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Wairarapa’s warming sea water

A new report has highlighted how marine heatwaves are resulting in significant warming of Wairarapa’s coastal waters.

Marine heatwaves have become longer, stronger, and more frequent across coastal New Zealand since 1982 – especially in the past 10 years.

The ‘Seasonal trends in marine heatwaves’ report – the result of research by organisations including Canterbury University, Otago University, and National Institute for Water and Atmospheric Research [Niwa] – noted there has been general warming of the upper ocean in the southwest Pacific that washes up on Wairarapa’s coast.

The shelf and coastal waters adjacent to New Zealand have warmed but “display high variability in magnitude and seasonality”, with the strongest warming occurring east of Wairarapa, and in the eastern Tasman Sea, which lands on the west coast of New Zealand.

Authors of the study said marine heatwaves can have severe impacts on near-shore ecosystems and have called for better monitoring of these habitats.

The Times-Age reported in December that Wairarapa’s waters were more than 1 degree Celsius warmer than usual in November.

Niwa said November’s sea surface temperatures were between 1.1 degrees Celsius to 1.8degC warmer than average across New Zealand.

Although Wairarapa was on the lower end of the spectrum at the time, it wasn’t exempt from a marine heating event scientists nicknamed “the blob”.

An article published in the Proceedings of the National Academy of Sciences journal, ‘The Drivers and the Implications of Marine Heatwaves’, found that extreme marine heatwaves can have deadly impacts.

One of the largest recorded marine heatwaves was a goliath pool of warm water about 2.6degC above normal that appeared in the Pacific Ocean during the winter of 2013.

The article said tens of thousands of dead tuna crabs washed up on San Diego beaches, kelp forests vanished, and hundreds of thousands of seabirds died because of the blob.

The blob stuck around for about three years and caused the collapse of the area’s cod fishing industry, worth $100 million per year.

The latest report, using data presented by a 2019 report, said there is strong annual surface warming along the Wairarapa coast, warming more
than 0.3degC per decade.

Similarly, the east coast of the South Island recorded warming of 0.2degC to 0.3degC per decade.

“Here, the Wairarapa coastline and east coast of the South Island are situated within North Cook Strait and East Coast South Island sub-regions, respectively, where we generally found significant positive increases across marine heatwave metrics and seasons, but with no significant winter trends for marine heatwave mean intensity.”

The report concluded by urging more effective, adequate, and standardised monitoring of coastal habitats, which it said is “currently almost non-existent”.

Grace Prior
Grace Prior
Grace Prior is a senior reporter at the Wairarapa Times-Age with a keen interest in environmental issues. Grace is the paper’s health reporter and regularly covers the rural sector, weather, Greater Wellington Regional Council, and coastal stories.

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