High ocean temperature shocks 'more frequent'

| 6th August 2019
A total of 12 ecosystems experienced warming events each year over the past seven years. 

A total of 12 ecosystems experienced warming events each year over the past seven years. 

Unusually high ocean temperatures are occurring more frequently than researchers previously thought, a new study suggests.

The warming events, including marine heatwaves, are disrupting marine ecosystems and the people who rely on them, scientists say.

They examined 65 large marine ecosystems from 1854-2018 to identify the frequency of surprising ocean temperatures.

Warming

This was defined as an annual mean temperature two standard deviations above the mean of the previous three decades.

The "surprises" were noted all over the world, including the Arctic, North Atlantic, eastern Pacific, and off of Australia. Researchers also found that the warming events occurred at nearly double the rate they expected.

Dr Andrew Pershing, chief scientific officer at the Gulf of Maine Research Institute, said: "Across the 65 ecosystems we examined, we expected about six or seven of them would experience these 'surprises' each year.

"Instead, we've seen an average of 12 ecosystems experiencing these warming events each year over the past seven years, including a high of 23 'surprises' in 2016."

Scientists also looked at the effect of the warming on sea life and human communities.

Trends

In natural communities like coral reefs, fish, and plankton, new species that prefer warmer conditions can often replace cold-loving species that suffer when an ecosystem warms.

While the changeover of species should be able to keep pace in gradually warming conditions, in ecosystems that are experiencing change much faster they are expected to suffer reductions in both biomass and diversity.

An increase in ocean "surprises" also affects humans, the study published in Proceedings Of The National Academy Of Sciences observed.

According to the study, as the planet continues to warm, ecosystems and human communities will adapt to the changing conditions.

However, scientists say it is unclear whether such adjustments will keep pace as the climate trends accelerate.

This Author

Nina Massey is the PA science correspondent.

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