Ocean Warming : False Security

The human race has been treating the World Ocean as a dumping ground for global warming and excess carbon dioxide emissions.

It’s where most of the heat ends up, and almost half the anthropogenic carbon dioxide emissions as well.

Research shows that as humanity pours more carbon into the sky, the oceans are able to react by taking up more of it.

The Southern Ocean in particular is showing a healthy response, pulling more and more of our emissions down from the atmosphere.

On the face of it, the oceans are increasing their capacity to suck carbon out of the air, either by biological means or through simply mixing with the air, so some argue that we should relax and rely on these carbon sinks to avert dangerous warming of the ground level atmosphere – maintaining a healthy atmosphere for all land-based life.

However, this net reduction in atmospheric carbon dioxide due to this increased ocean carbon pump is masking the effects of global warming – for the time being. The oceans are warming, and this combined with increased overturning is resulting in the oceans giving up more carbon dioxide from their depths as a result.

For now, the ocean carbon sink is holding up and compensating for some global warming, but there are concerns should the carbon pump fail, or the effects of global warming overtake it.

The very latest research into changes in the World Ocean show clear trends in salinity – how fresh or how salty seawater is. These changes are associated with the higher energy in the Earth system : more heat captured by the ocean is making wind patterns more powerful, which makes ocean overturning stronger.

Of special concern is the effect this could have on the Southern Ocean. A stronger overturning would increase the upwelling of deep ocean water, which would draw long-sequestered carbon-rich gases from the deeps to the surface of the sea, where it would outgas to the atmosphere.

This is the scenario recently suggested to explain part of the process of how the Earth came out of the last glacial period over 15,000 years ago (“What causes the CO2 rise?”)

The biological productivity of the oceans, the levels of greenhouse gases in ocean water, and the strength of the carbon sinks will continue to be of intense concern as time passes.

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