CHAPTER 22 Recent glacier changes in the Mongolian Altai Mountains: Case studies from Munkh Khairkhan and Tavan Bogd Brandon S. Krumwiede, Ulrich Kamp, Gregory J. Leonard, Jeffrey S. Kargel, Avirmed Dashtseren, and Michael Walther ABSTRACT 22.1 INTRODUCTION The glaciers of the Mongolian Altai mountains play a vital role in the regional ecosystem and have created a unique physical landscape; however, there are limited data regarding the current state of the glaciers, the physical landscape, the climate, and the responses of glaciers to climate change in this region. The purpose of this study was to map recent glacier changes in the Munkh Khairkhan and Tavan Bogd ranges, to evaluate the methodologies and classifications employed, and to develop an understanding of how climate change influences glaciers and geomorphology within the region. Through the use of multitemporal ASTER and Landsat imagery and geomorphometric analysis of digital elevation models (DEMs), it was possible to monitor the glaciers and landscape dynamics. Supporting fieldwork in the Munkh Khairkhan range was conducted in the summer of 2009. The results from our analyses indicate that in the Munkh Khairkhan range there has been a decrease in glacier area of 30% and an increase in equilibrium line altitude (ELA) by 22 m between 1990 and 2006; in the Tavan Bogd range, home of the highest altitudes in Mongolia, glacier extents decreased by 4.2% between 1989 and 2009. This decrease in glacier area will impact landscape development, meltwater contribution to regional hydrology, and the people who depend on these glaciers to maintain their nomadic way of life. Glaciers serve as key indicators of climate change. Small alpine glaciers in areas with high precipitation and high ablation rates respond rapidly in length, thickness, and volume—commonly in just a decade—to these changes. Others, particularly large glaciers in areas subject to a cold dry climate, integrate climate change signals and respond over many decades or up to a century or more (Jóhannesson et al. 1989, Beniston 2000, Raper and Braithwaite 2009). Glaciers play an important role in shaping the landscape around them by eroding bedrock and depositing various sediments. They also serve as a source of water input to regional hydrology, impacting fluvial geomorphic processes, and providing a source of water for both the ecosystem and for human consumption. One region of particular interest is the Altai Mountains of western Mongolia (Fig. 22.1). At present, it is still uncertain how many glaciers there are and how large the glacierized areas are in Mongolia. In the literature, the estimates range between 120 and 731 glaciers and glacierized areas are given totals between 300 and as much as 659 km 2 (e.g., Selivanov 1972, Baast 1999, Klinge 2001, Enkhtaivan 2006). Kadota et al. (2011) reported 577 glaciers covering an area of 425 km 2 in the Mongolian Altai; this was based on a survey of 2000–2002 Landsat imagery. These glaciers contain 10% of Mongolia’s estimated volume of fresh water 482 Recent glacier changes in the Mongolian Altai Mountains Figure 22.1. Location of the two study regions, the Munkh Khairkhan and Tavan Bogd ranges, within the Mongolian Altai mountains. (Davaa et al. 2007). Baast (1999) estimated that the area occupied by glaciers in the Mongolian Altai decreased by 6% between the 1960s and the end of the 1990s. While many studies on glaciers and glacial variation have been conducted in the northern and western parts of the Mongolian Altai such as those undertaken on the Tavan Bogd range, especially its Potanin Glacier (Enkhtaivan 2006; Kadota and Davaa 2007; Khrutsky and Golubeva 2008; Tuvjargal et al. 2008; Kadota et al. 2011; Konya et al. 2010; as well as the Tavan Bogd sections in this chapter), only very limited work has been done in the Munkh Khairkhan range within the central Mongolian Altai. Studies focused on understanding the spatial significance of the range in the overall Asian land mass, climate effects on geomorphic processes, glacial chronology, and landscape evolution of the region are areas that need to be improved to understand the Mongolian Altai and the surrounding region as a whole. This work expands on the few previous studies carried out for glacier research in the Munkh Khairkhan and Tavan Bogd ranges. By applying and evaluating satellite and field-based techniques we have been able to identify glacier changes and their association with shifting climate. 22.2 REGIONAL BACKGROUND 22.2.1 Quaternary history of glaciers in the Mongolian Altai During the Pleistocene it is believed that glaciers up to 500 m thick covered 20,700 km 2 in the Mongolian Altai (Klinge 2001, Lehmkuhl et al. 2004, Enkhtaivan 2006). However, the extent and history of Pleistocene glaciations in the Mongolian Altai is not completely understood and still under debate (Lehmkuhl et al. 2004, 2011, Rudaya et al. 2009). The largest glacial advances of the Quaternary are Regional background 483 believed to have occurred between 70,000 and 15,000 years ago during the MIS 2 (Sartan Glaciation) and MIS 4 (Early Zyrianka Glaciation) of the Wisconsin (Würm) glacial period (Lehmkuhl et al. 2004; MIS stands for Marine Isotope Stage). Typically, glacial extent was controlled by topography, underlying lithology, and climate (Klinge 2001, Lehmkuhl et al. 2004, Khrutsky and Golubeva 2008). To date, no glacial deposits older than the local Last Glacial Maximum (LGM) have been found within Mongolia (Klinge 2001, Lehmkuhl et al. 2004, Bader et al. 2008). There is a close connection between equilibrium line altitude (ELA) and local climate (Benn and Lehmkuhl 2000, Lehmkuhl et al. 2004); since the LGM, ELAs in some parts of western Mongolia have increased in elevation by 500 m (Bader et al. 2008); in Tavan Bogd, the ELA rise since the LGM was 320 m (Lehmkuhl et al. 2011). ELA rises correspond to a warmer climate (Batima et al. 2005). During the Holocene and Recent there has been an oscillation between cooler drier climates and warmer moister climates, which has affected glacier and lake levels in the Mongolian Altai (Starkel 1998). Rudaya et al. (2009) used pollen and diatoms collected from lake sediment cores from Hoton Nuur in western Mongolia to reconstruct the climate between 11,000 years ago up to the present. This demonstrated that prior to 10,000 years ago the climate in the Mongolian Altai was probably cool and dry. Between 10,000 and 5,000 years ago, the climate became warmer and more humid, allowing expansion of the tree line in the mountains. From 5,000 years ago the climate again shifted towards drier and cooler conditions with a scattering of brief periods of increased warmth and humidity from 3,000 to 2,000 years ago (Starkel 1998, Rudaya et al. 2009). 22.2.2 Recent history of glaciers in the Mongolian Altai Some recent studies have used tree ring analysis of Siberian larch (Larix sibirica) to reconstruct the climate from 1215 to 2004 (Davi et al. 2009). Their results suggested that Mongolia is currently undergoing significant climatic change, with an increasing moisture trend starting in the 20th century and continuing into the 21st century. Over the last century the climate has steadily warmed in the Mongolian Altai by 3–4 C, including a 1.66 C warming over the last 60 years; the 20th century was the warmest in the last 1,000 years (Batima et al. 2005). This general trend of temperature increase in Mongolia is slightly above the overall trend in the Northern Hemisphere (Jacoby et al. 1996, 1999). Almost all of this warming is confined to the winter months with little to no change during summer (WWF Russia, 2001). Spatially, the warming is more pronounced in mountains and associated valleys, and least in the Gobi Desert (Batima et al. 2005). Instrumental records from the 1940s to 2001 also indicate that there is both a seasonal and spatial change in temperature and precipitation (Batima et al. 2005). Batima et al. (2005) have documented pronounced warming in mountainous areas and their associated valleys from 1971 to 2001. In the Altai Mountains this warming is concurrent with an increase in precipitation by 2–60 mm and a change in precipitation occurrence: typically, most precipitation falls during late spring and early summer; however, over the last 30 years, snowfall, which accounts for 20% of annual precipitation in Mongolia, has tended to occur earlier in autumn and last later into the spring (Batima et al. 2005). Climatic change may also be causing an increase in extreme weather events. Much of this may be due to a weakening of the Siberian High that has dominated over recent decades (Gong and Ho 2002). Weakening of the Siberian High results in warmer temperatures and increased precipitation during the winter. These warmer winter events cause snowmelt at a time when the ground below remains frozen. As the meltwater cannot penetrate into the frozen ground, it refreezes at the surface either on top of shallow snow cover or on vegetation, causing large losses of livestock as a result of not being able to forage. These harsh winters are called zud or dzud (‘‘white death’’) and can have a devastating impact on local livestock and their dependent herder populations. Moreover, from 1999 to 2002 Mongolia experienced some of the worst drought conditions on record, when 3,000 water sources dried up (Batima et al. 2005). These unforgiving conditions during both the winter and summer had a severe impact on the people of Mongolia, whose primary income is largely dependent on livestock and agriculture, causing economic hardship for individual nomadic families and for Mongolia as a whole. A basic