Topography-Albedo Feedback and the Shifting Arctic Ice Pack

Over the past few decades, the Arctic sea ice cover has shifted from consisting of largely multiyear ice to predominantly seasonal ice. With a relatively smooth surface, seasonal ice has significant topographical differences compared to rough, hummocky multiyear ice. During melt pond formation and evolution, pond geometry is determined by local surface topography. We utilize level set and partial differential equation modeling approaches to quantitatively understand the connection between sea ice surface topography, albedo during melt pond evolution, and the shift away from multiyear ice. We find that the smoother topography of seasonal sea ice leads to rapid melt pond formation and coverage, lowering albedo. We investigate how this effectively lowers overall Arctic albedo and enhances ice-albedo feedback as the year-to-year proportion of seasonal to multiyear ice increases. Further, we illustrate how the smoothing of the Arctic ice pack induces a novel, longer timescale feedback – the topography-albedo feedback. We propose that topography-albedo feedback is a key mechanism fueling the shift away from multiyear ice, amplifying climate change.