Four decades of warming and marine heatwaves in the Eastern Mediterranean, Aegean and Black Sea: a reproducible multivariate satellite analysis
Doğu Akdeniz, Ege ve Karadeniz'de kırk yıllık ısınma ve deniz sıcak hava dalgaları: yeniden üretilebilir çok değişkenli bir uydu analizi
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Abstract
The Mediterranean and the Black Sea are among the fastest-warming marine regions, yet analyses that combine temperature, heat content and the carbonate system are rarely published in a form that others can re-run. We analysed daily NOAA OISST v2.1 sea surface temperature (SST) for four boxes (Eastern Mediterranean, Aegean, Black Sea and Western Mediterranean), Copernicus Marine ocean heat content (0–700 m) and SOCAT surface fCO₂ for the Mediterranean, all retrieved from the open GOMD platform through a notebook that stops when a series is missing instead of substituting data. Annual mean SST increased significantly in all boxes over 1982–2025, by 0.402 °C per decade in the Eastern Mediterranean, 0.394 in the Aegean, 0.509 in the Black Sea and 0.386 in the Western Mediterranean (Mann–Kendall p < 10⁻⁶). A Pettitt change point in 1998 separates two Eastern Mediterranean regimes whose means differ by 0.91 °C. With a fixed 1982–2011 threshold, marine-heatwave days increased from 2.5 to 213 per year in the Eastern Mediterranean and from 4.4 to 167 in the Aegean between 1982–1991 and the last ten years, showing that the region now spends most of the year above its former 90th percentile. In a standardised matrix of 28 years, the first principal component explained 80.8% of the joint variance, a lag-1 Ridge model reduced the out-of-sample forecast error of Eastern Mediterranean SST from 0.283 °C (persistence) to 0.230 °C, and transfer entropy from SST to fCO₂ was 0.65 bits. The results agree with independent satellite analyses and show how a fixed baseline turns transient extremes into a quasi-permanent state.
Keywords
Sea surface temperature; Marine heatwaves; Eastern Mediterranean; Aegean Sea; Black Sea; Ocean heat content; fCO₂; Reproducibility
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