Geography 120, Instructor: Chaddock In Class 13: Glaciers and Icecaps Name: Fill in the correct terms for these descriptions: Ablation zone: n zne:

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1 Geography 120, Instructor: Chaddock In Class 13: Glaciers and Icecaps Name: Fill in the correct terms for these descriptions: Ablation zone: The area of a glacier where mass is lost through melting or evaporation at a greater rate than snow and ice accumulate. n zne: The area of a glacier where mass is increased through snowfall at a greater rate than snow and ice is lost through ablation. A relatively small glacier that forms in high elevations near the tops of mountains. A sharp-edged ridge of rock formed between adjacent cirque glaciers. The sliding of a glacier over the ground on a layer of water. A bowl-shaped depression carved out of a mountain by an alpine glacier. 1

2 A glacier that forms over large areas of continents close to the poles. Crevasse: A deep, nearly vertical crack that develops in the upper portion of glacier ice. Erosion: The granular ice formed by the recrystallization of snow; also known as névé. Fjord: A deep glacial trough submerged with seawater. Glacial drift: A high mountain peak formed when the walls of 3 or more cirques intersect. Inter A moraine deposited along the side of a valley glacier. Medial moraine: A moraine formed when two adjacent glaciers flow into each other and their lateral moraines are caught in the middle of the joined glacier. Striations: A small lake that fills the central depression in a cirque. Name 3 formations associated with Ablation: Name 3 formations associated with Accumulation: Terminal moraine: 2

3 Glaciers and icecaps: Storehouses of freshwater Even though you've probably never seen a glacier, they are a big item when we talk about the world's water supply. Almost 10 percent of the world's land mass is currently covered with glaciers, mostly in places like Greenland and Antarctica. Glaciers are important features in the hydrologic cycle and affect the volume, variability, and water quality of runoff in areas where they occur. river a hundred miles (161 kilometers) long. In a way, glaciers are just frozen rivers of ice flowing downhill. Glaciers begin life as snowflakes. When the snowfall in an area far exceeds the melting that occurs during summer, glaciers start to form. The weight of the accumulated snow compresses the fallen snow into ice. These "rivers" of ice are tremendously heavy, and if they are on land that has a downhill slope the whole ice patch starts to slowly grind its way downhill. These glaciers can vary greatly in size, from a football-field sized patch to a Glaciers affect the landscape Glaciers have had a profound effect on the topography (lay of the land) in some areas, as in the northern U.S. You can imagine how a billion-ton icecube can rearrange the landscape as it slowly grinds its way overland. In this picture you can see the bowl-shaped valley in a glacial valley in Wyoming where an ancient glacier forced its way through the landscape. Many lakes, such as the Great Lakes, and valleys have been carved out by ancient glaciers. A massive icecap can be found in Greenland, where practically the whole country is covered with ice (shouldn't it be called Whiteland)? The ice on Greenland approaches two miles (3.2 kilometers) in thickness in some places and is so heavy that some of the land has been compressed so much that it is way below sea level. 3

4 Ice and glaciers come and go There are many long-term weather patterns that the Earth goes through. The climate, on a global scale, is always changing, although usually not at a rate fast enough for people to notice. There have been many warm periods, such as when the dinosaurs lived and many cold periods, such as the last ice age of about 20,000 years ago. During the last ice age much of the northern hemisphere was covered in ice and glaciers, and, as this map from the University of Arizona shows, they covered nearly all of Canada, much of northern Asia and Europe, and extended well into the United States. Glaciers are still around today; tens of thousands of them are in Alaska. Climatic factors still affect them today and during the current warmer climate today, they can retreat in size at a rate easily measured on a yearly scale. Stored water as part of the water cycle The water cycle describes how water moves above, on, and through the Earth. But, in fact, much more water is "in storage" at any one time than is actually moving through the cycle. By storage, we mean water that is locked up in its present state for a relatively long period of time. Short-term storage might be days or weeks for water in a lake, but it could be thousands of years for deep ground-water storage or even longer for water at the bottom of an ice cap, such as in Greenland. In the grand scheme of things, this water is still part of the water cycle. Ice caps around the world The vast majority, almost 90 percent, of Earth's ice mass is in Antarctica, while the Greenland ice cap contains 10 percent of the total global ice mass. The Greenland ice cap is an interesting part of the water cycle. The ice cap became so large over time (about 600,000 cubic miles (mi 3 ) or 2.5 million cubic kilometers (km 3 )) because more snow fell than melted. Over the millennia, as the snow got deeper, it compressed and became ice. The ice cap averages about 5,000 feet (1,500 meters) in thickness, but can be as thick as 14,000 feet (4,300 meters). The ice is so heavy that the land below it has been pressed down into the shape of a bowl. In many places, glaciers on Greenland reach to the sea, and one estimate is that as much as 125 mi 3 (517 km 3 ) of ice "calves" into the ocean each year one of Greenland's contributions to the global water cycle. Ocean-bound icebergs travel with the currents, melting along the way. Some icebergs have been seen, in much smaller form, as far south as the island of Bermuda. 4

