Sonntag, 8. November 2009

No more ice on Kilimanjaro ?

After Thompson et al. 2009, interview to Dr. Thompson mp3

The glacial record in Africa is restricted to the highest peaks of this continent, mainly to mountains of east Africa: Mount Kilimanjaro (5895m), Mount Kenya
(5.199m), the Ruwenzori (5.119m) and on the northern margin of Africa in the High Atlas. Traces of two Pliocene-Pleistocene glaciations have been found on Mt Kilimanjaro, the oldest of which have been dated to about 2.0My (OSMASTON, 2004). Younger, in part uncertain glacier advances are dated to 1,0My, 0,4My and during the last glacial maximum (20.000y). Today three main glaciers persist on the summit of the volcano - the Northern Ice Field (NIF), the Southern Ice Field and the Furtwängler Glacier; some smaller glaciers are distributed on the slope of the mountain. Cores taken from all three glaciers showed that the ice cover on Kilimanjaro persisted for at least 11.700 years.

Isotopic record of oxygen isotopes from the Northern Ice Field (NIF), after THOMPSON et al. 2002

In modern times the dramatic loss of Kilimanjaro´s ice cover has attracted global attention, and has been a symbol for changing climate in Africa in popular media. The glaciers have considerable lost volume and surface, from 12,06 square kilometer in 1912 to 2,6-2,5 square kilometer in 2000. In the last 7 years ulterior 26% of this remaining ice are gone, leaving 1,85 square kilometer back. But not only the ice covered surface - easy to observe by aerial photographs - diminishes, but more important the glaciers are rapidly thinning, up to 0,5m thickness loss per year. This glacier mass lost is harder to determinate (mostly by measuring with stakes you got only punctual data) but crucial to understand the glacier balance.
If this melting rate persists, until 2022-2033 there will no more glacier ice left on the summit.

The widespread retreat of glaciers in Africa suggests a common driver, and not only local factors like deforestation, land use or humidity change on the slopes of Mount Kilimanjaro. The long record that this ice fields provided, demonstrate that for more then 11.000 years ice persisted without essential melting or mass lost, even during the end of the humid phase in Africa and change to more drier climate and subsequent droughts (p.e. 4.200 years ago). This seems to minimize the influence of changing precipitation on the glacier mass balance, and emphasizes changing in the temperature regime on the summit of the mountain.


EHLERS, J. & GIBBARD, P.L. (2007): Glaciations. In (ed): ELIAS, S.A. (2006): Encyclopedia of Quaternary Science. Elsevier : 290-300

OSMASTON, H. (2004). Quaternary glaciations in the East African mountains. In J. Ehlers and P. L. Gibbard (eds): QuaternaryGlaciations - Extent and Chronology, Part III: South America, Asia, Africa, Australasia, Antarctica: 139-150.

THOMPSON, L.G. et al. (2009): Glacier loss on Kilimanjaro continues unabated. Proceedings of the National Academy of Sciences.

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