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Drying causes Mount Kenya glacier to melt

15.09.2016

A study published in Cryosphere earlier this year has found that the largest glacier on Mount Kenya, the Lewis Glacier, is melting because of decreasing atmospheric moisture rather than increasing temperatures. In the tropical climate of East Africa, glaciers are an unexpected, yet vitally important part of the ecosystem. Since 1900, African glaciers have lost a staggering 80 percent of their surface area, contributing to regional water shortages. While rising temperatures may seem like an obvious cause of global glacier retreat in many regions, the glaciers of east Africa are a unique exception.

African glaciers have all but disappeared, except for in three locations in East Africa: Mount Kenya in Kenya, Mount Kilimanjaro in Tanzania and the Rwenzori Range in Uganda. Scientists have been studying the few remaining African glaciers in hopes of preserving what is left of the rapidly melting ice. While headway had been made in understanding the causes of melting on Kilimanjaro, the melting on Mount Kenya, Africa’s second tallest mountain has remained a mystery until now.

The complex climatic features of Mount Kenya, combined with the lack of observational data, has made it difficult to pinpoint an exact cause of Lewis Glacier’s retreat. Lindsey Nicholson, a researcher at the Institute of Atmospheric and Cryospheric Sciences, led a study in 2013 that concluded a combination of causes was responsible for the melt, rather than one factor in particular.

Building on her previous work, the team, led by University of Graz’s Rainer Prinz and Lindsey Nicholson, set out to collect the data they needed to gain a more accurate understanding of why Lewis Glacier was melting. They installed an automatic weather station on the glacier at an elevation of 4 828 metres, and collected 773 days of data over the course of two and a half years.

In conjunction with the data from the weather station, the team used a model to predict how much Lewis Glacier would melt under a range of different scenarios. By manipulating variables - including precipitation, air temperature, air pressure and wind speed - in the model, the team was able to see which factors played the biggest role in glacier melt.

The team found that moisture had the biggest impact on Lewis Glacier’s surface area, rather than air temperature or a combination of other climatic factors. Despite differences in location and elevation, the glaciers of Mount Kenya and Kilimanjaro are melting for the same reason: East Africa is getting progressively drier, and the lack of water is impacting much more than just the glaciers.

News by Anna LoPresti, glacierhub.org

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Photo: Jojo Barlow, Mount Kenya Trust