Greenhouse ocean study offers warning for future

May 17, 2011
New research suggests the Earth will see mass extinctions of marine life because of high levels of greenhouse gases. Photo by Oktaviani Marvikasari.

The mass extinction of marine life in our oceans during prehistoric times is a warning that the Earth will see such an extinction again because of high levels of greenhouse gases, according to new research by geologists.

Professor Martin Kennedy from the University of Adelaide (School of & Environmental Sciences) and Professor Thomas Wagner from Newcastle University (Civil Engineering and Geosciences) have been studying 'greenhouse oceans' - oceans that have been depleted of oxygen and suffered from increases in carbon dioxide and temperature.

Using core samples drilled from the ocean bed off the coast of western Africa, the researchers studied layers of sediment from the Late Cretaceous Period (85 million years ago) across a 400,000-year timespan. They found a significant amount of organic material - - buried within deoxygenated layers of the sediment.

"Our research points to a mass mortality in the oceans at a time when the Earth was going through a greenhouse effect, with high levels of carbon dioxide in the atmosphere, and rising temperatures, leading to a severe lack of oxygen (hypoxia) in the water that marine animals are dependent on," Professor Kennedy says.

"What's alarming to us as scientists is that there were only very slight natural changes that resulted in the onset of hypoxia in the deep ocean. This occurred relatively rapidly - in periods of hundreds of years, or possibly even less - not gradually over longer, geological time scales, which suggests that the Earth's oceans are in a much more delicate balance during greenhouse conditions than originally thought, and may respond in a more abrupt fashion to even subtle changes in temperature and CO2 levels than previously thought."

Professor Wagner says the results of their research, published in the Proceedings of the National Academy of Sciences (PNAS), have relevance for our modern world: "We know that 'dead zones' are rapidly growing in size and number in seas and oceans across the globe. These are areas of water that are lacking in oxygen and are suffering from increases of CO2, rising temperatures, nutrient run-off from agriculture and other factors."

Professor Kennedy says: "If you consider that the amount of in our atmosphere has doubled over the past 50 years, this is like hitting our ecosystem with a sledge-hammer compared to the very small changes in incoming solar energy (radiation) which was capable of triggering these events in the past. This could have a catastrophic, profound impact on the sustainability of life in our oceans, which in turn is likely to impact on the sustainability of life for many land-based species, including humankind."

Professor Kennedy says the geological record offers a glimmer of hope thanks to a naturally occurring response to greenhouse conditions. "After a hypoxic phase, oxygen concentration in the ocean seems to improve, and marine life returns. Our results show that natural processes of carbon burial kick in. Importantly, this rescue comes from the land, with soil-formed minerals acting to collect and bury excess dissolved organic matter in seawater. Burial of that excess carbon ultimately contributes to CO2 removal from the atmosphere, cooling the planet and the .

"This is nature's solution to the greenhouse effect and it could offer a possible solution for us. If we are able to learn more about this effect and its feedbacks, we may be able to manage it, and reduce the present rate of warming threatening our oceans."

Explore further: Better forecasts for sea ice under climate change

More information: www.pnas.org/

Related Stories

Oceans losing ability to absorb greenhouse gas

Jan 11, 2010

(PhysOrg.com) -- Like a dirty filter, the Earth's oceans are growing less efficient at absorbing vast amounts of carbon dioxide, the major greenhouse gas produced by fossil-fuel burning, reports a study co-authored ...

The Carbon Cycle Before Humans

Feb 16, 2010

Geoengineering -- deliberate manipulation of the Earth's climate to slow or reverse global warming -- has gained a foothold in the climate change discussion. But before effective action can be taken, the Earth's ...

Recommended for you

Better forecasts for sea ice under climate change

6 hours ago

University of Adelaide-led research will help pinpoint the impact of waves on sea ice, which is vulnerable to climate change, particularly in the Arctic where it is rapidly retreating.

"Ferrari of space' yields best map of ocean currents

14 hours ago

A satellite dubbed the "Ferrari of space" has yielded the most accurate model of ocean circulation yet, boosting understanding of the seas and a key impact of global warming, scientists said Tuesday.

Researcher studies deformation of tectonic plates

17 hours ago

Sean Bemis put his hands together side by side to demonstrate two plates of the earth's crust with a smooth boundary running between them. But that boundary is not always smooth and those plates do not always ...

User comments : 3

Adjust slider to filter visible comments by rank

Display comments: newest first

GSwift7
1 / 5 (1) May 18, 2011
If you consider that the amount of carbon dioxide in our atmosphere has doubled over the past 50 years, this is like hitting our ecosystem with a sledge-hammer


If you read that part and didn't notice anything wrong with it, then you need to read it again. CO2 measurements from mauna loa:

ftp://ftp.cmdl.no..._mlo.txt

April 2011 - 393.18
April 1961 - 319.48
March 1958 - 315.71 (beginning of the instrument record)

Doubling?

2*320 = 640
omatumr
1 / 5 (2) May 18, 2011
If you consider that the amount of carbon dioxide in our atmosphere has doubled over the past 50 years, this is like hitting our ecosystem with a sledge-hammer


If you read that part and didn't notice anything wrong with it, then you need to read it again. CO2 measurements from mauna loa:

ftp://ftp.cmdl.no..._mlo.txt

April 2011 - 393.18
April 1961 - 319.48
March 1958 - 315.71 (beginning of the instrument record)

Doubling?

2*320 = 640


Except for the CO2 data, the story reads well.

The story of CO2-induced global warming seems to be independent of data.

See: "Earth's Heat Source - The Sun",
Energy and Environment 20, 131-144 (2009)

http://arxiv.org/pdf/0905.0704

With kind regards,
Oliver K. Manuel
Former NASA Principal
Investigator for Apollo
Howhot
3 / 5 (2) May 21, 2011
It doubles percentage wise in terms of increase. Just typical statistics. However, in terms of real damages being caused by this CO2 calamity, it is happening and it's going to get worst.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.