Glaciers:
Clues to Future Climate?
Glaciers:
Clues to Future Climate?
by Richard S. Williams, Jr.
Cover photograph:
The ship Island Princess and the calving
terminus of Johns Hopkins Glacier, Glacier
Bay National Monument, Alaska (oblique
aerial photo by Austin Post, Sept. 2, 1977)
Oblique aerial photo of valley glaciers in
Mt. McKinley National Park, Alaska (photo
by Richard S. Williams, Jr., Oct. 4, 1965)
Vertical aerial photo of severely crevassed glaciers on the slopes of Cotopaxi, a nearly sym-
metrical volcano, near the Equator in north-central Equador (photo courtesy of U.S. Air Force).
A glacier is a large mass of ice having its genesis on land and repre-
sents a multiyear surplus of snowfall over snowmelt. At the present time,
perennial ice covers about 10 percent of the land areas of the Earth.
Although glaciers are generally thought of as polar entities, they also are
found in mountainous areas throughout the world, on all continents
except Australia, and even at or near the Equator on high mountains in
Africa and South America.
2
Streamflow from the terminus of the Mammoth Glacier, Wind River Range, Montana (photo
by Mark F. Meier, August 1950).
Present-day glaciers and the deposits from more extensive glaciation in
the geological past have considerable economic importance in many
areas. In areas of limited precipitation during the growing season, for
example, such as parts of the Western United States, glaciers are consid-
ered to be frozen freshwater reservoirs which release water during the
drier summer months. In the Western United States, as in many other
mountainous regions, they are of considerable economic importance in
the irrigation of crops and to the generation of hydroelectric power. Lakes
and ponds are numerous where continental ice sheets once covered New
England and the upper Midwest, and the glacial deposits act as major
3
ground-water reservoirs. The same deposits have substantial economic
value as sand and gravel for building materials, and are often the basis, as
in Massachusetts, for the largest mineral industry in a State.
Glaciers, however, can also pose dangers to ocean transportation. For
example, the west side of Greenland produces a large number of icebergs
which travel south into the shipping lanes of the North Atlantic. Some of
Greenland's icebergs have been known to drift as far south as Delaware
before melting completely. Antarctica often produces large tabular ice-
bergs from its many ice shelves, some of which may exceed the area of
Rhode Island.
Interior view of a crevasse in Blue Ice Valley
on the Greenland Ice Sheet: A glaciologist
Oblique aerial view of crevasses at an ice- can be seen descending a rope ladder,
fall on Le Conte Glacier, Washington. 65 feet (20 meters) below the ice sheet sur-
face (August 1955).
4
In Alaska, glaciologists of the U.S. Geological Survey have carried out
a long-term study of the rate of retreat of the Columbia Glacier. This
large valley glacier's snout ends as a tidal glacier in Prince William
Sound, a waterway traversed by large oil tankers en route to and from
Valdez, the southern terminus of the trans-Alaskan pipeline. In 1980, U.S.
Geological Survey glaciologists predicted that the 425-square-mile (1100-
square-kilometer) Columbia Glacier would begin an accelerated retreat
during the 1980's, thereby increasing the hazard to shipping because of an
increased production of icebergs.
The terminus of the Columbia Glacier, Prince William Sound, Alaska: The glacier, located 25
miles (40 kilometers) west-southwest of Valdez, Alaska, is expected to begin a rapid retreat in
the early 1980's. By 1986 the glacier is expected to have receded 5 miles (8 kilometers), and
the resulting discharge of large numbers of icebergs into shipping lanes serving Valdez, the
southern terminus of the trans-Alaskan pipeline, could pose a continuing hazard to the pas-
sage of oil tankers (oblique aerial photo by Larry Mayo, August 1, 1976).
5
Other glacial hazards include "surging" glaciers. Such glaciers may
suddenly advance several miles (several kilometers) in a few months.