characterization of glaciers in the Mongolian Altai relative to other glaciers worldwide is still lacking (Lehmkuhl et al. 2004, Khrutsky and Golubeva 2008). Most of the current glaciers in the Mongolian Altai fall into one of three types: cirque, 484 Recent glacier changes in the Mongolian Altai Mountains valley, and plateau; the latter dominate the region (Lehmkuhl et al. 2004, Kadota and Davaa 2007). Many recent glacial studies were primarily focused on understanding glacier retreat (Kadota and Davaa 2007, Bader et al. 2008, Khrutsky and Golubeva 2008, Kamp et al. 2013) and mass balance (Tuvjargal et al. 2008). Like most glaciers around the world, those in Mongolia are generally retreating. There are also reports of an increase in the rate of glacier shrinkage within the Mongolian Altai (Bader et al. 2008, Khrutsky and Golubeva 2008). In the Tavan Bogd region and the Turgen, Kharkhiraa, and Tsambagarav massifs, mean glacier length retreat was 2.5–5.7 m yr1 with a corresponding reduction in area of 10–30% from 1970 to 2000 (Kadota and Davaa 2007, Khrutsky and Golubeva 2008). During the 1960s, 1970s, and late 1990s in these four study areas, warmer temperatures did not seem to dramatically affect glacial area; however, thinning of the glaciers may have occurred (Kadota and Davaa 2007). During 1987, 1988, and 1993 some glaciers began to advance in the Turgen–Kharkhiraa region (Khrutsky and Golubeva 2008) while others remained stationary. Glacial margins and thickness fluctuations in the Mongolian Altai have been mapped using a combination of satellite imagery, aerial photos, topographic maps, and fieldwork (Kadota and Davaa 2007, Khrutsky and Golubeva 2008, Kadota et al. 2011, Kamp et al. 2013). Unfortunately, satellite imagery and aerial photos covering the Mongolian Altai are in short supply due to poor data quality associated with cloud and snow cover. Kamp et al. (2013) described glacial recession from 1910 to 2010 in the Turgen range based on repeat photography and satellite imagery. Kadota and Davaa (2007) were only able to compare glacial area from 1:100,000-scale topographic maps from 1970/1971 and Landsat imagery from 2000; more recent fieldwork at Potanin Glacier, undertaken by joint Japanese/Mongolian-sponsored teams, has focused on determination of ice thickness and velocity (Kadota et al. 2011), and meteorological and ablation studies (Konya et al. 2010). Khrutsky and Golubeva (2008) also used Landsat imagery from 1992 and 2002 to determine the dynamics of glaciers in the Turgen–Karkhiraa range. Only one study has been performed in the Mongolian Altai using Advanced Land Observing Satellite/Phased Array L-band Synthetic Aperture Radar (ALOS/ PALSAR) data to calculate glacier and snow depth (Tuvjargal et al. 2008). 22.3 REGIONAL CONTEXT AND STUDY AREAS 22.3.1 Geography and climate Within Mongolia’s far northwestern corner, the Mongolian Altai Mountains emerge from the Mongolia–Russia–China trinational border area and extend for 1,300 km southeast along the Mongolian–Chinese border before bending east and terminating within the Gobi Desert (Fig. 22.1). The Altai is centrally located in the Eurasian land mass in a transition zone between the boreal taiga forest biomes of Siberia to the north and the Gurbantunggut, Taklamakan, and Gobi Desert biomes to the south and east. Although detailed climatological information is sparse, these mountains appear to impose an abrupt climatic boundary along western Mongolia, highlighting the importance of understanding climatic variation in this region. The Mongolian Altai is in an area well known for its extreme continental climate due to its central location on the Eurasian land mass. The winters are dominated by a strong Asian anticyclone (the Siberian High), while the summers in the mountains are short and cool. Modern climate information has been systematically recorded in Mongolia ever since the early 1940s (Batima et al. 2005). However, the national climate station network is sparse and climate data for the Mongolian Altai are limited to only six meteorological stations that are situated in the valleys between the mountain ranges, thus making it difficult to estimate the climate and weather at higher elevations. In the valleys of the Mongolian Altai, mean temperature is 30 to 34 C in January and less than 15 C in July (Batima et al. 2005). For Ulaangom (939 m asl, 49 55 0 N, 92 03 0 E; Fig. 22.1) located in a basin northeast of the Turgen–Kharkhiraa Mountains in the northern Mongolian Altai, measured mean annual temperature is 4 C, and mean monthly temperature ranges between 32 C in January and 19 C in July (Jansen 2010). In Ulaamgom, measured mean annual precipitation is 136 mm and the rainy season extends from June to September (Jansen 2010). In general, winter is dominated by the Mongolian anticyclone and dry cold weather, infrequent precipitation, and drying winds, so that fallen snow sublimates rapidly (Khrutsky and Golubeva 2008). In the mountains above 2,500 m winter precipitation from snow amounts to 400–500 mm, but maximum annual precipitation generally occurs in July (Khrutsky and Golubeva 2008). Regional context and study areas There is a paucity of long-term climate data for the Tavan Bogd region, although recent efforts have seen the emplacement of automated weather stations on the glaciers there (Konya et al. 2010). Specifically, Konya et al. (2010) observed meteorological conditions within the ablation zone of Potanin Glacier during the 2007/2008 seasons and reported a mean annual air temperature on the glacier of 8.8 C (at 3,040 m asl). Minimum and maximum air temperatures for this year were 29.6 C (January 18, 2008) and 7.6 C (July 21, 2007), respectively. Measured only over the summer months (June 12 to September 8, 2007), precipitation was 191.6 mm rain, with much of this (37%) falling over three wet days in late July. This seasonal total, however, was 3.5 times higher than precipitation that fell in Olgii, the aimag (provincial) capital located about 150 km to the east (and lower at 1,710 m asl); this is likely due to the occurrence of orographic precipitation in the mountainous Tavan Bogd. 22.3.2 Munkh Khairkhan range The Munkh Khairkhan range is located in the central Mongolian Altai (Fig. 22.1). Munkh Khairkhan 485 Uul (Eternal Sacred Mountain Peak) is the second highest peak in Mongolia with an elevation of 4,208 m asl and is capped by ice and snow with glaciers extending into valleys on both the north and south sides of the range (Fig. 22.2). The remoteness of this location makes it a pristine study area free from severe anthropogenic impacts, providing an ideal opportunity to understand local glacier and landscape sensitivity to climate influences. Our study area covers 685 km 2 , of which 308 km 2 are located within the Munkh Khairkhan National Park, founded in 2006. Specifically, the study area is focused on three valleys located in the northern part of the range: Shuurkhai, Doloo Nuur, and Khokh Nuur (Fig. 22.2). Shuurkhai (Stormy Looking) is situated on the north side of the Munkh Khairkhan range and extends 28 km to the east; it contains Shuurkhai Glacier, Khar Tsünkh (Black Bag) Glacier, and Arts (Juniper) Glacieret (Fig. 22.2). Joining Shuurkhai Valley from the south is Khokh Nuur (Blue Lake) Valley, which is 10 km long and contains another glacier, called Arts Glacier. Doloo Nuur (Seven Lake) Valley contains Doloo Nuur Glacier and extends to the north for 15 km. Munkh Khairkhan soum (village) is the closest settlement to the national park and has a Figure 22.2. Munkh Khairkhan range, central Mongolian Altai showing study area (red area) and Munkh Khairkhan National Park boundaries (white line). 486 Recent glacier changes in the Mongolian Altai Mountains population of 800 people. Meltwater originating from the glaciers in Munkh Khairkhan National Park is the source of drinking water for the village and livestock within the region via the Dund Tsenkher Gol (Middle Blue River). The Munkh Khairkhan region is geographically and ecologically significant in that it sits in the transition zone between deserts and steppe to the south and east, and the boreal taiga forest to the north. Plant species common to the study area include edelweiss (Leontopodium alpinum), short grasses, wild onions, and saxaul bushes (Haloxylon spp.). At higher elevations, juniper (Juniperus) can be found intermixed among boulder fields. Several varieties of mosses and lichens are also present in areas next to streams, lakes, and periglacial features. 