CO2 and ocean acidification: running into the buffers?
The oceans are an enormous store of carbon, substantially greater than on land or in the atmosphere, and play a key role in the global carbon cycle, especially in helping regulate the amount of CO2 in the atmosphere.
The oceans are important because they have taken up 27-34% of the CO2 produced by humankind through the burning of fossil fuels, cement manufacturing and land use changes since the industrial revolution.
Whilst this has somewhat limited the historical rise of CO2 in the atmosphere, thereby reducing the extent of greenhouse warming and climate change caused by human activities, this has come at the price of a dramatic change to ocean chemistry. In particular, and of great concern, is the measurable change in ocean pH and carbonate and bicarbonate ion concentration - 'ocean acidification'. Our understanding of the impact of CO2 on the carbonate chemistry is such that we know with very high certainty that ocean acidification will continue.
Lessons from the deep past
Ocean acidification events in the Earth's past may help us interpret the future of our oceans in a world of increasing CO2 emissions.
As a result of an ocean acidification event 55.5 million years ago -
- The mass extinction of many benthic shell forming organisms may have occurred.
- Many pelagic shell forming organisms survived.
- Recovery took hundreds of thousands of years.
- Until 200 years ago atmospheric CO2 had been const ant for 650,000 years and possibly for 20 million years.
- In the last 200 years ocean acidity has increased by 30%, a rate much faster than anytime in the last 65 million years. Substantial extinctions of benthic and planktonic organisms could result.
Why it matters
Links to Arctic sea ice...
- Winter time sea ice acts as a lid preventing CO2 returning to the atmosphere.
- Sea ice produces brines which sink and take CO2 with them.
Increasing ocean acidification has the potential to harm marine ecosystems and alter the oceans' ability to take up excess CO2 from the atmosphere leading to a direct impact on future climate change.
Socio-economic impacts of ocean acidification are difficult to predict. However, the goods and services provided by the marine environment to the UK are important; for example, multi-million pound fisheries, fish meal and aquaculture industries employ tens of thousands of people and if impacted by ocean acidification this could have a direct economic effect. Globally, coral reefs have been valued at $30 billion and provide food, tourism and shore protection. Any threat to them will be important for the economies of some of the UK's overseas territories.
PHOTOS from top: Donna Roberts, Donna Roberts.