Catastrophic outburst floods, resulting from the failure of ice-dammed
lakes or from subglacial volcanic or geothermal activity, occur frequently
in Iceland and in Alaska, less frequently in the State of Washington, and
occasionally in other locales.
The terminus of Eyjabakkajökull in Iceland is shown after completion of a 2-mile (3-kilo-
meter) surge forward. Note the fragmented nature of the glacier (oblique aerial photo by
Richard S. Williams, Jr., July 25, 1973).
6
The link between climate and glaciers is of great interest to scientists.
Not only have geologists and other scientists established that glaciers
were more and less extensive at various times in the past than at present
but also that changes in climate were the cause. The enigma, of course, is
what causes such changes in climate?
Map showing the maximum areal extent of
glacial ice during the Pleistocene Epoch
(Ice Age) in the north polar area (from Polar
Regions Atlas, May 1978, CIA).
Landsat image of parts of Vest Spitsbergen,
Edgeøya, and Nordaustiandet eastern
Svalbard, Norway: Several glaciers are shown
extending into the sea on July 18, 1976 (NASA
image 2543-11155).
7
The South Cascade Glacier, Cascade Mountains, Washington (oblique aerial photo by Austin
Post, September 23, 1965).
Within the past 3 million years, glaciers—in the form of icecaps and
ice sheets—repeatedly advanced to cover as much as 30 percent of the
total land area of the Earth. This land area includes most of Canada, all of
New England, much of the upper Midwest, large areas in Alaska, all of
Greenland, Svalbard, other Arctic islands, Scandinavia, most of Great
Britain and Ireland, and much of the western part of northern Russia.
Parts of southern South America, central Asia, the Alps, and many other
mountainous areas in Asia also experienced an increase in glacier extent.
Glaciers in Antarctica also expanded somewhat, but more in ice thickness
than in ice area because of the limiting effect of the surrounding oceans.
8
The snow- and glacier-covered Mount St. Helens, Washington, on April 10, 1980, prior to the
catastrophic eruption of May 18, 1980.
Although four or five major glacial advances have been identified by
geologists who have studied glacial deposits in Europe and North
America, stratigraphic evidence from the Tjörnes area of Iceland suggests
that as many as 10 major glacial advances may have occurred within the
past 3 million years or during what is popularly referred to as the Ice
Age.
Geologists recognized during the 19th century that the Earth has been
repeatedly subjected to glaciation many times more extensive than the
areal distribution of present-day glaciers. More recent evidence, from
geochronological evidence (isotopic age dating), has shown that the last
continental-size glaciers in Europe, Asia, and North America were still
melting away only 10,000 years ago. These findings have caused scien-
tists and nonscientists alike to ask themselves two questions with pro-
9
Mount St. Helens, Washington, at about noon on May 18, 1980: The billowing eruption plume
of volcanic ash (tephra) and other volatiles emanates from the 1-mile-wide (1 1/2 kilometers)
summit crater and extends well into the stratosphere. Volcanic dust in the stratosphere can
reduce the amount of solar energy reaching the Earth's surface. This can result in climatic
cooling if such dust veils persist for several months or years (oblique aerial photo by Robert
M. Krimmel).
10
found implications: What caused the continental glaciers to advance and
retreat, and because there have been so many glacial advances within the
past 3 million years, is the world still emerging from the last glacial
retreat or are we already heading back into the next glacial advance?
Because variation in climate causes glaciers to advance or retreat,
glaciers can serve as excellent indicators of climatic change. Geologists
and other scientists study sedimentary deposits on land and in the sea to
determine how long glacial intervals lasted, the frequency of repetition,
the length of interglacial intervals, the variation in ocean surface tempera-
ture during the past 3 million years, and many other factors. These empir-
ical or observational data are then compared with the various theories of
glaciation to attempt to ascertain the actual causes of glaciation and to
identify the clues to look for in determining whether we are still coming
out of or going back into a glacial interval.
