Increased Discharge in the Tianshan Glacierized Watersheds

Western Tianshan Mountains in Xinjiang, China, overlooking the glacier-fed Sayram Lake (Source: Jaymar Alvaran/Creative Commons).

In the arid and semi-arid regions of Central Asia, including western China, the glaciers of the Tianshan Mountains are an important water source for the inhabitants of the area. But accelerated glacier retreat is an unfortunate product of the changing climate, and the Tianshan glaciers are no exception. A recent study published in Hydrological Processes by Chinese scientists Min Xu, Hao Wu and Shichang Kang explored how the glacierized watersheds of the Tianshan Mountains have changed over almost 60 years.

Home to some 8,000 glaciers and spanning across approximately 7,200 square kilometers, the Tianshan Mountains are among the largest mountain systems in the area as well as a “water tower” of Central Asia. According to the study, the snow and glaciers yield 40 to 70 percent of the total river discharge of the region, feeding the water that supplies approximately 50 million people in Kyrgyzstan, Uzbekistan, northern Tajikistan, and the Xinjiang province of western China. The researchers used non-parametric tests and wavelet transforms to assess the changes of temperature, precipitation, discharge, glacier volume and runoff of six various watersheds of the Tianshan from 1957 to 2004, ultimately examining how different rivers have responded to climate change.

The study concluded that the glacierized region of the Tianshan Mountains has undergone significant change in the past several decades and that “regional climate warming was obvious.” Additionally, they found patterns in the results. For temperature, “the warming trend increased gradually from east to west, and the increase in temperature was greater on the north slope than on the south slope,” according to the paper. The results mentioned similar patterns for precipitation. From the eastern to central region, the trend increased but was followed by a trend decrease from central to western. However, despite the decline, the value in the west was still higher than in the east. As for the discharge, it also generally increased from east to west. Lead scientist Min Xu explained to GlacierHub that the main reasons for the differences in trends across the regions are the variations in precipitation and glacier area, which are generally larger in the west. This pattern reflects the predominant atmospheric circulation, which comes from the west; the moisture-bearing winds deposit the largest amount of precipitation on the first mountains which they encounter.

Image of the Tianshan Mountains (Source: travelingmipo/Creative Commons).

One of the significant concerns regarding the increase in glacier discharge is how the waters supported by Tianshan Glacier meltwater stand concerning the peak water value—as glacier retreat advances, rivers first carry more water, reflecting the more rapid melting, but then later have lower flow, because the glaciers are depleted.

Although this study does not address the concept of peak water directly, it does report on three highly relevant points. First, there is an overall upward trend across the six discharge locations. These results thus indicate that the calculated trends are currently pre-peak value. Second, the patterns do vary from river to river depending on the geography. For instance, where the exact position is in the mountains. Additionally, where on the individual mountains, whether the north or south slope or high or low elevation. These differences demonstrate the variability in predicting peak value. And third, not all glaciers are melting at similar rates and react to climate dynamics differently. Many higher glaciers have remained relatively stable regarding discharge variability. But scientists do expect even the upper glacier watersheds to exhibit more substantial fluctuations as glaciers will shrink under a warming climate.

Such a phenomenon will have broad ramifications across the region. “Changes in the spatial and temporal distribution of water resources due to climate change will lead to unbalanced developments in the productivity of the region, which would aggravate discrepancies of the economy,” glaciologist Shiqiang Zhang of Northwest University in China told GlacierHub. “It is very important to evaluate the fluctuations of glaciers and water resource changes on the watershed scale under the changes in climate, which not only provides references for assessing the changes of water resources in future, but also provide important suggestions for water management in Central Asia.”

Image of a glacier-fed river feeding into Ala-Kul Lake deep inside the Tianshan (Source: Journeys On Quest/Creative Commons).

Hongkai Gao, postdoctoral research associate at the Julie Ann Wrigley Global Institute of Sustainability at Arizona State University, shared his remarks on the importance of the study. “It is essential to study runoff changes of glacier-fed watersheds in different climatic regions of the Tianshan Mountains,” Gao told GlacierHub. “This study helps us to gain a better understanding on the recent changes in the Central Asian ice cover with regard to the ongoing climate change and for the assessment of the contribution of the glaciers’ meltwater to the total runoff.”