5 Ice caps influence the weather Just because water in an ice cap or glacier is not moving does not mean that it does not have a direct effect on other aspects of the water cycle and the weather. Ice is very white, and since white reflects sunlight (and thus, heat), large ice fields can determine weather patterns. Air temperatures can be higher a mile above ice caps than at the surface, and wind patterns, which affect weather systems, can be dramatic around ice-covered landscapes. Some glacier and ice cap facts Glacial ice covers percent of all land. According to the National Snow and Ice Data Center (NSIDC), if all glaciers melted today the seas would rise about 230 feet (70 meters). Glaciers store about 75% of the world's freshwater During the last ice age (when glaciers covered more land area than today) the sea level was about 400 feet (122 meters) lower than it is today. At that time, glaciers covered almost one-third of the land. During the last warm spell, 125,000 years ago, the seas were about 18 feet (5.5 meters) higher than they are today. About three million years ago the seas could have been up to 165 feet (50.3 meters) higher. Largest surface area of any glacier in the contiguous United States: Emmons Glacier, Washington (4.3 square miles or 11 square kilometers) North America's longest glacier is the Bering Glacier in Alaska, measuring 204 kilometers long. Glacial ice can be very old in some Canadian Arctic icecaps, ice at the base is over years old. The land underneath parts of the West Antarctic Ice Sheet may be up to 2.5 kilometers below sea level, due to the weight of the ice. Antarctic ice shelves may calve icebergs that are over 80 kilometers long. The Kutiah Glacier in Pakistan holds the record for the fastest glacial surge. In 1953, it raced more than 12 kilometers in 3 months, averaging about 112 meters per day. Glacial ice often appears blue when it has become very dense. Years of compression gradually make the ice denser over time, forcing out the tiny air pockets between crystals. When glacier ice becomes extremely dense, the ice absorbs all other colors in the spectrum and reflects primarily blue, which is what we see. When glacier ice is white, that usually means that there are many tiny air bubbles still in the ice. 5

6 Ice caps and global water distribution Even though the amount of water locked up in glaciers and ice caps is a small percentage of all water on (and in) the Earth, it represents a large percentage of the world's total freshwater. As these charts and the data table show, the amount of water locked up in ice and snow is only about 1.7 percent of all water on Earth, but the majority of total freshwater on Earth, about 68.7 percent, is held in ice caps and glaciers. Water source Ice caps, Glaciers, & Permanent snow One estimate of global water distribution Water volume, in cubic miles Water volume, in cubic kilometers Percent of total water Percent of total freshwater 5,773,000 24,064, % 68.7% Total global freshwater 8,404,000 35,030, % -- Total global water 332,500,000 1,386,000, Source: Gleick, P. H., 1996: Water resources. In Encyclopedia of Climate and Weather, ed. by S. H. Schneider, Oxford University Press, New York, vol. 2, pp

7 On the left is a photograph of Muir Glacier taken on August 13, 1941, by glaciologist William O. Field; on the right, a photograph taken from the same vantage on August 31, 2004, by geologist Bruce F. Molnia of the United States Geological Survey (USGS). According to Molnia, between 1941 and 2004 the glacier retreated more than twelve kilometers (seven miles) and thinned by more than 800 meters (875 yards). Ocean water has filled the valley, replacing the ice of Muir Glacier; the end of the glacier has retreated out of the field of view. The glacier s absence reveals scars where glacier ice once scraped high up against the hillside. In 2004, trees and shrubs grow thickly in the foreground, where in 1941 there was only bare rock. 7

8 Photographer Name : Grant, Ulysses Sherman Glacier Name : McCarty Glacier Publisher : National Snow and Ice Data Center/World Data Center for Glaciology, Boulder Date of Original Media : 1909/7/30 State/Province : AK Country : U.S.A. Coordinates - Latitude : Coordinates - Longitude: Photographer Name : Molnia, Bruce F. Glacier Name : McCarty Glacier Publisher : National Snow and Ice Data Center/World Data Center for Glaciology, Boulder Date of Original Media : 2004/8/11 8

9 Photographer Name : Wright, Charles Will Glacier Name : Carroll Glacier Publisher : National Snow and Ice Data Center/World Data Center for Glaciology, Boulder Date of Original Media : 1906/8/ Photographer Name : Molnia, Bruce F. Glacier Name : Carroll Glacier Publisher : National Snow and Ice Data Center/World Data Center for Glaciology, Boulder Date of Original Media : 2004/6/21 State/Province : AK Coordinates - Latitude : Coordinates - Longitude: Keywords : Terminal moraine Notes : Northwest-looking photograph taken several hundred meters up a steep alluvial fan located in a side valley on the east side of Queen Inlet, Glacier Bay National Park and Preserve, Alaska. Source : U.S. Geological Survey 9

10 1. Observing the photos that show these glaciers at 100 years apart, what are some of the things you notice in the landscape, i.e., vegetation, water bodies, geological formations? 2. What effect will the melting of these glaciers have on the overall water availability for countries throughout the world? 3. Name some of the critical issues in glacier melting, and how you see the world addressing these issues. 10