Among the more prominent theories of events that have triggered
global climatic changes and lead to repeated glaciation are: (1) known
astronomical variations in the orbital elements of the Earth (the so-called
Milankovitch theory); (2) changes in energy output from the Sun; and (3)
increases in volcanism that could have thrown more airborne volcanic
material into the stratosphere, thereby creating a dust veil and lowered
temperatures.
The years 1980, 1981, and 1982, for example, saw several major vol-
canic eruptions adding large quantities of particulate volcanic material
and volatiles to the stratosphere, including the catastrophic eruption of
Mount St. Helens, Wash., on May 18, 1980, and a large eruption of
Mount Hekla, Iceland, on August 17, 1980. The 1982 series of eruptions
from El Chichón volcano, Mexico, caused death and destruction in the
populated area around the volcano, but a further reaching impact may
result from the effect on Earth's climate because of the enormous ejection
of volcanic material into the stratosphere.
The potential climatic effect of the Laki volcanic eruption in Iceland
in 1783, the largest effusive (lava) volcanic eruption in historic time, was
noted by the diplomat-scientist Benjamin Franklin in 1784, during one of
his many sojourns in Paris. Franklin concluded that the introduction of
large quantities of volcanic particles into the Earth's upper atmosphere
could cause a reduction in surface temperature, because the particles
would lessen the amount of solar energy reaching the Earth's surface. The
11
Landsat image of northwestern Greenland on July 29, 1976, shows the well defined edge of
the Greenland Ice Sheet in the lnglefield Land area and numerous outlet glaciers emptying
into fiords. Sea ice fills the Nares Strait between Greenland and Ellesmere Island, Northwest
Territories, Canada (NASA image 2554-17283).
12
Landsat image of the McMurdo Sound area, Antarctica, location of the primary U.S. scien-
tific and logistics base in Antarctica: This image was used for the first Landsat image map of
Antarctica (1:500,000 scale), published by the U.S. Geological Survey in 1978 (NASA image
1174-19433, January 13, 1973).
13
Sketch map of North
America shows the
approximate areal
extent of the conti-
nental ice sheet at
its maximum. Also
shown is the postu-
lated coastline of
North America dur-
ing this glacial maxi-
mum and the pre-
sent-day shoreline
(dashed line) (from
USGS Yearbook, FY
1979).
14
15
catastrophic eruption of the Tambora volcano, Indonesia, in 1815 was fol-
lowed by a so-called "year-without-a-summer." In New England, for
example, frost occurred during each of the summer months in 1816.
Some of the observational evidence matches certain aspects of these
three theories and other theories as well. Whatever the actual cause or
causes of climatic change, the irrefutable fact is that repeated periods of
glaciation have occurred, and that the last such glacial interval ended in
the geologically recent past—at the dawn of human civilization.
Long-term variations in climate are difficult to measure because of the
rather short period of time in which scientifically valid meteorological
observations have been made. For example, most weather stations in
North America have observational records of less than 100 years. Long-
term variations in climate, however, are measured in decades, centuries,
and even millenia. This is one of the reasons why glaciers can be such
valuable indicators of climate. Glaciers tend to "average" out the short
term meteorological variations and reflect longer term variations which
Landsat image of Vatnajökull, Sept. 22, 1973, the largest—3,200 square miles (8,300 square
kilometers)—icecap in Iceland. Repetitive Landsat images of Vatnajökull, acquired since 1972,
have enabled glaciologists to monitor dynamic changes of this icecap in a time-lapse manner
(NASA image 1426-12070).
16
take place over several decades or centuries. Large ice sheets such as in
Greenland and Antarctica have even greater response times, probably
over several millenia (thousands of years) or tens of millenia.
