Expert Commentary

The geological record of ocean acidification

2012 paper published in the journal Science on historic patterns in carbon dioxide and ocean acidification and the implications for the future.

In the past, studies of large-scale changes to the Earth’s oceans have been restricted both by the limited nature of physical sampling and the reality that often these changes occur over great lengths of time.

A 2012 paper published in the journal Science, “The Geological Record of Ocean Acidification,” takes a new approach by examining the geological record to determine levels of atmospheric carbon dioxide, global temperatures and ocean acidification over the past 300 million years. The goal of the study — which was the combined work of scientists from nearly 20 research universities — was to find periods of the Earth’s history that are analogs for current and future global conditions.

Findings of the paper include:

  • The current rate of ocean acidification is faster than at any time in the past 300 million years.
  • The most recent de-glacial transition phase, while similar in temperature and increases in CO2 levels, was “two orders of magnitude slower than current anthropogenic change.”
  • The period 56 million years ago known as the Paleocene-Eocene Thermal Maximum was determined to be the closest future analog. This period of sustained CO2 release was associated with a decline in ocean pH of between 0.25 and 0.45 units. However, current acidification is occurring at almost 10 times this rate.
  • Historically sustained periods of acidification and CO2 increase — which were similar but not as extreme as the last 1,000 years — have led to the collapse of coral reefs and, in one instance, to the extinction of 96% of marine life.

The authors conclude that the geological record reveals that “the current rate of [CO2] release stands out as capable of driving a combination and magnitude of ocean geochemical changes potentially unparalleled in … Earth history, raising the possibility that we are entering an unknown territory of marine ecosystem change.”

In related research, a 2012 study published in Climatic Change estimates that ocean acidification could lead to economic losses for the shellfish industry in excess of $100 billion over the course of this century.

Tags: science, greenhouse gases, global warming, oceans

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