The Balearic Sea breaks heat records and chains three months of "marine heatwave"

PalmaThe Balearic Sea is experiencing an unprecedented heat episode for the month of August. The average sea surface temperature has reached 29.5 degrees over the last ten days, a figure that is 3.7 degrees above the usual values for this time of year. On August 15, satellites also recorded an absolute record of 29.7 degrees, according to data from the Balearic Coastal Prediction and Observation System (Icts-Socib).

"It's a lot, especially because it's been like this for many days," explains to EFE oceanographer and Socib researcher Mélanie Juza, who describes the situation as "unprecedented in August in the Balearic Sea." What particularly worries scientists is not only the maximum value reached, but the duration of the episode: "We are only halfway through the month," she warns.

The heat, in fact, is not exclusive to the open waters analyzed by satellites. Buoys operated by Ports de l'Estat and Socib itself have also registered extraordinarily high temperatures at different points in the Archipelago. At Dragonera, 33 degrees were reached on August 5, the highest value ever recorded by this buoy. Since then, almost every day between 12:00 PM and 3:00 PM, 30 degrees have been reached, and on the 16th, 31.2 degrees were reached.

In Maó, the buoy registered 32.3 degrees on August 8, while in the Bay of Palma, 31 degrees were recorded on the same day. The Pollença tide gauge, for its part, reached 32.1 degrees on August 11. "These are many values above 30 degrees, many of which are records," points out Juza.

Three months with an extraordinarily warm sea

The current episode is not, however, a one-off phenomenon. Socib detected the first marine heatwave in the Balearic Islands in May, earlier than usual, with an anomaly of more than four degrees on average. Since mid-June, the Balearic Sea has been immersed in a new marine heatwave that has continued with varying intensities and has reached a particularly high severity in recent weeks.

Scientists consider there to be a marine heatwave when the temperature exceeds 90% of a zone's historical records for at least five consecutive days. What differentiates the current episode, however, is the persistence and repetition of the phenomenon.

"We are facing an unprecedented scenario, because we have very intense, very long, and recurrent marine heatwaves for several consecutive years," explains Juza. This 2026 is, according to the researcher, the fifth consecutive summer with exceptional marine temperatures, a situation that causes thermal stress whose extent is still unknown.

Posidonia, among the affected species

The warming of the sea is not just a meteorological data. High temperatures can have direct consequences on marine ecosystems, from the loss of seagrass meadows to the mortality of organisms, alterations in the growth and reproduction of species, and changes in their abundance and distribution.

In the case of oceanic posidonia, it is already known that temperatures above 28 degrees can cause alterations. The problem is that now these values are not recorded punctually, but during increasingly longer periods and after several exceptionally warm summers.

"Perhaps we will also witness an exhaustion of species or plants, with so many summers and so much thermal stress over the years," warns Juza. The researcher points out that there are still many unknowns about the cumulative effects of this phenomenon, as the scientific community better knows the consequences of punctual episodes than those of a succession of years with extraordinarily high temperatures.

More heat in autumn and tropical nights

The warming of the sea can also have consequences beyond marine ecosystems. One of the concerns of scientists is what may happen when autumn arrives, as an exceptionally warm sea brings more heat and humidity to the atmosphere, conditions that can contribute to intensifying episodes of storms and torrential rains.

Warm waters also hinder the nocturnal cooling of coastal areas and favor the persistence of tropical nights, with direct effects on the comfort and well-being of the population.

Furthermore, the warming of the water column causes thermal expansion that contributes to the rise in sea level. In the Balearic Islands, this phenomenon can end up having consequences on the coastline, ecosystems, infrastructures, and the communities that live there.

The Socib researcher believes that the current scenario requires strengthening ocean monitoring. "What is not observed and not known cannot be managed," she argues. For this reason, she calls for continued monitoring, analysis, and prediction of the evolution of the sea to anticipate the effects of climate change.

At the same time, she recalls that, to limit global warming, the scientific community agrees that the only way is an immediate and sustained reduction in greenhouse gas emissions, along with the protection of oceans from other pressures such as pollution, overfishing, and maritime traffic.