Positive Association Between Coastal Sea Surface Temperatures and Humid Heat Stress on Nearby Land

Abstract

Large populations along Earth's coastlines are exposed to climate hazards including extreme humid heat. Considering observed coastal ocean warming and increased coastal marine heatwave (MHW) activity, we seek to uncover if, how, and where coastal ocean temperatures are linked with heat and humidity on land nearby. We analyze near‐coastal sea surface temperatures (SST) and corresponding land heat characteristics at 1,474 global coastal locations from 1990 to 2023 and find coastal MHW occurrence is associated with positive terrestrial heat/humidity anomalies across seasons, and that warmer coastal SST are associated with more frequent hot/humid extremes on land. We highlight an increase in concurrent marine and terrestrial (THW) heatwave days at many locations, which appears largely driven by MHW trends. Coastal MHW, THW, and concurrent events share similar buildup characteristics, but concurrent and MHW events are more humid than THW and display temperature anomalies which peak at the surface rather than aloft.