22.3.3 Tavan Bogd range The Tavan Bogd (Five Holy Peaks) range is located in the extreme northwestern corner of Mongolia (Fig. 22.3) and is largely contained within the Altai Tavan Bogd National Park. This compact, northwest to southeast-trending range occupies 2,400 km 2 and contains Khuiten Uul (Cold Mountain), which at 4,374 m asl is the highest mountain in Mongolia, and four other major peaks: Burged (Eagle, 4,310 m asl), Naran (Sunny, 4,280 m asl), Olgii (Motherland, 4,100 m asl), and Malchin (Herdsman, 4,050 m asl). Figure 22.3. Tavan Bogd range, far northwest Mongolia showing study area (dashed yellow line) and approximate international boundaries (red line) (map base: ASTER GDEM V2 with local SRTM infill). Figure 22.4. Aerial views of Potanin and Alexandra Glaciers, Tavan Bogd National Park. (Top) Potanin and Alexandra Glaciers and principal peaks of Tavan Bogd. Khuiten Uul (4,374 m asl) the highest peak in Mongolia is shown at top center of photo. (Bottom) Terminus area of Potanin and Alexandra Glaciers. Note dead ice zone and proglacial lake development (photos courtesy of M. Saandar, August 29, 2011). Figure can also be viewed in higher resolution as Online Supplement 22.1. The study area comprises roughly 1,500 km 2 , merely a subset of the complete Tavan Bogd range, and includes Potanin and Alexandra Glaciers, which at 10 and 8.5 km in length, respectively (excluding a 2 km proglacial zone of small lakes and dead ice, Fig. 22.4) are the largest glaciers in Mongolia. Potanin Glacier emanates just below the summit of Mt. Khuiten Uul, flows eastward and terminates in a valley at an elevation of 2,870 m asl. Alexandra Glacier starts south-southeast of Khuiten Uul and joins the terminus area of Potanin Glacier in the lower valley. These glaciers, and the numerous other valley and mountain (cirque-like) glaciers and glacierets that dominate the region, are Data and methods centered around the Tavan Bogd massif, which itself is situated on the Mongolia–Russia–China trinational border located at the ice-domed summit of Nairamdal Uul (Friendship Peak, 4,180 m asl). It was decided that these glaciers—for the sake of physical, geographic, and hydrological continuity—would be included within this Mongolia-based study as representative of Tavan Bogd glaciers, despite the fact that several of the glaciers presented here overlap or occur completely within the boundaries of Russia and/or China, and therefore fall within the remit of those countries’ respective GLIMS regional centers. Note that all glacier outlines submitted to GLIMS from this study reflect the proper regional center within which the glacier actually occurs. We have delineated both glacier and regional center boundaries as best we can. Apart from Potanin and Alexandra Glaciers, there were no proper names or designations identified for the other glaciers in this region, and therefore we gave them provisional designations for the sake of this work and future reference to it (Fig. 22.16; Table 22.7). The absence of glacier names and designations reflects the paucity of surface and satellite-based survey work conducted to date for this remote group of glaciers. Northwestern Mongolia hosted thick and more widespread glacier ice during peak Pleistocene glaciations (Fig. 22.14); this in part is evident from the U-shaped valleys present within the Tavan Bogd range. Lehmkuhl et al. (2011) indicated that the ELA for this region during the LGM was at 3,019 m asl, or 381 m below its modern day value of 3,400 m asl. Today, meltwater from Tavan Bogd feeds Tsagaan Gol (White River), Tsagaan-Us Gol (White-water River), and Sogog Gol (Doe River), which supplies the small scattering of ethnic Kazakh villages dotting the region (including Sogog village) with a seasonal surface water resource. 22.4 DATA AND METHODS 22.4.1 Topographic maps Soviet topographic maps from 1970 to 1972 covering the study areas at scales 1:100,000, 1:200,000, and 1:500,000 were downloaded from http://en. poehali.org/maps (Table 22.1). They were manually georeferenced using the World Geodetic System 1984 (WGS 84) reference frame. These maps aided preliminary reconnaissance of the study areas and evaluation of the glaciers at the time of map 487 publication. However, glacier margins were not delineated from these maps due to their small scales limiting the detail of smaller glaciers in the study areas. 22.4.2 Satellite imagery Satellite imagery including Corona, Landsat (MSS, TM, ETMþ), Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), and EO-1 ALI (Earth Observing-1 Advanced Land Imager) were reviewed for processing; however, the availability of imagery covering the study areas was limited by the number of scenes available, the poor image quality of many scenes due to the presence of clouds and snow cover in most imagery, and sometimes poor sensor gain settings for ASTER data. ASTER imagery was downloaded from the Land Processes Distributed Active Archive Center (LP DAAC) located at the USGS Earth Resources Observation and Science (EROS) Center; Landsat imagery was downloaded from the Global Land Cover Facility (GLCF) at the University of Maryland. EO-1 ALI imagery and additional Landsat images were also acquired from the Earth Explorer website (http://earthexplorer.usgs.gov/). For the Munkh Khairkhan range, 11 ASTER Level 1B and seven Landsat scenes were selected covering 1990 to 2008 (Table 22.1). For the Tavan Bogd study area, two Landsat TM scenes (spanning 20 years) and four ASTER Level 1B scenes spanning 5 years were selected (Fig. 22.5 and Online Supplement 22.2). The TM scenes cover the entire Tavan Bogd range, whereas only one ASTER scene covers the entire range and the other three have partial coverage. One cloud-free Landsat MSS scene from September 1972 was examined, although not used as a result of poor gain settings and poor spatial resolution compared with the TM and ASTER imagery. ALI imagery was also too cloudy. Each ASTER scene covers an area of 60 60 km with 15 bands divided into three spectral resolution groups: visible and near infrared (VNIR, bands 1, 2, 3N, 3B) with 15 15 m resolution; shortwave infrared (SWIR, bands 4–9) with 30 30 m resolution; and thermal infrared (TIR, bands 10–14) with 90 90 m resolution. The imagery had already been georeferenced using the Universal Transverse Mercator (UTM) projection. Landsat imagery selected for this study used two sensors: Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETMþ). TM scenes cover an area of 185 172 488 Recent glacier changes in the Mongolian Altai Mountains Table 22.1. Data used in the Munkh Khairkhan study. Satellite imagery Scene ID Date Sensor p141r027_5dt19900916 9/16/1990 Landsat TM L5140027_02720060820 8/20/2006 Landsat TM L5140028_02820060820 8/20/2006 Landsat TM p140r027_7dk20000827 8/27/2000 Landsat ETMþ p140r028_7dk20000827 8/27/2000 Landsat ETMþ p141r027_7dk20020808 8/8/2002 Landsat ETMþ L71141027_02720050816 8/16/2005 Landsat ETMþ AST_L1B_00301022001050642_20090420191641_32169 1/2/2001 ASTER AST_L1B_00304152001051039_20090420191630_31956 4/15/2001 ASTER AST_L1B_00301282002050247_20090420191731_1285 1/28/2002 ASTER AST_L1B_00310042002045519_20090420191651_32303 10/4/2002 ASTER AST_L1B_00310032005045926_20090420191641_32170 10/3/2005 ASTER AST_L1B_00308032006050008_20090420191731_1296 8/3/2006 ASTER AST_L1B_00309042006050001_20090420191630_31951 9/4/2006 ASTER AST_L1B_00301192007045416_20090420191741_1561 1/19/2007 ASTER AST_L1B_00306052008050045_20090420191731_1303 6/5/2008 ASTER AST_L1B_00311122008050033_20090420191701_343 11/12/2008 ASTER AST_L1B_00311282008050048_20090420191741_1558 11/28/2008 ASTER Soviet topographic maps Map number Scale L-46-01 1:500,000 L-46-08 1:200,000 L-46-27 1:100,000 L-46-28 1:100,000 L-46-39 1:100,000 L-46-40 1:100,000 Data and methods 489 especially for multitemporal comparisons. Based on reviewing the image quality of both Landsat and ASTER imagery, the ideal seasonal window for image collection over the two study areas is late July to early September, coinciding favorably near the end of the ablation season for late August and September images. 22.4.3 GPS data Figure 22.5. Tavan Bogd study area (dashed yellow line) and international boundaries (red line). Landsat TM 4, 3, 2 RGB composite images from (top) September 3, 1989 and (bottom) August 8, 2009. Both panels of this figure can also be viewed in higher resolution as Online Supplement 22.2. km and ETMþ scenes cover an area of 183 170 km. While several ASTER scenes contained clouds, snow, or shadows that limited analysis, Landsat scenes from 1989 to 2009 proved to be of greater use due to fewer clouds, snow, and shadows. Additionally, Landsat imagery covered a larger timescale than ASTER imagery, and the near-anniversary date pairs of Landsat images, acquired in the same month over different years, allowed for high-quality multitemporal comparison of the glaciers and landscape. The ETMþ sensor also had technical issues affecting the quality of the data, including the wellknown Scan Line Corrector (SLC) failure of 2003, which produced data gaps within individual scenes. Although this problem can in part be corrected by using older Landsat TM scenes to fill in the missing data ‘‘gaps’’, such postprocessing introduces an error in any quantitative analysis of the imagery, For the Munkh Khairkhan study area, GPS observations were collected in summer 2009 using a Trimble Recon XC GPS receiver and a Garmin GPSMAP 76 CSx GPS receiver. Linear features were collected along the terminus of Shuurkhai Glacier and along the crest of moraines and till ridges. Within this study area, 139 points and 46 line features were collected using the Trimble unit and 94 points were collected using the Garmin unit. Trimble GPS data were differentially corrected using Trimble Pathfinder Office software. Base station data used to differentially correct field GPS data were selected from the Scripps Orbit and Permanent Array Center (SOPAC) located in Urumqi, China, 450 km away from the study area. Unfortunately, this was the nearest station to the study area that contained useful base data. After differentially correcting the data, 116 of the 139 points collected had a position dilution of precision (PDOP) of 5 (minimum 1.7, maximum 5, mean 2.9, standard deviation 0.8) and were used as ground control points (GCPs). Often a PDOP value of <4 is considered excellent, while 5–8 is acceptable, and >9 is poor (GISLab 2003); thus, a PDOP of 5 was selected as a quality cutoff value. Although this value is not very low, it does allow for a greater number of points spread throughout the study area; selecting a smaller PDOP value would result in fewer points being available for comparison, which would limit the extent for DEM assessment throughout the study areas. The vertical error of GPS data was calculated to be 7.7 m. 22.4.4 Pan-sharpening Landsat images of the Munkh Khairkhan range collected in August of 2000, 2002, and 2005 were taken by the ETMþ sensor and included a panchromatic band 8, which was used for pan-sharpening to improve image resolution employing ESRI ArcGIS 9.3. This improved the resolution from 30 30 m to 15 15 m allowing the imagery to be compared on an equal footing with ASTER VNIR imagery. 