[[link removed]]
SUNDAY SCIENCE: HOW WE DISCOVERED THAT THE OCEAN’S SURFACE ABSORBS
MUCH MORE CO₂ THAN PREVIOUSLY THOUGHT
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Daniel Ford, Ian Ashton, Jamie Shutler
November 7, 2024
The Conversation
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*
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_ The oceans play a pivotal role in drawing down atmospheric carbon
dioxide (CO₂) and have so far acted as a brake on the full impact of
climate change. _
Measurements were taken from on board the royal research ship
Discovery as it travelled through the North Atlantic Ocean., Daniel
Ford, CC BY-NC-ND
The oceans play a pivotal role in drawing down atmospheric carbon
dioxide (CO₂) and have so far acted as a brake on the full impact of
climate change. Current estimates of the CO₂ from the atmosphere
that disappears in the ocean, commonly referred to as the ocean CO₂
sink, suggests that around 25% of all human CO₂ emissions have been
taken up by the oceans.
In our recent journal paper in Nature Geoscience
[[link removed]], we show that a
thin layer at the ocean surface called the “ocean skin”, a layer
thinner than a human hair, increases this ocean CO₂ uptake by about
7%. That sounds like a small difference, but this additional uptake is
equivalent to the CO₂ absorbed by the entire Amazon rainforest each
year.
This long-term uptake of carbon into the ocean has negative
implications for ocean health. It is slowly causing the acidification
of the oceans
[[link removed]]
– as sea water takes up more CO₂ it is altering the ocean
chemistry and lowering its pH, and this cannot easily be reversed.
Since the 1990s, scientists have suggested
[[link removed]] that a cooler skin would
enhance CO₂ uptake by the oceans. As such, estimates of CO₂
absorption that ignore this effect would be inaccurate.
Since then, the sea surface temperature researchers have shown that
the ocean skin is slightly cooler than the waters just below. This
surface skin is, on average, ~0.17°C cooler. A temperature change
like this increases the concentration of CO₂ in this tiny sliver of
water. This matters because it’s this water that is in direct
contact with the atmosphere.
Because the exchange of CO₂ between the ocean and atmosphere is
controlled by the concentration difference between the surface and the
layer of water below, this cooler skin increases the absorption of
CO₂ into the ocean.
European researchers
[[link removed]]
confirmed these concentration driven processes in 2007. They used
equipment similar to a powerful microscope with a camera to visualise
oxygen gas concentrations within these tiny layers in a laboratory. In
recent years, the impact of the surface layer on global ocean carbon
has been evaluated using theory, modelling and satellite-based
observations, but until now, nobody had actually measured this effect
in the sea.
To carry out our research, the European Space Agency helped us
[[link removed]] put specialist measurements on board two
research ships taking part in the annual Atlantic Meridional Transect
scientific cruises [[link removed]] that each year hosts UK and
international scientists.
In 2018, we collected data from our kit on board the royal research
ship James Clark Ross as it travelled approximately 9,000 miles
(14,500km) from Harwich in south-east England to Port Stanley on the
Falklands.
In 2019, the equipment was installed on the royal research ship
Discovery which went from Southampton, UK, to Puntas Arenas, Chile.
This ship sailed through very rough seas in the North Atlantic and
near the Falklands, but experienced a mirror glass ocean with no real
waves near the Equator, so our measurements reflected a wide range of
different sea conditions.
Up, up and away?
On each voyage, two sets of measurements were taken. For one set of
measurements, we used a micro meteorological system to measure wind
speed and air temperature, combined with atmospheric gas measurements.
Collectively, this is known as the “eddy covariance system” and it
tracks how much CO₂ gas is in the air moving up (away from the
surface) as opposed to that moving down. This tells us how much CO₂
is being absorbed or emitted by the ocean.
The second set of measurements sampled water collected from an inlet
pipe on the ship. From this, we measured the gas in the water and its
temperature. We then combined this with a high specification thermal
camera that measures the temperature of the ocean skin.
[view of wavy ocean, sunrise on horizon]
[[link removed]]
Measurements were taken in various different sea states during two
trips on royal research ships. Daniel Ford, CC BY-NC-ND
[[link removed]]
Together, both sets of measurements should provide the same result if
the ocean skin had no effect. Any differences between them revealed
how the ocean skin was affecting the ocean’s CO₂ sink.
Accurate estimates of the CO₂ absorbed by the oceans are critical to
calculating global carbon budgets. These budgets quantify how carbon
moves around global systems and are used to guide international policy
on reducing emissions.
The ocean and atmosphere are the two primary reservoirs of carbon that
can be accurately observed. Accurately estimating these, constrains
all other parts of the global carbon budget and allows us to assess
what is termed the “remaining budget”. This identifies how much
more carbon can be emitted before a specific climate target is
breached. Importantly, we cannot estimate the carbon absorbed by all
the land on Earth without first estimating the carbon absorbed by the
oceans. Therefore, the ocean CO₂ uptake being approximately 7%
higher will have implications for the whole global carbon budget and
Earth’s carrying capacity for further emissions.
As the UN’s climate summit, Cop29, approaches in Azerbaijan, this
research helps define the problem of CO₂ emissions more accurately.
Climate experts will need to reassess the global carbon budget to
reflect our new findings and this additional ocean uptake will cause
an imbalance in the budget, potentially indicating that the land-based
carbon sink is smaller than currently thought, so less effective in
helping remove atmospheric emissions.
The oceans sucking up more of our carbon emissions than previously
thought sounds positive. But this news means that climate change,
along with other human activities, such as over fishing and pollution,
are putting increased pressure on ocean health. It could also imply
that the land’s capacity to absorb CO₂ has been overestimated, and
that more attention should be paid to conserving ocean ecosystems.
As the need to reduce emissions and meet reduction targets ramps up,
insights about how the ocean skin works will help scientists
understand how the ocean will respond to our emissions. Unfortunately
though, it won’t let anyone off the hook.
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[[link removed]]_[The
Conversation]
Daniel Ford
[[link removed]], Research
Fellow in Biological and Physical Oceanography, Earth and
Environmental Science, _University of Exeter
[[link removed]]_;
Ian Ashton [[link removed]],
Senior Lecturer in Offshore Technology, _University of Exeter
[[link removed]]_,
and Jamie Shutler
[[link removed]],
Professor of Earth Observation and Climate, _University of Exeter
[[link removed]]_
This article is republished from The Conversation
[[link removed]] under a Creative Commons license. Read
the original article
[[link removed]].
Can These Ex-Hollywood Chimps Find a Place Among the Apes?
[[link removed]]
Emily Anthes
The New York Times
Behind the scenes at a Chicago zoo, chimpanzees who spent years
entertaining humans are learning to befriend their own kind.
November 15, 2024
* Science
[[link removed]]
* Climate Change
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* oceans
[[link removed]]
* CO2
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* COP29
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