The Khumbu Icefall funnels ice from the Western Cwm below Everest, Lhotse and Nuptse to the glacier below. The ice here has receded at an average of 30m/y in the past 20 years, but it has also shrunk vertically, losing up to 50m in thickness. Everest Base Camp was at 5,330m when Hillary and Tenzing climbed Mt Everest in 1953, today it is at 5,270m.
The glacier is also getting flatter: the darker debris makes the ice beneath melt faster near Base Camp, but the thicker layers of boulders and sand further down insulate the ice. Glaciologists say this flatter profile means the ice moves slower, leading to more ponding, and more rapid melting of the ice underneath.
The velocity of the glacier is 70m/y at Base Camp, and it slows down to 10m/y further below, but is zero at the terminus situated at 4,900m. This means the ice is decelerating as it is squeezed, and the pressure is being released by the melting of the ice mass.
Researchers monitoring the supraglacial ponds say their area has grown by 70% in the past ten years alone. The ponds are fringed by ice cliffs and caves which accelerate the melting. The melted ice has carved an outflow channel through the left lateral moraine, so there is no large glacial lake on the Khumbu like as elsewhere in Nepal.
Scientists conclude that the Khumbu Glacier is not about to vanish, and the Icefall is not going to turn into a water fall any time soon. However, the permanent ice catchment of the glacier above 6,000 could start to deplete under the worst-case ‘beyond catastrophic’ scenario of +5°C warming.
Nepalis paying price for climate change
Climactic change, Editorial