Will Oceans Contimue to Absorb CO2 as They Do Now?

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 them.

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 burning.

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