Glaciers may retreat when their ice melts or ablates more quickly than snowfall can accumulate and form new glacial ice. 1 hour ago — Lee Billings and Casey Dreier, 2 hours ago — Ronjini Joshua | Opinion, 17 hours ago — Daniel Cusick and E&E News, 20 hours ago — Ewen Callaway and Nature magazine. The Trift also happens to be one of the fastest retreating glaciers in the world.. It retreats—that is, its terminal edge, the end of the glacial tongue, ends at progressively higher elevations—whenever melting exceeds accumulation. The loss of glaciers will also represent a major aesthetic loss for humans who flock to places like Glacier National Park for the scenery, as well as a potential blow to recreational activities such as high-altitude mountaineering. Global ice cover and glacial extent have varied widely over the past 750,000 years, advancing during numerous ice ages, and retreating during intermediate warming periods called interglacials. Experts say those glaciers are influenced by different climates, allowing scientists to compare how glaciers respond in different regions. Glaciers in mid- and high-latitude regions of the Northern Hemisphere, such as the northwestern United States, southwestern Canada, and Alaska, have lost mass quickly over the last century due to accelerated summer melting, despite some increases in precipitation. Explore our digital archive back to 1845, including articles by more than 150 Nobel Prize winners. Gulkana drains west into the Yukon River. Glaciers Advance, Glaciers Retreat Until 10,000 years ago, continental-scale ice sheets came and went many times for seven million years. Climate Change: In Context. It also influences the rich diversity of species in the marine ecosystem that are important to tourism and fishing industries. Kaser, Georg, et al. Losses have also been extreme in the European Alps, where glaciers have shrunk 30–40%, and New Zealand, which has lost 20–32% of its glacierized area over the past century. The world's rapidly melting glaciers has disastrous consequences on the animals that rely on them for survival., "Glacier Retreat Facts about glaciers. A new study of Greenland's shrinking ice sheet reveals that many of the island's glaciers are not only retreating, but are also undergoing other physical changes. Diaz, Henry F., and Nicholas E. Graham. Glaciers are sensitive indicators of climate change because their size and mass change relatively quickly in response to long-term climate variations (such as changing temperature, precipitation, and cloud cover) over the course of decades, rather than to short-term weather patterns. Pick a style below, and copy the text for your bibliography. Most online reference entries and articles do not have page numbers. “Modern Glacier Retreat on Kilimanjaro as Evidence of Climate Change: Observations and Facts.” Royal Meteorological Society 24 (2004): 329–339. While this is certainly positive news, a closer look reveals some bad and potentially ugly news too. Glacial retreat: “With few exceptions, all the alpine glaciers of the world are losing mass and it is predicted that this trend will continue as global warming progresses. Credit: NASA/JPL-Caltech/USGS. To see if a glacier is growing or shrinking, glaciologists check the condition of snow and ice at several locations on the glacier at the end of the melt season. The reduction of the Zongo Glacier in Bolivia, for example, is already creating freshwater supply problems for downstream human communities. The shrinkage and loss of alpine glaciers, which provide important water sources in much of the world, will have direct and severe implications for humans and ecosystems alike. Some of those changes are causing the rerouting of freshwater rivers beneath the glaciers, where it meets the bedrock. Mathematical extrapolations from the data that do exist on mass balance indicate that the global rates of glacier mass loss are increasing rapidly, roughly doubling during 1990/1991–2003/ 2004 over the mass loss rates from 1960/1961–1989/ 1990. In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. If human greenhouse-gas emissions continue to rise unchecked and current warming trends continue, climate models predict the disappearance of many glaciers before the end of the twenty-first century. Earth's south polar ice cap is the Antarctic ice sheet. Moving up to 300 feet in a single year, the glacier’s retreat is marked each decade. As the glaciers move across the ground they grind against the earth and carves out valleys. Glaciers in alpine areas act as buffers. The great abundance of water on the surface of Earth includes a great quantity of ice in the Polar Regions and high…, Albedo Earth's climate has changed throughout history. Climate change gave the initial push to the Columbia’s retreat over three decades ago, but once destabilized its decline was accelerated due to glacial mechanics. Now, long-term data exist for glaciers on every continent. Records for changes in glacier