Global trends of fronts and chlorophyll in a warming ocean

Abstract

Ocean fronts affect phytoplankton and higher trophic levels, including commercially important fisheries. As the oceans warm, uncertainty remains around the trends in fronts. Here we examine changes in sea surface temperature fronts (frequency, density, and intensity) and the concentration of chlorophyll, over recent satellite records (2003 – 2020) in ocean warming hotspots - areas that are warming faster than other parts of the ocean. Commonalities exist across hotspots with comparable dynamics. Most equatorial and subtropical gyre hotspots experienced a decline in frontal activity (frequency, density, strength) and chlorophyll concentration, while in high-latitude hotspots, frontal activity and chlorophyll concentration mostly increased. Continued warming may accentuate the impacts, changing both total biomass and the distribution of marine species. Areas with changing fronts and phytoplankton also correspond to areas of important global fish catch, highlighting the potential societal significance of these changes in the context of climate change.