Recent acceleration of ice loss in the Northern Patagonia Icefield based on an updated decennial evolution

Abstract. Ice elevation changes of the Northern Patagonia Icefield (NPI) were analyzed by comparing three Digital Elevation Models (DEM) corresponding to 1975 (constructed based on topographic maps), the SRTM DEM of 2000 yr and a SPOT 5 DEM of 2005. In addition, the glacier length fluctuations and the surface area evolution between 2001 and 2011 of 25 glaciers of the NPI were studied: the information extracted from the Landsat ETM+ satellite image of 11 March 2001 was compared to the measurements performed based on the Landsat ETM+ satellite image of 19 February 2011. From a global point of view, the majority of the studied glaciers thinned, retreated and lost surface between 2001 and 2011, only few glaciers (Leones, Nef, Pared Sur and Soler) located on the eastern side of the NPI have been stable. Glaciers located on the western side of the NPI suffered a stronger wasting compared to the glaciers located on the eastern side.

Overall, over the ablation areas of the NPI (below 1150 m a.s.l.) a more rapid thinning of 2.6 m yr⁻¹ occurred between 2000 and 2005 yr compared to the period 1975–2000, in which a mean thinning of 1.7 m yr⁻¹ was measured for the same zones of the NPI. For the whole period (1975–2005) the most important thinning of the ablation areas has been estimated for HPN-1 Glacier (4.4 m yr⁻¹) followed by Benito (3.4 m yr⁻¹), Fraenkel (2.4 m yr⁻¹), Gualas (2.1 m yr⁻¹) and Acodado glaciers, all of them located on the western side of the NPI.

Between 2001 and 2011, a noteworthy retreat of 1.9 km was experienced by Gualas Glacier and by Reichert Glacier with 1.6 km, both located on the north-western side of the NPI. On the south-western side of the NPI, during the same decennia, Steffen Glacier experienced a remarkable retreat of 1.6 km as well. During the 2001–2011 period, Steffen Glacier more than doubled its rate of retreat (compared to the 1979–2001 period) and experienced the disintegration of its main front as well as a lateral tongue that retreated 3.1 km. The most significant retreat observed on the eastern side was experienced by Colonia Glacier (1 km).

Area loss was also relevant during the period 2001–2011. Overall, the icefield experienced a reduction of 50.6 km² which represents a 1.3 % relative to the surface area calculated for 2001 yr. The most remarkable surface reduction was observed for HPN-1 Glacier that lost 3.2 % of its surface estimated in 2001, followed by Steffen Glacier (2.8 %).

We suggest that the glacier shrinking observed in the NPI is controlled firstly by atmospheric warming, as it has been reported in this area. Nevertheless, updated climatic studies are needed in order to confirm this suggestion. If the detected past climate trends persist, in the future, glaciers of the NPI will continuous or even increase their rate of shrinking generating important consequences for this region like the production of Glacier Lake Outburst Flood events or the decrease of the melt-water runoff in the long-term future.