Simulating 135 years of post-hatchling sea turtle dispersal in a dynamic North Atlantic Ocean

After emerging from sandy beaches, sea turtle hatchlings enter oceans where surface circulation influences their distribution and survival. Studies report associations between sea turtle nesting and climate indices in the years and decades prior to nesting. Here we investigated the relationship between climate indicators and predicted dispersal of hatchling sea turtles to better understand the mechanisms by which climate may influence sea turtle population dynamics. We used the Simple Ocean Data Assimilation (SODA) model to simulate dispersal for 135 cohorts of loggerhead sea turtles (Caretta caretta) from nesting locations along the eastern U.S. coast. Simulations revealed 68% of 6.075 million particles traveled east of 60°W (NEA), with 78% dispersing to within 501-2000 km of a reference location in the Azores Islands, Portugal. Time series analysis revealed the lowest NEA dispersal during 1896-1900, but highest dispersal a century later. NEA particle dispersal significantly (and positively) correlated with eastward current, salinity, cyclonic activity, ocean temperature, solar irradiation, and (since 1958), atmospheric CO₂. These findings, coupled with significant associations between climate indices and oceanographic conditions extracted from the SODA model, suggest valuable context can come from further examining lagged climate associations with population trends for sea turtles.