New study casts light on climate change and oceanic oxygen levelsA commonly held belief that global warming will diminish oxygen concentrations in the ocean looks like it may not be entirely true. According to new research published in Science magazine, just the opposite is likely the case in the northern Pacific Ocean, with its anoxic zone expected to shrink in coming decades because of climate change. An international team of scientists came to that surprising conclusion after completing a detailed assessment of changes since 1850 in the eastern tropical northern Pacific's oxygen minimum zone (OMZ). An ocean layer beginning typically a few hundred to a thousand meters below the surface, an OMZ is by definition the zone with the lowest oxygen saturation in the water column. OMZs are a consequence of microbial respiration and can be hostile environments for marine life. Using core samples of the seabed in three locations, the scientists
measured the isotopic ratio of nitrogen-15 to nitrogen-14 in the organic
matter therein; the ratio can be used to estimate the extent of anoxia
in these OMZs. The core depth correlates with age, giving the team a
picture of how the oxygen content varied over the time period. "The prevailing thinking has been that as the oceans warm due to increasing atmospheric greenhouse gases, the oxygen content of the oceans should decline," Thunell says. "That's due to two very simple processes. Read more at ScienceDaily. |