Although the differences in mass loss estimations may not seem high, the finding is important because lake-terminating glaciers comprise about 25% glacier area in the Himalayas, said Tobias Bolch, study co-author and professor at Graz University of Technology in Austria.
Such improvements in estimates may be especially important for the western Himalayas and Karakoram, where the largest expansion of glacial lakes is expected, the study said.
The study looked at one particular kind of glacier: those that terminate in a lake or a body of water. Glacial lakes are growing in the Himalayas and other high mountain areas due to rising temperatures.
For this study, a team of international scientists used satellite data and formulas to estimate the change in the volume of glacial lakes in the Himalayas for the period between 1990 and 2020 and thus quantify the mass loss happening under the lake as the submerged part of the ice turns into water. They then cross-checked their findings with field measurements of 16 glacial lakes.
The study found that glacial lakes had increased in number by roughly 47% between 2000 and 2020, or an increase of 179 lakes per decade. Lakes increased by 33% and lake volume by 42% in the same period. The expanding glacial lakes resulted in roughly 2.7 gigatonnes of under-water ice loss, scientists calculated, adding to the total ice loss numbers.
Most of these “lake-terminating” glaciers are located in the central Himalayas, eastern Himalayas, and the Nyainqentanglha mountains in Tibet. It is also in these areas where the underestimation of ice loss has been highest, the study found, as glacial lakes have grown.