Glaciers and Glaciology of Alaska: Anchorage to Juneau, Alaska July 21-29, 1989

74 Pages·2012·9.37 MB·English

Glaciers and Glaciology
of Alaska
Anchorage to Juneau, Alaska
July 21-29, 1989
Field Trip Guidebook T301
Leaders:
Robert M. Krimmel Mark F. Meier
American Geophysical Union, Washington, D~C.
Copyright 1989 American Geophysical Union
2000 Florida Ave. N.W., Washington, D.C. 20009
t
ISBN: 0-87590-596-X
Printed in the United States of America
Columbia Glacier. near Valdez, Alaska, has been undergoing rapid retreat since the early
1980's. For at least the previous century this glacier terminus was stable at a position
on a terminal moraine shoal (the approximate crest of which is shown as a heavy dashed
line) over which the water depth is no greater than about 30 meters. Water south of the
moraine shoal is over 200 meters deep, and in the forebay (the area between the moraine
shoal and the terminus ice cliff) the water is up to 330 meters deep. The forebay is
packed with floating ice, some of these icebergs have had a volume of over one million
cubic meters. The large icebergs can not cross the moraine shoal, and break up within the
I
forebay. This glacier does not float. The portion of the glacier seen in this vertical
photograph moves up to 15 meters per day. That movement is more than compensated for by
calving, resulting in net glacier retreat. Successive terminus positions are indicated on
the photograph. A team of glaciologists from the U.S. Geological Survey is documenting
this rapid retreat. .
ICC FIELD TRIP T301:
GLACIERS AND GLACIOLOGY OF ALASKA
TABLE OF CONTENTS
INTRODUCTION•••••••••••••••••••••••••• Page 1
oj ••••••••••••••••••••••••••••,.
GLACIERS••••••••••••••••••••••••'•••••••,•••••••••••'•••• Page 3
oj •••••••••••••
ANCHORAGE TO WHITTIER•••••••••••••••••••••••••••••••••••••••••••••••Page 8
PRINCE WILLIAM SOUND•••••••••••••••••••••••••••••••••••••••••••• ~ •••Page 10
VALDEZ TO YAKUTAT BY AIR Page 23
YAKUTAT TO GUSTAVUS BY AIR••••••••••••••••••••••••••••••••••••••••••Page 47
GLACIER BAy ~ ••PageS1
JUNEAU ICEFIELD '•••••Page 54
REFERENCES , Page 54
APPENDIX••••••••••••••••••••••••••••••••••••••' Page .56
v
Leaders:
Robert M. Krimmel
U.S. Geological Survey
Ice and Climate Project
University of Puget Sound
Tacoma, WA 98416
Mark F. Meier
Inst. of Arctic and Alpine Research
Campus Box 450
University of Colorado
Boulder, CO 80309
vii
Glaciers and Glaciology
of Alaska
IGC FIELD TRIP T301:
GLACIERS AND GLACIOLOGY OF ALASKA
Robert M. Krimmel
U.S. Geological Survey, Ice and Climate Project
University of Puget Sound, Tacoma, Washington
Mark F. Meier
Institute of Arctic and Alpine Research
University of Colorado, Boulder
Abstract. The field trip Glaciers and INTRODUCTION
Glaciology of Alaska for the 28th
International Geological Congress will begin This guidebook provides a general overview
in Anchorage on 21 July 1989 and end in of the pr~ncipal glaciological features and
Juneau on 29 July 1989. Travel will be by research of southern Alaska. The trip will
bus, charter boat, and charter aircraft, with cover more than 1,000 km by road, boat, and
stops at Portage Glacier, Whittier, Columbia air (Fig. 1 and 2). There will only be a few
Glacier, Valdez, Yakutat, Glacier Bay, and stops during which detailed accounts will be
Juneau. given of specific features. More often the
There is nearly 75,000 square kilometers features will only be seen at a distance from
of glacier ice in Alaska. The major portion a boat, or briefly, from a plane. The route
is concentrated in the Chugach and St. Elias selected emphasizes the glacial features that
Ranges through which the field trip may be seen, but actual observation will be
traverses. In the region are major advancing extremely weather-dependent.
