Manifestations and mechanisms of the Karakoram glacier Anomaly

Due to ongoing climatic change, glacier mass loss and retreat are observed all over the globe. The changes are beyond historic precedence, affect ice masses from the polar ice sheets to the highest mountain glaciers, and cause concerns ranging from rising sea levels to water scarcity. The impacts on water resources are particularly important when glaciers supply water to downstream populations, as is the case in High Mountain Asia (HMA).

Amongst this general picture of glacier wastage, one region stands out because of its anomalous behavior: The Karakoram. Located in the border regions of China, India, and Pakistan, the Karakoram and the nearby Western Kun Lun have been identified as a region in which glaciers were in balance or even slightly gaining mass during recent decades. Geodetic assessments show negligible to slightly positive volume changes, analyses of surface ice flow velocities show steady to increasing ice flow, and glacier inventories reveal a concentration of surge-type glaciers that is unique to HMA.

In this contribution, we review the present-day understanding of what has been known as the “Karakoram Anomaly” since the early 2000s. We show that evidence is accumulating for the Anomaly extending into the Western Kun Lun and Pamirs, and for being due to a combination of factors, including (i) an increase in westerlies-dominated winter snowfalls, (ii) an increase in diurnal temperature ranges possibly related to large-scale deforestation, (iii) a summer cooling linked to the weakening of the monsoon, (iv) an increase in atmospheric moisture likely due to an expansion of  regional irrigation, (v) an increase in summer accumulation resulting from both the summer cooling and the increased moisture, and (vi) reduced ablation due to a moisture-related increase in cloudiness and decrease in incoming shortwave radiation.

Our work assesses the relative level of confidence of the individual mechanisms, and highlights potential pathways that may further improve our understanding.