Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Noise breaks ice

16.01.2002


The last ice-age was interrupted by numerous bouts of warmth.
© Photodisc


Noise may have flipped the stable cold state (bottom) of North Atlantic Ocean currents to the warm state (top).
© Physical Review Letters


Natural randomness punctuated past ice ages with warm spells.

Natural randomness in the world’s climate system may have caused the frequent, fast and fleeting returns to warm conditions during past ice ages, say two German scientists1.

Andrey Ganopolski and Stefan Rahmstorf at the Potsdam Institute for Climate Impact Research think that the flickering character of ice-age climate is a signature of stochastic resonance. This is the counter-intuitive phenomenon where noise amplifies the effect a weak signal has on its surroundings.



Global climate during the past 10,000 years - since the last ice age ended - has remained relatively stable. Conversely, the ice age itself was interrupted by numerous warm episodes of a few hundred years each.

Some of these, called Heinrich events, are thought to have resulted from surges of the great ice sheet that covered much of North America. Others, called Dansgaard-Oeschger (D/O) events, were, till now, a mystery.

During D/O events, temperatures in the North Atlantic region typically rose by 5 to 10 ºC in just a few decades before sinking again over the ensuing centuries. Last year, Richard Alley of Pennsylvania State University and co-workers showed that the time between successive D/O events is often about 1,500, 3,000 or 4,500 years2.

The researchers suggested that the events were caused by some kind of periodic influence on climate that repeated every 1,500 years. They also proposed that the mechanism of D/O events might involve stochastic resonance.

Normally a signal, such as a radio transmission, is hindered by random variations - radio static, say, or noise. But in some circumstances a little noise can actually enhance the signal. This usually happens in a system that flips to a new state when a signal exceeds a certain threshold. Such systems are said to exhibit stochastic resonance.

Stochastic resonance was first invoked in 1982 in an attempt to explain why ice ages often recur every 100,000 years. Although that idea was later found wanting, stochastic resonance was subsequently discovered in a host of other situations. Living organisms use it to detect weak signals in a noisy environment.

Ganopolski and Rahmstorf have now discovered a way in which stochastic resonance may have generated D/O events every 1,500 years, or multiples thereof. They have developed a sophisticated computer model of the global climate system that takes into account the movements of the atmosphere and oceans. The model suggests that during ice ages there are two ways for water to circulate in the North Atlantic Ocean.

In the usual ’cold’ state, ocean currents carry relatively warm Atlantic water north until it sinks south of Greenland and returns towards the Equator in a bottom current. This state is prone to switching to another, temporary, state. Here, warm ocean surface waters travel even further north, into the Nordic Sea, before sinking. This brings warmer temperatures to the high-latitude North Atlantic region.

By forcing their model with a periodic signal that alters the ocean salt content every 1,500 years, the researchers mimic the typical pattern of ice-age D/O events - but only if there is also some random noise in the system.

There is evidence of a 1,500-year periodic forcing in many climate records. It is widely suspected to originate from repetitive changes in the activity of the Sun. By itself, this influence would not have induced the profound shifts in ice-age climate; but stochastic resonance could have enabled the weak signal to imprint itself on the ocean circulation.

References
  1. Ganopolski, A. & Rahmstorf, S. Abrupt glacial climate changes due to Infectious noiseInfectious noise. Physical Review Letters, 88, 038501, (2002).
  2. Alley, R. B., Anandakrishnan, S. & Jung, P. Stochastic resonance in the North Atlantic. Paleoceanography, 16, 190 - 198, (2001).


PHILIP BALL | © Nature News Service
Further information:
http://www.nature.com/nsu/020114/020114-4.html

More articles from Earth Sciences:

nachricht Impacts of mass coral die-off on Indian Ocean reefs revealed
21.02.2017 | University of Exeter

nachricht How much biomass grows in the savannah?
16.02.2017 | Friedrich-Schiller-Universität Jena

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Positrons as a new tool for lithium ion battery research: Holes in the electrode

22.02.2017 | Power and Electrical Engineering

New insights into the information processing of motor neurons

22.02.2017 | Life Sciences

Healthy Hiking in Smart Socks

22.02.2017 | Innovative Products

VideoLinks
B2B-VideoLinks
More VideoLinks >>>