Climate ChangeEnvironment

In 2023 new record of ocean temperature. And the Mediterranean is the hottest

INGV and ENEA also contributed to the study

2023 ended with a new record of global warming at +1.48 degrees compared to the pre-industrial era. But it is not the only indicator to have marked a record last year and to throw a more and more worrying light on the state of health of the Planet. 2023 was also the year of the new record of ocean temperature. Both the thermal content, the stratification of the water and the salinity have increased dramatically. And the Mediterranean Sea is the fastest-warming basin of all.

To measure “ocean fever” is a study published in the journal Advances in Atmospheric Science and conducted by an international team, coordinated by the Institute of Atmospheric Physics of the Chinese Academy of Sciences and also composed of Italian scientists from INGV and ENEA.

15 ZettaJoule more than in 2022

The most significant figure concerns the amount of additional heat retained by the ocean masses. The oceans cover 70% of the planet and absorb, alone, about 90% of the solar radiation that reaches the Earth. They are therefore a fundamental “buffer” to limit global warming. But they suffer the consequences.

In an exceptional year like 2023, the amount of heat accumulated by the oceans increased by between 8 (according to the NOAA calculation) and 15 (calculation of IAP-CAS) ZettaJoule compared to 2022 in the layer between 0 and 2000 meters deep. “To get an idea, 1 ZettaJoule is equivalent to twice the amount of energy that feeds the world economy every year”, ENEA specifies in a note.

The effects of the ocean temperature record

This immense amount of energy embedded in the oceans has direct consequences for the climate and the environment. The variation of atmospheric precipitation and the evaporation of surface water change the salinity of the ocean. Salt areas are becoming increasingly salty, while areas with less salt water are becoming less salty.

The consequences? They affect marine life, ocean currents and atmospheric interactions. Less oxygen is transported deep down the water column, damaging deep ecosystems. Excess heat and moisture enter the atmosphere and trigger more violent storms, rains and stronger winds. “With a greater risk of flooding, even on the Italian territory“, says ENEA.

The Mediterranean warms faster than all

On the other hand, the Mediterranean, as emerges from the study, is the sea that is warming faster than all. And in 2023 it reached the highest thermal value since the beginning of the surveys.

Since 2013, there has been a clear warming in the water layer between 150 and 450 meters deep, extending to the deepest (up to 700 meters) and northernmost waters. In this case, between 2013 and 2016 the heating was higher than 0.4 ºC, followed by a slight decrease and a stationary period. Water temperature has risen again since 2021, reaching its record, for the moment, in September 2023“, explains Simona Simoncelli, INGV researcher and co-author of the study.

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