Monday, 1 October 2018

Lower Barun Glacial Lake

Glaciers in the Himalaya are leaving behind 1000s of glacial lakes as they thin and retreat. Here, Lower Barun Glacier has formed a lake >200 m deep and growing. The lake featured in a recent study by Haritashya et al. (2018) investigating three large glacial lakes in Nepal icluding Thulagi and Imja.

3D view of Lower Barun Glacier and lake. [Credit: Scott Watson]

Area change of Imja, Lower Barun, and Thulagi Glacial Lakes as monitored using Landsat
satellite images from the early mid-1970s to 2017. Second- and third-order polynomial projections are
fitted to each lake area data to extrapolate possible future growth up to 2025.[Credit: Haritashya et al. 2018]

Bathymetry of Lower Barun Lake. [Credit: Haritashya et al. 2018]

Saturday, 24 February 2018

Himalayan glaciers, mountains and the role of citizen science

An edited version of this aritcle appeared in the Nepali Times  23 Feb - 1 Mar 2018 #898

The mountain environment is rapidly changing. The climate of recent times is breaking down, leading to warming temperatures and changing precipitation patterns, which directly impact Himalayan glaciers.  Nepal is home to some of the highest altitude glaciers in the world, yet many will diminish to shadows of their former selves in the coming centuries. Glaciers are retreating to pockets of sun-hidden refuge, where lower air temperatures prolong their existence in the shade of the high mountains. The calm of this environment is enjoyed by many. Tourists are transient but many Nepali call this landscape of extremes their home. Whilst scientific research is still working to understand how rapidly glaciers will disappear, working with those affected to mutually share observations and adaptation strategies is now critical. Glaciers are vast reservoirs of water, pathways to the highest peaks on earth and home to communities of living things. When experiencing their beauty, we also should consider their demise and be proactive towards global strategies to slow the rate of change and engage with sustainable adaptation strategies.

Glaciers are intrinsically linked to and indeed shape the mountain environment. In turn, sediment and rock transported onto the surface of debris-covered glaciers shapes their evolution. This insulating layer of rocks and sediment can reach several metres thick and obscures the vast thickness of ice beneath. Yet these glaciers are shrinking rapidly. Khumbu Glacier, thinned by an average of ~1 m per year (19842015) where the insulating debris is thinnest close to Everest Basecamp. The spatial distribution of thinning leads to a flatter glacier profile, although local relief can still exceed tens of metres. A flatter glacier is more prone to water ponding on the surface, which can eventually form large glacial lakes. When ice is melting faster than the replenishment at higher elevations, the glacier also slows down, which also promotes ponding. At Everest Basecamp, Khumbu Glacier is flowing down-valley at over 30 metres per year. Yet there is virtually no movement 7 km further down the glacier adjacent to the village of Lobuche. Exposed ice cliffs and supraglacial ponds (existing on the glacier surface) are hot-spots of melt. The ponds absorb and transmit thermal energy into the glacier interior, such that the process can become a positive feedback loop, leading to an expanding network of ponds. With a pond at their base, ice cliffs rapidly retreat across the glacier, generating meltwater and leaving a trail of fallen debris.

Supraglacial ponds on a stagnating part of Khumbu Glacier
Stagnating glaciers provide new habitat for birds, bees, small mammals, macroinvertebrates (small critters living in ponds), and occasionally grazing livestock. Vegetation grows when the glacier slows and the surface stabilises. However, when lakes develop the situation can become problematic. When dammed by a wall of sediment and rocks of unknown stability, these lakes can threaten downstream communities and require close monitoring using satellite imagery and in the field. The hydropower potential of these lakes could one day be tapped, however, some lakes will inevitably breach their dams and cause downstream flooding, often triggered by large avalanches. Awareness, early warning, and adaptation is key.

Thulagi Glacial Lake
Access to water resources will change as snow cover reduces and glaciers disappear, also requiring community adaptation. There is often disconnect between scientists, mountain communities, transient mountain visitors, and government and non-government agencies. Scientists should be open about observed and predicted changes, but also the associated uncertainties. Open Access publishing allows scientific research to be read by all. Communities can retain vast historical knowledge of previous environmental stresses, and are well placed to describe ongoing changes and their adaptation requirements. Engagement is therefore key for research to be targeted efficiently and used to guide adaptation strategies.

Anyone can volunteer time and become a citizen scientist: communities, mountaineers and tourists can all contribute to targeted data collection and analysis. Communities are well placed for continual observations targeted to local needs, such as stream and river flows, timing of the growing seasons, and documentation of flood events. Local and international mountaineers access the highest peaks on earth and can bring back snow and rock samples, maintain weather stations, capture repeat photography and provide specialist knowledge of changes in the high-mountain environment. Tourists can also capture repeat photography, and may also have the opportunity to capture aerial imagery from helicopter flights, which can be used to reconstruct the environment in 3D. There are opportunities for everyone to engage with research that is ultimately geared towards improving our understanding of global change and how best to adapt.

C. Scott Watson is an environmental research scientist and runs the outreach website  Tweets @CScottWatson. This article follows the publication of ‘Everest's thinning glaciers: implications for tourism and mountaineering’ in the journal Geology Today

Sunday, 21 January 2018

New publication: Everest's thinning glaciers: implications for tourism and mountaineering

A new open access paper by Scott Watson and Owen king reveals the implications of glacier thinning on mountaineering and tourism in the Everest region of Nepal.

Parts of Khumbu Glacier have thinned by up to 80 m 1984−2015 and over 197,600,000 m³ of ice melted over study period, which is approximately 71,000 Olympic size swimming pools worth of water. As the glacier slows down and this water increasingly ponds on the surface, access becomes difficult for trekking routes passing over the glacier surface, such as the Kongma La Pass trail.

The paper also includes observations from several Everest mountaineers, suggesting that rockfall activity is likely to increase in the high-mountain environment as snow and ice melts from mountain slopes, requiring changes to climbing routes on the world's highest peaks.

Surface elevation change on Khumbu Glacier (1984-2015) generated by differencing digital elevation models

Glacier velocity in the Everest region derived from feature tracking on two Planet Labs satellite images. The lower parts of these glaciers are stagnant.

The Kongma La Pass trail is rerouted around supraglacial ponds and ice cliffs, which block access. Few such ponds existed in 1984 (left panel).