Global Distribution and Decadal Trends of Coastal Marine Cold Spells: Insights From an Ensemble of Satellite Sea Surface Temperature Products

Abstract

Marine cold spells (MCSs) exert severe impacts on coastal ecosystems, yet global assessments in coastal regions, which host diverse and complex marine systems, remain limited. Here we integrate four satellite sea surface temperature (SST) products to quantify the spatial distribution and decadal trends of coastal MCS worldwide. We further assess the relative contributions of long‐term SST change and internal variability. Hotspots of MCS cumulative intensity are concentrated in mid‐ to high‐latitude coastal cold‐water zones, particularly along the Gulf of Alaska and the North American west coast, the Peru–Chile upwelling system, the Kuroshio–Oyashio and Okhotsk–Bering margins, and the southeast Australian shelf. Over 1992–2021, coastal MCS generally weakened, with frequency and duration decreasing by 0.62 ± 0.48 events/decade and 1.15 ± 2.53 days/decade, respectively. Cumulative cold stress also weakened, as indicated by a spatial mean cumulative‐intensity trend of 1.69 ± 5.97°C days/decade. Long‐term SST change is more strongly associated with trends in MCS frequency, duration, and annual cumulative days, whereas internal variability plays a comparable role in shaping intensity trends. Multiple SST products show broad agreement in the mean state and trends of coastal MCS, but differ markedly in the inferred balance between long‐term SST change and internal variability. The average OISST‐referenced event‐scale co‐identification rate across the four products is 28.47% ± 13.84%, highlighting substantial inter‐product uncertainty in MCS detection and underscoring the value of multi‐product ensemble approaches for characterizing consistent large‐scale patterns and long‐term trends in coastal MCS assessments.