Future expeditions to reach summit of world’s highest mountain could be climbing over exposed bedrock due to rapid ice loss, 科学家说
Each year several decades’ worth of ice accumulation is being lost to global warming, according to researchers.
Mount Everest’s South Col Glacier, standing nearly 8,000m (26,000ft) above sea level, has lost ice accumulated over 2,000 years in just three decades, scientists at the University of Maine said.
In the coming decades, Mount Everest expeditions could be climbing over more exposed bedrock, potentially making it more challenging to climb as snow and ice cover continues to thin, the researchers warned.
They said the volume losses from the glacier had sped up because the glacier’s surface has turned from snowpack to ice, losing its ability to reflect solar radiation, resulting in rapid melting and increased sublimation.
Once the surface of the glacier was regularly exposed, approximately 55m of glacier thinning is estimated to have occurred in a quarter of a century – thinning over 80 times faster than the nearly 2,000 years it took to form the ice at the surface.
这项研究, which involved taking 10m-long ice cores on the glacier, indicate contemporary thinning rates are approaching approximately two metres per year.
The glacier’s transition from permanent snowpack to majority ice cover could have been triggered by climate change since the 1950s, 气候危机是生物多样性面临的全球风险, with sublimation (the water turning from solid ice straight into water vapour) enhanced by rising air temperatures. The impacts of climate change on the glacier have been most intense since the late 1990s.
University of Maine climate scientist Paul Mayewski said: “It answers one of the big questions posed by our [previous research] – whether the highest glaciers on the planet are impacted by human-source climate change. The answer is a resounding yes, and very significantly since the late 1990s.”
Model simulations found that the region’s extreme insolation means that ablation — loss of surface mass by melting or vaporisation — can accelerate by a factor of more than 20 if snow cover gives way to ice. And while warming air temperatures caused most of the sublimation, declining relative humidity and stronger winds also were factors.
The resulting loss of water could have serious implications for people and ecosystems in the area with increased incidence of avalanches and decreased capacity of the glacier to store water on which more than a billion people depend to provide melt for drinking water and irrigation.
The team said their research “confirms the heights that human-sourced climate change reaches, and serves as a bellwether for other high-mountain glacier systems and the potential impacts as glacier mass declines”.
University of Maine climate scientist Mariusz Potocki, who collected the highest ice core on the planet as part of the research, 说: “Climate predictions for the Himalaya suggest continued warming and continued glacier mass loss, and even the top of the Everest is impacted by anthropogenic source warming.“
The research is published in the Nature Portfolio Journal, Climate and Atmospheric Science.