mass balance are not nearly as complete, as they are generally restricted to relatively easy-access glaciers and stretch back only to the mid-twentieth century. This widespread glacier retreat is most likely the result of climbing global temperatures brought on by human emissions of greenhouse gases such as carbon dioxide (CO2) combined with a natural warming phase. “Modeled Climate-Induced Glacier Change in Glacier National Park, 1850–2100.” BioScience 53 (2003): 131–140. Statistics predict future levels of glacier loss will reach an all-time high. The retreat of the Columbia Glacier contributes to global sea-level rise, mostly through iceberg calving. Introduction “They were able to see a pretty pronounced gradient of both physical and biological composition of what’s living in the bay. Melting Alaskan glaciers are among the biggest contributors, accounting for about 30% of mountain glacier inputs to sea level rise. The 2004 photograph documents the continued thinning and retreat of East Fork Teklanika Glacier. Materials deposited by a glacier as it retreats are called ground moraines. Most of the world’s mountain (alpine) glaciers have been retreating since about 1850. Since the 1990s, the retreat of glaciers in Alaska has made a disproportionally large contribution to global sea-level rise. Glaciology is the study of ice and its effects. Glaciers that terminate in a lake or the ocean also lose mass through iceberg calving. Patagonia's changes likely stem in part from warmer, drier conditions, but accelerated glacial flow, resulting in the accelerated loss of large chunks of ice at glacier termini through a process known as calving, also plays a role. Retreat of the Gangotri Glacier Currently 30.2 km long and between 0.5 and 2.5 km wide, Gangotri glacier is one of the largest in the Himalaya. Climate Change 2007: The Physical Science Basis: Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. The most important greenhouse gases are water vapor, carbon dioxide, methane, nitrous oxide, and various artificial chemicals such as chlorofluorocarbons. Higher temperatures and less snowfall have been causing many glaciers around the world to retreat recently. During that time, the Gulkana Glacier has steadily diminished due to significantly warmer summers in interior Alaska and a relatively unchanged level of snowfall. The tropical Andes also enjoyed periods of glacial advance in the early 1970s and again in 1999 corresponding to cold La Niña conditions in the tropical Pacific. General retreat of glacier tongues started in earnest after 1800, and accelerated across the globe after 1850 and through the twentieth century, with a slight lull during the 1970s before escalating rates of loss began in the 1980s and 1990s. CALVING: Process of iceberg formation when huge chunks of ice break free from glaciers, ice shelves, or ice sheets due to stress, pressure, or the forces of waves and tides. “Detailed and continuous records of this length are exceedingly rare in our field, and thus these are indispensable to our understanding of the changes we’re observing across this region.”. To study those impacts, the glaciologists are teaming up with ecologists, oceanographers, biologists and botanists to assess how socio-economically important species like salmon are likely to fare in the warmer Alaska of the future. All but the latter are naturally occurring, but human activity over the last several centuries has significantly increased the amounts of carbon dioxide, methane, and nitrous oxide in Earth's atmosphere, causing global warming and global climate change. ; A retreating glacier doesn't actually travel backward, but is melting faster than it is gaining new ice. Those early findings, repeated twice a year for the last 50 years, became the baseline for the government’s Benchmark Glacier program, the longest continuous glacier research in North America. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates. Meanwhile, the Wolverine Glacier, which is also shrinking, has experienced slightly cooler summers and more variability in winter temperatures. Click here for the original story. . A glacier grows wherever snow accumulates faster than it melts. The scientists check snow levels against stakes they’ve inserte… 16 Oct. 2020 . The marker for 1917 is about a mile from the glacier’s current point. ICE SHEET: Glacial ice that covers at least 19,500 square mi (50,000 square km) of land and that flows in all directions, covering and obscuring the landscape below it. "Glacier Retreat Then, copy and paste the text into your bibliography or works cited list. The albedo of an object or material is its tendency to reflect light. The glaciers and famous snows of Mount Kilimanjaro in Kenya, Africa, will also likely disappear by mid-century for the first time in over 11,000 years if a long-term dry spell, likely part of the climate change picture, persists. When warming temperatures melt the surface of a land glacier, the land glacier only