Glaciers

Glaciers Environmental Science 1 De Mesa, Carla S. Tadios, Gia Marie T.

• Glaciers - large mass of mobile, permanent ice formed on land by the consolidation and recrystallization of snowflakes, that shows evidence of down slope or outward movement due to the pull of gravity (Grolier International, 1999)

Definition

Location: Bernese Alps, 671.000 / 169.000 (local Swiss coordinate system); length (1973): 5.75 km; orientation: north; surface area (1973): 16.55 km2 Photos below: 2003 (left) and 2004 (right).

Definition • may terminate on land, in the ocean, or in lake and vary in size from small features about 1km long to the great Antarctic ice sheet, which covers 12, 500, 000 km2 (Grolier International, 1999). • constitute much of the Earth that makes up the cryosphere • most glacial ice today is found in the polar regions, above the Arctic and Antarctic Circles (Glaciers, http://jove.geol.niu.edu), and on all of the continents except Australia (Grolier International, 1999).

Definition • At the present time, glacier ice covers about 10 per cent of the Earth’s land surface (Hambrey and Alean, 2004). • In geological terms, we are living in a glacial era that began in Antarctica some 35 million years ago. – the latter stages of this era have included many alterations between periods of full glaciation, when much of the northern hemisphere was covered by ice, and interglacial periods characterized by much less ice, such as at the present day. – The most recent full- scale glaciations, when ice covered up to 30 per cent of the land, ended as recently as 10, 000 years ago and, if the planet were allowed to follow its natural cycle, a return to such condition would be expected in a few thousand years’ time.

Table 1. Distribution of glacerized (glacier- covered) areas of the world (World Glacier Monitoring Service, 1989. World glacier inventory. IAHS (ICSI)- UNEP- UNESCO) Region

Area (km2)

Africa

10

Antartica

13, 593, 310

Asian and Eastern Europe

185, 211

Australasia (i.e. New Zealand)

860

Europe (Western)

53, 967

Greenland

1, 726, 400

North America excluding Greenland

276, 100

South America

25, 908

World Total

15, 861, 766

taken from Hambrey and Alean, 2004

Glaciers and ice sheets cover a tenth of the Earth`s surface

Antartica- the icy continent

Glaciers come in all shapes and sizesSensitive indicators of climatic change

Glaciers have shaped a third of the land surface

The world’s highest peak, Mount Everest (8848 m) on the left, feeds the Khumbu Icefall and then the Khumbu Glacier which flows beneath Nuptse 7861 m) towards the right The Sherpa villages of the Khumbu Himal are overlooked by some of the world’s highest peaks and their extensive glaciers. Near Dingboche Bhuddist prayer flags provide a foreground for the ice-draped peaks of Thamserku Mer de Glace from Montenvers, near Chamonix, France, one of the first glaciers to be studied by 19th Century scientists, and now a popular destination for tourists and climbers

Photos: Michael Hambrey and Jürg Alean, 2004

Glacial Process • glacial ice forms by compaction and re-crystallization of snow in which snowflakes are melted preferentially at their edges first because it is the region where the surface area most closely equals the volume • snow that survives (usually in shaded areas) at least one full season is converted to a granular type of ice called firn. • with enough snow accumulation and time, pressure from overlying snow may be build up enough to convert firn into crystalline ice and cause flow

Glacial Process • glaciers form where more snow falls than melts • a glacier's accumulation area, located at higher elevations, accrues a wealth of snow and ice • ablation area, located at lower elevations, loses ice through melting (downwasting) or calving • glacier's terminus or face advances when more snow and ice amass than melt, and it retreats when melt exceeds accumulation • when melt equals accumulation, a glacier achieves equilibrium and its face remains stationary. Whether the glacier's face is advancing or retreating, glacial ice persistently glides down-valley (Icefields and Glaciers, http://www.fs.fed.us).

At the end of the summer season, alpine glaciers have a clear demarcation between the accumulation area and the ablation area known as the equilibrium line, as here on Vadret Pers, Engadin, Switzerland

High elevations in the tropical Andes receive large quantities of snow during the rainy season in summer. This peak of Nevado Parón (5600 m) bears the characteristic mushroomlike growths of snow and ice, as well as ice cliffs that feed into the glacier In slow below moving or stagnant temperate glaciers, ice crystals can attain large sizes, as this example from Columbia Glacier, Alaska demonstrates The accumulation of snow in the heart of Antarctica amounts to only a few The crevasse wall clearly centimetres shows the accumulation per year, and layering, the most much of that prominent of which is reworked by bound a year’s wind accumulation of snow

Ice avalanches in high mountain terrain contribute to the build-up of ice in the accumulation area, as here on Nevado Chacraraju (6172 m), Cordillera Blanca, Peru

