"For nearly a year now, a bizarre heating event has been unfolding across the world's oceans," reports Wired.
"In March 2023, global sea surface temperatures started shattering record daily highs and have stayed that way since..."
Brian McNoldy, a hurricane researcher at the University of Miami. "It's really getting to be strange that we're just seeing the records break by this much, and for this long...." Unlike land, which rapidly heats and cools as day turns to night and back again, it takes a lot to warm up an ocean that may be thousands of feet deep. So even an anomaly of mere fractions of a degree is significant. "To get into the two or three or four degrees, like it is in a few places, it's pretty exceptional," says McNoldy.
So what's going on here? For one, the oceans have been steadily warming over the decades, absorbing something like 90 percent of the extra heat that humans have added to the atmosphere...
A major concern with such warm surface temperatures is the health of the ecosystems floating there: phytoplankton that bloom by soaking up the sun's energy and the tiny zooplankton that feed on them. If temperatures get too high, certain species might suffer, shaking the foundations of the ocean food web. But more subtly, when the surface warms, it creates a cap of hot water, blocking the nutrients in colder waters below from mixing upwards. Phytoplankton need those nutrients to properly grow and sequester carbon, thus mitigating climate change...
Making matters worse, the warmer water gets, the less oxygen it can hold. "We have seen the growth of these oxygen minimum zones," says Dennis Hansell, an oceanographer and biogeochemist at the University of Miami. "Organisms that need a lot of oxygen, they're not too happy when the concentrations go down in any way — think of a tuna that is expending a lot of energy to race through the water."
But why is this happening? The article suggests less dust blowing from the Sahara desert to shade the oceans, but also 2020 regulations that reduced sulfur aerosols in shipping fuels. (This reduced toxic air pollution — but also some cloud cover.)
There was also an El Nino in the Pacific ocean last summer — now waning — which complicates things, according to biological oceanographer Francisco Chavez of the Monterey Bay Aquarium Research Institute in California. "One of our challenges is trying to tease out what these natural variations are doing in relation to the steady warming due to increasing CO2 in the atmosphere."
But the article points out that even the Atlantic ocean is heating up — and "sea surface temperatures started soaring last year well before El Niño formed." And last week the U.S. Climate Prediction Center predicted there's now a 55% chance of a La Nina in the Atlantic between June and August, according to the article — which could increase the likelihood of hurricanes.
Thanks to long-time Slashdot reader mrflash818 for sharing the article.
Read more of this story at Slashdot.
