For the third straight year, ocean temperatures worldwide have hit the highest levels ever recorded, a new study shows.
It comes the same day Niwa announced 2021 was New Zealand’s hottest year on record.
The report, to which 23 researchers from 14 institutes around the world contributed, was published in the Advances in Atmospheric Sciences journal.
Contributor Dr Kevin Trenberth, a University of Auckland honorary academic, said the study showed a substantial climate problem.
“Although the global mean surface temperature is not the highest on record, the ocean is clearly the highest on record, and global warming is still with us,” he said.
The scientists used a large collection of datasets to analyse the ocean’s heat and the impact it had, dating back to the 1950s.
Trenberth said the ocean’s temperature was “relentlessly increasing globally” – a “primary indicator of human-induced climate change”.
The study found while all oceans had seen increased temperatures, warming was more prevalent in the Atlantic and Southern Oceans.
Trenberth said ocean warming had far-reaching consequences and could disrupt New Zealand’s ocean ecosystems and other wildlife, through marine heat waves that had formed in the waters offshore.
“These marine heat waves affect all marine life right from the smallest phytoplankton, the zooplankton, to marine mammals, otters and seals and whales.”
Birds and other wildlife could also be impacted, he said.
“There have been documented cases where there have been quite spectacular disruptions to the whole marine web of life.”
Trenberth said many places around New Zealand were currently experiencing a marine heat wave, as a high pressure system was being set up just east of the country.
Fish and other marine life were likely to spend the next couple of months swimming south to find cooler water, he said.
It was also possible the rise in sea temperatures could contribute to increased shark sightings over the summer as they swam further south.
The study attributed the long-term ocean warming mainly to an increase in greenhouse gas concentrations which were anthropogenic, or caused by humans.