Glaciers respond to a negative mass balance either by recession of the snout or down-wasting. Here Mueller Glacier in the Southern Alps of New Zealand is down-wasting into an incipient lake

Small Antarctic glaciers, separate from the ice sheet, show steep vertical cliffs if their snouts are stationary or advancing

Table 2 Variants and Sub- categories of Alpine and Continental Glaciers

Cirque Glacier (variant)- glacier in a depression, Ice sheets (variant)- relatively large in size

Types of Glaciers

usually at the head of valleys Niche Glacier (variant)- very small glacial form ice shelf (sub-category)- an ice cap or ice sheet which exists in a shallow hollow on a steep which extends out over the water, such as the

Glaciers can be divided into 2 general types, Alpine or Mountain Glaciers, those Glaciers which originate on a mountain or in a mountain range, and the Continental Glaciers, the large masses of Glacial ice in Greenland and Antarctica (Walker, 2007).

mountain slope

Antarctic Ross

Cirque Glacier (variant)- glacier in a depression, Ice sheets (variant)- relatively large in size usually at the head of valleys Niche Glacier (variant)- very small glacial form ice shelf (sub-category)- an ice cap or ice sheet which exists in a shallow hollow on a steep which extends out over the water, such as the mountain slope

Antarctic Ross Ice Shelf

Piedmont Glaciers (variant)- extend from their iceberg (sub-category)- a piece of an ice sheet or ice mountain origin all the way onto a plain

shelf which floats out into the oceans

confluent glacier (sub-category)-merging of 2 or more glaciers tidewater

glacier

(sub-category)-valley

glacier

which reaches the sea, and thus calves small icebergs, but is often subject to being eroded at the terminus by wave action

Tidewater glacier glacier cliff reflected in pool on melting sea ice, Nordenskiöldbreen, Billefjorden, western Spitsbergen

The largest glacier in the European Alps, the Grosser Aletschgletscher from the air. The glacier descends for 23 km from peaks of over 4000 m, and supplies meltwater for a major electrical power station owned by the Swiss railway system

A small ice cap on the northeast side of James Ross Island, Antarctic Peninsula region forms a white domeshaped feature, capping the dark grey volcanic rocks below

The smallest glaciers are only a few hundred metres across, such as this tiny cirque glacier (Teton Glacier) in Grand Tetons National Park,

Cirque glaciers such as Skoltbre on the peak of Oksskolten (1916 m) in Nordland, Norway

Glaciers that flow through narrow valleys and then reach an open plain spread out as broad lobes known as piedmont glaciers

Fast-flowing glaciers that reach the sea discharge large numbers of iceberg

Glacier ice can cling to surprisingly steep mountainsides where it builds up to form avalanche-prone hanging glaciers as here on the NE peak of the long ridge of Ombigaichan (over 6000 m), Khumbu Himal, Nepal

Earth’s Glacial Record • many people are aware that the Earth was repeatedly affected by ice ages over the last two million years, when ice sheets extended from the polar regions to cover ground now occupied by such major cities as Chicago, New York, Edinburgh, Birmingham, Berlin, Oslo, Stockholm and Moscow • major ice ages occurred in the earlier geological past, as far back as 3000 million years ago there is a belief in some quarters that the world was almost totally covered by ice six or seven hundred million years ago - the age of the «Snowball Earth»

The legacy of glaciation in regions that lost their glaciers after the last glaciation 12,000 years ago, are some of the world’s finest landscapes. Crummock Water, with the Central Fells of the Lake District beyond is one of the classic glaciated areas in Britain There are several lines of evidence for glaciation in ancient rocks. One of the most useful is the presence of rocks mixed with particles ranging from clay to boulder size Evidence of glaciation from 20002500 million years ago is shown by this ‘tillite’ – a mixture of coarse and fine fragments in a very hard rock, Whitefish Falls, Ontario, Canada

China has abundant evidence of Late Proterozoic glaciations, spanning at leats three time intervals. Not only are there are extensive tillites, but there are grooved and striated pavements underlying them, as here in Henan Province Evidence of another glaciation in the Kaokoveld, a hot desert area of northern Namibia. Here, a Permian-Carboniferous landscape has been preserved for most of its life by younger sediments. These have now been exhumed, revealing classic glacial landforms such as this glacial trough at Omutirapo The last full-scale glaciation in Britain transported large amounts of material southwards. The Isle of Arran in SW Scotland had its own centre of ice dispersal, producing these whitish granite erratics

The last glaciation in the United States saw the erosion of many fine glacial troughs, such as the Yosemite Valley in California. The oversteepened valley sides include El Capitan on the left

