Antarctica thinning seen by Envisat

Image of the Month - June 2012

Height variations from Envisat altimeter between September 2002 and October 2010. Most of the altitude variations are between -15 and +15 cm/year, often due to interannual meteorological variations. Closer to the coasts, however, some glaciers can loose up to several meters in altitude per year, especially in West Antarctica. (Black line : Pine Island Glacier area, see below) (Credits LEGOS)
Pine Island Glacier height variations from 2004 vs 2003, as measured by Envisat altimeter. Click to see the animation from 2004-2003 to 2010-2009 (Credits LEGOS)

Antarctica is the biggest fresh water reservoir on Earth, storing about 70% of it. It also plays an active role in the climate due to the strong feedback induced by its high albedo, and can significantly contribute to sea level rise by its melting.
Antarctica is completely iced, but not still: glaciers are flowing all over the continent. Moreover, those glaciers react differently depending on the geographical area.

Between September 2002 and October 2010, Envisat radar altimeter measured the elevation of the Antarctic ice sheet along a repetitive track. Each ground track was observed about 85 times during this time. This long and regular time series is processed using an along-track algorithm to depict in detail the spatial and temporal pattern of elevation change for the whole ice sheet. One advantage of the finer along-track spacing of measurements is that it reveals places of dynamic thinning in regions of rapid ice flow.  In West Antarctica, in the "Pacific" part, thos processing show that glaciers are thinning, losing up to several meters a year. Those that are reaching the Admunsen Sea even undergo an acceleration in their thinning which is measurable by altimetry. In East Antarctica, some glaciers are losing thickness, but without any observable acceleration.

Now that the Envisat mission has ended, other missions can measure up the poles: Cryosat, dedicated to these applications, and soon Saral, that will take over the Envisat's tracks.

See also:


  • Flament, T. and F. Rémy (2012): Dynamic thinning of Antarctic glaciers from along-track repeat radar altimetry, Journal of Glaciology (accepted)