Glacier retreat, rock weathering and the growth of lichens in the Churup Valley, Peruvian Tropical Andes
Abstract
The most heavily glacierized tropical range in the world - the Peruvian Cordillera Blanca - has been losing ice since the end of the Little Ice Age (LIA). In this study, the decline of the Churup glacier (9°28'18" S; 77°25'02" W) and associated processes were documented employing multi-proxy approach including the analysis of remotely sensed images (1948-2016), the Schmidt hammer rock test and lichenometric dating.
It is shown that Churup glacier has lost the vast majority of its estimated LIA extent (1.05 +- 0.1 km2; 45.0x106 - 57.4x106 m3). The rate of glacier retreat is documented to vary in space (SE, SW and NW-facing slopes) and time, with the peak between 1986 and 1995.
With an area of 0.045 km2 in 2016, it is expected that the complete deglaciation of the Churup valley is inevitable in the near future. Recently (post-LIA) exposed bedrock surfaces have shown higher R-values (54.2 - 66.4, AVG 63.3, STDEV 2.9) compared to pre-LIA exposed surfaces (46.1 - 59.3, AVG 50.1, STDEV 4.9), confirming the links to the duration of rock weathering.
The Lichenometric dating is applied to recently exposed areas and elevations above 4800 m a.s.l., revealing only limited reliability and agreement with the age of deglaciation estimated from remotely-sensed images in such an environment.