Sea surface temperature trends in the Aegean sea (2008–2024): from spatiotemporal warming patterns to a Spatial heat vulnerability index

Abstract In this study, a multi-layered spatiotemporal analysis of sea surface temperature (SST) changes in the Aegean Sea for the 2008–2024 period was conducted to establish a scientific basis for regional adaptation strategies. High-resolution (1 km, daily) satellite data from the Copernicus Marine Service ( n = 6210 days) were utilized. Methodologies including pixel-wise linear regression, seasonal decomposition, Marine Heatwave (MHW) detection, and phenology analysis were applied. Four main risk factors derived from these analyses (chronic warming, increase in extreme events, thermal stress, biological calendar shift) were synthesized to produce a spatial Heat Vulnerability Index map. Results reveal a robust basin-wide linear warming trend of 0.67 °C per decade. This warming exhibits significant spatial and seasonal heterogeneity; the North Aegean was identified as the primary hotspot, with warming rates exceeding 1.0 °C per decade (up to 0.10 °C/year), particularly during the Winter months. A statistically significant increase was found in the annual frequency of MHWs (Slope: +0.35 events/year) and the total number of days spent under extreme heat conditions (Slope: +6.85 days/year). Tangible impacts include a lengthening of the coastal swimming season by 11 days over the 17-year period and an advance of the “marine spring” by more than 40 days per decade in the South Aegean. The final HVI map identifies the North Aegean and Thracian coasts as the most vulnerable regions requiring the highest priority for adaptation efforts. These findings demonstrate the critical need for regional authorities to develop spatially-targeted, evidence-based proactive strategies. This study represents the first high-resolution, multi-criteria vulnerability mapping of the Aegean Sea based on a long-term daily SST dataset.