Seventy-six years of mean mass balance rates derived from recent and re-evaluated ice volume measurements on tropical Lewis Glacier, Mount Kenya

Abstract

[1] Lewis Glacier on Mt Kenya has a unique history of detailed study, making it among the best documented tropical glaciers. Here we present (i) a new ice volume determination based on a bedrock DEM constructed from GPR data acquisition and (ii) the glacier's mean mass balance rates over the last 76 years derived from volume and area estimates based on seven historical maps and the newly determined bedrock topography. Total ice volume in 2010 was 1.90 ± 0.30 × 10 6 m 3 with a mean (maximum) ice depth of 18 ± 3 m (45 ± 3 m), which is one order of magnitude larger than previously published values. In 2010, the glacier had lost 90% (79%) of its 1934 glacier volume (area), with the highest rates of ice volume loss occurring around the turn of the century. Computed mean mass balance rates, covering the whole period of glaciological surveys of Lewis Glacier, provide the longest record of tropical glacier change and show that the mean mass balance rate varies consistently with global estimates, but the magnitude is always more negative than in other regions. Citation: Prinz, R., A. Fischer, L. Nicholson, and G. Kaser (2011), Seventy-six years of mean mass balance rates derived from recent and re-evaluated ice volume measurements on tropical Lewis Glacier, Mount Kenya, Geophys. Res. Lett., 38, L20502,

Climatic controls and climate proxy potential of Lewis Glacier, Mt. Kenya

“…Kenya and has been retreating since the late 19th century. Since 1934 the negative mass balance rate has been in line with global estimates of glacier mass balance but since the early 1970s it has been significantly more negative than the global mean (Prinz et al, 2011). Past studies on Mt.…”

“…Several authors have surveyed LG since 1934 (Prinz et al (2011) and references therein) and reconstructed the late 19th century maximum extent (L19) from moraines and sketches (Patzelt et al, 1984). The most recent mapping was performed in 2010 (Prinz et al, 2011(Prinz et al, , 2012 and is used as a topographic reference in this paper. An automatic weather station (AWS) was installed on the glacier surface at an elevation of 4828 m which is ∼ 30 m below the upper limit of the glacier.…”

Micrometeorological conditions and surface mass and energy fluxes on Lewis Glacier, Mt Kenya, in relation to other tropical glaciers

“…Where concurrent data are available the geodetic and glaciological measurements of mass balance are within error of each other. Between 1934 and 2010 Lewis Glacier lost 16.67 ± 3.82 × 10 6 m 3 (90 %) of its 1934 volume and 0.394 ± 0.015 × 10 6 m 3 (79 %) of its 1934 surface area (Prinz et al, 2011). Mean specific mass balance rate between 1934 and 1974 ranged between −0.22 ± 0.40 and −0.54 ± 0.63 m w.e.…”

“…Thus, despite its small size, LG remains an important glacier to understand in the context of both global glacier changes and the climatic changes recorded by tropical glaciers. The geodetic mass balance of LG spanning 1934-2010 has been determined from field maps (Prinz et al, 2011), and, within this period, 20 yr of detailed annual mass balance data have been compiled for the mass balance years of 1979-1996(Hastenrath, 2005 and (Prinz et al, 2012. Where concurrent data are available the geodetic and glaciological measurements of mass balance are within error of each other.…”

“…Three glacierized areas remain in equatorial East Africa ( (Cullen et al, 2006;Prinz et al, 2011;Kaser and Osmaston, 2002;Cullen et al, 2013). The Lewis Glacier (LG) on Mt Kenya has abundant historical glaciological data and is also the only benchmark tropical glacier outside of South America (WGMS, 2008).…”