Scientists used geological samples to estimate ocean oxygen during a period of global warming 56 million years ago – and found "limited expansion" of seafloor anoxia (absence of oxygen).
Global warming – both past and present – depletes ocean oxygen, but the new study suggests warming of 5°C in the Paleocene Eocene Thermal Maximum (PETM) led to anoxia covering no more than 2% of the global seafloor.
However, conditions are different today to the PETM – today’s rate of carbon emissions is much faster, and we are adding nutrient pollution to the oceans – both of which could drive more rapid and expansive oxygen loss.