Most glacial ice is encompassed in the two largest ice sheets,
Antarctica and Greenland, which together contain an estimated 97 per-
cent of all the glacial ice and 77 percent of the freshwater supply of the
planet. During a maximum global advance of glaciers, however, it is esti-
mated that North America contained volumetrically more ice than the
combined present-day total of Antarctica and Greenland, and that sea
level dropped by as much as 300 feet (90 meters). If all the present
glacial ice were to melt from Antarctica and Greenland, the oceans would
rise another 300 feet (90 meters) and inundate most of the coastal cities
of the world. Some glaciologists have suggested that the West Antarctic
Ice Sheet is inherently unstable and could suddenly surge forward under
climatic conditions similar to the present time, resulting in a 7 to 20 feet
(2-6 meters) global rise in sea level, depending on the size of the surge.
Until the launches in 1972, 1975, 1978, and l982 of the Landsat series
of spacecraft, glaciologists had no accurate means of measuring the areal
extent of glacial ice on Earth. Landsat 1, 2, and 3 multispectral scanner
(MSS) images, obtained from an orbital altitude of 570 miles (920 kilo-
meters), covered about the same area, 10,000 square miles (34,000 square
kilometers) every 18 days, and had a pixel (picture element) resolution of
about 260 feet (80 meters). Such satellite images provide a means for
delineating the areal extent of ice sheets and icecaps and for determining
the position of the termini of valley, outlet, and tidal glaciers on a com-
mon base of data for the entire globe. To take advantage of this data, a
"Satellite Image Atlas of Glaciers" is being prepared by the U.S.
Geological Survey in association with a number of other U.S. and foreign
scientific organizations. If Landsat-type surveys of the planet are contin-
ued for several decades, a means of monitoring long-term changes in
glacial area will also become possible—thereby giving us a way of moni-
toring global climate change.
Iceland, an island in the North Atlantic at about 65º North latitude, is
about the size of the Commonwealth of Virginia or about 40,000 square
miles (103,000 square kilometers). About 10 percent of the area of
Iceland is covered by glaciers, mostly occurring as icecaps of various
sizes, the largest of which is Vatnajökull, with an area of about 3,200
square miles (8,300 square kilometers). Six other glaciers have areas in
excess of 19 square miles (50 square kilometers). Many of the icecaps of
17
A thousand-year history of Iceland’s temperature (from Polar Regions Atlas, May 1978, CIA).
18
Iceland, such as Vatnajökull, Langjökull, Hofsjökull, Myrdalsjökull, and
Eyjafjallajökull, are extremely dynamic, with heavy annual accumula-
tions of snow—over 20 feet (6 meters) per year in the interior of
Vatnajökull. Rapid movement is nearly 6 feet (2 meters) per day in one of
the outlet glaciers of Vatnajökull, and extensive melting occurs at lower
elevations.
For a variety of reasons the glaciers of Iceland are well suited to serve
as an indicator of changes in climate in at least the Northern Hemisphere.
The historical record of pre-1900 observations has been well documented
over the years by several Icelandic scientists such as Thoroddsen and
Thorarinsson. The Danish Geodetic Survey began to survey and produce
maps of Iceland in the early part of the 20th century just after the end of
what is now called "The Little Ice Age," the cool climatic period between
about the mid-1500's and the late 1800's. Many of the terminal moraines
deposited by Iceland's glaciers most distant from the present-day ice mar-
gins (termini) were formed during the latter part of the 19th century. The
warmer first half of the 20th century has seen all of Iceland's glaciers
diminish in size in response to this period of climatic warming. For
example, Glámujökull, an ice cap in northwest Iceland, which appeared
on late 19th century and early 20th century maps with an area of 89
square miles (230 square kilometers) and 1.7 square miles (4.5 square
kilometers), respectively, has subsequently completely disappeared and
no longer appears on modern maps.
U.S. military maps were made during the 1940's, and a revised map
series is presently in production. The Iceland Geodetic Survey has also
published revised maps and has begun a new series of orthophotomaps in
association with the United States. Landsat images of Iceland permit an
excellent means of monitoring changes in the area of Icelandic glaciers at
more frequent intervals. Already, Landsat images of Iceland have been
used to good advantage by U.S. Geological Survey and Icelandic scien-
tists to document changes resulting from two glacial surges; the velocity
of an outlet glacier has been measured, and existing maps have been
revised.
