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atlantic ocean
Coral Bleaching 'Off the Charts' in Atlantic as NOAA Warns Ocean Going 'Crazy Haywire'
"We had to add additional bleaching alert levels to appropriately categorize just how hot it was," said a coral reefs expert at the agency.
May 17, 2024
The phrase "off the charts" is no exaggeration in the National Oceanic and Atmospheric Administration's latest warning about a global coral bleaching event that scientists have linked to rising ocean temperatures and heat stress.
Derek Manzello, coordinator of NOAA's Coral Reef Watch Program, told reporters Thursday that about 60.5% of the world's coral reefs are now experiencing heat stress severe enough to cause bleaching, which can make the reefs more vulnerable to disease and harm the biodiversity they support.
Manzello said at the press briefing that after observing the first months of the coral bleaching event, which began in early 2023, NOAA changed its existing bleaching alert system because conditions were so abnormally warm in the Atlantic Ocean, Gulf of Mexico, and Caribbean Sea.
The agency's new bleaching alert system categorizes heat stress for coral reefs on a scale of 1-5, with Alert Level 5 representing ocean heat that could kill "approximately 80% or more of corals on a particular reef," Manzello said.
"We had to add additional bleaching alert levels to appropriately categorize just how hot it was," he said, with Level 5 "analogous to a Category 5 hurricane or cyclone."
"I hate that I have to keep using that word 'unprecedented.'... But, again, we are seeing unprecedented patterns again this year."
The world's oceans, Manzello, said, are going "crazy haywire."
In the Caribbean this year, heat stress off the coasts of Panama, Costa Rica, Nicaragua, and Colombia are now at levels that in previous years weren't seen until the summer months.
"I hate that I have to keep using that word 'unprecedented,'" Manzello toldThe New York Times. "But, again, we are seeing unprecedented patterns again this year."
The bleaching that took place last year resulted in coral mortality of at least 50% and as high as 93% in reefs off the coast of Huatulco, Mexico, according to a team of Mexican scientists.
In the Atlantic, fossil fuel-driven planetary heating has been exacerbated by El Niño—the natural phenomenon that causes warmer-than-normal ocean surface temperatures—and has caused the "most unprecedented and extreme" bleaching-level heat stress observed in the past year.
Manzello said 99.7% of reef areas in the Atlantic have experienced heat stress that could cause bleaching.
"The Atlantic Ocean has been off the charts," he said.
Scientists have recorded four global bleaching events since 1998 and have linked all of them to warmer ocean temperatures. Since 1950, the world has lost half of its coral reefs, according to a 2021 study.
Along with serving marine life, a quarter of which rely on coral reefs at some point in their life cycles, reefs also protect coasts from storms, whose growing severity in recent years scientists have also linked to planetary heating.
The current bleaching event has affected reefs off the coasts of at least 62 countries and territories.
Scientists earlier this year confirmed that 2023 was the hottest year in human history and the warmest year on record for the world's oceans, which absorb more than 90% of excess heat from greenhouse gas emissions.
"I am very worried about the state of the world's coral reefs," Manzello said. "We are seeing [ocean temperatures] play out right now that are very extreme in nature."
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'Cliff-Like' Collapse of Critical Current System More Likely Than Thought: Study
"The new study adds significantly to the rising concern about an AMOC collapse in the not-too-distant future," said one scientist. "We will ignore this at our peril."
Feb 10, 2024
A study published Friday warned that a systemic collapse of the Atlantic Ocean currents driving warm water from the tropics toward Europe could be more likely than researchers previously estimated—an event that would send temperatures plummeting in much of the continent.
The Atlantic Meridional Overturning Circulation (AMOC), which includes the Gulf Stream, could be headed for a relatively sudden shutdown that René Van Western, who led the Dutch study published in Science Advances, called "cliff-like."
"We are heading towards a tipping point."
For many millennia, the Gulf Stream has carried warm waters from the Gulf of Mexico northward along the eastern North American seaboard and across the Atlantic to Europe. As human-caused global heating melts the Greenland ice sheet, massive quantities of fresh water are released into the North Atlantic, cooling the AMOC—which delivers the bulk of the Gulf Stream's heat—toward a "tipping point" that could stop the current in its tracks.
An AMOC shutdown would cause temperatures to rise in the Southern Hemisphere but plunge dramatically in Europe. In the study's model, London cools by an average of 18°F and Bergen, Norway by 27°F. An AMOC failure would also cause sea levels to rise along North America's east coast.
"We are moving closer [to the collapse], but we we're not sure how much closer," van Westen toldThe Associated Press. "We are heading towards a tipping point."
According to the study:
Although AMOC collapses have been induced in complex global climate models by strong freshwater forcing, the processes of an AMOC tipping event have so far not been investigated. Here, we show results of the first tipping event in the Community Earth System Model, including the large climate impacts of the collapse. Using these results, we develop a physics-based and observable early warning signal of AMOC tipping: the minimum of the AMOC-induced freshwater transport at the southern boundary of the Atlantic. Reanalysis products indicate that the present-day AMOC is on route to tipping. The early warning signal is a useful alternative to classical statistical ones, which, when applied to our simulated tipping event, turn out to be sensitive to the analyzed time interval before tipping.
"The research makes a convincing case that the AMOC is approaching a tipping point based on a robust, physically based early warning indicator," said Tim Lenton, director of the University of Exeter's Global Systems Institute. "What it cannot and does not say is how close the tipping point, because... there is insufficient data to make a statistically reliable estimate of that.
"We have to plan for the worst," added Lenton, who was not involved in the Dutch study. "We should invest in collecting relevant data and improving estimation of how close a tipping point is, improving assessment of what its impacts would be, and getting pre-prepared for how we could best manage and adapt to those impacts if they start to unfold."
Stefan Rahmstorf—who leads the Earth Systems Analysis department at the Potsdam Institute for Climate Research in Germany and was not part of the new study—called the research "a major advance in AMOC stability science."
"The new study adds significantly to the rising concern about an AMOC collapse in the not-too-distant future," Rahmstorf told The Associated Press. "We will ignore this at our peril."
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