Patrick Wagnon, from The French National Research Institute, marking the snow layer with artificial colour in the accumulation zone (~ 5700 masl) of Mera Glacier for the accumulation measurement the following year. Photo: Arbindra Khadka/ICIMOD

Mera Glacier, in the Everest region, is one of few glaciers in the HKH region whose glaciological mass balance data have been compared and reanalysed with geodetic measurements. Comparison of glaciological and geodetic data requires several years of measurement records and provides insight into biases in the field measurements. Field-based monitoring activities of Mera Glacier began in 2007, and today, it is one of the few glaciers in the region with reasonable years of mass balance series to compare with geodetic data.

Comparing glaciological and geodetic data

Our latest study discusses the geodetic and glaciological measurements of Mera Glacier, investigates the reasons for the differences, and compares the results with those from other parts of the region. We used glacier mass balance data from 2012 to 2018, which was collected from a network of bamboo stakes installed on the glacier. Our study finds that glacier mass balance data is consistent in the lower zone of Mera Glacier, but there is a slight overestimation in its upper zone.

Glaciological mass balance calculations do not consider the influence of natural processes such as snowdrift, sublimation, and other wind-driven ablation processes on glacial surfaces. These important factors are significant at high elevation. The large spatial variability of mass balance is driven by the local topography, aspect change, and wind direction. The measurement network on Mera Glacier is not dense enough to capture this variability, and thus the systematic overestimate of Mera Glacier’s mass balance is attributed to an overestimation in the accumulation zone.

The limited number of measuring sites is due to the difficulties in accessing these sites at high altitudes, which has led to a limited stake measurement network in the upper part of the glacier. Thus, these measurements do not accurately reflect spatial variations in snow accumulation.

Glacier mass loss

Contrary to the findings of earlier studies which suggest the overall mass balance of Mera Glacier is in balance, reanalysed data from 2007-2019 suggests that the glacier has been losing mass. This finding is consistent with the trend observed in regional averages for the central Himalaya. Our study also observed a succession of negative mass-balance years since 2013, but this mass loss is low compared to other glaciers in the Everest region.

Moving forward

ICIMOD and our partners will continue monitoring Mera Glacier and improve measurements of the accumulation zone by exploring alternative methods such as modelling, observation, and remote sensing to better understand the different factors affecting mass balance.

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