Last year we published a paper which included a detailed geodetic mass balance of the Lewis glacier since 1934.
Geodetic glacier mass balance refers to any method for determining mass balance by repeated mapping of glacier surface elevations to estimate the volume balance. From the volume balance you then need information on the density of the volume of snow or ice gained or lost.
The paper is: Prinz, R., A. Fischer, L. Nicholson, 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. Geophysical Research Letters, 38, L20502, doi:10.1029/2011GL049208.
Lewis glacier, which is basically on the equator, is the best documented glacier in low-latitudes, and just recently I finally drew up a plot of how our geodetic mass balance compares to the global glacier mass balance estimates, so here it is:
Specific mass balance refers to the total glacier mass loss divided by the area of the glacier and you should note that (1) the Lewis glacier mass balance is approximately decadal intervals and the others are pentadal and (2) variation in mass balance of a specific glacier can be strongly influenced by topographic and other factors specific to that location.
Despite these caveats, it does seem that the pattern of change in the specific mass balance at Lewis glacier is in-line with the global averages, although the balance rate from the mid-1970’s until 2004 was much more negative than was typical world-wide.