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| Global Warming - nog bewyse? [boodskap #21531] |
Vr, 05 Maart 1999 00:00  |
ferdinand
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Gerkry van www.nasa.gov
RELEASE: 99-33
NASA RESEARCHERS DOCUMENT
SHRINKING OF GREENLAND'S GLACIERS
Greenland's southeastern glaciers are rapidly thinning and
their lower elevations may be particularly sensitive to potential
climate changes, a NASA study suggests.
"The results of this study are important in that they could
represent the first indication of an increase in the speed of
outlet glaciers," said Bill Krabill, principal investigator at
NASA Goddard Space Flight Center's Wallops Flight Facility,
Wallops Island, VA. An outlet glacier acts as a major ice
drainage region for an ice sheet.
"The excess volume of ice transported by these glaciers has
had a negligible effect on global sea level thus far, but if it
accelerates or becomes more widespread, it would begin to have a
detectable impact on sea level," Krabill said.
In the March 5 issue of SCIENCE, researchers report the
glacial thinning is too large to have resulted from increased ice-
surface melting or decreased snowfall. The researchers believe
the thinning, as much as 30 feet over five years in some
locations, is the result of increasing discharge speeds of
glaciers flowing into the Atlantic Ocean.
Krabill said surface-melt water might be seeping to the
bottom of glaciers. Such seepage may be reducing the friction
between the ice and the rock below it, enabling the glaciers to
slide with less friction across the bedrock and thus allow more
ice to slip off into the ocean, according to Krabill.
"The results of this study are significant because they
provide the first evidence of widespread thinning of low-elevation
parts of one of the great polar ice sheets. The results also
suggest that the thinning outlet glaciers must be flowing faster
than necessary to remove the annual accumulation of snow within
their basins," said Krabill.
"Why they are behaving like this is a mystery," said Krabill,
"but it might indicate that the coastal margins of ice sheets are
capable of responding quite rapidly to external changes, such as a
potential warming of the climate."
Researchers noted that while some internal areas of Greenland
that were surveyed showed ice thickening, areas along the coast
showed ice thinning. "Taken as a whole, the surveyed region is in
negative balance," Krabill said.
In 1993 and 1994, NASA researchers surveyed the Greenland ice
sheet using an airborne laser altimeter flown on a NASA P-3
aircraft and measured the thickness of the entire ice sheet. Ten
flight lines flown in 1993 in Southern Greenland were resurveyed
in 1998. The flight lines in Northern Greenland flown in 1994
will be resurveyed in May 1999. Throughout the study, pilots have
used the Global Positioning System and other navigational
equipment to fly the same flight path some 400 meters above the
icy surface.
The results showed three areas in the South accumulating at
rates up to ten inches per year. These areas located in the
internal sections of Greenland are in regions of high snowfall.
In the outer regions of the ice sheets, the researchers
reported large areas of thinning, with the rate of thinning
increasing rapidly towards the ocean. Most-rapid thinning rates
(more than three feet per year) were observed in the lower depths
of East-coast outlet glaciers, the researchers reported.
The researchers noted that the areas of thinning in the East
also saw warmer than normal temperatures for 1993 to 1998.
"However, we also observe areas of thinning near the West coast,
where many locations were cooler than normal," the researchers
reported.
These surveys have established baseline data sets that will
be extended with information from NASA's ICESAT spacecraft. The
ICESAT satellite laser altimeter will be launched in 2001 to
measure ice-surface elevations in Greenland and Antarctica.
Further information on the Greenland mapping project,
including the technology behind the science, can be found on the
web at:
http://aol.wff.nasa.gov/aoltm.html
The Office of Earth Science enterprise, NASA Headquarters,
Washington, DC, sponsors the Greenland and Antarctic ice mapping
projects as part of NASA's ongoing efforts to understand the total
Earth system and the effects of natural and human-induced changes
on the global environment.
-end-
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| Re: Global Warming - nog bewyse? [boodskap #21563 is 'n antwoord op boodskap #21531] |
Ma, 08 Maart 1999 00:00  |
Arthur Hagen
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Ferdi Greyling heeft geciteerd...