According to Milankovitch and other 20th century theoretical climatol-
ogists, the glaciers in the area around 65º North latitude are especially
sensitive to astronomical variations in the orbital elements of the Earth.
In the Northern Hemisphere, glaciers on Baffin Island, Canada; in the
Alaska Range, Alaska; in the southern tip of Greenland; in Iceland; and
in Norway are at the right location. Except for Greenland, with its mas-
19
sive ice sheet, all the other geographic areas mentioned contain only rem-
nants of a once far more extensive glacial ice cover during the
Pleistocene. The glaciers of Iceland, as with some of those in these other
areas, are important as long-term indicators of climatic change because of
their latitudinal location and because they are apparently just large
enough not to be affected by short-term climatic variation yet are small
and dynamic enough to respond to changes caused by climatic variation
over several decades. Landsat images of Iceland and other areas at 65º
North latitude are providing a practical and cost-effective means of mak-
ing a rapid inventory of changes in glacial area.
The Earth can be considered a natural "spaceship" as it and other plan-
ets and stars of the galaxy travel through the universe. Climate is one
aspect of the planetary environment which has an impact on every living
thing; even a small change in climate can have a devastating effect on
plant and animal life and on humans and their economies. Because cli-
matic changes have global significance, scientists judiciously search for
the correct clues to these changes. This search often requires making
observations in remote areas—both on land and in the sea.
Only recently have scientific tools been developed that can make the
necessary observations. With improved technology for extracting cores
from the sea bottom and with existing and planned Earth resources sur-
vey satellites, geologists, glaciologists, and other scientists now have the
tools to study and monitor a variety of environmental factors and phe-
nomena. Many decades of observations by many scientists will be neces-
sary, however, to begin to unravel the climate-glacier puzzle. But a start
has been made to try to understand the enigma of climatic change and to
understand the response of glaciers to such change. In turn, by studying
the response and changes in glaciers, we can better understand—and
anticipate—the range of past and possible future climatic changes.
Scientists of the U.S. Geological Survey are among those who are deeply
involved in the study of the many facets of an incredibly complex envi-
ronmental problem, one which has extraordinary significance to the eco-
nomic well being of human societies.
Changes in climate over time produce variations in seasonal and annu-
al temperature and precipitation at different latitudes, a fact confirmed
by the geologic record and by meteorological observations during the
past 200 years or so. Floods, droughts, higher space heating and cooling
costs, variations in agricultural yield, higher snow removal costs, changes
in sea level, and variation in length of time of ice-free conditions in navi-
20
Oblique aerial photo of Muir Glacier Bay National Monument, Alaska.
gable waterways have an impact on the economics of various human
endeavors. The monitoring of glaciers gives scientists one of the most
important indicators in determining whether observed climatic change is
regional or global. This knowledge can then be used by governments to
make long-range plans to better cope with the economic impact of such
climatic changes.
21
As the Nation's principal conservation agency, the
Department of the Interior has responsibility for
most of our nationally owned public lands and nat-
ural resources. This includes fostering the wisest
use of our land and water resources, protecting our
fish and wildlife, preserving the environmental and
cultural values of our national parks and historical
places, and providing for the enjoyment of life
through outdoor recreation. The Department
assesses our energy and mineral resources and works to assure that their
development is in the best interests of all our people. The Department also
has a major responsibility for American Indian reservation communities
and for people who live in Island Territories under U.S. administration.
This publication is one of a series of general interest publications prepared
by the U.S. Geological Survey to provide information about the earth
sciences, natural resources, and the environment. To obtain a catalog of
additional titles in the series "General Interest Publications of the U.S.
Geological Survey," write:
USGS Information Services
Box 25286, Federal Center
Denver, CO 80255
