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The World’s Thinning Glaciers

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Glaciers around the world are melting. Millions of people around the world who depend on them are likely to be impacted.


One of the signs of climate change that has received the most attention is the shrinking of glaciers around the world. Sometimes it is presented as a cause of sea level change, but it has only a minor effect on sea level. The Greenland Ice Cap and the Antarctic Ice Cap are far larger bodies of ice, and they will (and already do) contribute more to rising sea levels than do all the glaciers around the world. Further, much of the predicted rise in sea level is due to nothing more than the thermal expansion of water. You know, things expand as they heat up. Well, the oceans are projected to heat up only a little, but there is so much of them that expansion contributes significantly to the rise in sea level.

Melting glaciers matter for a different reason: people depend on them for water. Glaciers form the headwaters of many of the world’s rivers, great and small. Not meaning to make a comprehensive list, in Asia, the Indus, the Ganges, the Brahmaputra, the Yangtze, the Huang-ho (Yellow), and the Oxus all arise from glacial melt. In Europe, the Danube, the Rhine, and the Po all receive substantial glacial melt. In South America, the Madeira (largest tributary of the Amazon) receives glacial melt from about 1,000 miles of the east slope of the Andes. Finally, in North America, the Missouri, Columbia, Snake, Yukon, McKenzie, and Fraser Rivers all receive significant glacial melt.

Figure 1. Source: Schaner, Voisin, Nijssen, and Lettenmaier, 2012.

Figure 1 is a map indicating river basins for which at least 5% (green), 10% (yellow) 25% (orange), and 50% (red) of discharge is derived from glaciers in at least one month. (The “at least one month” qualification matters – glaciers melt much more during the warmer months of the year). Notice that one of the 2 largest blotches of color is located along the northwest coast of North America. This is a high mountain region that is very far north and close to an ocean: a perfect recipe for glaciers. The other is located in Central Asia, where the highest mountains in the world are located, and which receive the famous monsoons of India.

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Table 1. Source: Schaner, Voisin, Nijssen and Lettenmaier, 2012.

Table 1 shows the number of people and the land area that depend on glacial melt. Considering the world as a whole, an estimated 120 million people depend on rivers that get 50% or more of their water from glacial melt (1.8% of the world’s population). About 600 million people depend on rivers that get 5% or more of their water from glaciers (8.9%of the world’s population). So, we are talking about substantial numbers of people. Should the earth’s glaciers decline substantially, some of these people would be likely to lose access to water entirely, at least for part of the year. For others, important life-sustaining activities, such as agriculture or transportation, would be curtailed.

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Figure 2. Source: WGMS, 2017, updated, and earlier reports.

So what is the status of the world’s glaciers? Sadly, it is not good! The World Glacier Monitoring Service (WGMS) is a joint project of the World Data System, the International Association of Cryospheric Sciences, the United Nations Environment Program, the United Nations Education, Scientific, and Cultural Organization, and the World Meteorological Organization. The WGMS studies and monitors the world’s glaciers, and serves as a repository for data on them. They have a set of 30 glaciers around the world that have been repeatedly measured for at least the last 30 years (some much longer), with few or no gaps. Figure 2 shows the status of these 30 glaciers. The year is represented on the x-axis, and the change in mass is represented on the y-axis. The units on the y-axis are meter water equivalents, which are equal to metric tons per square meter of surface. Thus, in 2015, the year of greatest loss, these 30 glaciers collectively lost about 1.1 metric tons of ice per square meter of surface. When you consider that the earth has hundreds, if not thousands, of glaciers, then it becomes clear that we are talking about a lot of ice that is melting into water.

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Figure 3. Source: WGMS, 2017, updated, and earlier reports.

Many of these glaciers are hundreds or thousands of feet thick, and the loss in mass represents thinning of the glacier (melting from the top or bottom) every bit as much as it represents retreat (melting at the bottom end of the glacier). Figure 3 shows the cumulative loss in mass of these same 30 glaciers since 1950. Don’t be confused by the early values above 0 – the glaciers have been losing mass throughout, but for some reason, the WGMS set 1976 as zero, not 1950.

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Figure 4. Source: WGMS, 2017, updated, and earlier reports.

