Everdrill: Accessing the interior and bed of a Himalayan debris-covered glacier to forecast future mass loss

The Hindu-Kush Himalaya is a region that is commonly known as the 'third pole' given the volume of glacier ice that is stored in the mountains - more than anywhere on earth outside the Arctic and Antarctic. Crucially, many millions of people living in the foothills and further downstream rely on the meltwater from these glaciers for their daily drinking, sanitation and irrigation needs. The region as a whole is known to be extremely sensitive to climate change, and the speed at which warming is taking place is greatest at high-elevation - where the glacier ice is located. It is still largely unknown, however, how climate is likely to change across the region in the future, and the impact this will have on melting glacier ice and those that rely on it in their everyday lives.

It is difficult to predict the impacts of future climate change in the region, because we know so little about the glaciers other than what we can measure at the surface. Many glacier models that are designed to predict glacier evolution therefore assume many of the parameters that are unknown, but these parameters are also very important to their functioning - for example the temperature of the ice, the thickness of the ice, and the existence or otherwise of sediment at the ice-bedrock interface. In this project we aim to collect real measurements of these subsurface properties and thus make much more robust predictions of how these glaciers may chance with climate.

We will drill six boreholes at four locations into the Khumbu Glacier, Nepal, which descends from Mount Everest and is one of the largest in the Himalayan region. It is debris-covered for its lowermost eight kilometres but pocked with clean-ice exposures that we can exploit with a hot-water drill. We will gather visual footage of each borehole interior and install a multi-sensor array at the bed at each of the four locations. The arrays will log water pressure, temperature, electrical conductivity and turbidity and how each of these parameters changes through the seasons. At two additional boreholes we will install englacial temperature and tilt strings to determine the thermal and deformation profiles of the glacier.

Existing glacier models are poorly tested to their sensitivity of variability in the input data. It is important to know how the model responds to small changes in the predicted climate for example, compared with small changes in basal water pressure or temperature. These sensitivity tests tell us about the uncertainty in our predictions as well as how the whole climate-glacier system works. We aim to test the sensitivity of the glacier model that we are using to a range of different parameters by adjusting them individually and analysing the change in prediction in each case. Ultimately, we will include our real-world data in the model and make robust predictions of debris-covered glacier evolution under a warming climate.

This work will inform regional policy makers concerned with future water supply, local humanitarian aid agencies who will work with foothill dwellers in periods of flood and drought, the Intergovernmental Panel on Climate Change (IPCC) which will inform future climate summits on the world stage, and local people who are dependent on glacier runoff for irrigation, hydro-electric power production and sanitation.