Tuesday, December 30, 2008

2008 Winter Sea Ice Data

This catches us up on the apparent total impact generated by the warming that took place in 2007. It was hardly obvious at the time, but all that warm water ripped into the ability of the sea ice to accrete. A lot less than normal was thus produced this past winter.

Those conditions do not exist this winter, and we are been subjected to a full press arctic chill. It is reasonable to anticipate a full season’s ice production this winter, if not even an increase. 2007 showed us just how quickly the sea ice can be reduced with the right conditions. Had the conditions of 2007 continued, then all the ice would have been easily removed by 2012, as then projected. Once again the weather has changed. Expect to complain about cold winters for a decade at least.

Of course diehards are already claiming that global warming is now preventing the next ice age.

Right now, the right question should be how much further this sudden cooling downswing has to go before it plateaus. Notice I did not say rebound. Rising seems to take a very long time and likely averages less than a tenth of a degree per year, and there is no assurance that it will climb as high as this time.

It would be nice to link this process directly to solar radiation with a high degree of real certainty. That way it would become possible to model other effects properly including CO2. This time around, it looks like the CO2 enthusiasts jumped on the wrong trend and are now having it thrown back in their faces.


Posted on December 19th, 2008

ScienceDaily (Nov. 3, 2008) — Last winter, the thickness of sea ice in large parts of the Arctic fell by nearly half a metre (19 per cent) compared with the average thickness of the previous five winters. This followed the dramatic 2007 summer low when Arctic ice extent dropped to its lowest level since records began.

Up until last winter, the thickness of Arctic sea ice showed a slow downward trend during the previous five winters, but after the summer 2007 record low extent, the thickness of the ice also nose-dived. What is concerning is that sea ice is not just receding but it is also thinning.

Some scientists blamed the record summer 2007 ice extent low on unusually warm weather conditions over the Arctic, but this summer, sea ice extent reached the second lowest level since records began, even though the Arctic had a relatively cool summer. Dr Katharine Giles, who led the study and is based at the Centre for Polar Observation and Modelling at University College London – part of the National Centre for Earth Observation, says: “This summer’s low ice extent doesn’t seem to have been driven by warm weather, so the question is, was last winter’s thinning behind it?”

The team of researchers, including Dr Seymour Laxon and Andy Ridout, used satellites to measure sea ice thickness over the Arctic from 2002 to 2008. Winter sea ice in the Arctic is around two and half metres thick on average. Ice thickness can be calculated from the time it takes a radar pulse to travel from a satellite to the surface of the ice and back again.

The research - reported in Geophysical Research Letters - showed that last winter the average thickness of sea ice over the whole Arctic fell by 26cm (10 per cent) compared with the average thickness of the previous five winters, but sea ice in the western Arctic lost around 49cm of thickness. This region of the Arctic saw the North-West passage become ice free and open to shipping for the first time in 30 years during the summer of 2007.

The team is the first to measure ice thickness throughout the Arctic winter, from October to March, over more than half of the Arctic, using the European Space Agency’s Envisat satellite. Before this, Christian Haas of the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany, had discovered thinner ice in a small region around the North Pole. Whilst the overall loss of older, thicker ice led researchers to speculate that Arctic sea ice had probably thinned, this is the first time scientists have been able to say for definite that the ice thinning was widespread and occurred in areas of both young and old ice.

“The extent of sea ice in the Arctic is down to a number of factors, including warm weather melting it as well as currents and the wind blowing it around, so it’s important to know how ice thickness is changing as well as the extent of the ice,” added Giles.

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