Climate, in 2022 new record for ocean warming

The results of the Another year of record heat for the oceans study, published in the journal Advances in Atmospheric Science

New record for ocean warming accompanied by an increase in stratification and variation in water salinity. According to the Another year of record heat for the oceans study, published in the journal Advances in Atmospheric Science, in 2022, for the seventh consecutive year, the heat content of ocean waters set a new record. The article signed by an international team of 24 researchers from 16 institutes, including Simona Simoncelli of the National Institute of Geophysics and Volcanology (Ingv) and Franco Reseghetti of the National Agency for New Technologies, Energy and Sustainable Economic Development (Enea) analyzes observations, from the 1950s to today, belonging to two international datasets: the first from the Institute of Atmospheric Physics (Iap) of the Chinese Academy of Sciences (Cas), the second from the National Centers for Environmental Information (Ncei) of the National Oceanic and Atmospheric Administration (NOAA).

“The datasets, IAP and Ncei, are consistent and both show a record value of heat accumulated in the top 2000m of the ocean in 2022,” comments Tim Boyer of Ncei/Noaa. Specifically, compared to the record value reached in 2021, the ocean heat content (Ohc, Ocean Heat Content), estimated in 2022 between the surface and 2000m depth, has increased by about 10 Zetta Joule (Zj), equivalent to about 100 times the world’s electricity production of 2021, about 325 times that of China, 634 times that of the United States and just under 9,700 times that of Italy. To give an idea of ​​the enormity of the stored energy value, 10 Zj of heat can keep 700 million 1.5 liter kettles of water boiling all year long.

For Professor Lijing Cheng of the Chinese Academy of Sciences, first author of the work, “global warming of the ocean continues and is manifested both with new records in the thermal content of the waters but also with new extreme values ​​for salinity. The areas already salty waters become even more salty while the areas with softer waters become even less salty: there is a continuous increase in the intensity of the hydrological cycle”.

Three key indicators of climate change related to the ocean confirm the continuous increase in temperature in combination with ever higher levels of salinity and the increase in its stratification, i.e. the separation of water into layers that can reduce up to no mixing and exchanges between the surface and deeper areas. The 2022 data confirms that all these phenomena continue on a global scale even if not homogeneously in the various basins.

Among many consequences, increased salinity and ocean stratification can alter the way heat, carbon and oxygen are exchanged between the ocean and the atmosphere. This is one factor that can cause deoxygenation within the water column that is of grave concern, not only for marine life and ecosystems, but also for humans and terrestrial ecosystems. All this contributes to reduce marine biodiversityfor example by displacing important fish species, causing critical situations in fisheries-dependent communities and their economy, thus creating a knock-on effect on the way in which populations interact with their immediate environment.

At the same time, meteorological anomalies were clearly evident in 2022, which will be remembered for the repeated heat waves particularly in Western Europe with new records of atmospheric temperatures in many times of the year combined with a significant reduction in precipitation. The resulting drought in these areas has had a negative impact not only on agricultural activities but also on people’s quality of life (due to high energy consumption, air conditioning and the production of electricity itself), also increasing the risk of fires. In other areas, however, floods have occurred, often sustained by the increase in evaporation in the warmer seas. All this contributes to modifying the hydrological cycle, underlining the interactive role played by the oceans.

As for the Mediterranean the basin that warms fastest among those analyzed in the study is confirmed, but the heat content in 2022 is at the same level as in 2021 according to estimates by the Iap-Cas (Institute of Atmospheric Physics, Chinese Academy of Sciences). The data of the Mediterranean reanalysis model produced and distributed by the European marine service Copernicus instead indicate a decrease compared to 2021. These differences can be attributed to the different data processing techniques and their spatio-temporal distribution. Short-term (inter-annual) variations are in any case a characteristic part of the system and further investigations are currently underway.

“Ingv and Enea are already collaborating within the Macmap project, funded by Ingv and conducted in collaboration with Grandi Navi Veloci (GNV), which aims to study climate change through seasonal monitoring of the temperature of the Ligurian and Tyrrhenian seas along the Genoa-Palermo section and to analyze the reanalysis data and climate models ranging from 1950 to 2050”, highlights Simona Simoncelli of Ingv.

“The collaboration with this international team, in particular with Professor Cheng, allows us to keep the attention on global warming and its impact on the ocean and consequently on man and the economic activities closely related to it – adds Franco Reseghetti of Enea – We believe that continuing to systematically monitor these changes in the ocean remains the only way to understand and be more aware of their consequences and to be able to develop effective strategies for mitigation and adaptation”.