490 Recent glacier changes in the Mongolian Altai Mountains 22.4.5 Glacier mapping Both ASTER and Landsat imagery have multiple bands covering various parts of the electromagnetic spectrum allowing for the creation of visible, infrared, and thermal images all of which are used in glacier mapping (Klein and Isacks 1998, Bishop et al. 2003, Paul et al. 2004, Bamber 2006, Bolch et al. 2008, see also Chapter 4 of this book by Kääb et al.). For Landsat, one common false-color composite (FCC) image combination is provided by TM bands 5, 4, 3, which help delineate clean glacier ice/snow and vegetation (Paul et al. 2004, Bolch and Kamp 2006). Other useful FCC combinations include TM bands 5, 4, 2, which also help differentiate water bodies (Klein and Isacks 1998); and TM bands 7, 5, 4, which help to delineate snow/ice from the surrounding landscape and to identify changes in the landscape, including areas of saturated ground and stream drainage networks. The same band combinations can also be applied to ETMþ data, allowing for comparison between data from both TM and ETMþ sensors. Similarly, ASTER band composite 3N, 2, 1 can be closely compared with ETMþ and TM bands 4, 3, 2. To identify the spatial extent of snow/ice of the Munkh Khairkhan study area, a land cover classification was performed for all TM and ETMþ Landsat imagery (Table 22.1) using all bands as input within the Maximum Likelihood Classification Spatial Analyst tool in ESRI ArcGIS 9.3 (Fig. 22.6). Around 3% of the area was misclassified as water bodies, particularly areas of light snow along the margins of the glaciers; these areas were removed. The remaining total snow/ice area was Figure 22.6. Munkh Khairkhan study area: an example of the Maximum Likelihood Supervised Classification of a Landsat image used to delineate glacier snow and ice (August 16, 2005). Snow/ice are light blue, water bodies are blue, vegetated areas are green. Note the misclassification of snow near glacier margins as water bodies. Data and methods then divided into two subclasses: glacial snow/ice, and snow/ice not associated with glaciers. Glacial snow/ice areas were delineated by creating polygon shapefiles with the aid of topographic references, including breaks in glacier margin slopes, topographic divides, and near each glacier’s headwall that included the snow/ice area below the headwall as defined by GLIMS (Raup et al. 2006). Area calculations for each glacier polygon were performed allowing quantitative comparison from one year to the next. The excessive amount of lateseason off-glacier snow, clouds, and shadow present in the ASTER imagery made it challenging to use any classification methods. However, the snow and shadows present in some ASTER scenes proved useful for identifying landscape features by highlighting topographic features including ridges and depressions. Another method that has been used to delineate clean glacier ice from its surroundings involves the use of NIR and SWIR band ratios, especially bands 4 and 5 from Landsat TM or ETMþ sensors (Paul et al. 2002, Kääb et al. 2003, Bolch and Kamp 2006, Kamp et al. 2011). The ASTER band ratios of bands 3 and 4 approximate the same spectral signature as Landsat TM and ETMþ bands 4 and 5. They have also proved useful in mapping clean glacial ice, and can be more accurate than Landsat band ratios (Kääb et al. 2003, Kamp et al. 2011). A continuing problem with using band ratios (and some other spectrally based classification schemes) is the difficulty in mapping debris-covered glaciers (Bolch and Kamp 2006, Kamp et al. 2011). Landsat-based band ratios were used in this study and the results for glacier mapping were similar to those created using the Maximum Likelihood Classification. For the Tavan Bogd range, a Landsat TM imager pair, separated by 20 years (September 3, 1989 and August 8, 2009) was used for glacier mapping (Fig. 22.5 and Online Supplement 22.2). Although ASTER’s VNIR band spatial resolution is 15 15 m, compared with 30 30 m for TM imagery, there were no high-quality repeat ASTER image pairs available for the entire Tavan Bogd range. ALI imagery, with its 30 30 m spatial resolution in VNIR/SWIR and 10 10 m panchromatic capability, was also too cloudy. In addition the time span for the TM pair exceeded 20 years, compared with only 5 years for the best ASTER (partial coverage) pair. Glacier mapping was achieved using a semiautomated algorithm that included the following 491 steps: TM images were subset to include only the region of interest (Fig. 22.5). Co-registration was unnecessary as the pair was well co-registered with a relative image-to-image accuracy exceeding <0.5 pixel. Dark object subtraction (DOS) was completed for each VNIR/SWIR band to remove the effects of path radiance within visible bands (e.g., TM1, TM2) and to subsequently boost the signalto-noise ratio, particularly within areas of shadows, when applying band ratio techniques (Crippen 1988). Several low-turbidity lakes within the scenes were selected as the ‘‘dark objects’’. A snow/ice mask was generated using a thresholded normalized difference snow index (NDSI ¼ [TM2 TM5]/ [TM2 þ TM5]) (Hall et al. 1987). On visual inspection of the normalized image, an NDSI threshold of >0.6 was selected to represent pixels of ice and snow and a binary raster snow/ice mask was created. Several water bodies, such as lakes, ponds, and streams were misclassified as ice/snow, and subsequently removed by applying a water mask computed by the TM band ratio: TMVIS /TMNIR (TM2/TM4) (Kargel et al. 2005). Unsupervised classification, principal component analyses, and generation of a normalized difference water index (NDWI) were also trialled to isolate an effective water mask; however, no water classes were consistently identified, and therefore any remaining areas of water were manually removed when misclassified as glacier ice. Next, a median filter was applied to the NDSI binary classification image to remove noise and small isolated pixel areas of transient snow cover. The resultant snow/ice binary raster was vectorized and polygons were generated that represented individual and clustered glaciers. A minimum (snow/ ice) filter was applied which removed snow/ice polygons <0.1 km 2 , many of which appeared to be transient snow patches, with possibly a few glacierets. Additionally, any remaining nonsupraglacial water bodies and transient snow patches were manually removed, and previously excluded debris-covered glacier areas manually added to the ice polygon areas. The 2009 image contained noticeably more transient snow patches which required manual removal; some nonglacier patches were identified by intersecting polygons generated from the less snow-covered 1989 image with polygons from 2009. Finally, the 13 largest glacier basins were manually delineated using the underlying original TM images and an ASTER GDEM2 mosaic. Glacier area was calculated for the 13 largest glaciers, and for total ice within the subset area, 492 Recent glacier changes in the Mongolian Altai Mountains both for the earlier and later TM images. All work was completed using Leica’s ERDAS Imagine image-processing software and ESRI ArcGIS 9.3. 22.4.6 Error analysis (area accuracy and change precision) The primary source of error is inaccurate delineation of glacier ice extent, both from semiautomated and manual classifications. Systematic errors associated with the semiautomated classification of glacier ice in the Tavan Bogd and Munkh Khairkhan study regions are primarily based on deficiencies in the classification algorithm. These might include factors such as consistent misclassification of debris-covered ice (which could make measured areas smaller than the actual glacier), selection of NDSI threshold values (which could make the measured value either systematically too small or too large), and the vectorization of classified ice from raster-based data, among others. Fortunately, Tavan Bogd contains very little debris-covered glacier area, and most glaciers have relatively clean ice surfaces and high-contrast contact with adjacent land cover, and so systematic errors in glacier margin location are likely less than 1 pixel. Of the 13 largest glaciers, debris cover ranges from virtually 0 to 8%, with most glaciers covered by only 2%. The more heavily debris-covered areas have been manually classified by on-screen digitizing of vector polygons, but elsewhere we used automated classification algorithms. It was much the same in the Munkh Khairkhan region: smaller glaciers were present with clean ice and only minor areas were obscured by debris. When optimal classification conditions prevail (i.e., debris-covered glaciers are absent), there appears to be a general underestimation of glacier ice by a maximum of 1 pixel, and probably no cases involve overestimation of glacier area. This error likely has a variety of causes, including deficiencies in the classification algorithm listed above, among others. In any case, we take a conservative assessment of our measurements and define the systematic error as 1 pixel. The percentage error of area determinations, Aer , then is proportional to sensor resolution and is given