The warming of the seas runs parallel to warmer air, and if this trend persists, the impact could be severe. For now, waters around the Iberian Peninsula — Cantabrian, Atlantic and Mediterranean seas — are showing temperatures well above normal. Even in mid-January the sea remains warm. That pattern fuels extreme storms and cyclones, endangering marine life and contributing to rising sea levels, among other effects.
Data reveal that the oceans in our region are recording temperatures far above typical levels. Readings show increases of about 5 to 6 degrees Celsius above seasonal norm. This continues the pattern seen last summer, when heat waves across the Mediterranean in June through August pushed surface temperatures into the mid to high 20s Celsius, setting new records and driving heat across the ecosystem.
According to Meteored, the Cantabrian Sea and the Atlantic waters around the Canary Islands surpassed historical values in multiple seasons. Now, in the heart of winter, with a drop in air temperatures, the surface temperatures of our seas have not yet returned to their long term averages.
The sea reflects the atmosphere
The elevated water temperatures align with unusual atmospheric warmth that has persisted since the start of astronomical winter. Even with a slight cooling around Christmas, the temperatures remain higher than typical for this time of year, and January is forecast to continue warmer than usual across the country.
As Yurima Celdrán explains on a dedicated weather portal, oceans and seas act as major climate regulators and absorb solar radiation efficiently. This means rising solar input and higher air temperatures contribute to warming the upper centimetres of the sea surface. Various processes — heat exchange between air and sea, evaporation, precipitation, atmospheric warming, and natural ocean circulation — interact to determine water temperatures in coastal zones and open seas alike.
Real data from harbor authorities show how monthly mean sea surface temperatures have shifted at key sites such as Cádiz, Valencia, Gran Canaria, and Galicia. In the Bay of Cádiz, December temperatures rose from 17.63°C in 2011 to 18.82°C in 2022. Valencia saw a smaller increase of about one tenth of a degree, while Estaca de Bares in Galicia rose from 14.2°C to 15.1°C in the same month year over year. Gran Canaria recorded a jump from 20.61°C to 21.89°C between 2017 and 2022 in December.
Rising sea temperatures trigger a chain of effects that pose risks to humans and all living beings. Warmer water carries more energy, leading to more intense evaporation and a moister atmosphere that can fuel stronger storms and rainfall events. Such changes challenge biodiversity, complicating the survival of species not adapted to rapid shifts in their environment.
Findings
Warmer seas raise mean water levels because water expands when heated. In addition, higher temperatures slow the formation of large ice masses elsewhere, which can contribute to sea level rise. Together, these factors have contributed to coastal flooding and erosion of critical marine habitats since the late 19th century. A warmer sea stores more energy and increases evaporation, feeding moisture into the atmosphere and potentially intensifying storms, including tropical and extratropical cyclones. The biodiversity field reports notable consequences for marine life as temperatures shift, posing challenges for many species that are not well adapted to rapid change.
A well-documented pattern shows that sustained ocean warming alters food webs, affects reproduction cycles, and reshapes habitat availability for fish and invertebrates across the regional seas. These dynamics emphasize the need for ongoing monitoring and adaptive management of coastal and marine ecosystems. This summary draws on observational data and climate assessments from credible regional monitoring programs.
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Note: Environmental monitoring agencies continually update sea temperature records and projections to support coastal communities and policy planning. For more context, researchers reference ongoing climate assessments and regional temperature histories with careful attribution to official data sources.
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Contact and further information are managed by official environmental authorities through public channels. This article summarizes observed trends and their potential implications for coastal zones and marine life based on established meteorological and oceanographic reporting. Data cited reflect long-running measurement programs and regional climate analyses. Attribution: regional ocean observations and climate studies provide the basis for these conclusions.