Walking on bare ground through a passage that had probably
not been ice-free for 10,000 years on Mt Kilimanjaro is
something Dunedin geographer Nicolas Cullen will not forget.
"It was very special," he said of his recent trip to the
glaciers on Africa's highest peak and the highest
free-standing mountain in the world.
It was his sixth trip to the glaciers since 2005 and it
confirmed the research he and surveyor Dr Pascal Sirguey have
recently completed, remapping the glaciers to discover the
extent of the their retreat in the past century.
Published online this week in The Cryosphere Discuss, the
paper "A century of ice retreat on Kilimanjaro: the mapping
reloaded" discussed how reinterpreting historical maps of the
area and comparing those with satellite images removed
uncertainty about the location and extent of past and present
By doing this, they had been able to show that between 1912
and 2011 the glaciers had retreated from their former extent
of 11.40sq km to 1.76sq km, which represented an about 85%
loss in ice cover, Dr Cullen, of the University of Otago,
That was consistent with other recent assessments but they
had identified differences from previously published maps.
His trip to Kilimanjaro had meant he could validate what the
team had discovered by re-mapping.
He discovered that in the past 12 months the northern ice
field, Kilimanjaro's largest glacier, had split into two
parts. In a satellite image a year ago, the glacier was still
"There is now a passage you can walk through that is ice-free
for possibly the first time in 10,000 years."
Kilimanjaro's height made it an ideal example of climate
variability affecting glaciers, he said.
While there was ongoing debate about the role temperature and
moisture played in the retreat of the glaciers, Dr Cullen
believed their reduction was just as much due to them being
"starved of snow than a rise in air temperature".
"Kilimanjaro is useful for reconstructing climate variability
and change, but is not necessarily directly linked to global
Dr Sirguey was putting together an animation of the research
for National Geographic.