by: Aer ¼ 100% ðn mÞ=Agl ð22:1Þ where n ¼ number of pixels defining the perimeter of the glacier area, m ¼ spatial resolution of the sensor bands applied expressed as an area of the pixel (e.g., 900 m 2 for a 30 30 m TM pixel), Agl ¼ the area of the glacier, and the factor 100 is there to convert to percentage. For the Tavan Bogd region we calculated systematic errors, assuming an uncertainty of 1 pixel (either 1 pixel too wide or too narrow), for the largest 13 glaciers ranging from 5.1 to 15.3%, with most other large glaciers falling near the 10% mark. Systematic error was more substantial for small glaciers. We measured glaciers down to 0.01 km 2 ; however, due to the ballooning of errors at small glacier sizes, we cut off our tabulated glaciers at 0.1 km 2 , where systematic errors calculated by eq. (22.1) were 50%. Total area error of all glaciers combined in the Tavan Bogd region in 1989 was 14%. These calculations were also applied to glaciers in the Munkh Khairkhan region with a resulting error of 16% in 1990 and 14% in 2006. Recall, however, that this represents the maximum estimated error and is likely an error biased toward underestimation of glacier area (i.e., there is probably more ice present than reported). Furthermore, measured areas tend to be consistent as far as classifications of both the earlier and later datasets are concerned. Therefore, ice area percentage change from 1989 to 2009 represents a far more robust value than the absolute accuracy of any given glacier area. Much like the classic definition of precision versus accuracy, where repetition of measurements made on different but similar datasets results in precision of values fit well within the envelope representing accuracy, the same pertains to many kinds of scientific measurements, where relative precision greatly exceeds absolute accuracy. Thus, it is possible to measure area differences that are smaller than systematic error limits. We believe that both accuracy and precision reporting in our scientific discipline would mark an improvement. In cases where glacier margins comprise clean ice and any debris-covered fringe is much less than a pixel wide, as is the case for some Mongolian glaciers, classifications based on either automated or manual delineation can be better than 1 pixel. Furthermore, in these cases, the error may tend to be random (i.e., there is equal probability that any given glacier extent measurement will be located either inside or outside the actual glacier margin, perhaps by as much as a pixel either way). Where this occurs, area determination error is much less than 1-pixel systematic error. If random errors are 1 pixel, then glacier area error is reduced by a factor n 1=2 when compared with systematic error. Hence, after reducing the equation, random error percentage, which we define as area precision, Ap , is Data and methods given by: Ap ¼ 100 ðn 1=2 mÞ=Agl ð22:2Þ If a glacier is delineated by 100 pixels (or polygon vertices)—along the perimeter, for instance—random error—precision from eq. (22.2)—is one tenth that of systematic error—accuracy from eq. (22.1). For manual digitization, there may be fewer vertices of the vectorized polygon representing the glacier, but systematic error may still be defined by equation (22.1). However, percentage precision for manual digitization, Ap;m , is instead given by: Ap;m ¼ 100 ð j 1=2 Þ ðn mÞ=Agl ð22:3Þ where j ¼ the number of manual vertices of the vectorized polygon. In our work, because there were so few debris-covered glaciers and relatively little need for manual digitization, precision can generally be given by eq. (22.2), and eq. (22.3) is irrelevant. Random errors for Tavan Bogd glacier area determinations range between 0.13 and 6.7%, with the largest errors associated with smallest area glaciers (0.1 km 2 ). Random errors for the 13 largest glaciers range between 0.13 and 0.50%. Random errors for Munkh Khairkhan glacier areas are similarly only a fraction of systematic errors. The assumption of random error still probably underestimates accuracy (accuracy is worse than estimated) even when there are ideal clean ice boundaries, because there will still be some amount of systematic error, perhaps half a pixel at best. However, random error is easily calculated, and it probably gets as close as possible to an evaluation of repeatability of measurements made on different but very similar images (e.g., same sensor systems, similar time of year, and the same classification algorithm), and hence may be used to define what changes may be deemed reliable. Lessening large systematic errors for future work would require their accurate identification and mitigation within the classification algorithm. Providing multispectral sensors with higher spatial resolution would help greatly toward this aim. 22.4.7 Digital elevation models Digital elevation models (DEMs) play an important part in many morphometric glacier–mapping, terrain analysis, and surface process–modeling methods, particularly for creating such parameters 493 as slope, aspect, and curvature (Bishop et al. 2003, Kamp et al. 2003, Paul et al. 2004, Bolch 2005, Surazakov and Aizen 2006, Toutin 2008, see also Chapter 4 of this book by Kääb et al.). DEMs used for this study included the new ASTER Global Digital Elevation Map (GDEM—a product of the Japanese Space Agency, METI, and NASA) Version 1 dataset—made available in June 2009—and the SRTM dataset. Both of these datasets are available to download free: ASTER GDEM data were accessed from LPDAAC, while SRTM data were downloaded from the Consortium for Spatial Information–Consultative Group for International Agriculture Research website (CGIAR-CSI 2008). The more recent ASTER-based GDEM2 upgraded dataset, now available, was unavailable at the time our analysis was conducted. For the Munkh Khairkhan study area, 11 ASTER scenes were processed at the University of Nebraska-Omaha using SilcAst 1.01 software to generate DEMs without GCPs. These DEMs were used to generate a new ‘‘mean ASTER DEM’’ (see below) that provided additional detail of the study area surface. The ASTER GDEM, SRTM DEM, and mean ASTER DEM were then assessed for accuracy to determine which would be used for geomorphometric analysis. DEMs do not always have the requisite accuracy needed for geomorphometric or dynamical analysis, and inaccurate DEMs can result in misleading information that would seriously compromise morphometric analysis (Toutin 2008). Clouds, shadows, and other artifacts often contribute to inaccurate DEM generation; therefore, DEMs must be examined for errors. To do this, SilcAst-generated ASTER DEMs were compared against GPS field observations and topographic map spot elevations to assess the accuracy of DEM elevation estimates (Kumler 1994, Bishop and Shroder 2004). In the Munkh Khairkhan study area, the elevations of Munkh Khairkhan peak at 4,208 m asl and other surrounding peaks were compared with elevations derived from each SilcAst-generated DEM. Elevations that were significantly higher (in some cases >100 m) suggested that clouds or other problematic issues were present; therefore, these scenes were excluded from further analysis. Other artifacts were also observed in SilcAst-generated ASTER DEMs (Fig. 22.7); they appeared to be associated with shadows mainly in the Shuurkhai Valley, due, it appears, to seasonal and time-of-day Sun angle in relation to the east–west trend of the range and associated steep north-facing slopes. These shadows created pseudo-hills and pseudo-flat surfaces in the 494 Recent glacier changes in the Mongolian Altai Mountains Figure 22.7. Munkh Khairkhan study area. (A) SilcAst-generated DEM from the ASTER scene on November 28, 2008. (B) SilcAst-generated ASTER DEM from the ASTER scene on January 2, 2001. Note how the shadows create artifacts within the DEM including pseudo-hills (A) and pseudo-flat surfaces with jagged edges (B), typically representative of a lake or other body of water. Figure can also be viewed in higher resolution as Online Supplement 22.3. DEM, which adversely affected geomorphometric analysis. For the Munkh Khairkhan study area, 3 of the 11 SilcAst-generated DEMs were selected (ASTER scenes from January 2, 2001, April 15, 2001, and November 28, 2008). Differentially corrected GPS points with PDOP values of <5 were overlaid on all three DEMs in ArcGIS. The elevation cell value for each underlying DEM was then compared with the corresponding GPS point. Individually, the scenes have relatively low accuracy with mean absolute error (MAE) values from 9.7 to 11 m and root mean square error (RMSE) values from 12–18 m when compared with GPS elevation values (Fig. 22.8; Table 22.2). There was a maximum elevation error of 129 m between GPS and DEM elevation values according to the SilcAst November 28, 2008 dataset. Based on these values, it was determined that a single SilcAst-generated DEM dataset could not be used for geomorphometric analysis. To compensate for the lack of accuracy of each individual SilcAst-generated ASTER DEM, a method similar to that proposed by Muller (2008) was used, in which the three SilcAst-generated ASTER DEMs were averaged to produce a new mean ASTER DEM (Fig. 22.9). This helped to smooth the errors of all three DEMs resulting in a more accurate mean ASTER DEM with a horizontal error of 15 m and a vertical error of 10 m (Fig. 22.8; Table 22.3). Following the same methods used to analyze each individual SilcAst-generated DEM, differentially corrected GPS points were placed on top of the ASTER GDEM, mean ASTER DEM, and SRTM DEM. Again, the elevation cell value of each underlying DEM was compared with the corresponding GPS point. When compared with the ASTER GDEM and SRTM DEM, the mean ASTER DEM’s accuracy proved to be better than the ASTER GDEM dataset, but not as accurate as the SRTM DEM dataset. However, the mean ASTER DEM had the highest spatial resolution of 15 15 m allowing topographic features to be shown in greater detail than was the case with the SRTM DEM. Based on this comparison between the three types of DEMs, the newly created mean ASTER DEM was selected for generating DEM-derived datasets and geomorphometric analysis. For the Tavan Bogd study area, several data tiles from the ASTER GDEM2 dataset (made available from NASA and METI in October 2011) were mosaicked and used as a basemap, this was additional to mosaicked SRTM tiles that were infilled with GDEM2 data (necessary for occasional zones where SRTM data are missing). Both DEM products provided topographic guidance for the delineation of glacier basins (Fig. 22.3). Data and methods 495 Figure 22.8. Munkh Khairkhan study area. (Top) Sample distribution of DEM elevation values between 3,000 and 3,200 m asl for three ASTER DEMs generated using SilcAst compared with GPS elevation values. (Bottom) Sample distribution of DEM elevation values between 3,000 and 3,200 m asl for mean ASTER DEM, ASTER GDEM, and SRTM DEM compared with GPS elevation values. 