Dire projections for Switzerland’s Great Aletsch Glacier
From the Journal of Glaciology:
“We model the future evolution of the largest glacier of the European Alps – Great Aletsch Glacier, Switzerland – during the 21st century. For that purpose we use a detailed three-dimensional model, which combines full Stokes ice dynamics and surface mass balance forced with the most recent climate projections (CH2018), as well as with climate data of the last decades. As a result, all CH2018 climate scenarios yield a major glacier retreat: Results range from a loss of 60% of today’s ice volume by 2100 for a moderate CO2 emission scenario (RCP2.6) being in line with the Paris agreement to an almost complete wastage of the ice for the most extreme emission scenario (RCP8.5). Our model results also provide evidence that half of the mass loss is already committed under the climate conditions of the last decade.”
“Renowned Danish-Icelandic visual artist Olafur Eliasson’s large-scale works such as Ice Watch and New York City Waterfalls spark critical dialogue about climate change and our relationship to nature. His work is driven by interests in perception, movement, embodied experience, and feelings of self, engaging the broader public sphere through architectural projects, interventions in civic space, arts education, policy-making, and issues of sustainability.”
Eliasson will speak at Columbia University on September 26, 2019, 6:30 PM – 8:00 PM as part of its Year of Water program. Details about the Eliasson event can be found here.
“Studies of early human settlement in alpine environments provide insights into human physiological, genetic, and cultural adaptation potentials. Although Late and even Middle Pleistocene human presence has been recently documented on the Tibetan Plateau, little is known regarding the nature and context of early persistent human settlement in high elevations. Here, we report the earliest evidence of a prehistoric high-altitude residential site. Located in Africa’s largest alpine ecosystem, the repeated occupation of Fincha Habera rock shelter is dated to 47 to 31 thousand years ago. The available resources in cold and glaciated environments included the exploitation of an endemic rodent as a key food source, and this played a pivotal role in facilitating the occupation of this site by Late Pleistocene hunter-gatherers.”
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 staggering80 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.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.
African glaciers have all but disappeared, except for three locations in East Africa: Mount Kilimanjaro in Tanzania, Mount Kenya in Kenya, 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 meters, 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.
The glaciers on the peak of Kilimanjaro lie significantly above the regional freezing point—year round, the peak is cold enough to maintain its ice levels, even as surface temperatures in East Africa have steadily increased. Yet, Kilimanjaro’s glaciers continue to retreat and are projected to disappear completely by 2020. Temperature changes fail to explain the severity of the mountain’s glacier retreat.
Observational studies have showed that Kilimanjaro is receiving less cloud cover that leads to increased radiation from the sun, and less precipitation, causing infrequent snowfall. The IPCC has projected a10% decrease in rainfall during the already dry season from June through August, amplifying the impacts of regional dryness and drought.
The impact of a drying climate has greatly impacted Kilimanjaro, and caused its glaciers to retreat from sublimation–a process by which the ice changes directly into water vapor rather than melting into water. The theory that moisture is the main factor impacting glacier melt on Kilimanjaro has, up until now, been assumed to be a product of the mountain’s height and not generalizable to all East African glaciers. Prinz and Nicholoson’s findings suggest that drying may be the main reason for glacier melt throughout the region as a whole.
Mount Kenya’s glaciers are at lower elevations compared to Kilimanjaro’s, and lie much closer to the regional freezing level. It was therefore expected that rising temperatures would affect the glaciers of Mount Kenya, and no scientific studies had proved or disputed this assumption.
Droughts, desertification, and crop failure have become increasingly common in tropical Africa, and according to the study this is primarily caused by shifting ocean conditions that are preventing moisture from circulating over East Africa. The lack of moisture means there is not enough precipitation—either as rain over the savannas or snow on the mountain peaks—to sustain the glaciers or the populations that rely on them. In order to preserve the last remaining African glaciers, it will be necessary to understand and prevent changes in water, rather than only changes in temperature.
The Rwenzori Mountains of equatorial East Africa are widely known to be the legendary “Mountains of the Moon” described by Ptolemy in 150 A.D. as ‘the Mountains of Moon whose snows feed the lakes, sources of the Nile’. Indeed, snow and ice on these glaciated mountains that straddle the border between the Democratic Republic of Congo (DRC) and Uganda supply water to lakes that are a source of the White Nile as it flows north from Uganda into the Sudan. The mountains are also a hotspot of biodiversity featuring rare Afro-alpine fauna and flora.
