Ocean Oxygen Levels Falling As Waters Warm


Corresponding 4X increase in Dead Zones.

Although the planet has broken all time global temperature records for the past three years, the effects of abrupt climate change are manifested even more in the waters of the global sea – at least for the time being. Much of the heat and CO2 from the atmosphere is currently absorbed into the oceans, a slow motion doom machine that is only less alarming because it is not easily observed. As a result, rapidly warming waters are wreaking all kinds of havoc with the planetary ecological balance and few citizens of planet Earth are aware of the impending disaster.

Sea Ice Collapse: Higher water temps have melted the sea ice fields at both poles to new low minimum and maximum extents, driving an irreversible positive feedback loop. The feedback loop is easy to understand: When the sun’s rays strike dark open water rather than white ice, the heat is sucked right into the ocean rather than reflected back into space. The water continues warming, melting more ice.

Ice Shelf Collapse: The coastlines of Antarctica and Greenland are defined by floating ice shelves, which are mostly in the water, but which hold back the massive land-based glaciers behind them. These shelves are being dissolved from the bottom up by warming waters, and are now beginning to crack away and fall into the sea. As a result, the flow of the glaciers into the sea has accelerated, contributing to sea level rise.

Rising Seas: In addition to trillions of gallons of new water pouring into the seas from melting land ice, the actual volume of the planetary ocean expands as the water heats up. Simple physics.

Slowdown of Gulf Stream/Ocean Circulator: The addition of fresh water changes the water density of the oceans in the Arctic regions. The great Ocean Circulator (of which the Gulf Stream is the most famous component) keeps Europe relatively mild, among other effects. Read more here.

Water Chemistry: The oceans have also become about 30% more acidic since the mid-nineteenth century as billions of tons of Carbon is absorbed by the seas. The early effects of this process – which is understood to be irreversible – is that shellfish, crabs and other marine animals are having problems forming shells. There have already been early panics in these fisheries as the problem spreads.

There is nothing to like about these developments, but worse is yet to come as scientists detect the first confirmation of the expected decrease in ocean Oxygen levels.

Earlier in February, the first in-depth study on global ocean oxygen content was published in Nature by oceanographers of GEOMAR Helmholtz Centre for Ocean Research Kiel. Based on literally millions of global measurements, the researchers report a decline in dissolved oxygen of 2% over the past 50 years. While there are always variations in oxygen levels from location to location, the study showed that percentages dropped throughout the ocean, with only a few minor exceptions. The trend confirms expectations of long standing models and also projects a continuation of the condition in the decades to come.

At its core, the cause is as simple as high school chemistry: as water temperature climbs, it is less able to dissolve oxygen. In addition, warmer water absorbs less oxygen at the surface-to-air interface, reducing to amount of total oxygen available. And in today’s warmer oceans, there is less turnover between differing depths (stratification), which further reduces the oxygen penetration to lower levels.

Although this is only the beginning of a long ride down, the potential effects of oxygen depletion on marine life should be obvious. There is already growing evidence that the habitats of large predator fish are shrinking due to reduced oxygen.

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