496 Recent glacier changes in the Mongolian Altai Mountains Table 22.2. Munkh Khairkhan study area: MBE, MAE, and RMSE values for three ASTER DEMs compared with differentially corrected GPS elevation values. SilcAst SilcAst SilcAst 11/28/2008 4/15/2001 1/2/2001 Table 22.3. Munkh Khairkhan study area: MBE, MAE, and RMSE values for three types of DEMs compared with differentially corrected GPS elevation values. Mean MBE (m) 2.8 6.6 7.7 3.8 MAE (m) 11.0 11.0 9.7 10.0 RMSE (m) 18.0 14.0 12.0 14.0 MBE ¼ mean bias error, MAE ¼ mean absolute error, and RMSE ¼ root mean square error. 22.4.8 DEM-derived datasets Several topographic-based parameters and derivatives can be extracted from a DEM including slope, curvature, aspect, hillshading, and solar radiation ASTER GDEM Mean DEM SRTM MBE (m) 4.7 3.5 3.3 MAE (m) 8.6 6.8 6.2 RMSE (m) 11.0 9.7 9.5 MBE ¼ mean bias error, MAE ¼ mean absolute error, and RMSE ¼ root mean square error. insolation, which are useful for geomorphological mapping and glacial analysis (Bishop et al. 2003, Kamp et al. 2003, Paul et al. 2004, Bolch and Kamp 2006, Surazakov and Aizen 2006). All of these datasets were generated from the mean ASTER DEM using ESRI ArcGIS. Figure 22.9. Munkh Khairkhan study area: the resulting mean ASTER DEM covering the Shuurkhai Valley created from three ASTER DEMs using SilcAst. Artifacts within the DEM (Fig. 22.7) have been smoothed out in the final product. Data and methods For slope, the same thresholds that Bolch and Kamp (2006) used to delineate glaciers in the Alps and Tien Shan were applied, and these classes helped to identify some of the landforms within the study areas. However, smaller features were often obscured, making it difficult to delineate the extent of larger features, including glaciers. Plan curvature and profile curvature assisted in delineating ridges and valleys within the study area. Aspect was an aid to identification of areas exposed to direct sunlight and areas that were shaded. Hillshading is often used to improve the visual aspect of a DEM. Typically, the (default) light source is set at an azimuth of 315 and a solar zenith angle of 45 . While hillshading did help to identify some features in this study, it often obscured others, especially if the landform was near a larger and steeper feature such as a cliff, or if the orientation of the landform minimized shading due to shape. To improve the identification of surface features, hillshading was performed from eight azimuths (0, 45, 90, 135, 180, 225, 270, and 315 ) and a solar zenith angle of 45 . All hillshades were then merged to compute a mean hillshade (Fig. 22.10). This method is comparable with the multidirectional, oblique-weighted (MDOW) shaded relief image developed by Mark (1992), which incorporates four azimuths (225, 270, 315, and 225 ), a zenith of 30 , and weighting using a generalized aspect map. This method improves the visual quality of hillshade, while still maintaining shadows since the four azimuths used are between 225 and 360 . By applying light from eight azimuths equally spaced around a circle, shadows were minimized and the resulting hillshade improved geovisualization, helped to identify additional features, and smoothed some of the textural differences present in standard hillshade. It was especially useful in delineating cirques and features in east to westoriented valleys. 22.4.9 Geomorphometric analysis Geomorphometric analysis, using the surface toolset within ESRI’s ArcGIS Spatial Analyst toolbox to generate datasets, was performed on ASTER DEM-derived datasets. This allowed comparison of geomorphic parameters covering the study areas. Similar methods have been used to delineate glaciers and landforms in high mountainous regions of the world (Bishop et al. 2003, Kamp et al. 2003, Paul et al. 2004, Bolch and Kamp 2006). So that different features could be delineated, each dataset 497 Figure 22.10. Munkh Khairkhan study area: comparison between typical hillshade (top) and mean hillshade from eight different directions using a zenith angle of 45 (bottom). The same mean ASTER DEM has been draped over both using the same color palette and transparency level, while both hillshades are using the same black to gray palette with a minimum–maximum stretch applied underneath. was individually analyzed to identify patterns that matched field observations. Morphometric glacier-mapping (MGM) methods use DEMs and satellite imagery as input to delineate the extent of glacierization in highmountain regions (Bolch 2005, Bolch and Kamp 2006, Kamp et al. 2011). This method is useful for larger glaciers consisting mostly of clean ice; however, smaller glaciers, like those found in the Munkh Khairkhan region, and debris-covered glaciers present a problem. Often manual delineation or other methods are needed for these types of glaciers (Bolch and Kamp 2006, Bane 2009). MGM uses a classification of satellite imagery together with a classification of various geomorphometric 498 Recent glacier changes in the Mongolian Altai Mountains parameters. Slope is often a critical parameter used to identify glaciers and delineate them from other land cover classes. Usually, a threshold value of 24 is used to identify the smooth parts of a glacier; however, this value makes it difficult to determine the boundary between the toe of a terminus and an outwash plain (Bolch and Kamp 2006). Variations in slope classification schemes did seem to identify features including U-shaped valleys, cirques, and hanging valleys; however, smaller features were often obscured. Slope combined with elevation, hillshading, and imagery analysis helped to identify both present and past extents of glacial activity within the study area. Breaks in glacierized and unglacierized terrain were determined based on the texture of slope and hillshading. Unglacierized terrain appears rugged at fine scales, while glacierized terrain has a smoother texture at fine scales associated with glacial erosion of the surface. Elevation combined with hillshade products was used to delineate terminal moraines from the surrounding surface. Similarly, draping imagery over hillshade improved the visual reorganization of surface landforms. By combining these methods meso and macroscale features could be analyzed. Present ELA calculations were performed using the toe-to-summit altitude method (TSAM) because it is easy to use in remote areas and has proved useful for other glaciers in Mongolia (Benn and Lehmkuhl 2000, Bader et al. 2008). 22.5 RESULTS 22.5.1 Glacial change in the Munkh Khairkhan range Results from five different years between 1990 and 2006 showed that the snow/ice area of the Munkh Khairkhan range shrank by 30%, losing 12 km 2 in area (Fig. 22.11; Table 22.4). Glaciers make up only a small portion of the total snow/ice area, but even so show a mean loss in area of 13% (Table 22.5). However, one glacier, Khar Tsunkh, Figure 22.11. Munkh Khairkhan study area: multitemporal (1990–2006) comparison of snow/ice area overlays on DEMs. Results Table 22.4. Munkh Khairkhan study area: changes in snow/ice/glacial areas between 1990 and 2006. Year Total snow/ Ice/ Glacial area (km 2 ) Snow/ Ice area Glacial Glacial area area of total area (km 2 ) (km 2 ) (%) 1990 39.7 32.9 6.8 17.1 2000 29.8 23.9 5.9 19.8 2002 26.4 21.0 5.4 20.3 2005 29.4 23.4 6.0 20.3 2006 27.6 21.7 5.9 21.4 D1990–2006 (km 2 ) 12.1 11.2 0.9 N/A 30.5 34.1 13.1 þ4.3 D1990–2006 (%) increased in area by 6%. In 1990, glaciers made up 17% of the total snow/ice area, and in 2006 this area increased to 21%, while snow/ice areas not classified as glacial decreased, from 33% in 1990 to 22% in 2006 (Table 22.4). The greatest losses in glacial area and changes in ELA can be found in glaciers located farther to the east (Fig. 22.11; Tables 22.5 and 22.6). Results showed that there was a mean ELA increase of 1.4 m yr1 between 1990 and 2006 (Table 22.6). Climate data from 1997 to 2008 for the Munkh Khairkhan range were evaluated to see whether temperature and precipitation might correlate with 499 snow/ice area change. It appears that both temperature and precipitation may have impacted the amount of snow/ice present in the area, especially during 2005 when there was a decrease in annual temperature and an increase in annual precipitation leading to an increase in snow/ice area (Figs. 22.12 and 22.13). During the LGM it is estimated that 106 km 2 of glacial ice were held in the Shuurkhai Valley and its associated tributary valleys, while in the Doloo Nuur Valley and its contributing valleys there were 38 km 2 of glacial ice. The Shuurkhai Valley Glacier is estimated to have extended 26 km from its source toward the east, while the Doloo Nuur Valley Glacier is estimated to have extended for 23 km to the north (Fig. 22.14). The ELA during the LGM was 3,450 m asl for the Doloo Nuur Valley Glacier and 3,300 m asl for the Shuurkhai Valley Glacier. A comparison of LGM ELAs with present ELAs shows an increase of 260 m for the Doloo Nuur Valley Glacier and 375 m for the Shuurkhai Valley Glacier. By using cross-sectional data extracted from the mean ASTER DEM together with trimlines viewed in satellite imagery of the Shuurkhai Valley, the LGM glacier was estimated to be 125–150 m thick. 