Drifting To Daylight How Migration Routes for the Arctic Tern Are Influenced by Climate Change Induced Global Wind Pattern Changes

Abstract

Some Arctic tern populations migrate from Antarctic regions to Svalbard during boreal spring (March-May). During this migration, they encounter and are greatly influenced by the wind patterns over the Atlantic Ocean. Making use of tailwinds in the Atlantic Ocean, the migration route of Arctic terns has an S-shape. This study explored how climate change induced wind pattern changes in the Atlantic Ocean influence the migration route of the Svalbard population of Arctic terns. This was achieved by exploiting a least cost path (LCP) model using near surface wind (ERA5) and chlorophyll A (ESACCI-OC) data. First, a set of sensitivity experiments testing the impact of departure day and starting location were done. Then the model was fine-tuned and validated for an ensemble of four CMIP6 Earth System Models (ESMs) against the Arctic tern geolocator tracking data. In the present study, a total of 61 geolocators were used to log the migration paths of Arctic terns. Afterwards, future wind and chlorophyll A data from the ESM ensemble under four different climate scenarios (SSP119, SSP126, SSP245, and SSP585) were used to explore the changes in wind patterns and migration routes. The departure day was found to have a significant impact on the migration route. However, no clear departure window was observed. Furthermore, no significant changes in the migration route were found for all climate scenarios, though minimal changes were observed. Accordingly, no link between the expansion of the Hadley cell and changes in the migration route was found. Upgrading the model to 3D and increasing the spatial resolution could give more insight into migration routes and allow for a better representation of the complex wind pattern changes.