There are a lot of unsettling signals coming from the world’s oceans right now.
Even for those of us who watch things like temperature anomalies and extreme weather events as likely portents of the climate to come, the off-the-charts rise of global sea surface temperature this spring has been eye-popping. As is much of the language recently used to describe it: “record breaking,” “huge,” “alarming,” “unprecedented,” “uncharted,” “an extreme event at a global scale.” Perhaps most simply: “trouble.”
In mid-March, measures of global sea-surface temperature plotted against recent years took a sharp turn away from the pack. By April 1, it had hit a record high. Then, in line with historical seasonal patterns, it began to slightly decline — only to reverse course in the middle of the month, heating up to about three quarters of a degree above the 1982-2011 mean. That represented what Robert Rohde, the lead scientist of the Berkeley Earth institute, identified as the largest global ocean temperature anomaly on record.
Three-quarters of a degree might not sound like much, and the size of the anomaly has since shrunk, to a temperature level only about one-quarter degree above the previous record. But scientists talk about global temperature rise using very small numbers — sometimes describing the difference between 1 degree Celsius of warming and 2 as an almost civilization-scale chasm — and often find themselves gobsmacked when local surface temperature records are broken by even one full degree. Because the oceans are so large, it takes a lot more to heat them — which makes any extremes even harder to produce, and therefore more startling.
The recent temperature spikes are partly explained by the apparent shift from a “La Niña” cycle in the Pacific, which suppresses global temperatures, to an “El Niño” cycle, which elevates them. But this April, huge areas of the world’s oceans were two degrees above the 1971-2000 average. In places off the Pacific coast of South America it was as much as five degrees higher. Sea-surface temperatures off the Atlantic coast of North America were almost 14 degrees above the 1981-2011 average.
What do you call the arrival of events that have been predicted but, when predicted, were described as distressing or even terrifying? The question now governs an awful lot of our experience of the warming world, which confronts us routinely with events we may have known to expect but for which nevertheless we find ourselves often woefully underprepared — politically, socially, emotionally, and with inadequate built and human infrastructure.
And then there are the genuine surprises, since even in a world of loudly broadcast climate science, regular U.N. warnings, and even naked alarmism, there are still, pretty frequently, truly unexpected extremes. The 2021 heat wave in the Pacific Northwest and Canada, for instance, was judged at the time to be a once-in-a-millennium event, yet it was followed less than two years later by a heat event in May that was nearly as extreme. Another may be arriving this week to the east.
But some news from ocean science may prove more surprising still — perhaps genuinely paradigm-shifting. In a paper published in March, researchers suggested that under a high-emissions scenario, rapid melting of Antarctic ice could slow deepwater formation in the Southern Ocean by more than 40 percent by 2050, disrupting the “conveyor belt” that regulates and stabilizes not just the temperature of the oceans but much of the world’s weather systems. And after 2050? This key part of the circulation of the Southern Ocean “looks headed towards collapse this century,” study coordinator Matthew England told Yale Environment 360. “And once collapsed, it would most likely stay collapsed until Antarctic melting stopped. At current projections that could be centuries away.”
Then, last week, some of the same researchers confirmed that the process was already unfolding — in fact, that the Southern Ocean overturning circulation had already slowed by as much as 30 percent since the 1990s. “The model projections of rapid change in the deep ocean circulation in response to melting of Antarctic ice might, if anything, have been conservative,” said Steve Rintoul, a co-author on the new paper and one of the researchers who’d published the previous paper back in March. “Changes have already happened in the ocean that were not projected to happen until a few decades from now.”
The oceans have lately produced a number of other curiosities to chew over, as well: record low levels of Antarctic sea ice, with the “mind boggling fast reduction” scientists have called “gobsmacking” also potentially signaling a “regime shift” in the oceans; some perplexing trends in the El Niño-La Niña cycle, suggesting that warming may be making La Niñas more frequent and thereby scrambling some expectations for future extreme weather; and questions about the role large icebergs may be playing in the warming patterns of the world’s water.
Some of this research (on the circulation patterns of the Southern Ocean) is relatively novel. Some of it (about El Niño patterns and icebergs) is considerably more tentative or speculative. And the findings haven’t yet been stitched into a comprehensive picture of the changing dynamics of the world’s oceans, which means we don’t yet know exactly how precisely to revise our understanding of the near future as a result. But taken altogether, they do suggest that those ocean dynamics are changing — possibly pretty quickly. Reflecting on the anomalies and what’s to come, later this year, Jennifer Francis of the Woodwell Climate Research Center recently advised, “Expect chaos.”
On some level, this shouldn’t surprise us. Just under 90 percent of the additional heat caused by global warming goes into the ocean, according to one recent tabulation, which also found that the planet accumulated nearly as much additional heat in the past 15 years as it had over the previous 45. (Perhaps this should not be too surprising, given that almost third of all emissions ever produced from the burning of fossil fuels in the history of humanity were expelled into the atmosphere in those 15 years.)
It’s for this reason that the ocean is often described as a kind of release valve for warming — or sometimes a temperature sink — sparing our lands of some considerable additional heat. But what this means for oceans is that they are dealing with about 15 times as much impact and disruption from heat as those of us walking the earth and breathing air. And that, probably, we should be spending a lot more time looking there, in the world’s water, for the clearest signs of planetary distress.
“Although man’s record as a steward of the natural resources of the earth has been a discouraging one, there has long been a certain comfort in the belief that the sea, at least, was inviolate, beyond man’s ability to change and to despoil,” Rachel Carson wrote in a preface to “The Sea Around Us,” which won her a National Book Award and spent 86 weeks on the New York Times best-seller list, well before the publication of “Silent Spring.” “This belief, unfortunately, has proved to be naïve.”
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