Large-Scale Ocean-Atmosphere Interactions Drive Phytoplankton Accumulation in the Northern Antarctic Peninsula

Abstract

The northern Antarctic Peninsula (NAP) region is a highly productive ecosystem that supports a large krill-based food web. In summer 2006, the NAP region had substantially elevated phytoplankton biomass, with surface chlorophyll-a concentrations that reached the greatest level during 2001–2023. Using the long-term in situ data from the U.S. Antarctic Marine Living Resources program, satellite observations, and ERA5 reanalysis products, the mechanisms of the elevated chlorophyll-a anomalies in summer 2006 were analyzed. The results suggest that the position of the Amundsen Sea Low (ASL) shifted considerably westward that summer, resulting in strong positive sea level pressure anomalies west of the NAP, which induced southerly wind anomalies and reduced the advection of moist airflow toward the NAP. This in turn reduced the cloud coverage and increased photosynthetically available radiation over this region, which directly increased the phytoplankton photosynthesis. The intensified radiation also increased the ocean temperature and strengthened stratification, which increased phytoplankton growth rates and allowed phytoplankton to accumulate in the upper euphotic zone. This work underlines the important role of coupled atmospheric-oceanic processes in generating large phytoplankton biomass in the NAP region.