifies Arctic warming. We develop a numerical model for the temporal evolution of an idealized sea ice pack, validated by field data. This quantitatively shows how meter-scale differences in surface topography mechanistically alter summertime melt pond evolution, dramatically lowering albedo for younger, smoother ice. We discuss how changes in the age of the Arctic ice pack, irrespective of changes in extent, induce this nonlinear feedback effect, reinforcing the shift toward a younger Arctic ice cover. Differences in surface roughness between multiyear and first-year sea ice drive a topography-albedo feedback, helping explain the observed transition to a younger ice pack, as suggested by an idealized sea-ice model validated by field observations.