O2

Bubbles beneath the sea surface. © Shutterstock

The oceans are losing O2 thanks to global warming and the continued dumping of stuff like fertilizer at alarming rates. Due to GW, warm water holds less O2 than cold. Combine this with over fishing, habitat destruction and the slow motion deterioration of the AMOC and one sees something most ominous coming to pass as civilization moves further into the 21st century. 

(1) The shallow upper leg of the Atlantic Meridional Overturning Circulation carries warm, salty water northward. (2) The warm currents heat up the surrounding air and land, helping to create temperate weather over Western Europe. (3) The surface waters become cooler and denser as they near the Arctic, driving the currents deep below the surface and helping to propel the system. (4) The deep, cool waters run back down the Atlantic.

Oxygen, the element that sustains nearly all multicellular life on Earth, is disappearing from the world’s aquatic ecosystems. In a new review, scientists warn that this rapidly escalating, human-driven crisis threatens to upend the biosphere.

The paper, published June 30 in the journal Limnology and Oceanography, argues that aquatic deoxygenation should be added to the Planetary Boundaries framework. First introduced by a group of 28 internationally renowned scientists in 2009, the framework identifies nine ways that humanity is pushing crucial processes that maintain Earth’s stability and resilience past their limits. They are climate change, ocean acidification, biodiversity loss, atmospheric aerosol loading, stratospheric ozone depletion, freshwater change, land-use change, chemical pollution, and biogeochemical flows.

“The health and stability of our planet depends on the health and stability of aquatic ecosystems, which need oxygen to function normally,” lead author Erica Ferrer, a postdoctoral scholar at the University of California, Santa Barbara’s National Center for Ecological Analysis and Synthesis, said in a statement. “This study is designed to elevate the profile of aquatic deoxygenation as a global threat and show that it does not operate in isolation.”

Globally, the ocean has lost roughly 2% of its dissolved oxygen since the 1950s, and scientists expect it to lose another 1% to 7% by the end of the century, according to Copernicus, the European Union’s Earth observation and environmental monitoring initiative. While that may not sound like a significant reduction, it doesn’t take much to deprive organisms of the oxygen they need and upset delicately balanced aquatic ecosystems.

Something most ominous indeed.