PEuT Episode 4 ICE goes out today
- 11 Dec 06, 09:46 AM
Listen out. Ice is on tonight at 21.02 NNB Radio 4 FM and LW - and will also be on this site to listen to again.
Everyone is watching ice - land ice. What is happening to mountain glaciers, the Greenland ice sheet and the Antarctic are visions of the future, so the experts say. There are some extraordinary facts: The Antarctic Peninsula is one of the fastest warming places on Earth with an average increase in temperature across a year of 3 degrees C. The Sea temperature around the peninsula has gone up by a degree. The average increase in global temperature is less than a degree.
We understand that the Greenland Ice sheet, the second largest - Antarctica being the largest - is a bit of a "wild card". Some thought it was actually growing in mass two years ago, but recent data has shown that the ice sheet is melting fast. The glaciers that drain the ice sheet are flowing twice as fast than they did two years ago (now at 6km per year).
The sea ice is melting fast too. Local inuit fishermen tell us they are in the water in April and May these days, compared to June and July in the past. The Inuits on the East coast of Greenland tell us cod is freely available to them now - but marine mammals such as seals and polar bears are having a tough time as the sea ice melts.
We hear sea ice melt doesn't contribute to sea level rise - because it's sea water that has been frozen. But land ice melt does contribute, because it adds new water to the ocean...the principle being that land ice is formed by snow accumulation. And since the amount of water on Earth was basically fixed 4 billion years ago, the proportion tied up as ice on land is what dictates sea level. And, as we all know now, successive climate changes on earth have released this land ice or allowed it to grow. Hence sea level changes in the past.
Programme six handles how these natural cycles in the Earths history have been componded by our impacts in the last 100 years.
We hear ideas of a Blue Arctic - a possible mega fishery. But with one huge caveat - it needs to be left alone to develop as a functioning marine ecosystem. If it's plundered for the shrimp and squid (the early invaders of an ice -free world) then the food chain will not develop as a diverse and species rich ocean.
We also hear how the events in the poles are coming to us all. The island nations of the Pacific feel the pinch already as the coral reefs on which they depend are weakened by sea level rise exposing them to increased coastal erosion and destruction of shore line habitats.
Next week is biodiversity. The hub of the climate change issue. What is it and why should we care.
Update
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Oceans and Global Warming
Number of science reviews in this field have linked solar activity to the climate change. Rise in global temperature is always accompanied by the rise in CO2 concentration. Human contribution may be significant but it is not critical. By far the greatest amount of CO2 is released by the world’s oceans; they are also the largest absorbers. The release of CO2 is not, but its absorption is affected by the Sun. The culprits are UV and gamma radiations reaching the oceans’ surface during periods of high sunspot activity.
Some 3 years ago I wrote:
Increased solar activity results in an increase of the harmful radiation, reducing bio-mass of the oceans’ surface plankton through process of sterilisation by irradiation. Result of this is reduced uptake of CO2 from the atmosphere and rising in the ‘green-house’ effect. Reverse process takes place during reductions in the solar activity.
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I enjoyed last night's programme. However there were some "perhaps innocent howlers" from the presenter. Greenland is far from being of continental size. You can blame its disproportionate size on the map to Mr Mercator of projection fame. Though vast, it is actually one third the size of Brazil. Secondly, I did not hear one mention of the theory promoted so well by Horizon ( The Big Chill )some years ago, that accelerated warming of polar glaciers to the Alpine variety would have a catastrophic effect on the salinity of the North Atlantic. The Atlantic conveyor could be dissipated and Europe at least would be plunged into the deep freeze. At least Greenland would not have to melt in the thousand or so years stated by the programme.
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Trefor,
With regard to the role of the North Atlantic Conveyor (Gulf Stream) you will find loads of research and papers at the Woods Hole Oceanographic Institute's , in particular , Chronicling the Currents of the North Atlantic.
You are right in noting that, should the Conveyor stop or even simply change course, we may find our local climate getting considerably colder while the Earth's average temperature rises. A complex business, climate.
ed
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While it is true that the melting of floating ice does not effect sea level, today's programme did not make it clear that ice supported by land does not need to melt in order for it to cause a rise in sea level. All that needs to happen is for the ice to slide off the land into the sea, where it will float with the same effect as if it had melted, due to displacement. Not only are the Greenland glaciers on the move but I have read that satelite photographs show the entire ice sheet slipping seaward , due to ice trickling down through cracks from the surface to destabalise and lubricate the rock/ice interface. Was this effect taken into account in todays estimate of the rate of inevitable sea level increase?
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i thought last nytes progra,e was ver fun
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West Antarctica Total Disintegration - a worse case scenario?
Antarctica has aa total of 25.4 million km^2 of ice. West Antactica Ice Sheet (WAIS) has a volume of 2.2 million km^3 of ice. WAIS is that part of Antactica west of transantarctic mountains. The surface of earth is 510,072,000 km^2; while the ocean is 71% of such surface; giving 361 million km^2. So 2.2 million km^3 of ice / 361 million km^2 of ocean surface = 6.1 x 10^-3 km of sea surface rise from WAIS total melt. This is a 6 meter (18 feet) sea surface rise. However one has the caveat, that WAIS is approximately 1000 ft below sea level. So for average ice thickness of 4000 ft, then 1/4 of WAIS melt would seem to stay, forming an archipelago. Therefore resulting in only about 13.5 feet rise in sea level. This then is supposedly one of the worse case scenarios for global warming. See for references:
Wikipedia: WAIS, earth
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Based upon the retreat of glaciers worldwide, and opening of the Arctic ocean, and Greenland's hastened dissolution, global atmospheric warming would seem to be with us. But has there been any global oceanic warming? None yet definitivly detectable by thermal expansion of the oceans (i.e. proxy of sea surface rise). The specific heat of water is much greater (4x) than that of the atmosphere. And heat capacity is just specific heat x volume. So has the total enthalpy (heat) of coupled oceanic-atmospheric system changed significantly, in a fractional sense? The enormous heat capacity of the oceans would seem to serve as a buffer for increased heating of the planet. If one assumed an extreme scenario of tropical waters to 200 meters for most of planet, what would be the consequences? Has the Paleocene-Eocene Thermal Maximum, about 45 million years ago, already conducted such extreme experiment? See Nature's Past Experiment:
NATURE'S PAST EXPERIMENT
An experiment of nature on the effect of intense global warming has already occurred in the Eocene 38-55 million yrs. ago; the so-called Paleocene-Eocene Thermal Maximum (PETM).(1,4) There were no massive extinctions comparative to that of Cretaceous-Tertiary (K-T) period defining Mezozoic/Cenazocic eras at 65Myrs. At the Paleocene-Eocene divide, paleo-stratigraphic results show that there was deep water benthic foraminifera mass extinction associated with the increased temperature and hence dysoxic (less oxygenated) waters.(1) But most marine and terrestrial extinctions occurred with cooling at the end of the Eocene, and into the Oligocene epoch.(1) The consequences of the present warming are unknown in regards to extinctions. However nature already has conducted one experiment in regards to intense global warming, with seemingly not overwhelming catastrophic results.
1. Hallam Tony, Catastrophes and Lesser Calamities Oxford Univ Press, 2004, and references therein.
Other sources consulted.
2. Raup David M., Extinction: Bad Genes or bad Luck?, W.W. Norton, 1991, and references therein.
3. Stanley Steven M., Extinction, Scientific American Books, 1987, and references therein.
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