Striking evidence of ice-sheet-scale glaciation can be found in Central Park, New York, where the exposed bedrock surfaces carry striations formed at the bed of a sliding ice mass

a dam at Griesgletscher, Valais, Switzerland has been constructed to receive meltwater in summer for use in power generation in winter Large amounts of debris are transported by Breithorngletscher (right) and Schwarzgletscher (centre) flowing off Breithorn (4164 m) near Zermatt, Switzerland The dramatic granite peaks of the Torres del Paine, tower above a moraine-dammed lake

Transporting large debris on the Grosser Aletschgletscher, Berner Oberland, Switzerland

Some glacier facts Glaciers store about 75% of the world's freshwater, and if all land ice melted the seas would rise about 70 meters (about 230 feet). 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. Motion and change define a glacier's life. Glacial ice advances, then retreats. Glaciers grow and shrink in response to changing climate. Typically glacier movement and shape shifting occur over long periods of time (hundreds to thousands of years), but within historic memory such transformations in fewer than 100 years are not unknown.

Why Glaciers •By their movement, glaciers mark change and for this reason - among others - scientists study glaciers. By monitoring glaciers over time and around the world, researchers construct valuable records of glacial activity and their response to climate variation. •By comparing contemporary observations with historical and environmental records, such as agricultural records, pre-historic temperature or climate profiles, glaciologists acquire and provide an enhanced understanding of global processes and change.

Keeping track • Scientists track glacial change by measuring individual glaciers and comparing their size over time with records of the local and regional climate. • The Global Land Ice Measurements from Space (GLIMS) Coordination Center at the United States Geological Survey (USGS) in Flagstaff, Arizona team uses high-resolution satellite images from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument and the Landsat Enhanced Thematic Mapper Plus (ETM+), archived at the Land Processes Distributed Active Archive Center (LP DAAC), to track the size and movement of glaciers.

◄This ASTER image shows the lakes left behind by retreating glaciers in the BhutanHimalaya. (Image courtesy of Jeffrey Kargel, USGS/NASA JPL/AGU) ►This ASTER image, acquired on July 23, 2001, shows Aletsch Glacier, the largest glacier of Europe. (Image by Earth Observatory Team, based on data provided by the ASTER Science Team)

Current state of glaciers Glacial shifts usually occur at a glacial pace -- over centuries or millennia. But scientists are now watching that scope of change occur in a matter of years. Scientists say the melt rate has accelerated dramatically since the mid-1990s, which was the hottest decade in a thousand years, according to data from ancient ice cores and tree rings.

Shrinking Glaciers Glaciers everywhere in the world (with a very few exceptions) have been shrinking throughout the 20th Century, a prime signal of rapid global warming. 1979 1928 2000

South Cascade Glacier in the Washington Cascade Mountains

Glacier-ice shelf interactions: In a stable glacier-ice shelf system, the glacier's downhill movement is offset by the buoyant force of the water on the front of the shelf. Warmer temperatures destabilize this system by lubricating the glacier's base and creating melt ponds that eventually carve through the shelf. Once the ice shelf retreats to the grounding line, the buoyant force that used to offset glacier flow becomes negligible, and the glacier picks up speed on its way to the sea.

▼Disintegration of the Larsen B Ice Shelf: The event began on January 31, 2002. Several weeks later, the ice shelf had completely shattered.

▲Extent of Larsen Ice Shelf retreat: Colored lines mark the ice shelf's extent in 1947, 1961, 1993, and 2002.

MODIS image courtesy of Ted Scambos and Terry Haran, National Snow and Ice Data Center, University of Colorado, Boulder.

Jacobshavn Glacier retreat: The rapidly retreating Jakobshavn Glacier in western Greenland drains the central ice sheet. This image shows the glacier in 2001, flowing from upper right to lower left. Terminus locations before 2001 were determined by surveys and more recent contours were derived from Landsat data. The more recent retreat lines indicated in this image are longer than the earlier ones, and the increasing area of retreat suggests the possibility of increasing glacier acceleration as more ice flows into the fjord. Ice flowing into the fjord, however, would still have to pass through the same bottleneck of rock. Image courtesy NASA Earth Observatory, Cindy Starr, based on data from Ole Bennike and Anker Weidick (Geological Survey of Denmark and Greenland) and Landsat data.

▲The Pasterze, Austria's longest glacier, was about 2 kilometers longer in the 19th C. but is now completely out of sight from this overlook on the Grossglockner High Road. The MargaritzenStrausee, a dammed artificial lake, now is in the place where the glacier terminus was in 1875. Measurements of the Pasterze began in 1889 and it has been pulling back the entire time, in approximate step with regional temperatures that have been increasing. The glacier is now about eight Km long and loses about 15 meters per year. However in 2003 the Pasterze decreased 30 meters in length and 6.5 meters in thickness.

