Atlantic Ocean near Bermuda is warmer and more acidic than ever, 40 years of observation show
Data spanning 40 years shows changes in the subtropical North Atlantic Ocean near the island of Bermuda, including warming by 1°C
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BERMUDA ATLANTIC TIME-SERIES STUDY (BATS) TEAM ON BIOS’S RESEARCH VESSEL ATLANTIC EXPLORER
view moreCREDIT: JEFF NEWTON
Decade-long ocean warming which impacts ocean circulation, a decrease in oxygen levels that contributes to changes in salinification and nutrient supply, and ocean acidification are just some of the challenges the world’s oceans are facing.
In 1988, a comprehensive sustained ocean time-series of observations, called the Bermuda Atlantic Time-series Study (BATS), began at a site about 80 km southeast of the island of Bermuda. There, scientists take monthly samples of the physics, biology, and chemistry of the ocean’s surface and depths. In a new paper published in Frontiers in Marine Science, researchers have now presented the latest findings from this monitoring effort.
“We show that the surface ocean in the subtropical North Atlantic Ocean has warmed by around 1°C over the past 40 years. Furthermore, the salinity of the ocean has increased, and it has lost oxygen,” said author Prof Nicholas Bates, an ocean researcher at the Bermuda Institute of Ocean Sciences, a unit of the Julie Ann Wrigley Global Futures Laboratory at Arizona State University (ASU) and professor in the School of Ocean Futures at ASU. “In addition, ocean acidity has increased from the 1980s to the 2020s.”
Warm, salty, deoxidized, acidic
At the BATS monitoring station, ocean surface temperatures have increased by around 0.24°C each decade since the 1980s. Added up, the ocean is around 1°C warmer now than it was 40 years ago. In the last four years, ocean temperatures have also risen more sharply than in the previous decades, the researchers found.
Not only have the monitored waters gotten warmer, but also more saline at the surface, meaning more salt is dissolved in the water. Like surface temperature, this saltiness has disproportionally increased during the last few years, the newest data showed. “We suspect this is part of the broader, more recent trends and changes in ocean temperatures and environmental changes, like atmospheric warming and having had the warmest years globally,” Bates said.
At the same time, the data indicated that over the last 40 years the amount of oxygen available to living aquatic organisms has decreased by 6%. Acidity values, too, have changed: the ocean is now 30% more acidic than it was in the 1980s, resulting in lower carbon ion concentrations. This can, among other things, affect shelled organisms’ ability to sustain their shells.
“The ocean chemistry of surface waters in the 2020s is now outside of the seasonal range observed in the 1980s and the ocean ecosystem now lives in a different chemical environment to that experienced a few decades ago,” Bates explained. “These changes are due to the uptake of anthropogenic CO2 from the atmosphere.”
Importance of long-time data
Collecting data over extended time periods is important to predict upcoming shifts in conditions. “These observations give a sense of the rate of change in the recent past of ocean warming and ocean chemistry. They provide key indications of future changes in the next decades,” said Bates. “They also are proof of regional and global environmental change and the existential challenges we face as individuals and societies in the near future.”
The monitoring stations providing the data for the present study are just two out of the several long-term sustained ocean time-series sites located throughout the world’s oceans. Stations off Hawaii, the Canary Islands, Iceland, and New Zealand are also key to monitoring long-term oceanic changes. At some of those stations, similar processes have been observed, highlighting the challenges and complexities of understanding the long-term interactions between warming, salinification, and ocean acidification, the researchers said.
Bermuda Atlantic Time-series Study (BATS) team on BIOS’s research vessel Atlantic Explorer
CREDIT
Jeff Newton
Bermuda Atlantic Time-series Study (BATS) team on BIOS’s research vessel Atlantic Explorer
CREDIT
BATS
Bermuda Atlantic Time-series Study (BATS) team members in the lab
CREDIT
Jeff Newton
JOURNAL
Frontiers in Marine Science
METHOD OF RESEARCH
Observational study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Forty years of ocean acidification observations (1983-2023) in the Sargasso Sea at the Bermuda Atlantic Time-series Study (BATS) site
ARTICLE PUBLICATION DATE
8-Dec-2023
Coral reefs in peril from record-breaking ocean heat
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CREDIT: THE UNIVERSITY OF QUEENSLAND
view moreCREDIT: THE UNIVERSITY OF QUEENSLAND
Record breaking marine heatwaves will cause devastating mass coral bleaching worldwide in the next few years, according to a University of Queensland coral reef scientist.
The alarming finding is the result of an international study led by UQ’s Professor Ove Hoegh-Guldberg of UQ’s School of the Environment, who is currently attending the COP28 climate change meetings in Dubai.
“We were shocked to find heat stress conditions started as much as 12 weeks ahead of previously recorded peaks and were sustained for much longer in the eastern tropical Pacific and wider Caribbean,” Professor Hoegh-Guldberg said.
“Historical data suggests the current marine heatwaves will likely be the precursor to a global mass coral bleaching and mortality event over the next 12 to 24 months, as the El Niño phase of El Niño-Southern Oscillation or ENSO continues.
“Across July 2023, Earth experienced its warmest days on record since 1910, as well as the warmest month ever recorded for sea surface temperatures.
“This puts immense pressure on vital but fragile tropical ecosystems, such as coral reefs, mangrove forests, and seagrass meadows.
“For example, a coral reef in the Florida Keys called Newfound Harbor Key accumulated heat stress almost 3 times the previous record and it occurred 6 weeks ahead of previous peaks.”
Professor Hoegh-Guldberg said the findings come at a critical point in protecting global biodiversity, with commitment to climate change mitigation slipping in many nations.
“The latest environmental information indicates that we’re well off-track when it comes to keeping global surface temperatures from reaching a very dangerous condition by mid to late this century,” he said.
“Frankly, we’re hurtling in the opposite direction.
“Compounding this is the fact these devastating impacts appear to be rolling into a vast record-breaking global event.”
Professor Hoegh-Guldberg said that without serious and swift action, the persistence of coral reefs beyond the next few decades is in serious jeopardy.
“Our study shows that ENSO is a major determinant of the fate of the world’s coral reefs,” he said.
“Rising sea temperatures, coupled with other stressors such as ocean acidification and pollution, have severely weakened their resilience.
“This puts coral reefs and a quarter of the ocean’s biodiversity at serious risk of annihilation.”
Professor Hoegh-Guldberg said efforts to introduce of heat-tolerance genes into the natural coral population have shown promise, but the reality of scaling these efforts remains logistically challenging.
“Given the complex and interconnected nature of marine ecosystems such as coral reefs, a comprehensive approach is necessary for mitigating the impacts of changing oceanic conditions,” he said.
“The importance of reducing our emissions is underscored in our findings, where massive changes to oceanic warming are set to destroy coral reefs and many other ecosystems.
“With this in mind, there are extremely tough discussions underway at the COP28 climate meetings.”
This research is published in Science.
JOURNAL
Science
METHOD OF RESEARCH
Meta-analysis
SUBJECT OF RESEARCH
Not applicable
ARTICLE PUBLICATION DATE
7-Dec-2023
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