The warmest sea ever observed. During this month of April, every day, the average temperature of the ocean and sea water has been above 21 degrees Celsius. Experts warn: it is accelerating more and more, we are facing unexplored territory.
An extremely warm spring that follows an also particularly hot 2022. Climate change favors that more and more anomalies occur on the sea surface and that they are increasingly intense, especially in more fragile ecosystems such as the Arctic, the Mediterranean, the North Atlantic or the western Pacific.
The data recorded this April marks a record and unprecedented sequence since the United States National Oceanic and Atmospheric Administration (NOAA) began the series in 1980. The last time similar temperatures were reached was in February of 2016. On that occasion it was the El Niño phenomenon, which cyclically warms the waters of the tropical Pacific.
"The records should be an exception, not a phenomenon that is repeated year after year," explains Joaquim Garrabou, a CSIC member at the Institute of Marine Sciences. "The acceleration of these processes, produced by climate change, leads us to a scenario unknown," adds the researcher.
The pattern of warming of the oceans varies based on geographic location, ocean circulation, wind patterns, and underwater topography. This makes some areas especially sensitive to this phenomenon. In turn, these temperature changes have a direct impact on marine ecosystems, causing changes in the movement of species and massive mortality of those that are fixed in the substrate.
"The waters of the Mediterranean, being a closed sea, warm up faster and therefore the temperature anomalies are greater," explains Rubén del Campo, spokesman for the State Meteorological Agency (AEMET).
The general temperature of the Mediterranean has increased 20% faster than the world average for the planet's seas and oceans. With this increase, the Mediterranean becomes an ideal habitat for species from tropical environments. "In the coldest part of the Mediterranean the species cannot move because it is closed and this causes a gradual extinction of the number of individuals", explains Garrabou.
In Spain it happens more and more frequently. “For two decades the temperature has been, each year, higher than the normal period,” recalls del Campo. Since 1940, when the AEMET began its series, the three temperature peaks have been recently recorded, in 2017, 2020 and 2022.
From Maine to Delaware, the northeast coast of the United States is also warming faster than most regions of North America, due to a change in ocean currents, explains research published in Nature Climate Change. As a result, winters in the area have softened and summers have become warmer.
In the south of the continent, on the coast of Peru and Chile, the natural phenomenon of El Niño —which bears that name because it appears on dates close to Christmas— causes a warming of the area. 2022 was marked by La Niña, the opposite phenomenon that causes a cooling of the climate and camouflages the warming effects of climate change.
In the Bering Sea, the decrease in sea ice has produced unprecedented warm temperature anomalies in the area. If the Mediterranean Sea warms 20% faster than the global average, in the Arctic this occurs up to four times faster. In the case of the Bering Sea and northern Europe and Siberia, this process accelerates up to 7 times faster, compared to the period between 1979 and 2021, according to a study published in the journal Communications Earth.
Western Pacific waters, including those around the Philippines and Indonesia, have experienced significant temperature anomalies, driven by the natural El Niño phenomenon and climate change. With temperature spikes that produce marine heat waves that bleach coral reefs, vital ecosystems in the region.
The World Meteorological Organization warns that there is a 55% chance that this phenomenon will repeat itself in the second half of 2023. If temperature records have been broken in April 2023, the El Niño phenomenon could raise them even more in the what's left of the year
