miel282002:
Es otro ejemplo de la ley de Archibald: "a más calentamiento, más hielo".
Ha aumentado la masa de hielo continental en la antartida?.....
Sí:
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120013495_2012013235.pdf
Si? ,en base a
un solo estudio afirmas eso? mejor ver una foto de la mayoría de los estudios realizados con diferentes métodos de medición, entre ellos de altimetría igual que ese estudio de la nasa..
Figure 4.18(b) from the latest IPCC report is a nice visual depiction of different estimates of the Antarctic mass budget using elevation changes (box Z), gravimetry (boxes RL and V) and the flux component method (boxes RT and RT2).
The downside of this picture is that it becomes apparent that the observed trends are rather short (less than 15 years), that the uncertainty of the amount of mass loss is rather large (it's somewhere between 0 and -200 Gigatonnes per year) and that the error estimates of the different studies (depicted as the vertical extent of the boxes) sometimes do not even overlap. Cleary, more observations and improved data analysis are required for a clearer picture to emerge
Figure 2: Estimates of Total Antarctic Land Ice Changes and approximate sea level contributions using many different measurement techniques. Adapted from The Copenhagen Diagnosis. (CH= Chen et al. 2006, WH= Wingham et al. 2006, R= Rignot et al. 2008b, CZ= Cazenave et al. 2009 and V=Velicogna 2009)
Estimates of recent changes in Antarctic land ice (Figure 2) range from losing 100 Gt/year to over 300 Gt/year. Because 360 Gt/year represents an annual sea level rise of 1 mm/year, recent estimates indicate a contribution of between 0.27 mm/year and 0.83 mm/year coming from Antarctica. There is of course uncertainty in the estimations methods but multiple different types of measurement techniques (explained here) all show the same thing, Antarctica is losing land ice as a whole, and these losses are accelerating quickly.
Así llegamos a la conclusión de que un solo estudio de altimetría debe estar en loc correcto porque (muestra lo que yo quiero ver ) por lo que ignoro la mayoría de los demás que sí muestran perdidas netas (en el mismo periodo) y hasta después..
y también ignoramos el talón de aquilez de la altimetría láser (es afectado en gran medida por la cubierta nubosa) lamentablemente la Antártida tiene mucho de nubes la mayor parte del año
concretamente un 60 a 70% de cielo cubierto promedio durante el año y muchos mas en verano y en áreas costeras donde el deshielo es mayor ... Así que no me sorprendería para nada que la altimetría laser subestime en gran medida el deshielo de esta zona en particular...
The second method of measuring elevation change is through using laser altimetry which is essentially a laser beam that measures the height from the satellite to ice surface. This measurement technique is extremely accurate and has a higher resolution than even the new radar altimeters but also has a small footprint (10s of meters) and can be affected by cloud cover (Allison et al. 2009). The most commonly used laser altimeter equipped satellite “Icesat” has no longer any working lasers thereby making satellite borne laser altimetry for ice sheets currently unfeasible but still applicable for aerial surveys or when icesat-2 is launched in 2015.
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