Open ocean — marine heatwave
Key messages
- Marine heatwaves have become more frequent and longer in European regional seas, in particular in the Mediterranean Sea.
- Marine heatwaves are projected to further increase in frequency, magnitude and duration in future. The duration of marine heatwaves is projected to increase at least 20-fold along the European coastline under a high-emissions scenario, with much smaller increases under a low-emissions scenario.
Total duration of marine heatwaves
Definition
The total duration of marine heatwaves index represents the number of days in a year within prolonged periods of exceptionally high sea temperature values, defined as a period of at least 5 consecutive days with an SST above the 90th percentile and computed over an 11-day window centred on the same calendar day for a reference period. Variants of the index can adopt other heatwave definitions and different percentiles as thresholds to identify extreme conditions depending on the specific application. If daily data are not available, it is also reasonable to calculate the index using monthly data.
Index factsheet (ETC/CCA Technical Paper): Duration of marine heatwaves
Relevance
The index is mainly relevant for the management of marine ecosystems and fisheries. However, the rather complex definition of the index can make its interpretation difficult.
Past and future changes
As a consequence of mean ocean surface temperature warming, marine heatwaves have become more frequent globally and in European seas over the past century, leading to a considerable increase in the total duration of marine heatwaves, especially in the Mediterranean Sea. Marine heatwaves are projected to further increase in frequency, magnitude and duration. Under a high-emissions scenario (representative concentration pathway (RCP)8.5), the duration of marine heatwaves is projected to increase at least 20-fold along the European coastline; the increase is expected to be much smaller under a low-emissions scenario (IPCC, 2018: Extremes, Abrupt Changes and Managing Risks).
Chapters of the Europe's changing climate hazards report
- What will the future bring when it comes to climate hazards? — Overview
- Europe’s changing climate hazards — about the report
- Explore the hazards and the indices related to the six categories:
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Geographic coverage
For references, please go to https://www.eea.europa.eu/publications/europes-changing-climate-hazards-1/open-ocean/open-ocean-marine-heatwave or scan the QR code.
PDF generated on 28 Nov 2021, 12:34 AM
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