22.5.2 Glacial change in the Tavan Bogd range From 1989 to 2009 the total area of glacier ice within the Tavan Bogd study area decreased from 213 to 204 km 2 , or by 4.2% over the 20 years (Fig. 22.15 and Online Supplement 22.4). Total area of the 13 largest glaciers over the same period Table 22.5. Munkh Khairkhan study area: snow/ice/glacial area (km 2 ) of selected glaciers for 1990–2006. Year Doloo Lake Glacier Shuurkhai Glacier Khar Tsunkh Glacier Arts Glacieret Arts Glacier Total glacial area 1990 2.94 0.84 1.49 0.26 1.24 6.77 2000 2.55 0.81 1.44 0.20 0.90 5.91 2002 2.25 0.77 1.37 0.15 0.80 5.34 2005 2.65 0.77 1.55 0.18 0.82 5.96 2006 2.53 0.81 1.58 0.17 0.80 5.88 D1990–2006 (km 2 ) 0.41 0.03 þ0.09 0.10 0.44 0.89 D1990–2006 (%) 13.86 4.08 þ6.19 36.25 35.74 13.13 4,200 4,060 4,060 3,780 3,850 Shuurkhal Khar Tsünkh Arts Glacieret Arts Glacier 3,200 3,350 3,210 3,290 3,220 3,525 3,565 3,635 3,675 3,710 (m) ELA 8/20/2006 Summit Toe elevation elevation (m) (m) Doloo Nuur Glacier ELA: TSAM method 3,200 3,330 3,210 3,280 3,210 Toe elevation (m) 3,525 3,555 3,635 3,670 3,705 (m) ELA 8/16/2005 3,190 3,320 3,190 3,270 3,200 Toe elevation (m) 3,520 3,550 3,625 3,665 3,700 (m) ELA 8/8/2002 3,190 3,280 3,180 3,270 3,200 Toe elevation (m) 3,520 3,530 3,620 3,665 3,700 (m) ELA 8/27/2000 3,150 3,270 3,170 3,260 3,200 Toe elevation (m) 25 22 Average 40 20 15 10 (m) 1.38 1.56 2.5 1.25 0.94 0.63 (m/yr) DELA DELA 3,500 3,525 3,615 3,660 3,700 (m) ELA 9/16/1990 44 50 80 40 30 20 (m) DToe Table 22.6. Munkh Khairkhan study area: ELA calculations for individual glaciers using TSAM method after Benn and Lehmkuhl (2000). 2.75 3.13 5 2.5 1.88 1.25 (m/yr) DToe 500 Recent glacier changes in the Mongolian Altai Mountains Results 501 Figure 22.12. Munkh Khairkhan study area: comparison of mean annual temperature (village of Munkh Khairkhan) and total snow/ice area from 1990 to 2008. Climate data from 1990 to 1996 are missing from the record (MASPL 2009). Figure 22.13. Munkh Khairkhan study area: comparison of total annual precipitation (village of Munkh Khairkhan) and total snow/ice area from 1990 to 2008. Climate data from 1990 to 1996 are missing from the record (MASPL 2009). decreased from 142 to 132 km 2 , or 6.5% (Table 22.7, Fig. 22.16 and Online Supplement 22.5). The largest glaciers all decreased in area with percent losses ranging between 4.3 and 14.1% over the 20 years. The largest and most studied glaciers in the Tavan Bogd range, Potanin Glacier and Alexandra Glacier, lost 1.13 and 1.20 km 2 of ice area from 1989 to 2009, respectively (4.3 and 8.1% area, respectively). Generally, the larger glaciers lost a smaller percentage of ice, although this rela- tionship becomes noisy among the population of smallest glaciers. There does not appear to be any aspect-related correspondence with ice loss. Debris cover for these largest glaciers ranges from effectively 0 to 7.9%; and total debris cover decreased by 14% from 1989 to 2009. Between 1989 and 2009, Potanin Glacier receded by 516 m at a mean rate of 25.8 m yr1 . Over the same period, the adjacent Alexandra Glacier receded by 653 m at a mean rate of 32.7 m yr1 . 502 Recent glacier changes in the Mongolian Altai Mountains Figure 22.14. Munkh Khairkhan study area: general geomorphological map of today (top) and approximation of glacial extent during the LGM (bottom) based on data collected during the field campaign. Geographic features can be seen in Fig. 22.2. The black area was not studied for the project. 22.6 DISCUSSION 22.6.1 Munkh Khairkhan range Glacier mapping using a multimethod approach including fieldwork, satellite imagery, and DEM analyses allowed landscape features to be delineated. However, many of the glacial landforms mapped were identified manually through interpretation of satellite imagery and DEMs due to the limited performance of automatic methods such as morphometric glacial mapping (Bolch and Kamp 2006, Bane 2009, Kamp et al. 2011). Fieldwork, in particular, allowed first-hand understanding of the processes at work on the surface that cannot be seen in satellite imagery or DEMs. GPS observations proved to be critical for GIS-based mapping of small landform features that would not be visible in satellite imagery. The use of GPS to map moraine ridges in the field greatly improved the validity of each moraine ridge position, allowing comparison with satellite imagery and DEM-derived datasets including slope, curvature, and hillshading. Larger landform features with associated GPS observations were easy to identify in both ASTER and Landsat imagery, while locations without GPS observations were delineated based on imagery interpretation and comparison with slope, curvature, aspect, and elevation datasets. Due to the relatively small size of glaciers in the Munkh Khairkhan range the most useful method for delineating them was to create a polygon feature class derived from maximum likelihood classification of snow/ice from Landsat imagery. The thresholds for slope that Bolch and Kamp (2006) used to delineate glaciers were applied and found to be useful for outlining ablation areas on Doloo Nuur, Shuurkhai, and Khar Tsunkh Glaciers. However, accumulation areas on all glaciers and slopes on the smaller glaciers, such as Arts Glacieret and Arts Glacier, were not easily detected using slope classification, thus making it difficult to delineate them, similar to the results of Bane (2009). We therefore relied on the polygon feature classes created from maximum likelihood classification of Landsat imagery to delineate these features. Although this method worked best at delineating small glaciers and snow/ice areas, two limitations exist for accurate glacier mapping: spatial resolution of the imagery and debris cover present on two of the glaciers. Small glaciers require finer resolution imagery to delineate their areas: in the case of Arts Glacieret and Arts Glacier misclassification of only a few pixels can alter area calculations by a large percentage. Debris cover is present along the western edges of Doloo Nuur Glacier and Khar Tsunkh Glacier near their termini. Parts of these two glaciers were not classified as snow/ice and were not included in calculations because their spectral signature varied from clean snow/ice and was dependent on how much debris was present. While the area measurements may not be precise, they do provide an approximation that is useful in detecting change. From data collected for total snow/ice and glacial snow ice area, it is evident that glaciers in the Munkh Khairkhan range fluctuated in area between 1990 and 2006. Overall, there has been a decrease in total snow/ice area by 12 km 2 (30%) (Fig. 22.11; Table 22.4). This decrease in area showed that between 1990 and 2006 the glaciers in the Munkh Khairkhan range reduced in area at an annual rate of 0.3–2% and receded by 1.3–5.0 m yr 1 . Only Khar Tsunkh Glacier increased in area (by 6%, Table 22.5). For glaciers located in the Tavan Bogd, Turgen, Kharkhiraa, and Tsambagarav ranges, Kadota and Davaa (2007) calculated an annual recession rate of Discussion 503 Figure 22.15. Tavan Bogd study area: glacier extents for the 20-year period derived from Landsat TM imagery. International boundaries are delineated by the red lines. Note the dead ice zone and lake development below the termini of Potanin Glacier and Alexandra Glacier (base TM 4, 3, 2 RGB composite from August 8, 2009). Figure can also be viewed in higher resolution as Online Supplement 22.4. 