Limited forcing of glacier loss through land-cover change on Kilimanjaro

Abstract

A study shows that regional atmospheric change driven by land-cover change contributes little to glacier mass loss on Tanzania’s Mount Kilimanjaro. More generally, this finding suggests that local land-cover change may have limited impact on mountain glaciers in the tropics and elsewhere, compared with that of global climate change. Global climate change is primarily linked to changes in greenhouse gases, but land-cover change (LCC) has increasingly been recognized as another forcing on the regional scale1,2. The related effects on alpine glaciers are, however, not yet known. Here we present the first quantification of the contribution of LCC-driven atmospheric change to glacier mass loss, illustrated by the well-studied case of Kilimanjaro in tropical Africa3,4,5. We employ a novel multi-scale modelling approach6, which links atmospheric dynamics and local glacier mass balance in a fully physical way and is validated by in situ measurements. Using different model settings, this shows that local LCC since the 1970s has contributed 7±6% (17±12%) to mass loss of a southern slope glacier in the dry (wet) season, but this effect could reverse in the other mountain sectors and also decrease glacier mass loss. Thus, for the moment, the hypothesis that local LCC is another forcing of glacier loss on Kilimanjaro7,8 cannot be corroborated. More generally, our results indicate that the impact of local LCC on mountain glaciers is constrained by regional circulation (moisture trajectories), altitude (distance to forest), and outside the tropics by precipitation mechanisms (frontal systems). We therefore argue that attribution of glacier change and variability to large-scale climate dynamics3,9,10 is unlikely to be distorted by local LCC.