However, the concerns go beyond Central Asia. “The hydrological implications of climate change are a global concern,” Xu told GlacierHub. Melting glaciers across the world face changes in discharge and face peak water value. Once this peak water value has passed, “water resources are expected to diminish in glacier-fed watersheds, and significant economic and societal impacts are expected in peripheral regions,” Xu elaborated. “Therefore, we evaluate the fluctuations of glaciers and water resource changes on the watershed scale under the past climate change. This work will help us to understand the changes of runoff in future climate change and provide the references for adopting policies for water resource management.”

Adopting sustainable water resource policies now could partially offset the potential threat towards local peoples’ livelihoods and well-being to occur in the decades to come as a result of melting glaciers. Researching and understanding the trends, as these scientists did for the Tianshan, is the crucial first step to making effective policies.

Research Shows How Climate Change Drives Glacier Retreat

Shrinking glaciers are oft-cited examples of the effects of anthropogenic climate change, providing dramatic imagery in different parts of the world. However, this has mostly been based on global aggregates of glacier extent. Differing opinions also exist about the best way to measure glacial change all over the world.  A recent study by Roe et al., published in Nature Geoscience, confirms that climate change has contributed to the shortening of numerous glaciers around the world, but the study is not immune to controversy surroundings the methods used.

Retreating glaciers, such as these in the Himalayas, are a popular symbol of climate change (Source: NASA/Creative Commons).
Retreating glaciers, such as these in the Himalayas, are a popular symbol of climate change (Source: NASA/Creative Commons).

Using a combination of meteorological data and observations of glacier length, Roe et al. studied the influence of climate on 37 glaciers between 1880 and 2010. The glaciers were selected based on the continuity of length observations and the need for a wide geographical distribution.

Glacier mass-balance records are a more direct measure of the effect of climate than glacier length as they measure the difference between the accumulation and ablation (sublimation or melting) of glacier ice. However, most mass-balance records do not extend for more than two decades, contributing to the previous lack of confirmation of the effect of climate change on individual glaciers around the world.

The use of observations of glacier length helped to overcome this obstacle, but challenges were still encountered in obtaining long, continuous data sets, particularly for regions such as Asia and South America. In conversation with GlacierHub, Roe shared that many factors can affect the availability of continuous data sets. “For example, the collapse of the Soviet Union led to many glacier observation programs being abandoned,” he stated.

The researchers tracked changes in the length of 37 glaciers, including those highlighted here (Source: Roe et al./Nature Geoscience).
The researchers tracked changes in the length of 37 glaciers, including those highlighted here (Source: Roe et al./Nature Geoscience).

An additional challenge arose from the variation in conditions experienced by each glacier. “Every glacier is a unique product of its local climate and landscape,” Roe shared, citing the example of maritime glaciers, which typically experience a large degree of wintertime accumulation variability. “This can mask the signal of a warming that, so far, has mainly impacted the summertime mass balance,” he added.

Nevertheless, Roe et al. found that there was at least a 99% chance that a change in climate was needed to account for the retreat of 21 of the glaciers studied. “Even for the least statistically significant (Rabots Glacier in Sweden), there was still an 89% chance that its retreat required a climate change,” Roe said.

As glaciers tend to have decadal responses to changes in climate, their retreat since 1880 is likely to be a result of twentieth-century temperature trends. They also act as amplifiers of local climate trends, providing strong signal-to-noise ratios that serve as strong evidence for the effects of anthropogenic climate change. For example, one of the glaciers included in the study, Hintereisferner in the Austrian Alps, retreated 2,800m since 1880, with a standard deviation (a measure of the deviation of values from the mean) of 130m. This value is small compared to the amount of retreat, providing a strong signal of change.