loses its mass by run-off. In the years since the USGS launched its landmark Alaska glacier research, the scientists have also begun combining their field studies data with new information gathered with modern geophysical and remote sensing methods. Since higher elevations are cooler, the disappearance of the lowest portion decreases overall ablation, thereby increasing mass balance and potentially reestablishing equilibrium. A glacier retreats when its terminus does not extend as far downvalley as it previously did. CONCEPT The Columbia Glacier is a tidewater glacier that flows down the slopes of the Chugach Mountains and into Prince William Sound in southeastern Alaska. Since ice can appear on or in the earth as well as in its seas and other bodies of water and…, Glacier When a chunk of ice breaks off a glacier it is called “calving”. Scientific American is part of Springer Nature, which owns or has commercial relations with thousands of scientific publications (many of them can be found at, Amid Ice Melt, New Shipping Lanes Are Drawn Up off Alaska, Arctic Nations May Confront U.S. on Climate Change, Some Disaster Prevention Spending Reaps Higher Rewards, Climate Preparation Report Released by Panel Previously Disbanded by Trump. These data generally show that glaciers reached their most recent maximum during the Little Ice Age, a short and relatively mild cooling period that ended sometime in the nineteenth century. As Mendenhall Glacier retreats and uncovers bare rock, the wind carries seeds and moss spores onto barren land. When that chunk of ice floats in the water it is called an iceberg. Solomon, S., et al, eds. During this Great Ice Age these ice sheets would reach as far south as the upper Midwest of the United States. LA NIÑA : A period of stronger-than-normal trade winds and unusually low sea-surface temperatures in the central and eastern tropical Pacific Ocean; the opposite of El Nin˜o. “Contribution of Glacier Melt to Sea-Level Rise Since AD 1865: A Regionally Differentiated Calculation.” Climate Dynamics 13 (1997): 835–845. Presently, 10 percent of land area on Earth is covered with glacial ice, including glaciers, ice caps, and the ice sheets of Greenland and Antarctica. USGS FACT SHEET: Glacier Retreat in Glacier National Park, Montana In 2017, the USGS published a time series analysis of the glacier margins of the named glaciers of Glacier National Park . Generally, these glacier fluctuations show a strong statistical correlation with air temperatures over the last century, though other factors, such as changing cloud cover, snowfall, humidity, and climbing sea surface temperature, play roles of varying importance in different locations. So we’re getting some core baseline biological data to go with the physical drivers that go back 50 years.”. The short, steep, and shallow glaciers in tropical mountain ranges are particularly sensitive to climate change, responding over a scale of a few years. Daniel McGrath, a research geophysicist with the program, said much of the government’s ongoing climate research draws from the USGS’s 50 years of Alaska glacier studies. General retreat of glacier tongues started in earnest after 1800, and accelerated across the globe after 1850 and through the twentieth century, with a slight lull during the 1970s before escalating rates of loss began in the 1980s and 1990s. When ice glaciers melt faster, temperatures rise further, and more glaciers shrink, which creates a vicious cycle that is significantly ch… . THE FURKA PASS, Switzerland — On the hairpin bend of a Swiss mountain pass, a Victorian-era hotel built for tourists to admire the Rhone Glacier has … Most glaciers are found in the polar regions of the world. Most of the country of Greenland is covered with a giant icecap that is nearly two miles thick in areas. Mass balance refers to the equilibrium between a glacier's accumulation of snow and ice through precipitation and its ablation, or loss, of snow and ice by melting and sublimation. Retrieved October 16, 2020 from The speediness of the glacier’s retreat is due to the unique nature of tidewater glaciers, Colgan said. “Contribution of the Patagonia Icefields of South America to Sea Level Rise.” Science 302 (2003): 434–437. Glacier Bear boasts a chef's kitchen, great room and recreation room complete with a pool table and a custom bar showcasing local Montana spirits and beers as well as fine wines. Discover world-changing science. Just in the last 650,000 years there have been seven cycles of glacial advance and retreat, with the abrupt end of the last ice age about 11,700 years ago marking the beginning of the modern climate era — and of human civilization. ; Because of friction, the top of a glacier moves faster than the bottom. High-latitude and high-altitude ecosystems will also be affected. In 1966, a team of U.S. Geological Survey scientists journeyed to two small glaciers in Alaska to dig snow pits needed for measuring snow depth and density at the