Iron floating into the sea on aerosols is driving a loss of oxygen

(credit: Flickr user marya)

The oxygen minimum zone is the section of ocean that has the lowest oxygen saturation. While the thickness and depth of the OMZ varies, the Pacific Ocean's OMZ has been expanding in recent years. This has consequences for oceanic ecosystems, since animals struggle in this region, and its primary productivity is low. However, the cause of this oxygen decline is not fully understood. A paper published in Nature Geoscience uses climate modeling to indicate that aerosol particulate pollution may be contributing significantly to the acceleration of oxygen depletion.

To determine the relationship among atmospheric pollution, ocean dynamics, and the OMZ, researchers performed computational simulations of atmospheric chemistry and its impact on marine biochemistry. This modeling included fluctuations of aerosols that contained soluble iron and fixed nitrogen, coupled with a dust-iron dissolution scheme. The model also included hindcast simulations that tracked anthropogenic pollution increases between the years of 1750 and 2002.

The researchers’ model showed that the combination of climate variability and longterm increases in macro- and micronutrients going into the ocean alters the large-scale patterns of ocean productivity and dissolved oxygen. They also saw that variability in ocean circulation and pollution enhanced the deposition of soluble iron, whereas fixed nitrogen did not see the same effect.

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