2.Study Area
Ming Yong Glacier is a valley glacier situated in Deqin County, Yunnan
Province in Southwest China (Figure 1). Flowing from the east face of
the Meili Snow Mountain Range, this glacial catchment was selected due
to its location on the south-eastern edge of the Tibetan Plateau that
renders it particularly sensitive to climate change. Being part of the
Three Parallel Rivers of Yunnan – the upper reaches of Yangtze, Mekong,
and Salween – this area has received much attention from environmental
conservationists due to its rich biodiversity and diverse ecosystems.
Ming Yong Glacier flows from the east face of the Meili Snow Mountain
Range into the Upper Mekong River (also known as the Lancang
River).Thereafter, the Mekong continues its journey into the riparian
countries of Myanmar, Laos, Thailand, Cambodia, and Vietnam. The total
length of the Mekong is 4,350 km with a total drainage area of 795,000
km2.
The study area has a catchment area of 39.7 km2 with
27 km2 covered by glaciers (68%). The elevation of
the watershed ranges from 6684m at the Kawargarbo Peak to 2930m at the
glacier terminus with an average slope of 29% (Figure S1). The Ming
Yong glacial icefall is covered by a layer of supraglacial moraine and
debris that is contributed by sediments from the steep valley sides
(Figure 2b). From the glacial terminus to the confluence with the Upper
Mekong River, the Ming Yong River flows for about 6.1 km.. Due to
accessibility issues, water samples and discharge measurements were
taken from a single sampling station 3.1 km from the glacial terminus at
an elevation of 2342 m (Figure S1). Specifically, the sampling station
is located at 28°28’5.80”N, 98°46’58.57”E.
Ming Yong catchment is classified as a monsoon-influenced temperate
oceanic climate – dry winter and a warm, wet summer – under the
Köppen-Geiger climate classification (Beck et al., 2018). At least 70%
of its average annual precipitation is received during the warmest
months (Figure 2c-d). Due to the lack of a weather station at Ming Yong,
annual climate data was taken from the nearest weather station 13km away
at Deqin. The average annual temperature is 5.6°C and the average annual
precipitation of 641mm. Precipitation ranges from 6mm in December to
133mm in July. The average temperature is lowest at -2.2°C in January
and 12.7°C in July. Variation in annual temperature is approximately
14.9°C with its coldest month in January (-2.2°C ) and warmest month in
July 12.7°C.