[1875 image, photographer unknown, is courtesy H. Slupetzky, from the University of Salzburg archives. Gary Braasch photo made Aug 14, 2004]

◄In 1997 the U.S. Geological Survey began the Repeat Photography Project in the Montana park to compare how glaciers have changed over the last century. Photographers returned to locations where old-timers had taken photos long before they could possibly have imagined their scientific value.

►The Qori Kalis glacier in Peru, shown in 1978.

►The Qori Kalis glacier in Peru in 2000.

Glacier photos courtesy Lonnie Thompson, Ohio State University.

Effects of glacial melting Large amounts of land now covered by ice will be available for agriculture and mining. A melting glacier in Alaska is exposing what may be the richest lode of copper ever found in the state. Historically unnavigable areas may open, such as the famed Northwest Passage of the Arctic. Increased melting could result in temporary increases in meltwater available for human use.

Over time there will be less water to sustain the communities that have come to depend on that meltwater. Devastation of major rivers. Deprivation of the mountain ecology of its main life source, Hastening and expansion of desertification. More droughts and sandstorms for the regions that depend on glaciers for water supply. Failure of agriculture due to the loss of source of irrigation. Drying up of the source and failure of hydroelectric power plants.

• glaciers is their scenic value, whether it be regions with modern glaciers such as the Alps or Western Cordillera, or regions that have longsince lost their glaciers, such as the English Lake District or many parts of the Rockies • water for irrigation and the generation of hydro-electricity • the sediments from glaciers themselves are valuable as a provider of underground water supplies

One way of letting casual tourists enjoy glaciers is to excavate ice caves or ‘grottos’. This tunnel is beneath the Rhonegletscher,

A complex series of irrigation ditches, as here on the slopes of Huascarán, Cordillera Blanca, Peru, support extensive agriculture during the dry season

In some areas of Switzerland, the waters are collected from several glaciers and sent via tunnels to one holding reservoir

Weakening of tourism. Increased hazards or disasters for communities living near glaciers. Some glaciers may store up large amounts of water and then release it suddenly in a massive melt or calving or collapse, which may involve floods, landslides, or avalanches. Hazards to shipping and navigation due to the changes in iceberg production.

Glacier Hazards • Over the centuries, glaciers have been responsible for many natural disasters as a result of ice avalanches • Other disasters have arisen from the damming of lakes by glaciers and moraines, followed by failure of the dam • The worst disasters, accounting for tens of thousands of lives, have occurred in Peru, but other seriously affected regions have been the Himalaya and the Alps

A curious block of ice has fallen off a hanging glacier on the south side of the Mönch (4099 m), Switzerland

A major ice avalanche from a hanging glacier on the south flank of Mönch (4099 m), Switzerland. More than 300,000 cubic metres of ice fell

Satellite image of Huaraz and its relationship with the nearby Cordillera Blanca, Peru. An outburst flood from Laguna Cohup on 13 December 1947 killed 7000 people

Glacial lake outburst floods transport huge amounts of debris, including large boulders

Slowing or disruption of the ocean conveyor.

The ocean's system of currents takes 1,000 years to go full cycle. Warm water is chilled in the far North Atlantic and sinks. The cold, salty current flows south near the bottom.

• Glaciers and their surroundings are often havens for wildlife • ranging from the polar bear in the far north to the penguin in the deep south. • delicate flowers and small mammal species thrive in many alpine regions

Antarctic skua at Mirnyy Station, East Antarctica

Arctic wolf a regular visitor to a glaciological field station on

Emperor penguins are well known for breeding during the winter in Antarctica

Elephant seal on the sandy beach at Davis Station (East Antarctica)

Arctic fox (Alopex lagopus) in summer coat near the glacier midre Lovénbreen, NW Spitsbergen

Breaking of food chain. Endangered existence of polar animals and other organism Arctic sea ice is a habitat for polar bears. It is essential for catching prey and rearing young.

The small polar willow Saxifrage, one of the shrub on Axel Heiberg earliest plants to Island colonise deglaciated terrain

Fireweed on an alpine meadow near Triftgletscher, Berner Oberland, Switzerland

Vegetation in moist, mild areas such as near Fox Glacier, South Island, New Zealand

White arctic bell heather of East Greenland

Gemswurz and alpine forget-menot growing on a lateral moraine of Vadret da Morteratsch,

Increase in sea level submerging low-lying coastal regions and shrinking islands.

Sea level rise contributors: Comparison of volume (white), area (grey) and percent contribution to sea level rise (red) by small glaciers and ice caps, and the Greenland and Antarctic Ice Sheets.

Alteration of short and long term weather patterns. Increased number of earthquakes, volcanic eruptions and tsunamis.