22 Nov 2018 | Cryosphere

Preliminary Findings Suggest Debris Cover Does Not Accelerate Glacier Melt

Preliminary findings from in-situ observations of glaciers in the Karakoram indicate that debris cover does not accelerate glacier melt. This contradicts findings of earlier observations on Himalayan glaciers where thin debris layer has been shown to accelerate the glacier melt process.

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Stakes were installed at each layer – from 0 cm, 1 cm, 2 cm, 5 cm, 10 cm, 20 cm, 30 cm, and 40 cm. Picture: Sher Muhammad/ ICIMOD

The finding is an outcome of a joint field expedition carried out through September–October 2018 by researchers from the International Centre for Integrated Mountain Development (ICIMOD), the Institute of International Rivers and Eco-Security (IIRES), Yunnan University, and the Global Climate Change Impact Study Centre (GCISC).

Daily melt rates were observed on three glaciers – Hinarchi, Hoper, and Ghulkin – in the Karakoram. The team studied the impact of aspect-wise glacier melt at several debris cover variables – from no debris to a 40 cm thick layer. Temperature data loggers were installed at the debris surface and below debris layer thickness – of up to 40 cm – to assess the relation of temperature variability with surface melt.

The debris cover was adjusted between 0 cm and 40 cm, and a total of eight stakes were installed at debris thicknesses of 0 cm, 1 cm, 2 cm, 5 cm, 10 cm, 20 cm, 30 cm, and 40 cm. Stakes were measured every day for about a month to understand the melt rate with varying debris cover and the orientation of the respective glaciers.

“This is the first instance where melt with debris cover variability was observed daily, over a month, on three glaciers. This makes it the longest observed data collected in the Karakoram,” says Sher Muhammad, ICIMOD, who led the field expedition.

All three glaciers followed similar melt patterns in relation to debris thickness. However, the melt rates were slightly different comparatively given the individual aspects of the glaciers. A key finding from this observation was that debris cover does not accelerate melting in a 1 cm–40 cm range. The melt rate decreased with increase in debris cover.

An ad hoc lesson on measuring debris-cover distribution of glacier surface with dGPS. (From L-R: Shaukat Ali, GCISC; Yasir Latif, ITPCAS; Sher Muhammad, ICIMOD/IIRES; Roshan Din Khan, PMAS-UAAR). Photo: Expedition member.

The team also measured debris-cover distribution at glacier surfaces using differential GPS (dGPS). In situ data on debris distribution can be used to validate debris-covered distribution derived from remote sensing data, given the limited field data on Karakoram glaciers. Such measurements can further explain the contribution of glacier melt to river runoff and downstream impact.

The role of debris cover in the glacier melt process continues to be inconclusive and needs further investigation, including the role of cliffs, and supra-glacier ponds over the debris cover. Such observed data add value to further understand the melt process as affected by debris cover.

A detailed analysis of the data collected in relation to temperature changes and other parameters will be published at later dates.