Australia: The Land Where Time Began

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Synchronization of cycles in the Arctic and Antarctic

In a paper1 published in the American Journal of Science the authors present evidence in support of the hypothesis that cycles in the Arctic and Antarctic were synchronised during the last ice age, as well as probably at earlier times, temperature changes, on a millennial-scale, in the north and south Polar Regions being coupled and synchronised. According to the author1, the term synchronisation, as used here, refers to the way in which 2 or more nonlinear oscillators that are coupled adjust their natural rhythms, that are initially different, to a common frequency and a relative phase that is constant. New insights are brought into the dynamic processes, by a working hypothesis of polar synchronization, that links the Dansgaard-Oeschger (DO) abrupt temperature fluctuations to Antarctic temperature variability. Consistent with the polar synchronization, it is shown that the time series of the climatic events in the last glaciation, that are considered to be the most representative, as recorded in Greenland and Antarctica, can be transformed into one another by a π/2 phase shift, the temperature variations of Antarctica leading temperature variations in Greenland. According to the authors1 a model that consists of a few nonlinear differential equations suggests the possibility of the complex behaviour of global palaeoclimate being governed by simple rules, with the result that remarkably close time series simulations were produced by the model.

From Cosmos Magazine2

In the US 2 researchers, published in the American Journal of Science, and presented at the Fall meeting of the American Geophysical Union in San Franscisco, have found that the extent of ice in the Arctic Ocean are in sync with temperatures in the Antarctic, basing their work on studies carried out in the 17th century by Christiaan Huygens on swinging pendulums. Based on their research, Jose Rial & Jeseung Oh, both from the university of North Carolina, have shown mathematically that the heating-cooling cycles in the Arctic and the Antarctic were linked, enabling them to extend Arctic measurements back an extra 700,000 years. Ice cores from the Arctic recorded Arctic temperatures back 100,000 years, but using their model they were able to make use of the much longer corers from the Antarctic to extend the temperature swings recorded in the Arctic cores back to 800,000 years.

Huygens had observed while studying the pendulums that some of the times when he had pendulums of similar rhythms hanging from the same beam the pendulums would eventually swing in exactly the same beat. He called this 'an odd kind of sympathy' in a letter to the Royal Society. His suspected that the effect occurred because of subtle nudging of the pendulums by each other by subtle movements of the beam and later proved it mathematically.

There are also cyclical changes of the Earth's poles, conditions at which oscillate between warmer and cooler phases on a time scale of a few thousand years. During the last glacial phase, that ended about 12,000 years ago, these cycles were in the form of intermittent warming periods when the temperatures rose by up to 8oC, occurring in time periods of years to decades, the Dansgaard-Oeschger events, changes that were on a very large scale.

The 'polar seesaw'' theory is an attempt to understand the D-O events, according to which one pole warms as the other cools, possibly with a delay between the 2 oscillations. The computer models have so far failed to explain the seesaw effect, how the poles communicate with each other, a suggestion being that winds and currents are involved.

Rial & Oh suggest the behaviour of Huygens' clocks allow climatologists to cheat a bit. When considering the clocks it is not necessary to 'describe exactly how swing of the pendulum becomes a sound wave in a wall or in the air and how it speeds up or brakes the other one'. Over time, if the natural frequencies of the pendulums are not too different, it can be calculated that synchronisation will occur, mathematically all it is necessary to say is that they are in some way 'weakly coupled'. According to the authors2, in a similar manner, it is very plausible the conditions in the Arctic and the Antarctic aren't completely independent of each other, and this is all that is required to understand the potential for synchronisation.

The researchers2 compared the temperatures in Antarctica with the extent of sea ice in the Arctic Ocean, as the Antarctic is dominated by land the temperatures will fluctuate more, and the Arctic is mostly sea, where a large proportion of any extra energy available during a warming event will be expended on melting ice. The 2 graphs they produced had the same period with the Antarctic graph having a constant lead on the Arctic one. According to the researchers2 their results suggests it is not necessary to have a detailed picture of all the processes involved for some important aspects of the Earth's climate to be understood. They created a mathematical model of the poles in which the 2 poles are weakly coupled climatological oscillators.

The late Barry Saltzman, from Yale, suggested 20 years ago that each polar region can act like a kind of pendulum, reasoning that the swing of the pendulum emerges as when a pole becomes colder, for whatever reason, more sea ice will form which will then reflect more incoming solar radiation which will lower the temperatures even more. As sea ice is a good heat insulator the ocean doesn't cool, warming instead, as heat from the equatorial regions moves to the poles. This tropics-derived heat will eventually begin to melt the ice leading to more solar radiation reaching the water and less being reflected back to space. The result is that the pendulum swings in the opposite direction.

The model constructed by Rial and Oh, in which each pole is an oscillator, each having different properties depending on the predominance of land in the Antarctic and ocean in the Arctic, reproduced the fluctuations of climate that were recorded in the ice cores. They ran their model for much longer, as far as 800,000 years back, to simulate the entire Antarctic record of temperature, from which they deduced the Arctic temperature fluctuations back past the 100,000 years recorded in the core from the Arctic.

The phenomenon 'oscillation death', that occurs between 2 pendulums if the coupling becomes too strong, is suggested as another possible application of their idea. The mathematics that describes synchronisation predicts that 2 oscillators that are not quite the same, will begin to impede the swings of each and eventually they will stop.

It has been speculated by Rial and Oh that this occasionally happens on Earth, possibly giving rise to the warm periods, the interglacials, such as the one the Earth is in at the present, and has been since about 12,000 years.

Sources & Further reading

  1. Rial, J. A. "Synchronization of Polar Climate Variability over the Last Ice Age: In Search of Simple Rules at the Heart of Climate's Complexity." American Journal of Science 312, no. 4 (April 1, 2012 2012): 417-48.
  2. Den Hond, Bas, Dec. 2012, Antarctic, Arctic Cycles are in Sync, Cosmos Oline,
Author: M. H. Monroe
Last Updated 14/12//2012

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