Recent expansions of glacial lakes in the Bhutan Himalayas

Current conditions and secular changes in ice-contact lakes in the Bhutan–China border region were investigated using satellite imagery. More than 50 moraine dammed ice-contact or ice-proximal lakes were identified, of which 14 were evidently growing. In debris-covered areas of valley glaciers, lake growth is characterised by the initial appearance of supraglacial lakes and subsequent upstream expansion by a coalesced lake. In small debris-free or partially debris-covered glaciers, lake growth begins from a single lake. Lake growth has continued over a period ranging from 20 to 70 years, with a growth rate of <70 m/year in length and <0.04 km2/year in area. These values observed at the northern side of the main Himalayan range are smaller than those observed at the southern side. The initial appearance year, estimated from the expansion rate of most of the lakes in the southern and northern sides, ranges from the 1950s to the 1970s and before the 1950s, respectively.