remote mountainous locations. Europe's glaciers have lost about two thirds of their volume since 1850, but last year the Hornkees glacier in the Austrian Alps retreated by 446 feet while Pasterze glacier retreated by 177 feet. During the rainy season, water is stored in the glaciers and the melt water helps maintain river systems during dry periods. “How the climate has been changing over the past few decades of anthropogenic influence really has manifest itself quite well” in these studies, O’Neel said. GREENHOUSE GASES: Gases that cause Earth to retain more thermal energy by absorbing infrared light emitted by Earth's surface. This photograph by an astronaut on the International Space Station highlights the snout of the Upsala Glacier (49.88°S, 73.3°W) on the Argentine side of the North Patagonian Icefield. Glacier melt provides crucial soil moisture and ensures input of cold water to decrease stream temperatures in glacial basins during warmer seasons, maintaining certain plant communities and cold-adapted aquatic invertebrates and fish. Global warming creates temperature increases, causing glaciers to melt faster. Introduction "Glacier Retreat And they’re now modeling how glaciers will respond to future climate scenarios, particularly how coastal glaciers like Wolverine impact the ecosystem along the Gulf of Alaska. © 2019 | All rights reserved. Vuille, Mathias, et al. Meanwhile, Montana's Glacier National Park has lost all but 10 of its 27 original glaciers over the past century, and the extent of those remaining has also been vastly reduced. Glacier retreat results in the loss of the low-elevation region of the glacier. Holiday Sale: Save 25%, Although the mechanisms vary, together the glaciers are losing 75 billion tons of ice annually. “We had a team of biological oceanographers that went into Kings Bay, which is where Wolverine drains into,” he said. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list. Ice flow in this glacier comes from the north (right in this rotated image). In Patagonia, massive ice fields and their glaciers have lost about 0.77–3.2 cubic mi (3.2–13.5 cubic km) of ice per year from 1968 to 2000. A documented rise in tropical sea surface temperatures, which has forced tropical freeze levels to higher altitudes, is also an important factor in tropical, and potentially worldwide, glacier retreat. Glacierized areas cover over 15 million square kilometers (5.8 million square miles). Glacier retreat results in a variety of negative consequences, including increased sea levels, floods, and fresh water shortages. Glaciers are classifiable in three main groups: (1) glaciers that extend in continuous sheets, moving outward in all directions, are called ice sheets if they are the size of Antarctica or Greenland and ice caps if they are smaller; (2) glaciers confined within a path that directs the ice movement are called mountain glaciers; and (3) glaciers that spread out on level ground or on the … Cite this article Pick a style below, and copy the text for your bibliography. In the tropical Andes of Peru, for example, 10 monitored glaciers retreated 1,935-6,266 ft (590-1,910 m) between 1939 and 1994. “Recent Changes in Tropical Freezing Heights and the Role of Sea Surface Temperature.” Nature 383 (1996): 152–155. Most of Earth's alpine and non-polar glaciers, which tend to be smaller and more unstable, have shrunken rapidly over the last century. (October 16, 2020). The meltwater has a unique “glacial fingerprint” that is evident in the timing, volume and temperature of the water, as well as the nutrients it carries. Dark lines of rocky debris (moraine) within the ice give a sense of the slow ice flow f Therefore, it’s best to use citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites: If human greenhouse-gas emissions go unchecked and current warming trends continue, alpine glaciers in many places will likely disappear well before the end of the twenty-first century. But glaciers in both areas have resumed retreat since 2000. Since the 1990s, the retreat of glaciers in Alaska has made a disproportionally large contribution to global sea-level rise. ." <> (accessed December 2, 2007). New Zealand glaciers thickened and advanced from the late 1970s through the 1990s, as did some Scandinavian glaciers during the 1990s, potentially due to temporarily enhanced precipitation. They’re Formed by Snowflakes and Time. Glaciers form at high latitudes and altitudes where vast quantities of fallen snow accumulate over time and compress into thick masses of ice that flow downhill under their own weight. The program provides data on glacier health in a warming climate. Because they are perennial, glaciers provide an important base flow for streams and rivers beyond more unreliable and now dwindling snowpack melt, sustaining agriculture and drinking water supplies through seasonal variations in many mountain communities from the Andes to the Himalayas. With less traction, the glacier can be affected by tidal motion as far as 12 kilometers (7.5 miles) upstream, leaving the Main Branch unstable again. Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, cannot guarantee each citation it generates. Humans began tracking the length and extent of certain glaciers as early as 1534 in European mountain ranges, but thorough, internationally coordinated glacier monitoring did not start until 1894, when the. E&E provides daily coverage of essential energy and environmental news at Interesting Facts about Glaciers. “20th Century Climate Change in the Tropical Andes: Observations and Results.” Climatic Change 59 (2003): 75–99. The USGS reports that the state’s glaciers are losing 75 billion tons of ice annually, equal to the amount of water needed to fill Yankee Stadium 150,000 times each year. Over time, this measure shows whether a glacier's mass is growing (positive), shrinking (negative), or staying the same (zero). Mountain, or alpine, glaciers outside the poles hold only a tiny fraction of this ice, but produce meltwater essential for ecosystem health and for human use in populated areas. ." The USGS research has focused on two glaciers that represent two very different Alaska climates — the Gulkana Glacier in the eastern Alaska Range south of Fairbanks and the Wolverine Glacier in the Kenai Mountains on the southern coast of Alaska. In the tropical Andes, for example, many glaciers may vanish within 50 years at current rates of retreat. gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA). Some glaciers in Pakistan's Karakorum have thickened and advanced due to enhanced precipitation, though glaciers in Asian mountain ranges are generally retreating. Despite trends toward widespread glacier retreat, there are isolated exceptions. Sea level has risen about 5-9 in (13-23 cm) worldwide over the past century, with mountain glacier melt (excluding the glaciers of Greenland's ice sheet) contributing an estimated 1 in (2.7 cm) of this rise between 1865 and 1990. Climate Change: In Context. Widespread melting of glaciers will also play a part in climate change-induced sea level rise. Earth's north polar ice cap has two parts, a skin of floating ice over the actual pole and the Greenland ice cap, which does not overlay the pole. Rignot, Eric, et al. A bright, highly reflective surface, such as fresh snow, ha…, Intergovernmental Panel on Climate Change, The jumble of rock, gravel, and dirt making up ground moraines is called till. Facts about Washington’s retreating glaciers and declining snow pack from Ecology’s Water Resources Program Washington is especially vulnerable to climate change resulting from global warming, and a major reason for this is our dependence on glaciers and … Subscribers get more award-winning coverage of advances in science & technology. Glaciers gain mass through snowfall and lose mass through melting and sublimation (when water evaporates directly from solid ice). Under a doubling of CO2 emissions, the park's remaining glaciers will have completely vanished by 2030. Glaciers are essentially giant rivers of ice that are formed over eons as fallen snow is compressed into layers of ice. But related climate changes, especially increasing humidity and changes in precipitation and cloud cover, may play a larger direct role than temperature in the shrinkage of tropical glaciers. ALBEDO: A numerical expression describing the ability of an object or planet to reflect light. The branch resumed retreat, and in 2019 shed ample icebergs during an anomalously warm summer. In our solar system, only Mars and Earth have polar ice caps. Now that they are shrinking, they leave behind bare bedrock and glacial till. International Glacier Commission was established in Zurich, Switzerland. SUBLIMATION: Transformation of a solid to the gaseous state without passing through the liquid state. However, the date of retrieval is often important. Today, the federal benchmark glacier program extends beyond Alaska and includes research at the South Cascade Glacier in Washington state and the Sperry Glacier in Montana. Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. That glacier is a coastal system that flows into the Gulf of Alaska. New York: Cambridge University Press, 2007. This trend toward glacier retreat and eventual disappearance in the tropical Andes, which has accelerated markedly since the late 1970s and early 1980s, corresponds with a 0.16-0.27°F (0.09-0.15°C) increase in temperature per decade in the area from 1950 to 1994, with most of the warming taking place after the mid-1970s. When the glaciers advanced, they destroyed whatever ecosystems were in their path. At both locations, the long-term records show that summer warming has resulted in sustained mass loss, noted Shad O’Neel, head of the glacier research program at the USGS Alaska Science Center. The most vital ingredient for glacier-making is a location … Reprinted from ClimateWire with permission from Environment & Energy Publishing, LLC. ICE CAP: Ice mass located over one of the poles of a planet not otherwise covered with ice. Alpine glaciers have recently accelerated their retreat and large ice-sheet glaciers have been accelerating their flow to the sea along the coasts of Gre… “We’re trying to quantify the water flow, the water chemistry and then the vegetation that’s in the basin, the species that are there, all the way from the glacier terminus down to the ocean,” O’Neel explained. “It provides tangible evidence for how climate change is affecting the landscapes.”