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May 7, 2019
WILL OCEANS CONTINUE TO ABSORB CO2 AS THEY DO NOW?
Arshad M. Khan
Each year around 40 billion tons of CO2 is released into the air, but 20 billion tons is
recaptured through natural processes -- sometimes we just don't know how lucky we
are. We can thank the Amazon rain forest and vegetation in general, not forgetting
the seas which swallow about 10 billion tons. It is going to be difficult enough for
humans to deal with the remainder to abate global warming without the surprise
scientists dropped on us in a new paper published April 29, 2019. The oceans are
beginning to let us down.
As one might expect with a warming earth, mean ocean temperatures are also rising
and that means more bacteria, one cause of the problem. The vast populations of
photosynthetic plankton breathe in CO2 and release oxygen just like the vegetation
on land. As they die, they sink to the bottom of the sea taking the stored carbon with
So far so good but the aerobic bacteria get to munch on some of the dead plankton,
and in the process release back their CO2. Aerobic bacteria live in oxygenated
environments within 150 feet of the surface, so most of the CO2 simply bubbles back
up to escape into the air. As the bacteria have mushroomed with rising sea
temperatures, they are eating more and more of the dead carbon-laden plankton and
less is descending to the sea floor.
These effects are worse near the tropics where water temperatures are much higher.
In some areas tested, researchers found extremes of 85 percent of the carbon being
released into the atmosphere. This 85 percent carbon regeneration occurs also in
gyres (circulating ocean currents) as well as oxygen minimum zones (OMZ) near the
west coast of continents, contrary to expectation. Apparently, the warming oceans
are allowing the bacteria to thrive in these regions as well.
According to the study, the cooler subtropical areas in the center of the North Atlantic,
South Atlantic, North Pacific and South Pacific will feel the effect most strongly
because warming will enhance nutrient levels of the rich phytoplankton population
giving bacteria a feast.
As oceans warm further, the effect is expected to cause even more carbon
regeneration, meaning less will fall to the ocean floor. To make matters worse,
increasing CO2 will lower the capacity of the oceans to absorb more.
Moreover, increasing CO2 lowers pH and raises ocean acidity harming creatures like
starfish -- and thereby mushrooming populations of their prey the sea urchins. These
in turn are denuding kelp beds, destroying the habitat for fish and invertebrates that
shelter there. The latter are also having difficulty in making shells, and corals with
making skeletons, for all these need calcium carbonate that can not be produced as
easily in a higher pH ocean.
To make matters worse, global climate models have been under-predicting
temperature rise (2.0-4.5C); the latest have upped it to 5.0C reducing the time to act
on climate change. It is a sad story. The unwitting consequence of witting fossil fuel
The more we learn about the natural world, the more important it is revealed to be in
sustaining the delicate balance of our fragile home. To stop the rise in ocean
temperatures, we have to alleviate global warming. It is also one of the causes
threatening the extinction of a million species according to the just released UN
biodiversity report. The means to respond to climate change are there. We know
what they are. We just have to muster the will to use them.