Meltwater from Tibetan glaciers floods pastures

Jan 16, 2014 by Dr. Tobias Bolch
Zhadang glacier south of lake Nam Tso on the northern ridge of the Nyainqentanglha mountain range (Tibet, China) Credit: Tino Pieczonka; TU Dresden

The earth is warming up, the glaciers are shrinking. However, not all meltwater is causing sea-level rise as feared. In Tibet, as measurements taken by an international team of researchers including the University of Zurich reveal, a significant proportion of the meltwater remains on land. The consequences are, however, equally negative: it can cause lakes without an outlet to overflow and flood valuable pastureland.

Glaciers are important indicators of climate change. Global warming causes mountain to melt, which, apart from the shrinking of the Greenlandic and Antarctic ice sheets, is regarded as one of the main causes of the present global . Tibet's glaciers are also losing mass clearly, as scientists from the universities of Zurich, Tubingen and Dresden reveal using satellite-based laser measurements. Over the last decade, the research team has detected a "clear loss in mass of around 16 gigatons a year in around 80 percent of the Tibetan glaciers," says Tobias Bolch, a glaciologist from the University of Zurich involved in the study – that's more than four times the volume of water in Lake Zurich and around six percent of the total loss in mass of all the glaciers on Earth.

Some glaciers in Tibet are growing

However, the measurements also bore some positive news: Some glaciers in the central and north-western part of the Tibetan Plateau have actually grown in mass. While the glaciers in the monsoon-influenced southern and eastern part of the plateau have melted significantly, the scientists recorded a neutral or even slightly positive result in the continental central and north-western area of the country. Nonetheless, as Bolch notes, "On average, the entire region is clearly characterized by a loss in mass."

At a first glance, the evidence that not all of the meltwater flows into the ocean via the large Asian currents and causes the sea level to rise seems positive. "However, flooding is still a problem," says Bolch. After all, a large proportion of the melt – around two gigatons a year, as scientists have quantified for the first time – flows into lakes without an outlet on the plateau, causing them to burst their banks. "In many regions, this means that valuable pasture areas become submerged," explains the glaciologist.

Ice cap in central Tibet, false colour composite, glaciers appaer in blue, vegetation in green Credit: NASA, Landsat OLI; Bildbearbeitung: Tobias Bolch; Universität Zürich

Precise results thanks to a combined measuring technique

Stretching over an area of around 40,000 square kilometers, the Tibetan Plateau's glaciers account for over a third of High Asia's ice cover and are about twenty times the size of the ice surface of the Alps. For their study, the international team of researchers evaluated satellite-based laser measurements of the glacier surfaces on the Tibetan Plateau between 2003 and 2009. "Thanks to these measurements, we were able to gauge the temporal changes of the glacier heights and – combined with a detailed glacier inventory – changes in mass of the glaciers in Tibet, which are extremely difficult to access," say Tubingen scientists Niklas Neckel and Jan Kropacek, explaining the measuring technique.

Shrinking glacier in south-west Tibet. Credit: Niklas Neckel; Universität Tübingen

The results now published in Environmental Research Letters seem to contradict the data from a satellite mission based on other measuring methods, which indicates a slight increase in mass in the glacier ice for an almost identical period of time. For Bolch, the different measurement values depend on the amounts of meltwater that remain on the plateau and do not flow away into the sea – and which his team has now managed to measure accurately for the first time. He attributes the data from the other studies that points to glacial growth more to other influences on the calculations – such as an increase in rainfall.

Explore further: New research suggests Saharan dust is key to the formation of Bahamas' Great Bank

More information: Niklas Neckel, Jan Kropacek, Tobias Bolch and Volker Hochschild. Glacier mass changes on the Tibetan Plateau 2003 – 2009 derived from ICESat laser altimetry measurements. Environmental Research Letters. January 16, 2014. DOI: 10.1088/1748-9326/9/1/014009

add to favorites email to friend print save as pdf

Related Stories

State of Himalayan glaciers less alarming than feared

Apr 19, 2012

Ever since the false prognoses of the Intergovernmental Panel on Climate Change (IPCC), the Himalayan glaciers have been a focus of public and scientific debate. The gaps in our knowledge of glaciers in the ...

Tibetan glaciers melting, says Dalai Lama

Apr 02, 2011

(AP) -- The Dalai Lama said Saturday that India should be seriously concerned about the melting of glaciers in the Tibetan plateau as millions of Indians use water that comes from there.

Melting glaciers raise sea level

Nov 14, 2012

Anthropogenic climate change leads to melting glaciers and rising sea level. Between 1902 and 2009, melting glaciers contributed 11 cm to sea level rise. They were therefore the most important cause of sea ...

Recommended for you

Fires in Central Africa During July 2014

13 hours ago

Hundreds of fires covered central Africa in mid-July 2014, as the annual fire season continues across the region. Multiple red hotspots, which indicate areas of increased temperatures, are heavily sprinkled ...

NASA's HS3 mission spotlight: The HIRAD instrument

23 hours ago

The Hurricane Imaging Radiometer, known as HIRAD, will fly aboard one of two unmanned Global Hawk aircraft during NASA's Hurricane Severe Storm Sentinel or HS3 mission from Wallops beginning August 26 through ...

User comments : 0