Variations of the Lewis Glacier, Mount Kenya, 2004–2012

We present a new map of the Lewis Glacier, Mt Kenya (0°9’ S, 37°18’ E), which was determined with a differential global positioning system survey and ice thickness measurements from ground penetrating radar that was carried out in 2010. The Lewis Glacier is among the best monitored tropical glaciers and this new map provides a continuation of glaciological monitoring at this site. Glacier area for 2010 is 0.107 ± 0.001 × 106 m2 which is a 23% decrease since 2004. The formerly adjoining Gregory Glacier no longer exists. Surface mass balance measurements for the years 2010/11 and 2011/12 (-1.54 m water equivalent (w.e.) and -1.03 m w.e., respectively) are as negative as the minima measured between 1978 and 1996, and show a strong dependence on duration and depth of snow cover, which impact accumulation as mass input and ablation via the surface albedo.