Até agora pensava-se que os grandes degelos dos glaciares
através do aquecimento global limitava-se à Antártida Ocidental, mas agora através
das imagens dos satélites confirma-se também um grande ritmo de degelo na parte
Oriental da Antártida . As consequências na subida do nível do mar e
consequentes alterações do Clima serão desastrosas e Apocalípticas.
OVOODOCORVO
East Antarctica's glaciers are stirring
By Jonathan Amos
BBC Science Correspondent, Washington DC
East Antarctica has shown very little evidence of change
over the decades
Nasa says it has detected the first signs of significant
melting in a swathe of glaciers in East Antarctica.
The region has long been considered stable and unaffected by
some of the more dramatic changes occurring elsewhere on the continent.
But satellites have now shown that ice streams running into
the ocean along one-eighth of the eastern coastline have thinned and sped up.
If this trend continues, it has consequences for future sea
levels.
There is enough ice in the drainage basins in this sector of
Antarctica to raise the height of the global oceans by 28m - if it were all to
melt out.
"That's the water equivalent to four Greenlands of
ice," said Catherine Walker from Nasa's Goddard Space Flight Center in
Greenbelt, Maryland.
The glaciologist has been detailing her work here at the
Fall Meeting of the American Geophysical Union (AGU).
The glaciers in Vincennes Bay have shown the biggest change
in behaviour since 2008
Dr Walker has been making the most of a new initiative at
the agency to process huge numbers of satellite images to get a more resolved
and more timely view of what is happening in East Antarctica.
Previously, scientists had been aware that the region's
Totten Glacier was experiencing melting, most probably as a result of its terminus
being affronted by warm water coming up from the deep ocean. Pretty much
everything else in that part of the continent was considered stagnant, however.
The new satellite elevation and velocity maps change this
view. They make it clear that nearby glaciers to Totten are also starting to
respond in a similar way.
Marked change is detected in the Vincennes Bay and Denman
areas just to the west, and in Porpoise Bay and on the George VI coast to the
east.
Vincennes Bay - which includes the Underwood, Bond, Adams,
and Vanderford glaciers - has the most pronounced loss in ice mass. Elevation
is dropping at five times the rate it was in 2008 - with a total fall in height
over the period of almost 3m.
"They've also sped up about 3% from their 2008
velocity, which sounds small but is significant enough to change the flux
coming out of those glaciers because they are very deep," said Dr Walker.
Totten has long been recognised as the fastest moving
glacier in East Antarctica
Once again the melting culprit is likely to be warm water
that is being pulled up from the deep by shifting sea-ice and wind patterns in
the region.
The changes that are occurring are still quite subtle, and
they are only really discernible because of the new automated computer tools
that will search through the millions of satellite images taken of Antarctica.
Nasa is about to widen access to these tools through a
project called Inter-mission Time Series of Land Ice Velocity and Elevation, or
ITS_LIVE.
"I think we can anticipate that over the next five to
10 years, we're going to have a lot of observationally driven discoveries, such
as what Catherine is making, because of the new data that's coming
online," said Alex Gardner, a glaciologist with Nasa's Jet Propulsion
Laboratory in Pasadena, California.
Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter:
@BBCAmos
MUNDO 07.12.2018 às 12h16
Joe Raedle/Getty
Cientistas avisam que a subida do nível do mar causada pela
derretimento das massas de gelo da Gronelândia é preocupante
Um novo estudo mostra que os glaciares da Gronelândia estão
a derreter da forma mais rápida do que em qualquer altura dos últimos 350 anos
e que isso de deve ao aquecimento global.
Em comparação com o início da era industrial há mais 50% de
gelo derretido que está a sair da área da Gronelândia e a entrar no Oceano
Ártico. Só desde o séc. XX houve uma aumento de 30%.
O colapso dos glaciares está “no limite”, refere Luke
Trusel, um dos autores do estudo. “Como resultado disso a subida do nível do
mar é maior do que em qualquer altura dos últimos 350 anos, se não for milhares
de anos”, diz.
De acordo com a investigação, o aumento exponencial de água
proveniente da quebra dos glaciares deu-se em meados do séc. XIX, “quando
começámos a alterar o ambiente na Terra”.
As massas de gelo vão derreter-se de forma contínua por cada
grau de aquecimento do planeta, avisam, e o que se observou até agora é apenas
uma parte pequena daquilo que pode acontecer se não travarmos as alterações
climáticas.
Para realizar o estudo, os cientistas usaram uma broca para
perfurar o gelo e retirar amostras e estudaram que tipo de fusão ocorreu desde
o séc. XVII. Este método permite examinar mais a fundo as “responsabilidades”
das alterações climáticas no desaparecimento de glaciares do que as normais
imagens de satélite, que só existem desde 1970.
O mar subiu 10 a 20 cm no último século, mas nos últimos 20
anos a rapidez com que aumenta é muito maior.
Mesmo pequenas subidas podem hoje causa grandes destruições
costeiras, através da erosão do habitat, inundações e tempestades mais fortes.
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