0.3–1% between 1970 and 2000. Khrutsky and Golubeva (2008) calculated annual recession by 0.85% yr1 in the Turgen range and 1.2% yr1 in the Kharkhiraa range, and a general annual recession rate of 2.5–5.7 m between 1969 and 2002. Although both total snow/ice area and glacial area are decreasing, as time progresses glacier area becomes a larger part of total snow/ice area as snow/ice outside glacier areas continue to decrease (Table 22.4). Similar results were found in the Russian Altai in which flat-top glaciers lost more area than valley glaciers (Kadota and Davaa, 2007). This is due to the sheltering effect of the topography of cirques and the east–west orientation of the Shuurkhai Valley on the north side of the Munkh Khairkhan range (Fig. 22.2). The spatial distribution of glaciers within the region also affects the change in glacial area and ELA. In general, ELAs decrease from west to east, and the greatest losses in glacial area and change in ELA can be found in smaller glaciers located to the east (Figs. 22.11; Tables 22.5 and 22.6). This is due to the orographic climatic effect of the Munkh Khairkhan range, which blocks westerlies and their precipitation, resulting in reduced precipitation from west to east through the Mongolian Altai (Lehmkuhl et al. 2004). Although warming in the Mongolian Altai is responsible for glacier retreat, precipitation has a larger influence on smaller glacier fluctuations than temperature, especially when considering the local topography. There is a very close relationship between ELA and local climate, and fluctuations in ELA are important indicators of glacier response to climate change (Lehmkuhl et al. 2004). ELAs in 2006 calculated for the Munkh Khairkhan range were 504 Recent glacier changes in the Mongolian Altai Mountains Table 22.7. Tavan Bogd study area: selected glacier change for 1989–2009. Glacier_ID (name) 1989 2009 1989 to 2009 1989 to 2009 Area (km 2 ) Debris cover (km 2 ) Debris (%) Area (km 2 ) Debris cover (km 2 ) Debris (%) Area change (km 2 ) Change (%) TB-001 5.31 0.00 0.00 4.98 0.00 0.00 0.33 6.1 TB-002 12.28 0.00 0.04 11.52 0.00 0.00 0.76 6.2 TB-003 9.12 0.22 2.46 8.47 0.23 2.69 0.65 7.1 TB-004 5.86 0.20 3.41 5.32 0.15 2.77 0.54 9.3 TB-005 23.34 1.81 7.76 22.27 1.75 7.86 1.07 4.6 TB-006 9.92 0.27 2.69 9.18 0.21 2.25 0.74 7.5 TB-007 4.96 0.00 0.04 4.26 0.01 0.21 0.70 14.1 TB-008 11.30 0.08 0.73 10.49 0.13 1.23 0.80 7.1 TB-009 (Alexandra) 14.73 0.69 4.71 13.53 0.22 1.59 1.20 8.1 TB-010 (Potanin) 26.28 0.11 0.42 25.16 0.24 0.94 1.13 4.3 TB-011 9.82 0.00 0.02 9.34 0.00 0.00 0.48 4.9 TB-012 5.70 0.00 0.02 5.08 0.00 0.00 0.62 10.9 TB-013 2.91 0.00 0.02 2.68 0.00 0.00 0.22 7.6 Totals 141.52 3.40 2.41 132.28 2.92 2.21 9.24 6.53 between 3,525 and 3,710 m asl; Klinge (2001) and Lehmkuhl et al. (2004) reported ELAs between 3,000 and 3,600 m asl. As the area of a glacier decreases near its terminus, its ELA increases in elevation. Mean ELA increase for the Munkh Khairkhan range was 22 m between 1990 and 2006 (Table 22.6). LGM ELAs were also calculated for comparison with 2006 ELAs. Results showed an increase of 260 m for the Doloo Nuur Valley Glacier and 375 m for the Shuurkhai Valley Glacier. These values are of the same order as those found by Lehmkuhl et al. (2004), Kadota and Davaa (2007), and Bader et al. (2008) for other parts of the Mongolian Altai. Understanding how total snow/ice area and climate data fluctuate overall is hindered by the lack both of consistent climate records for the Munkh Khairkhan range and of clean, complete, and repetitive satellite imagery covering the study area. Although these data are lacking, some correlations can be made. Decreases in total annual precipitation from 1997 to 2001 and increased mean annual temperature correspond to a decrease in total snow/ ice area. Increases in total annual precipitation from 2002 to 2005 together with decreases in mean annual temperature during the same time period are linked to an increase in total snow/ice area (Figs. 22.12 and 22.13). However, this short time frame is only a subset of the larger timescale over which glaciers fluctuate. Geomorphic processes are dynamic and change in accordance with retreat in response to climate change. As ice is removed from the Munkh Khairkhan range, the granitic and metamorphic cirque walls and valley floors may begin to exfoliate. This would lead to increased mass-wasting events, produce talus slopes in unglacierized areas, increase the amount of debris deposited onto glaciers, and allow increased mobilization of sediment. Furthermore, increased melting of the glacier will result in more meltwater entering regional hydrology. This could potentially be beneficial for livestock and agriculture, but over decades or centuries—as the glaciers continue to shrink—the availability of meltwater Discussion 505 Figure 22.16. Tavan Bogd study area: glacier extents for the largest glaciers. International boundaries are delineated by the red lines. Note the dead ice zone and lake development below the termini of Potanin Glacier and Alexandra Glacier (base TM 4, 3, 2 RGB composite from August 8, 2009). Figure can also be viewed in higher resolution as Online Supplement 22.5. will decrease. Any increase in meltwater would also result in increased erosion along rivers and higher sediment loads, which would alter the landscape adjacent to the rivers. 22.6.2 Tavan Bogd range Similar to losses in glacier area reported for the Munkh Khairkhan range, glaciers in the Tavan Bogd range have also experienced ice loss in the latter part of the 20th century and early 21st century. Total area of glacier ice within this study area decreased from 213 to 204 km 2 , or by 4.2% over 20 years; this figure includes losses in total area of the 13 largest glaciers in Tavan Bogd, which over the same period decreased by 6.5%. This rate of ice area loss is consistent with the 6% decrease in glacier area reported between the 1960s and the 1990s (Baast 1999). Additionally, ablation (end of season) measurements collected by Kadota et al. (2011) on Potanin Glacier indicate that rapid thinning is occurring and perhaps accelerating, particularly at the lower portion and terminus areas where thinning rates averaged 2.6 m yr1 from 2004 to 2009; this, coupled with low surface velocities measured in the lowermost part of the glacier, suggests that ice influx is considerably less than ablation, resulting in the observed wastage and retreat. Potanin Glacier retreated 90 m between September 2003 and September 2009, a mean retreat rate of 15 m yr1 (Kadota et al. 2011). Our satellite-based study indicates that between 1989 and 2009 Potanin Glacier receded by 516 m, a mean rate of 25.8 m yr1 , and by 5.1% of its total length. Over the same period the adjacent Alexandra Glacier receded by 653 m, a mean rate of 32.7 m yr1 , and by 7.7% of its total length. In this respect, early 21st century retreat at Potanin Glacier may be decelerating. Continuous, long-term climate data are sparse in this remote region, and the nearest climate records are for a station in Olgii, 150 km to the east and at 506 Recent glacier changes in the Mongolian Altai Mountains a lower elevation (1,715 m asl) than the glaciers. Olgii climate data can be considered regional proxy data for the Tavan Bogd range. Mean air temperature in Olgii from 1961 to 2008 has increased by 2 C (a trend of 4.2 C per 100 years), including a rise in mean temperature of 1 C from 1989 to 2008 (Konya et al. 2010). Precipitation values are not immediately available for this region, although surface meteorological stations have been in place on Potanin Glacier since 2007/2008 (Konya et al., 2010). Nevertheless, the sharp rise in regional mean annual air temperature is consistent with a state of disequilibrium and the glacier wastage trend observed in Tavan Bogd in the latter part of the last century and up to recent years. Clearly, Potanin Glacier and other glaciers in the Tavan Bogd range are in a state of disequilibrium as a result of changing climate, and sustained and continued warming will likely lead to further shrinkage. Additional monitoring, from both field and satellite-based studies, is required to quantify and characterize the likely continuation of glacier ice loss in the Tavan Bogd range and its inevitable impacts on the ecosystem and communities that rely on this resource. 22.7 CONCLUSIONS Much of the work undertaken in this study focused on evaluating methods to improve the data quality available to DEMs and applying them in geomorphometric analysis. The increasing availability of different digital elevation datasets such as ASTER GDEM and SRTM facilitates comparison and quality assessment of the sources of elevation data. Three individual ASTER DEMs were selected, processed, and averaged together for this study. The end result was a mean ASTER DEM comparable with the SRTM dataset, but with higher resolution. The only downside to this method was the continued impact of artifacts on DEM accuracy. Based on field studies, satellite imagery, and DEM analyses, glaciers in the Munkh Khairkhan and Tavan Bogd ranges were responsible for the deposition of glacial till and large moraines throughout their respective valleys. These glaciers were also responsible for the formation of U-shaped valleys, cirques, and hanging valleys like those that occupy the north side of the Munkh Khairkhan range. The glaciers in both Munkh Khairkhan and Tavan Bogd were mainly retreating in the 1990s and 2000s. However, caution must be used due to the relatively limited time frame. This is especially true for the Munkh Khairkhan range, where the results could also be interpreted as showing the glaciers remaining stagnant between 2000 and 2006. These glacial changes were most likely associated with warming temperatures and changes in precipitation over the last few decades. Climate change affects different parts of the world at different rates, and the current increase in annual temperatures is causing most glaciers in the Mongolian Altai region to decrease in area, as evidenced in the Tavan Bogd range. Precipitation is also a key factor in glacial area fluctuation, especially for small glaciers impacted by orographic effects. This study has barely scratched the surface of the opportunities for glacier research that exist in the Mongolian Altai. Nevertheless, it should serve as a benchmark for future work. The Mongolian Altai is situated at the climatic boundary between the Atlantic influence from the west and the Pacific influence from the east. It is also a transition zone between deserts and steppe to the south and boreal/ taiga forest to the north. It can thus be considered a region particularly sensitive to small-scale climatic changes. Ultimately, however, it will fall to the people living here to deal with any alterations to their environment. 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