Global Warming Is Causing Oceans to Lose Oxygen, Find Out How

The melting ice caps and glaciers have become one of the main images used to prove the existence of global warming. However, a new study showed that the warming climate is not only affecting the Polar Regions, but also the amount of oxygen in the ocean.

The study, published in the journal Nature, showed that the average oxygen concentration in the world's ocean has decreased by more than two percent over the last 50 years.

"We were able to document the oxygen distribution and its changes for the entire ocean for the first time," said Dr. Sunke Schmidtko, an oceanographer at GEOMAR Helmholtz Centre for Ocean Research and lead author of the study, in a press release. "These numbers are an essential prerequisite for improving forecasts for the ocean of the future."

For the study, the researchers analyzed all available historic data on ocean salinity, temperature, depth and oxygen from all around the world. Using these data, in addition to current measurements, the researchers carefully reconstruct the development of the oxygen budget for the past 50 years.

The researchers found that the amount of oxygen concentration throughout the entire ocean has decreased during the study period, with the oxygen loss most notable in northern Pacific Ocean and southern Atlantic. The amount of oxygen lost is approximately 5 petamoles or 80 billion metric tons. Furthermore, the researchers discovered that the number of dead zones in the oceans, or areas with no oxygen, have quadrupled since 1960.

There are two possible ways how global warming can influence the levels of oxygen concentration in the ocean. The increasing atmospheric temperature is making the ocean surface warmer. Unlike colder waters, warmer waters absorb less oxygen from the atmosphere. Additionally, increasing ocean temperatures could also alter the ocean circulation. As the warmer water stabilize the stratification of the ocean, it weakens the circulation connecting the surface with the deeper parts of the ocean. Due to this, less oxygen is being transported into the deep sea.

Oxygen loss in the ocean can have detrimental consequences in the future. The researchers noted that the uneven distribution of oxygen throughout the ocean could have far-reaching consequences for fisheries and coastal economies.