1 research outputs found
Hydrological and climatological change associated with glacial recession in the Rwenzori Mountains of Uganda
The areal extent of tropical icefields in the Rwenzori Mountains of East Africa has
reduced steadily over the last century from 7.5 km^{2} 2 in 1906 to <1 km^{2} in 2003. Considerable debate persists regarding the impact of deglaciation on alpine
riverflow and changes in climate driving glacial recession in the East African
Highlands. Recent field surveys combined with historical observations reveal
continued, rapid retreat in the terminal positions of valley glaciers (Speke, Elena).
Observed acceleration in the rate of termini retreat since the 1960s is shown to
arise, in part, from the morphologies of the glaciers and the beds within which
those glaciers reside. Historical data combined with the first measurements of
alpine riverflow in the Rwenzori Mountains show that the contribution of
meltwater flows from dwindling icefields to alpine riverflow is negligible,
contributing <0.5% of the mean annual river discharge recorded at the base of
the mountains. Preliminary high-frequency monitoring of air temperature and
humidity in the vicinity of icefields on the Rwenzori Mountains indicates that
elevated daily maximum air temperatures coincide with episodic reductions in
relative humidity and increased meltwater fluxes observed during the dry season.
A sustained reduction in humidity to account for observed deglaciation is not
evident from records of lowland precipitation, humidity or river discharge. Lakelevel records in East Africa are also inconsistent with a sudden decrease in
regional humidity around 1880AD that is proposed to have triggered deglaciation
in the East African Highlands. Water levels in the lakes proximate to the icefields
of Mount Kenya and Kilimanjaro are rising in the late 19th century when glaciers
on these mountains are observed to be in retreat. Lake levels do not,
furthermore, indicate that enhanced humidity over the 19th century prior to
1880AD relative to the 20th century. Evidence of warming over the latter half of
the 20th century and an earlier onset of deglaciation (~1870AD) from
meteorological and palaeolimnological data suggest that the timing and drivers of
deglaciation in the Rwenzori Mountains are consistent with the recession of
alpine icefields elsewhere in the tropics