Ocean acidification 'worst in 300 million years'

A colony of coral in Indonesia begins to bleach. For many organisms such as corals calcification declines with increased acidification.

As we've been pointing out for some time now, the oceans have been doing the heavy lifting in removing extra heat from the atmosphere, which may have accounted for a pause in global warming over the last decade or two.

But it will only be a temporary respite. Meanwhile the oceans have trouble of their own as carbon dioxide dissolving in them increases acidification.

A World Meteorological Organization's latest Greenhouse Gas Bulletin out this week (PDF) reveals just how severe this problem is. "The current rate of ocean acidification appears unprecedented at least over the last 300 million years," it says.

It is the first time the WMO has included a section on ocean acidification in the Bulletin and Wendy Watson-Wright, Executive Secretary of the Intergovernmental Oceanographic Commission of UNESCO, welcomes it:

The inclusion of a section on ocean acidification in this issue of WMO’s Greenhouse Gas Bulletin is appropriate and needed. It is high time the ocean, as the primary driver of the planet’s climate and attenuator of climate change, becomes a central part of climate change discussions.

The WMO has a brief summary of the chemistry involved

As CO2 dissolves in seawater it forms carbonic acid (H2CO3), a weak acid that dissociates into bicarbonate (HCO3–) and hydrogen ions (H+). Increased H+ means increased acidity (lower pH).

But it is the figures that give real cause for alarm – the oceans are taking up about 4kg of CO2 per day per person. If that doesn't stop the consequences will be devastating as the WMO points out:

The potential consequences of ocean acidification on marine organisms are complex. A major concern is the response of calcifying organisms, such as corals, algae, mollusks and some plankton, because their ability to build shell or skeletal material (via calcification) depends on the abundance of carbonate ion. For many organisms, calcification declines with increased acidification. Other impacts of acidification include reduced survival, development, and growth rates as well as changes in physiological functions and reduced biodiversity

And the damage cascading through the food chain is almost incalculable – to the point where a vital food source is removed completely. A study published in Science last year, that looked at the state of the oceans 55 million years ago – the last time carbon dioxide levels spiked – might give us some idea of what we can expect.

...long-term geological record reveals an early Cenozoic warm climate that supported smaller polar ecosystems, few coral-algal reefs, expanded shallow-water platforms, longer food chains with less energy for top predators, and a less oxygenated ocean than today.

Not a pretty picture with a global population on its way to 9 billion.

  1. http://beta.cosmosmagazine.com/earth-sciences/has-global-warming-paused
  2. https://www.wmo.int/pages/mediacentre/press_releases/documents/1002_GHG_Bulletin.pdf
  3. http://www.sciencemag.org/content/341/6145/492
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