and retreating tidewater glaciers, major This guidebook gives some general
piedmont glaciers, and surging glaciers. information about glaciers so that the
Columbia Glacier is in the early stage of a participants will know what features are
drastic retreat; Hubbard Glacier is advancing important, and then discusses in more detail
and recently dammed a major fjord; Variegated calving and surging glaciers. The "road log"
Glacier recently made a major surge; the which follows the general glaciological
glaciers in Glacier Bay underwent a drastic information is fairly general due to
retreat during the last two centuries, uncertainties in the exact features that will
resulting in a glacially formed landscape be visited. Within the log are detailed
that has only a recent vegetation cover. sections concerning Columbia and Variegated
Southern Alaska has a diverse history, Glaciers. It is at these two glaciers that
climate, botany, and zoology. Many of the the most significant work in North America on
original native cultures of North America calving and surging glaciers has been done.
came together in Prince William Sound. We will spend more time at Columbia Glacier
Russian fur traders and gold miners came and than any other specific glacier. We will see
went, and fishing and tourism dominate the Variegated Glacier from the air, and may see
present economy. The climate of southern other glaciers in the process of actively
Alaska is maritime, with substantial surging. Some nonglaciological information
precipitation and mild temperatures. The is included in the log. An appendix at the
topography has a strong effect on the end of the guidebook includes more detailed
maritime air masses, resulting in heavy information on nong1acio1ogica1 subjects:
snowfalls and the development of active human history, history of glaciology,
glaciers ~n seaward-facing slopes. The climate, vegetation, marine mammals, land
succession of vegetation is remarkable, animals, and birds. A large portion of this
ranging from barren, recently ice-free areas trip will be used in travel between glaciers,
to forest-suffocating muskeg. Southern and the nong1aciologica1 subjects are
Alaska also is known for an abundance of included to help make these periods of travel
marine mammals, including sea otter, seal, more rewarding to all participants.
sea lion, porpoise, and various species of Landsat images are convenient source
whales. On land, bear, moose, deer, material to illustrate large geomorphological
wolverine, and mountain goat are common; features of Alaska. Notable features are
other wildlife is abundant also. indicated on the Landsat satellite images
T301: 1
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GULF OF ALASKA
50 0 50 100 150MILES
50 0 50 100 150KILOMETRES
FIGURE 1 The western portion of the route of the Glaciers and Glaciology of Alaska 28th
International Geological Congress field trip. The trip begins in Anchorage and ends in
Juneau after travelling by bus, boat, and plane to several communities and glaciers along
the route. Cities are indicated by a # symbol. A symbol G occurs at the location of the
termini of the indicated glaciers. The approximate route is delineated by a dashed
(-----) line. The boxes indicated by broad dashes (-- --) represent Landsat images that
are included in the tour guide. The numeral above each box indicates the figure number of
the respective Landsat image.
used as illustrations. Especially shorelines (water is dark in the near
interesting features are also illustrated infrared) and good definition of landforms.
with low-altitude oblique aerial photographs. Return beam vidicon (RBV) images are 90 km on
The location of major features are shown on a side with a 30 m pixel resolution at a
Figures 1 and 2, the location of other single panchromatic band in the visible
features are shown by letter designators on wavelengths. The RBV images frequently fail
the Landsat images. All Landsat images used to show shorelines, especially where the
in the guide predate 1982. With only a few water is sediment-laden. For this reason,
exceptions, there have not been changes in marine shorelines are highlighted with
the glaciers that can be detected at the additional linework on the RBV images
Landsat picture element (pixel) resolution of displayed in this guide. All of the images
30 or 79 m. were chosen to be nearly cloud-free and at a
Two types of Landsat images are used. time when snow covered only the accumulation
Multispectral scanner (MSS) images encompass zones of the glaciers. There are two scales
an area of 185 km on a side with a 79 m pixel of Landsat images used as figures. For the
resolution. Although four spectral bands are images identified as MSS each side is 185 lon,
imaged, this guide uses only band 7 (0.8-1.1 and for images identified as RBV each side is
~m), which usually gives well-defined 90 km. Each Landsat image is oriented so
T301: 2
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GULP OF ALASKA
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50 o 50 100
FIGURE 2 The eastern portion of the route of the field trip.
