Longer and more frequent marine heatwaves over the past century

TLDR

Heatwaves are climatic extremes that can devastate ecosystems and economies, yet a global assessment of how marine heatwaves have changed over the past century has been lacking. The study analyzes global daily satellite, in‑situ, and gridded monthly temperature records to detect century‑long increases in marine heatwaves. From 1925 to 2016, marine heatwave frequency rose 34 %, duration 17 %, and annual heatwave days grew 54 %, largely driven by rising mean ocean temperatures.

Abstract

Heatwaves are important climatic extremes in atmospheric and oceanic systems that can have devastating and long-term impacts on ecosystems, with subsequent socioeconomic consequences. Recent prominent marine heatwaves have attracted considerable scientific and public interest. Despite this, a comprehensive assessment of how these ocean temperature extremes have been changing globally is missing. Using a range of ocean temperature data including global records of daily satellite observations, daily in situ measurements and gridded monthly in situ-based data sets, we identify significant increases in marine heatwaves over the past century. We find that from 1925 to 2016, global average marine heatwave frequency and duration increased by 34% and 17%, respectively, resulting in a 54% increase in annual marine heatwave days globally. Importantly, these trends can largely be explained by increases in mean ocean temperatures, suggesting that we can expect further increases in marine heatwave days under continued global warming.