. They form over hundreds of years … Franz Josef Glacier / Kā Roimata o Hine Hukatere is a 12 km (7.5 mi) long temperate maritime glacier in Westland Tai Poutini National Park on the West Coast of New Zealand's South Island.Together with the Fox Glacier 20 km (12 mi) to the south, and a third glacier, it descends from the Southern Alps to less than 300 metres (980 ft) above sea level. Changes in humidity, precipitation, cloud cover, and albedo (reflectance) that accompany global warming may themselves have a greater impact on glacier retreat in some tropical mountains. The glacier has slowed its retreat, gained ice, and moved towards the ocean rather than inland. Today, the main reason glaciers have begun to melt is because of human activity. See Also Albedo; Arctic Melting: Greenland Ice Cap; Arctic Melting: Polar Ice Cap; Glaciation; Glacier. ." Therefore, that information is unavailable for most content. Glaciers, along with ice caps and ice sheets, cover about 10% of Earth's land mass—mostly in Greenland and Antarctica. Hall, Myrna H. P., and Daniel P. Fagre. Low-nutrient glacier debris depends on flowering lupine and alder to fix nitrogen in the soil. The retreat of glaciers in these areas will thus likely force changes in local vegetation and stream ecology, as well as alter stream sedimentation and open up new ground for plant colonization. Much of the fertile soil in the Great Plains of North America was formed from layers of till left by ancient ice sheets. The biggest and most notable impact of these glaciers melting is in the rise of sea level. According to the USGS, climate change could cause summer temperatures to warm by 3.6 to 7.2 degrees Fahrenheit, and snow accumulation to markedly decrease. A glacier is essentially a river of ice. Glaciers store about 69 percent of the world's fresh water. . However, some studies in the European Alps suggest that many alpine glacier retreat scenarios have been largely overestimated. Those changes could contribute to the loss of thousands of glaciers in Alaska and northwest Canada by the end of the century. © 2020 Scientific American, a Division of Springer Nature America, Inc. Support our award-winning coverage of advances in science & technology. However, these contributions are miniscule compared to the potential sea level rise that could result from the melting of the vast Antarctic and Greenland ice sheets. The resulting body of ice is…, Ice is the solid state of water . A glacier is a mass of ice larger than 247 acres (one tenth of a square kilometer) that starts on land, but can move out over co…, Introduction Oefner selected the Rhone Glacier and the Trift Glacier for this project because he hiked in the Swiss Alps as a child and saw the dramatic retreat in the glaciers on visits home as an adult. Glaciers in the Garhwal Himalaya in India are retreating so fast that researchers believe that most central and eastern Himalayan glaciers could virtually disappear by 2035. The areas measured are from 1966, 1998, 2005 and 2015/2016, marking approximately 50 years of change in glacier … Plant Succession at Exit Glacier Retreating glaciers at Kenai Fjords National Park create a perfect living laboratory in which to observe primary succession at work. USGS estimates that Alaska’s glaciers and ice fields are responsible for nearly 50 percent of the water that flows into the Gulf of Alaska. Glaciers are huge masses of ice that “flow” like very slow rivers. Glacial retreat created other features of the landscape. The Arctic, the high mountains of Asia, and Patagonian glaciers also play relatively hefty roles. During the last Ice Age, which ended about 10,000 years ago, glaciers, ice caps, and ice sheets covered 32% of Earth's land mass and 30% of its oceans. Zuo, Z., and J. Oerlemans. Alder, willow and cottonwood tree seeds systematically grow in deglaciated landscapes. Glaciers are large masses of ice that flow slowly downhill. Gangotri has been receding since 1780, although studies show its retreat quickened after 1971. Glaciation is the accumulation of ice in a given area when more snow falls in winter than melts in summer. Studies show that human-caused global warming is the leading cause of glacier retreat. The Chacaltaya glacier in Bolivia, meanwhile, lost about 60% of its ice volume between 1940 and 1983, and will likely disappear altogether within a decade. “All About Glaciers.” National Snow and Ice Data Center. Climate Change: In Context.