Glaciers on the Rwenzori Mountains have receded rapidly over the last century. The estimated extent of icefields determined by field surveys and remote sensing, has declined from 6.5 km2 in 1906 to 1.0 km2 in 2003. If present trends continue, glaciers are expected to disappear from the Rwenzori Mountains entirely within the next two decades.
A definitive explanation of the causes of deglaciation in the Rwenzori Mountains is hindered by the absence of sustained meteorological observations around the icefields. There is, however, evidence of both rising air temperatures and reduced cloud cover as potential drivers of glacial recession; these influences are related as warmer air requires more water vapour to form clouds. At present, icefields occupy a narrow elevation range between 4800 m above mean sea level (mamsl) – the elevation of the 0°C isotherm – and the mountains’ highest summit at 5109 mamsl. The icefields are consequently highly sensitive to current and projected warming.
As similarly reported in a GlacierHub post by Tsechu Dolma from the Himalayas, communities around the Rwenzori Mountains in Uganda and the DRC have experienced an increased frequency and intensity of flood events that have destroyed homes, crops, and transport links. In particular, the footbridges which connect communities are sometimes damaged or destroyed, making it difficult for children to attend schools, and farmers to travel to their fields or to markets. Longer droughts associated with the intensification of precipitation have also impaired crop production around the base of the mountains and increased demand for irrigation. Since projected warming as a result of climate change will amplify the risks of floods and droughts, the development of adaptive strategies to mitigate these impacts is critical.
This guest post was written by Richard Taylor a professor at University College London’s Department of Geography. If you’d like to write a guest post for GlacierHub, contact us at firstname.lastname@example.org or @glacierhub on Twitter.
An unusual form of life was recently discovered on a glacier located on a remote island in the Southern Ocean. Signy Island is part of the sub-Antarctic South Orkney Islands, about 600 kilometers northeast of the Antarctic Peninsula and 900 km southeast of Tierra del Fuego. The site of a former whaling station and the current home of a British research facility, Signy Island is largely covered with ice, the surface of which is pockmarked with holes in many sections. The life-form was found in one of these surface holes.
Material called cryoconite –windblown dust made of rock, soot and microscopic organisms– has settled on the surface of ice on Signy Island, as it has on many other glaciers and icesheets. Generally dark in color, cryoconite absorbs solar energy and melts the ice surface. The melting creates depressions in which cryoconite settles, further intensifying the melt. This process can create deep and sometimes narrow tubular holes which contain significant amounts of sediment.
Researcher Dr. Ronald Lewis-Smith from the Centre for Antarctic Plant Ecology and Diversity in Dumfriesshire, Scotland, collected sediment from the bottom of these ice tubes in November 1999. He carefully cultured the materials at the research station on Signy Island, and over the following months some plants began to grow. The first ones to appear, consisting of mosses and a kind of non-flowering plant called liverworts, were all native to the island. A more unusual one appeared after a few more months. Initially identified as a liverwort, it was sent to a laboratory in England, where it was cultivated on a base of sterilized moss from Signy Island.
As this plant grew, it became evident that it was a fern, and therefore not a native to the island. It took several years for it to grow large enough to be identified. Photographs of the plant and two fronds were sent to the Natural History Museum in London, where specialist identified it as Elaphoglossumhybridum. This species is found across a wide area of southern Africa, and also on islands in the southern Indian Ocean, as well as Tristan da Cunha and Gough Island in the South Atlantic Ocean.
These sites all lie to the north and the east of Signy Island. Some locations are as close as 1500 km to the island. However, the prevailing winds are from the west,. As the author states, “The most probable explanation for the spore, from which the present plant developed, reaching Signy Island was by encircling the Southern Hemisphere on an east–west trajectory at high altitude.” The survival of this viable spore is thus a testimony both to its ruggerd vitality and to the ability of the glacier to preserve it.
This fern could not grow in Signy Island’s current climate, but Lewis-Smith’s research does show that diaspores–plant seeds or spores –could be preserved in glacier ice and be viable for growth if the climate becomes more hospitable for them in the future. It is striking to think of the future of Signy Island when current warming trends progress further. Glaciers might contribute to the appearance of new species in two ways. Firstly, as they retreat, there will be an expansion of the ice-free areas in which plants can grow. And secondly, they may release biological material such as this spore, from which new species, not known on the island, may grow. Perhaps, thanks to climate change, Signy Island could one day resemble Fern Gully. The new ferns could be a testimony to the glaciers, which will be much diminished by that time.