Glaciers in most regions around the globe are retreating due to ongoing climate change. But glaciers in the Karakoram region of the Indus River Basin have not seen any significant area or volume change in the past four decades. This phenomenon has been labelled the “Karakoram Anomaly”.
A study recently published by scientists from the International Centre for Integrated Mountain Development (ICIMOD) and collaborating partners has provided further support for the Karakoram Anomaly, and has extended it back to the 1970s using declassified spy satellite imagery. Previous geodetic estimates of mass changes in the Karakoram revealed balanced budgets or a possible slight mass gain since 2000. Evidence for longer-term stability exists, but few mass budget analyses from before 2000 are available.Overview map of the study region
“Since at least the 1970s the glaciers in this region have been, on average, neither losing nor gaining mass unlike elsewhere in the Himalaya where glaciers are losing mass,” said Joseph Shea, Visiting Scientist at ICIMOD, and one of co-authors on the study. The study revisited existing information, and extended the time series back to some of the earliest available satellite imagery. It focused on the Hunza catchment in the central Karakoram where high heterogeneity of glacial behaviour was found in previous studies.
The study, led by Tobias Bolch of the University of Zurich, showed that glaciers in the Hunza River Basin (central Karakoram) were on average in balance or showed slight insignificant mass loss within the period 1973–2009. The study was also able to identify patterns of mass loss and gain for surging glaciers, which are common in the region. Surge-type and non-surge-type glaciers showed on average no significantly different mass change values. However, some individual glacier mass change rates differed significantly for the periods before and after 2000.
The Karakoram mountain range spans the borders of Pakistan, India, and China, with the northwest extremity of the range extending to Afghanistan and Tajikistan. Karakoram glaciers, which occupy a large portion of the glacierized area of the Indus Basin, continue to baffle scientists with their unusual behaviour. This study was performed within the Cryosphere Initiative of ICIMOD, with the targeted support of the UK Department for International Development (DFID).