NZ's southern waters experiencing marine heatwave

Waters around New Zealand’s South Island are as much as 6 degrees Celsius (42.8 degrees Fahrenheit) warmer than normal due to climate change, the weather phenomenon La Nina and a series of high pressure systems, according to scientists.

Metservice oceanographer Joao de Souza, who is part of the Moana Project, said that waters around the southern South Island were all well above normal for this time of year with temperatures in Fiordland 6 degrees warmer than normal.

The Moana Project said that water temperatures on the West Coast of the South Island are currently 4 degrees above average.

These temperatures are going to have significant consequence for an eco system that is built or adapted to cold waters, he said.

"There are always going to be winners and losers," he said, with those marine species that can't shift location likely to be more impacted.

New Zealand saw a number marine heatwaves last year with a previous heatwave in Fiordland resulting in severe bleaching of native sponges. There have also been anecdotes of species more common in warmer waters of New Zealand being spotted further south.

De Souza said their research showed that it was not just surface water temperatures that were rising but also water as deep as 100 metres, which meant the marine heatwave was impacting species who lived in deeper water.

The marine heatwave comes as a La Niña weather pattern has caused warmer than normal temperatures in New Zealand's South Island. This along with high pressure systems and climate change were factors in the heatwave, said de Souza.

He added that they expected marine temperatures to remain above normal until at least April.