This document accompanies the paper by Thompson et al. published November 3, 2009 in PNAS. The supplemental text on the PNAS web site indicated that additional information would be provided here. This addendum includes (1) a detailed discussion of each domain and its ice entities present in the different aerial photographs and (2) additional examples of the interpretative discrepancies between the areal coverage determinations by Cullen et al. (2003) and Thompson et al. (2002). Addendum
The discussion below reflects the new information published in our 2009 PNAS paper (10.1073/pnas.0909029106).
An aerial photograph taken on October 15, 2007 (below) was used to produce a current, detailed map of ice cover extent on the summit plateau. The compilation of six maps (lower right) of ice extent since 1912, the first four of which were assembled by Hastenrath and Greischar (J. Glaciology, 43, 1997), demonstrates a sustained loss of ice on Kilimanjaro over the last century. The three remaining ice fields on the plateau and on the slopes are both shrinking laterally and rapidly thinning. Summit ice cover (areal extent) decreased ~1% per year from 1912 to 1953 and ~2.5% per year from 1989 to 2007. Of the ice cover present in 1912, 85% has disappeared and 26% of that present in 2000 is now gone. From 2000 to 2007 thinning (surface lowering) at the summits of the Northern and Southern Ice Fields was ~1.9 and 5.1 m, respectively, which based on ice thicknesses at the summit drill sites in 2000 represents a thinning of ~3.6% and 24%, respectively. Furtwängler Glacier thinned ~50% at the drill site between 2000 and 2009. Ice volume changes (2000 - 2007) calculated for two ice fields reveal that nearly-equivalent ice volumes are now being lost to thinning and lateral shrinking.