The reference glaciers are concentrated in North America and Europe more than in other continents. However, consider Figure 4, which shows the cumulative mass lost by region. Western Canada/USA and Central Europe have had greater loss than any other regions. However, all regions have had significant loss, including Svalbard and Jan Mayen (3rd worst), and Asia Central (4th worst).

I thought I would illustrate the global nature of the retreat with reference to a few very well known glaciers. Though not necessarily the largest or most important, they are famous.

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Figure 5. Mt. Everest and the Khumbu Glacier. Source: NASA 2011.

To represent Asia, I chose the Khumbu Glacier. Located in Nepal, this is the glacier of Mt. Everest. Base camp sits on it; climbers walk up it and through the Khumbu Ice Fall (where the glacier pours over a cliff), before starting their ascent of the mountain itself. It was measured 3 times: 1970, 2000, and 2016. Between 1970 and 2000, it thinned by an average of 300 cm. (9.8 feet) per year. Between 2000 and 2016, it thinned faster, by an average of 500 cm. (16.4 ft.) per year. (The surface of most glaciers collect dust and debris, thus parts of the glaciers turn brown or gray.)

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Figure 6 Photo by John May, 2015.

To represent Europe, I chose the Mer de Glace, the famous glacier just east of Mt. Blanc (and the 2nd largest in Europe). The first measurement of the Mer de Glace was in 1570. I told you some of these measurements went back more than 30 years! By the early 1600s, the front of the glacier had advanced by about 1,000 meters. It then varied until the late 1800s, when it began retreating. By the early 2000s, the front of the glacier had retreated about 1,000 meters from its 1570 location, and about 2,000 meters from its location during the mid-1800s. Meanwhile, the thickness of the glacier was measured in 1980, 2003, and 2012. Between 1980 and 2003, it thinned at a rate of about 18-20 mm. per year (0.06-0.065 ft.) Between 2003 and 2012, the thinning accelerated to about 160 mm. per year (0.5 ft.).

Figure 7. Source: NASA.

To represent North America, I chose the Muir Glacier: the photos of its retreat are as dramatic as any around the world. It was first measured in 1880, and since then its front has retreated about 29,000 meters (95,144 ft. or 18 miles). The photos in Figure 7 were taken in 1941 and 2004, and show about 7 of those 18 miles of retreat.

I’ve discussed what climate change and snowpack loss in the Northern Rockies might mean for the water supply in the Missouri River, and those who want to explore that topic can find the post here.

Glacial loss matters in some locations more than others. A very large number of people are likely to be affected, especially in Asia. Those people often live at a subsistence level; what loss of the glaciers will mean to them is hard to know. What kind of famine, pestilence, migration, political instability, and war might result is anybody’s guess.

Sources:

NASA. 2011. Adapted from ”everest_ali_2011298_geo.tif.” Downloaded 2019-07-01 from https://visibleearth.nasa.gov/view.php?id=82578.

NASA. “Graphic: Dramatic Glacier Melt.” Global Climate Change. Downloaded 6/24/2019 from https://climate.nasa.gov/climate_resources/4/graphic-dramatic-glacier-melt.

Schaner, Neil, Nathalie Voisin, Bart Nijssen, and Dennis P. Lettenmaier. 2012. “The Contribution of Glacier Melt to Streamflow.” Environmental Research Letters. 7 034029. Downloaded 6/24/2019 from https://iopscience.iop.org/article/10.1088/1748-9326/7/3/034029.

WGMS. 2019. WGMS Flucuations of Glaciers Browser. Data accessed online 6/24/2019 at https://www.wgms.ch/fogbrowser.

WGMS (2017, updated, and earlier reports): Global Glacier Change Bulletin No. 2 (2014-2015). Zemp, M., Nussbaumer, S. U., Gärtner-Roer, I., Huber, J., Machguth, H., Paul, F., and Hoelzle, M. (eds.), ICSU(WDS)/IUGG(IACS)/UNEP/UNESCO/WMO, World Glacier Monitoring Service, Zurich, Switzer- land, 244 pp., based on database version: doi:10.5904/wgms-fog-2018-11. Downloaded 6/24/2019 from https://wgms.ch/global-glacier-state. (While this is the citation the source document suggests, the graphs used in this post were updated in January, 2019.)


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