Global ocean warming and rising, growing more acidic: Report

Marine heatwave events are becoming more common, increasing by one extra event every five to 10 years, says the report

The global sea surface temperature reached a record-high of 21.1°C in April, and from June to August, several areas of the global ocean experienced intense marine heatwave events, causing negative impacts on the climate, biodiversity and societies, according to new EU Copernicus Ocean State Report. 

Researchers found that oceans are heating up and rising faster now than they did last century. Marine heatwaves have become more frequent and intense, while marine cold spells have become less frequent in most of the world.

The report detailed a range of unusual patterns across ocean systems, including dips in ocean circulation, reduced heat exchange in ocean current systems and unexpected evolutions in biological production events. 

How is the ocean changing?  

The ocean is home to a vast array of plant and animal species and is critical in supporting global biodiversity and sustaining complex ecosystems. According to the report, the global ocean is warming and rising, growing more acidic and less oxygenated. 

To begin with, marine heatwave events are becoming more common, increasing by one extra event every five to 10 years, posing substantial threats to marine species and human activities that depend on the health of oceans. These heatwaves can permanently alter marine natural habitats and food chains, impacting the entire ecosystem.

The report found that Antarctic sea ice dramatically shrank this year, reaching the lowest recorded levels in May and June since the beginning of records. It is estimated to have lost an area more than seven times the size of Poland (2.2 million km²). Arctic sea ice is also consistently declining, losing approximately 3.5 million km² since 1979, an area seven times the size of Spain.

Sea level is rising the fastest in the Baltic Sea (+4.8 ± 0.84 mm per year), followed by the North West Shelf (+3.1 ± 0.83 mm per year) and the Iberian-Biscay-Ireland Seas (+3.0 ± 0.82 mm per year), the report said. Sea level rise poses significant threats to ecosystems and societies, negatively impacting livelihoods, infrastructures, and economies.

Moving on to evolutions in biological production events, the waters around Scotland saw two unusual blooms of coccolithophores— marine plankton—in the summer of 2021, turning the sea turquoise. The report said that unusual weather conditions like atypical temperature and wind variation were contributory factors. 

The report mentioned that following an intense cyclone, Storm Blas, in November of 2021, the Balearic Islands experienced the most intense upwelling event of the past nine years, leading to surface temperature drops of up to 6°C, lasting several days. Coastal upwelling plays a critical role linking offshore waters and coastal ecosystems, and impacts water quality, fisheries, and aquaculture. 

The report also investigated extreme events in the southwestern South Atlantic over the past quarter of a decade and looked at their socio-economic  implications. In the area around São Paulo in Brazil, the report said, increasing coastal  hazards are strongly linked to an increasing number of extreme wave events. 

Researchers also observed a drop in oceanic heat exchange of between 4%-9% over the Greenland–Scotland Ridge between 2017-2019, a system that plays a crucial role in shaping change in ocean circulation, and hence the climate of the Arctic and worldwide.

The system of currents that drive climate and weather around the world is changing and these unprecedented changes in the ocean pose a wide range of risks, notably to biodiversity, human well-being, infrastructure, and the prospects for sustainable development.

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