Ocean warming weakens the sea–land breeze in coastal megacities

This paper simulates sea–land breeze (SLB) evolution across 18 major coastal megacities under varying sea-surface temperatures (SST). The SLB driven by thermal contrasts between sea and land, forms a key circulation system in coastal cities which mitigates urban heat islands, improves air quality and supports urban liveability.

The results show that historical SST increases have reduced SLB days by 3–45% in 67% of these cities, with mid-latitude cities experiencing the largest declines (29–45%) as a result of a more than 5% reduction in diurnal sea–land thermal contrast. A further 0.52 °C (~2%) SST increase relative to historical levels induces a 4.5-fold reduction in SLB days in high-impact regions and heightened sensitivity in moderate-impact regions under high-emission scenarios. This erosion of SLB days, primarily driven by ocean warming, poses a critical yet overlooked threat to coastal liveability.