Why is the alarming “sea wave” in the Atlantic?

An unprecedented heat wave is currently hitting the waters of the Atlantic Ocean. In June, the ocean experiences particularly intense heat waves from southern Iceland to Africawith temperature differences of over 5°C off the British Isles. This extreme phenomenon, which is causing great concern, will, according to scientists, lead to an unseen slaughter of marine species.

A similar heat wave affected the waters of the Mediterranean last year, with a difference of more than 6 degrees in particular compared to the natural areas off Marseille in mid-July 2022 and its consequences for about fifty marine species. Episodes that could recur in the coming years with greater force due to global warming.

What do scientists say?

The warming of the Atlantic Ocean is no exception. between March and May, The average temperature at the surface of the oceans has already reached an absolute record in the 174 years of measurements, exceeding the 20th-century average by 0.83 degrees Celsius, according to data from the US Ocean Administration, NOAA. This marine heat wave, with temperatures exceeding 23 degrees Celsius in the North Atlantic, doesn’t exactly surprise scientists, who know that the oceans absorb 90% of the heat generated by global warming.

But the localization of this phenomenon surprised specialists. Temperature anomalies in this part of the North Atlantic are unheard of.confirms Daniela Schmidt, Professor of Earth Sciences at the University of Bristol, citing the British Science Media Centre.

Surprisingly, it goes so fast.Jean-Pierre Gattuso, director of research at CNRS (National Center for Scientific Research) and co-editor of the IPCC (United Nations Climate Experts) report, also supports.

What is its origin?

Several hypotheses have been put forward To explain this extreme phenomenon, such as the reduction of wind-borne desert dust or sulfur emissions from ships, two aerosols that have a cooling effect on the atmosphere. But it “remains in a state of hypotheses,” estimates Jean-Baptiste Sale, an oceanographer and climatologist at the National Center for Scientific Research.

As for El Niño, which causes water temperatures to warm for six to nine months and occurs about every five years, it appears to be too late to have an effect on the North Atlantic. “We’d prefer to expect an impact next spring,” explains Juliette Minot, an oceanographer at the IRD (Institute for Research for Development).

The researcher envisions a possible “modulation of sea currents” or a meteorological phenomenon that could be superimposed on global warming. Thus, the origin of this marine heat wave remains, for the time being, undetermined.

What are the risks of biodiversity?

Whatever the origin of this ocean heat wave, Scientists expect it to cause a “mass killing” of marine species, including corals and invertebrates. But these tragic consequences, occurring under the surface of the water, will remain unseen.

During heat waves in the Mediterranean, about fifty species (corals, gorgonians, sea urchins, mollusks, bivalves, poseidonia, etc.) Co-author of an article on this topic. Other species prefer to migrate towards the poles. According to the researcher, “the waters of Norway and Iceland, for example, will become more fishy,” at the expense of the countries of the tropical region.

by the end of the century, The Intergovernmental Panel on Climate Change projects a 50-fold increase in the frequency of these ocean heat waves in the most pessimistic scenario.with loops whose intensity will be multiplied by ten.

read more