Katie Miles, Author provided
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In 2017 and 2018, our EverDrill research team travelled to Nepal, to measure ice temperatures (using a converted pressure washer) on the Khumbu Glacier. Khumbu, whose ice is sourced in the Western Cwm of Mount Everest, flows down the flanks of the mountain from around 7,000 to 4,900 metres above sea level. Along with many other glaciers in the Everest region and across High Mountain Asia, the meltwater from Khumbu contributes to the water resources of huge populations in the mountain foothills.
We spent two field seasons (six to eight weeks each) drilling boreholes using a jet of hot, pressurised water to incise into the ice. In total we drilled 27 boreholes, ranging between 1-192m deep, across five sites. These boreholes are the first, deepest, and most spatially extensive achieved to date in the Himalaya using hot-water drilling.
Once the boreholes were drilled, we measured ice temperatures by installing strings of pre-built thermistor sensors linked to data-loggers located at the surface. We left them for six months and collected the data on a return trip in November 2017.
Katie Miles, Author provided
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Cold and warm ice
Why does it matter that we found warmer ice temperatures than we expected? Glaciologists acknowledge two thermal types of ice: “Cold” ice and “warm” ice. Cold ice is below the melting-point temperature, so when additional heat is applied (from the sun or warmer air temperatures), the ice simply becomes less cold (going from –15°C to –14°C, for example). Warm ice, alternatively, is at the melting-point temperature, so any heat input melts the ice to become water.
In short, this means that Khumbu will respond more sensitively to any future additional heat inputs, such as warming air temperatures. It has been shown that air temperature increases are amplified at high elevations. For example, a global temperature rise of +1.5°C has been predicted to result in a +2.1°C warming across High Mountain Asia and a significant loss of ice mass across the region. As these glaciers melt and recede, their contribution to water resources will initially increase. However, as the volume of ice mass remaining decreases, this contribution will steadily decline. While the timescale over which this might occur is unknown, predictions suggest that “peak water” may be reached as soon as the middle of this century. Our finding of warm ice within Khumbu supports the predicted sensitivity of such glaciers to warming air temperatures.
Katie Miles, Author provided |
However, this insulation of the lower glacier also results in the location of maximum melt shifting further up the glacier, to where the debris cover is thinner. In this area, the glacier melts by surface lowering, which in an extreme future scenario could lead to the detachment of the lower glacier, forming a new terminus at this higher elevation. While the lower, detached ice would become stagnant, it would still be protected from instant melting by its debris blanket. The new terminus above this would not, and melt rates could increase. Yet, our deepest borehole in this area of surface lowering was 192 metres, and did not reach the bed so the ice thicknesses remains unknown – but it could be that there is plenty of ice left in Khumbu to stop this happening.
These ice temperatures will now be fed into an ice flow model to better predict how the Khumbu Glacier will respond to climate warming and contribute to river discharges in the future. Meanwhile, we are still collecting temperature data to analyse and better understand how the highest glaciers in the world will be affected by climate change.
Links
- Melting glaciers around Mount Everest may be forming killer lakes
- Climate Change Is Melting Everest
- Warm ice in Mount Everest’s glaciers makes them more sensitive to climate change – new research
- Scientists Have Discovered 'Warm' Ice in The World's Highest Glacier
- Climate change, crowding imperil iconic route to top of Mount Everest
- Going, Going ... Glacier National Park's Iconic Glaciers Are Melting Away
- What a century of climate change has done to France’s biggest glacier
- Huge crater discovered in Greenland – here’s how the impact may have wiped out the mammoths
- Why we’re drilling into the world’s highest glacier on Everest with a converted car wash
- A bird’s eye view of New Zealand’s changing glaciers
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