Too much carbon dioxide really mucks with the chemistry of seawater, acidifying the oceans and potentially throwing sea life out of whack. Marine biologists have already spotted signs of trouble ahead...
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...while geoscientists are taking a look at the earth's past for clues about what's in store. Their latest prediction for the future, based on a new review of ocean acidification events from the past 300 million years: We ain’t seen nothin’ yet.
In an article published today in Science, a group of 21 ancient-ocean-and-climate specialists describe how they scoured the geologic record for events that went hand-in-hand with ocean acidification and elevated levels of carbon dioxide in the atmosphere. They identified eight historical events, including de-glaciations and mass extinctions.
Among them, the best analog for the future turned out to be an abrupt prehistoric warm-up from 56 million years ago called the Paleocene-Eocene Thermal Maximum, or PETM. During that event, global temperatures rose five degrees Celsius in response to a massive injection of heat-trapping greenhouse gases into the atmosphere (probably from a combination of sources, including volcanoes). That gas burst acidified the deep ocean so thoroughly that nearly all the calcium carbonate sediment from that time window dissolved away before it could be preserved.
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One of the study’s authors, Lee Kump of Pennsylvania State University, points out that the PETM may pale in comparison to what lies ahead. He and his colleagues discovered recently that the intense gas release that caused the PETM was only 10 percent of the rate at which greenhouse gases are building up in the atmosphere today. Such speediness indicates trouble because adjusting to rapid change is much more difficult, Kump explained in a recent article in Scientific American.
Indeed, the biggest lesson to come out of this latest scientific review is that, unfortunately, there is no perfect example from the past that is going to tell us what will happen in the future. As extreme as some of the past situations were, they all played out over much longer timescales that the changes happening today. We are infusing the atmosphere with carbon dioxide at a rate that is unprecedented in the history of the planet—and the consequences likely will be as well. In the words of the scientists themselves:
“…the current rate of (mainly fossil fuel) CO2 release stands out as capable of driving a combination and magnitude of ocean geochemical changes potentially unparalleled in at least the last ~300 My of Earth history, raising the possibility that we are entering an unknown territory of marine ecosystem change.”
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IMAGE:
Underwater ocean bubble cloud. (Duncan Rawlinson, Wikimedia Commons)
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