Enhanced westerlies drove penguin movement at 1000 yr BP on Ardley Island, west Antarctic Peninsula

Understanding responses by penguins to climate change in Antarctica is often complicated by other factors including microclimate and landscape effects. Here, we analyze an ornithogenic sediment profile to reconstruct penguin occupation history on the eastern side of Ardley Island, west Antarctic Peninsula, and synthesize the results from various studies on Ardley Island in the past 20 years. Penguins have inhabited the eastern side of this island since about 900 yr BP, with populations significantly increasing from ∼500 yr BP. On the western side, delineated by the Ardley Ridge Line, penguins began to abandon nest or molt sites at ∼1000 yr BP. By the time of 500 yr BP, the abandonment and population decline became a common tendency on the west side. This shift in occupation areas was likely driven by local microclimate and a change in wind patterns causing more snow to accumulate on the west side of the island. We found a linkage between this penguin movement and the Southern Westerly Winds, which became stronger at ∼1000 yr BP and impacted local conditions at Ardley Island, likely induced by more positive Southern Annular Mode (SAM). These results indicate that island topography, wind and snow patterns, combined with large-scale climate forcing can be just as important in determining penguin distribution as temperature and other environmental factors. This study provides a new perspective for investigating the possible impact of microclimate and site topography on penguin behavior.