Return of warm water 'blob' in the Pacific threatens marine life

By Adam Vaughan
NEW SCIENTIST

The reappearance of a vast ‘blob’ of abnormally warm water in the Pacific, around seven times the size of Alaska, has raised the prospect of serious impacts on marine ecosystems and the weather.

The marine heatwave stretches up the US and Canadian west coast, covering a similar extent to a mass of warm water in the region between 2014 and 2016, dubbed ‘the blob’. The US National Oceanic and Atmospheric Administration (NOAA), which reported the new patch this week, notes the last blob caused toxic algal blooms and massive die-offs of marine life.

“There’s definitely already been impacts and there’s likely to be further,” says Andrew Leising at NOAA. Algal blooms have already been seen off Washington state.

Simon Boxall at the University of Southampton, UK, says: “We do sometimes see anomalous warm or cold blobs in our oceans so shouldn’t necessarily assume the end of the world is coming. However, the fact it’s becoming more frequent will have an impact on ecosystems.”

Watched carefullyHe adds: “In the long term, if this is happening regularly, it could be we are seeing a difference because of climate change. It is something that needs to be watched carefully. It will bring changes to the area both in terms of ecology and weather.”

Scientists have different definitions of marine heatwaves, says David Ferreira at the University of Reading, UK. But typically, rises of 2-4°C over a region for a prolonged time would be considered a marine heatwave, he says.

While such blobs can’t be attributed to climate change, warmer average global temperatures create the conditions for them to appear, says Ferreira. “In the context of global warming, the warmer the background temperature the higher the probability you might get a blob.”

The climate phenomenon El Nino may also play a role in the formation of blobs, Leising adds.

Shallow blobOne of the key differences between this blob and the last one is the heat only goes down a fraction of the depth of the last event. The depth is a measure of how much heat is being stored, and gives a sense of how long the blob might persist, says Ferreira.

It is unclear clear how long this blob will last. The weather will be key and there are already some signs in the latest data – which comes via satellites and ocean buoys – that some cooling may have occurred in September, according to Leising. “But the jury is still out on whether it will dissipate,” he concludes.

If the blob lasts into next year, it is likely to have significant impacts on ecosystems and weather. “What’s happening in the Pacific is clearly very worrying,” says Jason Hall-Spencer of Plymouth University, UK. “The warming of the sea creates severe destruction to the marine ecology but also to our weather.”
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Hall-Spencer is in Japan this week to undertake marine research but expects his equipment to be destroyed by super typhoon Hagibis, one of the most powerful in decades, which is expected to hit Japan by the weekend
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Read more: https://www.newscientist.com/article/2219501-return-of-warm-water-blob-in-the-pacific-threatens-marine-life/#ixzz6MjSVRYWt