Hintereisferner was one of the 37 glaciers included in the study (Source: Creative Commons)
Hintereisferner was one of the 37 glaciers included in the study (Source: Woodsiailvensis/Creative Commons).

“We hope that these results will lead to a stronger scientific consensus about the cause of glacier retreat. The last round of the Intergovernmental Panel on Climate Change was quite timid, concluding only that it was ‘likely’ that a ‘substantial’ part of glacier retreat was due to human-caused climate change,” Roe added. IPCC nomenclature would make it “very likely” (≥90%) that all but one of the glaciers in this study have retreated because of climate change, allowing for stronger conclusions to be drawn.

Excitement about the results of this study was shared by Joerg Schaefer, professor at the Lamont-Doherty Earth Observatory: “Under Roe’s lead, the really smart glacier people find ways to explain this strange observation that glaciers are highly individual beasts if you look at short time scales (years and decades), but behave like a flock of well-behaved sheep when you look at longer (centennial and millennial time-scales),” Schaefer said in an interview with GlacierHub. “This will help us a lot down the road to better predict rates of glacier change for the next century.”

In contrast, Mauri Pelto, professor of environmental science at Nichols College who has been involved in the North Cascade Glacier Climate Project for 34 of years, expressed that the paper was interesting but not the first confirmation of glaciers being impacted by anthropogenic climate change. “This does not mean it is not worth writing about,” said Pelto, “but it needs to be placed in the context of the other key studies that were both earlier, and, I believe, stronger.”

For example, the authors looked at fewer glaciers than Oerlemans et al. (2005) while modelling each in more detail. Pelto notes that they also used far less data than Zemp et al. (2015) in making an even more compelling statement on the status of glaciers. Finally, the authors are not the first to conduct an attribution study: note Marzeion et al. (2014). While their statistical method is quite robust, their modelling approach that generates data does not have an impressive verification record, according to Pelto.

“Other recent studies better represent the certainty of glacier change being driven by climate,” Pelto concluded.

These opinions indicate that glacier retreat continues to attract attention and stimulate active debate, pointing to the importance of glaciers and climate change. The approach used in this study relies on glacier length, a less precise measure than mass-balance. However, its value lies in the ability to consider long meteorological and glacier length records for a number of glaciers, contributing to an important and growing body of knowledge about the effects of anthropogenic climate change on glaciers all over the world.

Photo Friday: Benchmark Glaciers in the USA

Glaciers contain about three quarters of the world’s fresh water and cover about 75,000 square kilometers of the U.S. The United States Geological Service (USGS) has been running the Benchmark Glacier program since the late 1950s to track glacier mass balance. Repeat measurements at four selected sites are used in conjunction with local meteorological and runoff data to measure the glaciers’ response to climate change.

Results from South Cascade Glacier in Washington and Gulkana and Wolverine glaciers in Alaska provide the longest continuous record of North American glacier mass balance. In 2005, Sperry Glacier in Montana was added to the program, allowing changes in glacier mass in the principal North American climate zones to be tracked.

South Cascade Glacier in Washington experiences some of the highest precipitation levels in the lower 48 states of the USA, exceeding 4500mm per annum in some places. Data was first collected from this glacier in 1959.

 

South Cascade Glacier as seen in 1928 (left) and 2006 (right) (Source: USGS)
South Cascade Glacier as seen in 1928 (left) and 2006 (right) (Source: USGS).

 

A researcher collecting a snow core sample from South Cascade Glacier (Source: USGS)
A researcher collecting a snow core sample from South Cascade Glacier (Source: USGS).

 

Gulkana Glacier can be found along the southern flank of the eastern Alaska range. It experiences a continental climate, with large temperature ranges and precipitation that is more irregular and lighter than that experienced in coastal areas.

 

Gulkana Glacier and surrounding peaks (Source: USGS)
Gulkana Glacier and surrounding peaks (Source: USGS).

 

Northern lights over the researchers’ cabin in 2014 (Source: USGS)
Northern lights over the researchers’ cabin in 2014 (Source: USGS).

