A San Diego researcher is among a group of scientists who think climate change may be making it harder for wide swaths of ocean to maintain proper oxygen levels.
Oceanographer Lisa Levin of the Scripps Institution of Oceanography in La Jolla has studied so-called ocean dead spots for years. She says wide swaths of water, both near shore and in the deep ocean, are not getting enough life giving oxygen.
Researchers who track oxygen levels say they have been falling since the middle of the 20th century and that’s changing underwater ecosystems. The environmental changes endanger businesses or countries that rely on the oceans for profit or sustenance.
“The well-oxygenated water at the surface is not mixed down into deeper water ... we have lots (of oxygen) in the air, lots right at the surface of the ocean. But the interior of the ocean is not receiving as much of that,” Levin said.
She said nutrient-rich runoff is feeding explosions of phytoplankton which consume oxygen near the surface. Also, warmer oxygen rich ocean temperatures near the surface also keep colder layers of deep oxygen-poor water from mixing.
“What we’ve had over the last quarter century is a strengthening of our undercurrent. These changes in circulation may be due to global warming, quite likely but not for sure yet,” Levin said.
The best way to slow or stop the trend toward more deoxygenated ocean water is to dramatically reduce greenhouse gas emissions on a global scale and to cut down on the amount of nutrient-rich runoff entering coastal waters, Levin said.
The findings are published in the current edition of the Journal Science.
