Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Unstable Atlantic deep ocean circulation under future climate conditions

21.02.2014
A new study looking at past climate change, asks if these changes in the future will be spasmodic and abrupt rather than a more gradual increase in the temperature

Today, deep waters formed in the northern North Atlantic fill approximately half of the deep ocean globally. In the process, this impacts on the circum-Atlantic climate, regional sea level, and soak up much of the excess atmospheric carbon dioxide from industrialisation — helping to moderate the effects of global warming.


Eirik Vinje Galaasen is preparing foraminifera shells from the last interglacial period for stable isotope analyses in the massspectrometer.

Credit: Photo: Gudrun Sylte

Changes in this circulation mode are considered a potential tipping point in future climate change that could have widespread and long-lasting impacts including on regional sea level, the intensity and pacing of Sahel droughts, and the pattern and rate of ocean acidification and CO2 sequestration.

Until now, this pattern of circulation has been considered relatively stable during warm climate states such as those projected for the end of the century. A new study led by researchers from the Bjerknes Centre of Climate Research at the University of Bergen (UiB) and Uni Research in Norway, suggests that Atlantic deep water formation may be much more fragile than previously realised.

The researchers Eirik Vinje Galaasen (UiB), Ulysses Ninnemann (UiB), Nil Irvali (Uni Research), and Helga (Kikki) Kleiven (UiB) and their colleagues from Rutgers University, USA (Professor Yair Rosenthal), Laboratoire des Sciences du Climat et de l'Environnement, France (Research Scientist Catherine Kissel) and the University of Cambridge, UK (Professor David Hodell) used the shells of tiny single-celled, bottom-dwelling foraminifera found in marine sediment in the North Atlantic Ocean to reconstruct the surface ocean conditions and concomitant deep ocean circulation of about 125,000 years ago. This is the last interglacial period, when the North Atlantic was warmer, fresher and sea level was higher than it is today and looked a lot like what climate models predict it will look by the end of this century.

"At that time, there were a series of sudden and large reductions in the influence of these North Atlantic waters in the deep ocean. These deep water reductions occurred repeatedly, each lasting for some centuries before bouncing back. The unstable circulation operated as if it was near a threshold and flickered back and forth across it," says Eirik Vinje Galaasen, a PhD student and now researcher at UiB's Department of Earth Science, who is the lead author of the paper published in the journal Science.

"These types of changes hadn't been noticed before because they are so short-lived. Geologists hadn't focused on century scale ocean changes because they are difficult to detect," adds Professor Ulysses Ninnemann, from UiB's Department of Earth Science and Galaasen's PhD adviser.

"Our study demonstrates that deep water formation can be disrupted by the freshening of the regional surface water, which might happen due to enhanced precipitation and glacier melting under future climate change scenarios," says Yair Rosenthal, a co-author on the paper.

The international team studied traces of deep ocean properties imprinted in the sediments on the seafloor. Coring into the seafloor mud they could look back in time to reconstruct changes in the abyssal ocean at a location South of Greenland that is sensitive to North Atlantic Deep Water. The mud at this location builds up 10󈝻 times as fast as normal, recording much shorter changes than at other sites. Although the changes are short from a geological perspective, a few centuries of reduced deep water could be a big deal for societies that would have to grapple with things like draughts and sea level changes that could accompany them.

No "The Day After Tomorrow" scenario: A popularised notion is that if the ocean circulation declines it could cause large cooling or, as in the case of the Hollywood movie The Day After Tomorrow, a new ice age. Although some cooling did occur locally south of Greenland when the circulation slowed, there was no evidence for really large cooling associated with these changes. It could be that human beings haven't been able to find it yet, but equally reasonable is that humankind simply don't get really big cooling as the ocean slows down because when it is really warm, sea ice cannot form, and this supercharges the cooling effect of ocean circulation changes. In any event, the super cooling or slide into the next ice age as popularised in a Hollywood blockbuster did not occur.

Will this happen to the future Earth? Many models have actually predicted a slow and gradual decline in North Atlantic circulation over the next century. However, different models offer widely different scenarios for what will happen in the future. While the climate of the last interglacial is not exactly what will be the case in a future greenhouse world, it does share some features, including being fresher and warmer by a few degrees Celsius in the northern Atlantic. Training models, if models can capture the types of changes we see in the past, may also be doing a good job at predicting the future. The seafloor evidence suggests that there were large and fast changes in circulation the last time the ocean looked the way it may look by the end of this century.

The Bjerknes Centre for Climate Research

The Bjerknes Centre for Climate Research (BCCR) is a cooperation on climate research among the four partners University of Bergen, Uni Research, the Institute of Marine Research and Nansen Environmental and Remote Sensing Centre, located in Bergen, Norway.

Key research themes are the climate system and climate changes in the past, present and future, caused by both natural and man-made changes.

The scientific staff consists of more than 150 researchers and scholars, who come from Norway and several other European countries, USA, Canada, China and several countries in Africa, Asia and South America.

The Bjerknes Centre is named after Vilhelm Bjerknes and his son Jacob Bjerknes, who were the leading figures of the Bergen School of the physics of atmosphere and ocean.

Gudrun Sylte | EurekAlert!
Further information:
http://www.uni.no
http://www.bjerknes.uib.no

More articles from Studies and Analyses:

nachricht New study: How does Europe become a leading player for software and IT services?
03.04.2017 | Fraunhofer-Institut für System- und Innovationsforschung (ISI)

nachricht Reusable carbon nanotubes could be the water filter of the future, says RIT study
30.03.2017 | Rochester Institute of Technology

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

Im Focus: Using graphene to create quantum bits

In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.

In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

Physicists discover mechanism behind granular capillary effect

24.05.2017 | Physics and Astronomy

Measured for the first time: Direction of light waves changed by quantum effect

24.05.2017 | Physics and Astronomy

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>