that true north is turned 150 counter size to those in Alaska are located in the
clockwise from up. Features of high Canadian Queen Elizabeth Islands and in the
interest, both along the route and elsewhere, Himalaya-Karakorum region of central Asia.
are indicated. A circle around the feature It is not certain which is the largest
designator in the caption indicates that a glacier in Alaska. Glaciers, of course,
low-altitude aerial photograph is also used change in size, and thus the "largest" may
as an illustration in the guide. shrink to become the second largest or vice
versa. More important though, different
measuring techniques may be used by different
GLACIERS observers. Field (1975) considered the
Bering Glacier to be the largest (5,800 km2)
The glaciers of southern Alaska in Alaska, but Dennis Trabant (U.S.
collectively form one of the major ice masses Geological Survey, written commun., 1988)
of the world. It is estimated that there are carefully measured the area of both Bering
74,700 km2 of ice in Alaska (Post and Meier, Glacier and the Seward-Malaspina Glacier
1980); more than one-half of this area is in complex from the best available maps and
the major coastal glacier systems including found them to be equal in area, 4,600-4,700
the Bering, Seward-Malaspina, and Hubbard km2, to the accuracy of his measurement. The
Glaciers. Together with the adjacent ice large difference between the Field and
masses of Yukon, Northwest Territories, and Trabant areas is an indication of the
British Columbia, the total glacierized area problems in measuring glacier area rather
is more than 100,000 km3• Considering the than a change in glacier area between the
entire Earth, only the Antarctic and measurements. It maybe said with certainty
Greenland ice sheets have significantly more that both these glaciers are large by all but
ice than Alaska. Ice masses of comparable Greenland and Antarctic standards.
T301: 3
w140 W136 W132
o
\D
Z
Skagway ~
<. ,
\...
'....
GULP OF ALASKA
co
LI\
Z 50 o 50
50 o 50 100
FIGURE 2 The eastern portion of the route of the field trip.
that true north is turned 150 counter size to those in Alaska are located in the
clockwise from up. Features of high Canadian Queen Elizabeth Islands and in the
interest, both along the route and elsewhere, Himalaya-Karakorum region of central Asia.
are indicated. A circle around the feature It is not certain which is the largest
designator in the caption indicates that a glacier in Alaska. Glaciers, of course,
low-altitude aerial photograph is also used change in size, and thus the "largest" may
as an illustration in the guide. shrink to become the second largest or vice
versa. More important though, different
measuring techniques may be used by different
GLACIERS observers. Field (1975) considered the
Bering Glacier to be the largest (5,800 km2)
The glaciers of southern Alaska in Alaska, but Dennis Trabant (U.S.
collectively form one of the major ice masses Geological Survey, written commun., 1988)
of the world. It is estimated that there are carefully measured the area of both Bering
74,700 km2 of ice in Alaska (Post and Meier, Glacier and the Seward-Malaspina Glacier
1980); more than one-half of this area is in complex from the best available maps and
the major coastal glacier systems including found them to be equal in area, 4,600-4,700
the Bering, Seward-Malaspina, and Hubbard km2, to the accuracy of his measurement. The
Glaciers. Together with the adjacent ice large difference between the Field and
masses of Yukon, Northwest Territories, and Trabant areas is an indication of the
British Columbia, the total glacierized area problems in measuring glacier area rather
is more than 100,000 km3• Considering the than a change in glacier area between the
entire Earth, only the Antarctic and measurements. It maybe said with certainty
Greenland ice sheets have significantly more that both these glaciers are large by all but
ice than Alaska. Ice masses of comparable Greenland and Antarctic standards.
T301: 3