 

A researcher measuring the thickness of the snow at Gulkana glacier (Source: USGS)
A researcher measuring the thickness of the snow at Gulkana Glacier (Source: USGS).

 

Wolverine Glacier is also located in Alaska, but is found in the Kenai Mountains on the coast. The maritime climate has low temperature variability and regular, heavy precipitation. Data collection at both Gulkana and Wolverine glaciers began in 1966.

 

Wolverine Glacier in 2014 (Source: USGS)
Wolverine Glacier in 2014 (Source: USGS).

 

The weather station at the top of Wolverine Glacier (Source: USGS)
The weather station at the top of Wolverine Glacier in Alaska (Source: USGS).

 

The crevassed surface of Wolverine Glacier (Source: USGS)
The crevassed surface of Wolverine Glacier in the Kenai Mountains (Source: USGS).

 

Sperry Glacier is located in the Lewis Range of Glacier National Park in Montana. The climate of the region is influenced by both maritime and continental air masses, but Pacific storm systems dominate. These systems result in moderate temperatures and heavy precipitation, which vary strongly with altitude.

 

Sperry Glacier in 1913 (top) and 2008 (bottom) (Source: USGS)
Sperry Glacier in 1913 (top) and 2008 (bottom) (Source: USGS).

 

Researchers inserting ablation stakes using a steam drill (Source: USGS)
Researchers inserting ablation stakes using a steam drill (Source: USGS).

Roundup: Drone Research, Tianshan Glaciers, and Indigenous Alaskans

Roundup: Drones, Glacier Mass and Vulnerability

 

Drone Research Points to Global Warming

From Pacific Standard: “Aaron Putnam is an hour behind them, hiking with a team of students, research assistants, and local guides. He’s a glacial geologist from the University of Maine, and he and his team are here to collect the surface layer of granite boulders implanted in those moraines that formed at the margins of the glacier…The team hopes that data derived from the rock can tell them when the ice melted. ‘This was the singular most powerful, most important climate event in human history. It allowed us to flourish,’ Putnam says. ‘But we don’t know why that happened.’ Putnam is trying to determine what caused the Ice Age’s demise; the answer could help us identify the triggers that cause abrupt climate change.”

Learn more about how the study of glaciers points to our climate’s future here:

1-a4zfkscplmtqbghacrjvrw
The research team photographs the landscape near the study’s sampling site (Source: Kevin Stark/Pacific Standard).

 

Central Asia Feels Effects of Global Warming

From Molecular Diversity Preservation International: “Global climate change has had a profound and lasting effect on the environment. The shrinkage of glacier ice caused by global warming has attracted a large amount of research interest, from the global scale to specific glaciers. Apart from polar ice, most research is focused on glaciers on the third pole—the Asian high mountains. Called the Asian water tower, the Asian high mountains feed several major rivers by widespread glacier melt. Changing glacier mass there will have a far-reaching influence on the water supply of billions of people. Therefore, a good understanding of the glacier mass balance is important for planning and environmental adaptation.”

Learn more about glacier mass balance and associated environmental adaption here:

800px-west_tian_shan_mountains
An aerial photo depicting a sector of the Tianshan mountains (Source: Chen Zhao/Flickr).

 

Perspectives from Indigenous Subarctic Alaskans

From Ecology and Society: “Indigenous Arctic and Subarctic communities currently are facing a myriad of social and environmental changes. In response to these changes, studies concerning indigenous knowledge (IK) and climate change vulnerability, resiliency, and adaptation have increased dramatically in recent years. Risks to lives and livelihoods are often the focus of adaptation research; however, the cultural dimensions of climate change are equally important because cultural dimensions inform perceptions of risk. Furthermore, many Arctic and Subarctic IK climate change studies document observations of change and knowledge of the elders and older generations in a community, but few include the perspectives of the younger population.”

Learn more about the younger generation’s perception of climate change and its impacts here:

800px-inupiat_family_from_noatak_alaska_1929_edward_s-_curtis_restored
An Indigenous Iñupiat Alaskan family (Source: Edward S. Curtis/Wikimedia Commons).