Nav: Home

Long-term data show a recent acceleration in chemical and physical changes in the ocean

October 16, 2020

New research published in Nature Communications Earth & Environment uses data from two sustained open-ocean hydrographic stations in the North Atlantic Ocean near Bermuda to demonstrate recent changes in ocean physics and chemistry since the 1980s. The study shows decadal variability and recent acceleration of surface warming, salinification, deoxygenation, and changes in carbon dioxide (CO2)-carbonate chemistry that drives ocean acidification.

The study utilized datasets from Hydrostation 'S' and the Bermuda Atlantic Time-series Study (BATS) projects at the Bermuda Institute of Ocean Sciences (BIOS). Both are led by Professor Nicholas Bates, BIOS senior scientist and the projects' principal investigator (PI), and Rod Johnson, BIOS assistant scientist and the projects' co-PI. Together, these time-series represent the two longest continuous records of data from the global open ocean.

"The four decades of data from BATS and Hydrostation 'S' show that the ocean is not changing uniformly over time and that the ocean carbon sink is not stable over recent time with variability from decade to decade," Bates said.

Of the two sites, Hydrostation 'S' is the oldest, located approximately 15 miles (25 km) southeast of Bermuda and consisting of repeat biweekly hydrographic observations of temperature, salinity, and dissolved oxygen conducted through the water column since 1954. The Bermuda Atlantic Time-series Study (BATS) site is located approximately 50 miles (80 km) southeast of Bermuda. It consists of monthly sampling of the physics, chemistry, and biology of the entire water column since 1988. The study's datasets represent more than 1381 cruises to Hydrostation 'S' from 1954 to 2020 and more than 450 cruises to BATS from 1988 to the end of 2019.

Results showed that, over the last 40 years, surface temperatures in the Sargasso Sea have increased by 0.85 +/- 0.12oC, with the summer surface temperatures rising at a higher rate than winter. Additionally, the winter (<22°C) ocean state has gotten shorter by almost a month, while the summer season (with waters warmer than 25°C) has gotten longer. During the same period, surface salinity also increased by ~0.11 +/- 0.02. Importantly, these data show evidence of decadal variability; however, during the last decade (2010-2019), rapid warming of 1.18oC and salinification of 0.14 has occurred.

The data also show a trend of dissolved oxygen (DO) decline in the Sargasso Sea since the 1980s, representing a loss of ~2% per decade. Given the ocean warming observed in the Sargasso Sea, the researchers estimate that the warming impact on DO solubility would likely have contributed to about 13% of the total decline of DO over the past nearly 40 years. The remaining deoxygenation (~87%) must have resulted from the combined effect of changes in ocean biology and physics.

The BATS and Hydrostation 'S' time-series data allow direct detection of the ocean acidification signal in the surface waters of the North Atlantic Ocean. The typical pH range of surface waters in the 1980s ranged from wintertime highs of ~8.2 to summertime lows of ~8.08-8.10, with the ocean remaining mildly alkaline at present (~7.98-8.05). The rate of pH change is ~0.0019 +/- 0.0001 year-1, which is a more negative rate than previously reported and represents a 20% increase in hydrogen ion concentration since 1983. These changes were accompanied with significant increases of dissolved inorganic carbon and CO2 and decreases in both calcite and aragonite saturation states.

"In forty years, seawater CO2-carbonate chemistry conditions are now altered beyond the seasonal chemical changes observed in the 1980s," Johnson said. "The modification of seawater CO2 -carbonate chemistry will continue with future anthropogenic CO2 emissions."

The observations off Bermuda reveal the substantial decadal variations and highlight the need for long-term data to determine trends in other ocean physical and biogeochemical properties, particularly when linking local measurements to basin-scale changes. Long-term data on ocean chemistry and physical from time-series sites such as Hydrostation 'S' and BATS provide critically needed and unparalleled observations that, when coupled with ocean-atmosphere models, allow for a more complete understanding of drivers of the global carbon cycle.
-end-


Bermuda Institute of Ocean Sciences

Related Bats Articles:

Why doesn't Ebola cause disease in bats, as it does in people?
A new study by researchers from The University of Texas Medical Branch at Galveston uncovered new information on why the Ebola virus can live within bats without causing them harm, while the same virus wreaks deadly havoc to people.
The genetic basis of bats' superpowers revealed
First six reference-quality bat genomes released and analysed
Bats offer clues to treating COVID-19
Bats carry many viruses, including COVID-19, without becoming ill. Biologists at the University of Rochester are studying the immune system of bats to find potential ways to ''mimic'' that system in humans.
A new social role for echolocation in bats that hunt together
To find prey in the dark, bats use echolocation. Some species, like Molossus molossus, may also search within hearing distance of their echolocating group members, sharing information about where food patches are located.
Coronaviruses and bats have been evolving together for millions of years
Scientists compared the different kinds of coronaviruses living in 36 bat species from the western Indian Ocean and nearby areas of Africa.
Bats depend on conspecifics when hunting above farmland
Common noctules -- one of the largest bat species native to Germany -- are searching for their fellows during their hunt for insects above farmland.
Tiny insects become 'visible' to bats when they swarm
Small insects that would normally be undetectable to bats using echolocation suddenly become detectable when they occur in large swarms.
Illumination drives bats out of caves
Researchers of the Leibniz Institute for Zoo and Wildlife Research and the Max Planck Institute for Ornithology have investigated how the illumination of bat caves affects the animals' behaviour and whether the colour of light makes a difference on their flight.
Bats may benefit from wildfire
Bats face many threats -- from habitat loss and climate change to emerging diseases, such as white-nose syndrome.
Ecology: Wildfire may benefit forest bats
Bats respond to wildfires in the Sierra Nevada Mountains in varied but often positive ways, a study in Scientific Reports suggests.
More Bats News and Bats Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: The Power Of Spaces
How do spaces shape the human experience? In what ways do our rooms, homes, and buildings give us meaning and purpose? This hour, TED speakers explore the power of the spaces we make and inhabit. Guests include architect Michael Murphy, musician David Byrne, artist Es Devlin, and architect Siamak Hariri.
Now Playing: Science for the People

#576 Science Communication in Creative Places
When you think of science communication, you might think of TED talks or museum talks or video talks, or... people giving lectures. It's a lot of people talking. But there's more to sci comm than that. This week host Bethany Brookshire talks to three people who have looked at science communication in places you might not expect it. We'll speak with Mauna Dasari, a graduate student at Notre Dame, about making mammals into a March Madness match. We'll talk with Sarah Garner, director of the Pathologists Assistant Program at Tulane University School of Medicine, who takes pathology instruction out of...
Now Playing: Radiolab

What If?
There's plenty of speculation about what Donald Trump might do in the wake of the election. Would he dispute the results if he loses? Would he simply refuse to leave office, or even try to use the military to maintain control? Last summer, Rosa Brooks got together a team of experts and political operatives from both sides of the aisle to ask a slightly different question. Rather than arguing about whether he'd do those things, they dug into what exactly would happen if he did. Part war game part choose your own adventure, Rosa's Transition Integrity Project doesn't give us any predictions, and it isn't a referendum on Trump. Instead, it's a deeply illuminating stress test on our laws, our institutions, and on the commitment to democracy written into the constitution. This episode was reported by Bethel Habte, with help from Tracie Hunte, and produced by Bethel Habte. Jeremy Bloom provided original music. Support Radiolab by becoming a member today at Radiolab.org/donate.     You can read The Transition Integrity Project's report here.