One of the biggest threats to marine life is oxygen-deficient water. The person and his activity are primarily responsible for this. A team at the Massachusetts Institute of Technology (MIT) has created a 3D atlas of oxygen-starved regions of the tropical Pacific Ocean. Researchers hope this atlas will help predict the effects of climate change on the sea.

Researchers will monitor how the level of oxygen in the ocean changes

“It’s broadly expected that the oceans will lose oxygen as the climate gets warmer. But the situation is more complicated in the tropics where there are large oxygen-deficient zones,” said Jarek Kwiecinski, who developed the atlas along with Andrew Babbin, the Cecil and Ida Green Career Development Professor in MIT’s Department of Earth, Atmospheric and Planetary Sciences . “It’s important to create a detailed map of these zones so we have a point of comparison for future change.”

Oxygen deficient zones

The map covers two major oxygen deficient zones (ODZ) in the Pacific – the first stretching out from the coast of South America, the second zone is off the coast of Central America. A large number of measurements were used to create 3D maps. Specifically, there are 15 million measurements that have been made in the last 30 years. Ocean data on oxygen levels at different depths and at different coordinates were analyzed in detail.

CTD-rosette of Niskin bottles capable of collecting water at depth and making continuous oxygen measurements. Credit: Mary Lide Parker

Measuring oxygen levels will also make it possible to see the potential boundaries of fisheries and marine ecosystems. This will make it possible to better manage fisheries and better protect the environment. Oxygen deficient zones are also among the main sources of nitrous oxide, which is considered a greenhouse gas. New technologies may lead to the creation of additional 3D maps in other parts of the world that are threatened by a lack of oxygen. The work was published in the journal Global Biogeochemical Cycles.

Chief Scientist Andrew Babbin plots sampling course.
Credit: Mary Lide Parker

Impact of the climate crisis on ocean deoxygenation

The number of low oxygen sites in the ocean is rising sharply. Areas completely depleted of oxygen – has quadrupled since the 1960s. In 2011 there were around 700 reported sites worldwide affected by low oxygen conditions. According to the International Union for Conservation of Nature, the world’s oceans have lost about 2% of their oxygen since the 1950s, and they are expected to lose 3% to 4% on average by 2100.

The reason is the warming of the oceans. When the oceans have a higher temperature, they lose their ability to hold oxygen. As a result, less oxygen enters the deeper layers of the ocean. Algal blooms also contribute to the formation of dead zones in the ocean. The fertilizer run-off is mainly responsible for this. This is happening along coastal areas, where oxygen is rapidly depleted. Lower oxygen levels in the ocean have a drastic impact on marine life. Ocean biodiversity is declining and dead zones with little oxygen are preventing many creatures from migrating. It is very important for scientists to understand how ODZs are evolving.

“How the borders of these ODZs are shaped, and how far they extend, could not be previously resolved,” Babbin said. “Now we have a better idea of ​​how these two zones compare in terms of areal extent and depth.”

“This gives you a sketch of what could be happening,” Kwiecinski added. “There’s a lot more one can do with this data compilation to understand how the ocean’s oxygen supply is controlled.”


Image credit: Jarek Kwiecinski and Andrew Babbin/MIT, Mary Lide Parker