Decadal wind-driven east-west asymmetry of chlorophyll-a in the Ross Sea region

The Ross Sea is the most productive region of phytoplankton around the Antarctic margin and supports the marine food web in the Southern Ocean. However, the long-term variability of chlorophyll-a production in this region is not fully understood. Here we explore the long-term changes in austral summer chlorophyll-a concentrations in the Ross Sea region across the 1997-2023 period. The results indicate a clear east-west asymmetric change in chlorophyll-a concentration between 180°W-130°W: decreasing (increasing) in the west (east), which is dominated by changes in wind forcing and sea ice coverage. Cyclonic wind anomalies drive regional sea ice divergence off Marie Byrd Land, while increasing coastal easterly winds off Marie Byrd Land and southerly wind anomalies in the western Ross Sea drive regional sea ice convergence. As a result, the availability of photosynthetically active radiation (PAR) increased (decreased), promoting (limiting) phytoplankton growth in the eastern (western) zone. The warming SST and potential increases in dissolved iron may also contribute to the chlorophyll-a blooms in the eastern zone.