Southern ocean warming 'off the scale'

The level of warming being caused by extreme marine heatwaves in the ocean off the southern South Island is "literally off the scale".

MetService oceanographer Dr Joao de Souza said the present heatwave was concentrated off Otago and around Stewart Island, bringing temperatures up to 6degC warmer than normal.

“Extreme marine heatwaves are just that – extreme. It’s the highest category in existence for marine heatwaves, reflecting how unusual this level of warming is, both in New Zealand and internationally.”

Over the next few days Otago water temperatures are expected to be over 5degC warmer than usual, bringing surface ocean temperatures to 19degC.

Temperatures around Stewart Island would be 4-6 degrees warmer than usual, "We are seeing steady temperatures above 18degC forecast for this weekend.”

The temperature rise was so pronounced that MetService might have to extend the colour scale used to denote the warming.

“Our graphics only go up to 5 degrees above normal, but now that we’re increasingly seeing even higher temperatures it may be time to change the scale. The warming is literally off the scale.”