Heat Waves Hit Huge Areas of the Ocean

A huge area of the ocean – four times the size of Europe – was hit last year by an unprecedented marine heatwave.

In January this year, large numbers of dead fish washed up on a nine-kilometre stretch of beach in north-western Australia. An estimated 30,000 fish died, probably as a result of a marine heatwave.

Temperatures were two to three degrees higher than normal in the water near the coast, which was enough to stress the wildlife in the area to the extent that it caused mass deaths.

The heat waves – defined as prolonged periods of extreme heat – affected a large area of the Indian Ocean and the southwestern Pacific Ocean last year, according to a recent report by the UN agency WMO.

The area affected, covering around 40 million square kilometres, is almost as large as Asia and is the largest since measurements began in 1993. In addition to fish deaths, heat waves are linked to coral bleaching.

Warmer oceans lead to several problems, including rising sea levels, as warm water expands and accelerates ice melt in polar regions. According to the report, this can also lead to changes in ocean currents and storm patterns.

High heat content in the oceans also means that more cyclones can occur, and that they become more powerful. The Philippines was hit by twelve typhoons between September and November, twice as many as during a normal season.

‘Sea level rise is an existential threat to entire island nations. It is becoming increasingly clear that time is running out to reverse this trend,’ said WMO Director-General Celeste Saulo in a statement.

^{Cover image: Damaged houses after a typhoon in the Philippines in November. Photo: AP/TT}