>
> NASA RESEARCHERS DOCUMENT
> SHRINKING OF GREENLAND'S GLACIERS
>
> Greenland's southeastern glaciers are rapidly thinning and
> their lower elevations may be particularly sensitive to potential
> climate changes, a NASA study suggests.
Bijzonder interessant, zulke studies. Je staat soms versteld wat
tegenwoordig allemaal gemeten kan worden.
Dat de NASA iets suggereert is niet hetzelfde als bewijs, dus het antwoord
op je vraag in de titel van deze plasing zal op zijn best "mogelijk...."
kunnen zijn.
Arthur
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| Re: Global Warming - nog bewyse? [boodskap #21597 is 'n antwoord op boodskap #21531] |
Di, 09 Maart 1999 00:00 |
ferdinand
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On Mon, 8 Mar 1999 18:33:04 +0100, "Arthur Hagen" wrote:
tegenwoordig allemaal gemeten kan worden.[/color]
>
> Dat de NASA iets suggereert is niet hetzelfde als bewijs, dus het antwoord
> op je vraag in de titel van deze plasing zal op zijn best "mogelijk...."
> kunnen zijn.>>
Dis nie 'n kwessie van bewys nie, Arthur.
Vir een rede omdat wanneer dit "bewys" kan word, sal dit reeds
heeltemal te laat wees.
Wat wel interressant is, is wie almal met watter inligting tot hulle
beskikking bekommerd begin raak daaroor.
N.S. In een van die nuwe New Scientists word geskryf van navorsing wat
daarop dui dat as die aarde se klimaat warmer word, sal daar
waarskynlik toestande ontstaan wat n soort plankton in die suidelike
oseane sal bevoordeel wat baie minder koolstofdioksied absorbeer (iets
soos 30% minder) as die wat tans floreer.
So iets sal natuurlik globale verwarming vinniger aanjaag.
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| Re: Global Warming - nog bewyse? [boodskap #21625 is 'n antwoord op boodskap #21531] |
Wo, 10 Maart 1999 00:00 |
Arthur Hagen
Boodskappe: 559
Geregistreer: Julie 2001
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Ferdi Greyling het geskry...
> Dis nie 'n kwessie van bewys nie, Arthur.
> Vir een rede omdat wanneer dit "bewys" kan word, sal dit reeds
> heeltemal te laat wees.
Dan moet jy spreek oor "Global Warming - nog aanwysings?"
Groete,
Arthur
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| Re: Global Warming - nog bewyse? [boodskap #21659 is 'n antwoord op boodskap #21531] |
Do, 11 Maart 1999 00:00 |
ferdinand
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On Wed, 10 Mar 1999 18:11:06 +0100, "Arthur Hagen" wrote:
Ferdi Greyling het geskry...
>> Dis nie 'n kwessie van bewys nie, Arthur.
>> Vir een rede omdat wanneer dit "bewys" kan word, sal dit reeds
>> heeltemal te laat wees.
>
> Dan moet jy spreek oor "Global Warming - nog aanwysings?">>
Het jy die vraagteken na die opskrif gesien, Arthur?
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| Re: Global Warming - nog bewyse? [boodskap #21660 is 'n antwoord op boodskap #21531] |
Do, 11 Maart 1999 00:00 |
Arthur Hagen
Boodskappe: 559
Geregistreer: Julie 2001
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Ferdi Greyling heeft geschreven...
> "Arthur Hagen" wrote:
>> Dan moet jy spreek oor "Global Warming - nog aanwysings?"
>
> Het jy die vraagteken na die opskrif gesien, Arthur?
Tuurlijk, ik heb 'm er zelf immers ook achter getypt? Je kwam in die plasing
met een verhaal. Ik dacht dat het vraagteken achter "bewyse" betekende dat
je vroeg of iemand soms dacht dat dat verhaal overtuigende bewijzen bevatte.
Later merkte je terecht op dat dit nooit het geval kan zijn, omdat je niet
vooraf met onomstotelijke bewijzen kan komen. Ik bedacht daarop dus dat je
over aanwijzingen had behoren te spreken.
Als je daarentegen wilde vragen of iemand al bewijzen voor hande had met
betrekking tot een wereldwijde stijging van temperatuur, dan had je verder
niets in die plasing moeten zetten. Dan was dat hele verhaal in die plasing
overbodige ballast.
Groeten,
Arthur
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