Glaciers of Antarctica: Ice Shelves, Ice Rises, Ice Rumples, and Ice Dolines, Study notes of Topography

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Satellite Image Atlas

of Glaciers of the World

A N T A R C T I C A

United States Geological Survey

Professional Paper 1386 - B

Cover: Landsat 1 MSS digitally enhanced false-color compo- site image of the Sentinel Range, Ellsworth Mountains, and Rutford Ice Stream. See page B 122.

U.S. DEPARTMENT OF THE INTERIOR

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY

Dallas L. Peck, Director

First printing 1988 Second printing 1993

Library of Congress Cataloging in Publication Data

Satellite image atlas of glaciers ofthe world.

(U.S. Geological Survey professional paper ; 1386) Bibliography: p. Supt. of Docs. no.: I 19.16:1386-B Contents: Trevor J. Chinn, and Landsat images of Antarctica, by Richard S. Williams, Jr., and Jane G. Ferrigno.

1. Glaciers-Remote sensing. sional paper ; 1386. GB2401.72.R42S28 1988 551.3‘12 87 - 600497

B. Antarctica I by Charles Swithinbank ; with sections on the “dry valleys” of Victoria Land, by

I. Williams, Richard S. II Ferrigno, Jane G. III Series: Geological Survey profes -

For sale by the U.S. Geological Survey, Map Distribution, Box 25425, Bldg. 810, Federal Center, Denver, CO 80225

The editors regret that the scanning software used to produce this Web version of the published document introduced several irregularities in the spacing and appearance of text and tables that could not be removed.

Foreword

On 23 July 1972, the first Earth Resources Technology Satellite (ERTS 1 or Landsat 1) was successfully placed in orbit. The success of Landsat inaugurated a new era in satisfying mankind's desire to better understand the dynamic world upon which we live. Space - based obser - vations have now become an essential means for monitoring global changes. The short - or long - term cumulative effects of processes that cause significant changes on the Earth's surface can be documented and studied by repetitive Landsat images. Such images provide a perma - nent historical record of the surface of our planet; they also make possible comparative two-dimensional measurements of change over time. This Professional Paper demonstrates the importance of the ap - plication of Landsat images to global studies by using them to deter - mine the current areal distribution of glaciers on our planet. As images become available from future satellites, the new data will be used to document global changes in glacier extent by reference to the image record of the 1970's. Although many geological processes take centuries or even millenia to produce obvious changes on the Earth's surface, other geological phenomena, such as glaciers and volcanoes, cause noticeable changes over shorter periods. Some of these phenomena can have a worldwide impact and often are interrelated. Explosive volcanic eruptions can produce dramatic effects on the global climate. Natural or culturally induced processes can cause global climatic cooling or warming. Glaciers respond to such warming or cooling periods by decreasing or increasing in size, thereby causing sea level to rise or fall. As our understanding of the interrelationship of global processes improves and our ability to assess changes caused by these processes develops further; we _will learn how to use indicators of global change, such as glacier variation, to more wisely manage the use of our finite land and water resources. This Professional Paper is an excellent ex - ample of the way in which we can use technology to provide needed earth - science information about our planet. The international collabo- ration represented by this report is also an excellent model for the kind of cooperation that scientists will increasingly find necessary in the future in order to solve important earth - science problems on a global basis.

Dallas L. Peck Director, U.S. Geological Survey

FOREWORD III

[Signature]

About this Volume

U.S. Geological Survey Professional Paper 1386, Satellite Image Atlas of Glaciers of the World, contains eleven chapters designated by the letters A through K. Chapter A is a general chapter containing introductory material and a discussion of the physical characteristics, classification, and global distribution of glaciers. The next nine chap - ters, B through J, are arranged geographically and present glaciologi- cal information from Landsat and other sources of data on each of the geographic areas. Chapter B covers Antarctica; Chapter C, Greenland; Chapter D, Iceland; Chapter E, Continental Europe (except for the European part of the Soviet Union), including the Alps, the Pyrenees, Norway, Sweden, Svalbard (Norway), and J a n Mayen (Norway); Chap - ter F, Asia, including the European part of the Soviet Union, China (P.R.C.),India, Nepal, Afghanistan, and Pakistan; Chapter G, Turkey, Iran, and Africa; Chapter H, Irian Jaya (Indonesia) and New Zealand; Chapter I, South America; and Chapter J , North America. The final chapter, K, is a topically oriented chapter that presents related glacio- logical topics. The realization that one element of the Earth’s cryosphere, its glaciers, was amenable to global inventorying and monitoring with Landsat images led to the decision, in late 1979, to prepare this Profes- sional Paper, in which Landsat 1,2, and 3 multispectral scanner (MSS) and Landsat 2 and 3 return beam vidicon (RBV) images would be used to inventory the areal occurrence of glacier ice on our planet within the boundaries of the spacecraft’s coverage (between about 81° north and south latitudes). Through identification and analysis of optimum Landsat images of the glacierized areas of the Earth during the first decade of the Landsat era, a global benchmark could be established for determining the areal extent of glaciers during a relatively narrow time interval (1972 to 1982). This global “snapshot” of glacier extent could then be used for comparative analysis with previously published maps and aerial photographs and with new maps, satellite images, and aerial photographs to determine the areal fluctuation of glaciers in response to natural or culturally induced changes in the Earth’s cli - mate. To accomplish this objective, the editors selected optimum Landsat images of each of the glacierized regions of our planet from the Landsat image data base at the EROS Data Center in Sioux Falls, South Da- kota, although some images were also obtained from the Landsat image archives maintained by the Canada Centre for Remote Sensing, Ottawa; Ontario, Canada, and by the European Space Agency in Kiruna, Sweden, and Fucino, Italy. Between 1979 and 1981, these optimum images were distributed to an international team of more than 50 scientists who agreed to author a section of the Professional Paper concerning either a geographic area or a glaciological topic. In addition to analyzing images of a specific geographic area, each author was also asked to summarize up - to - date information about the glaciers within the area and to compare their present areal distribution with historical information (for example, from published maps, reports, pho- tographs, etc.) about their past extent. Because of the limitations of Landsat images for delineating or monitoring small glaciers in some geographic areas, either on the basis of inadequate spatial resolution, lack of suitable seasonal coverage, or absence of coverage, information on areal distribution is necessarily derived from ancillary sources. Completion of this atlas will provide an accurate regional inventory of the areal extent of glaciers on our planet during the 1970’s. Richard S. Williams, Jr. Jane G. Ferrigno Editors

VI ABOUT THIS VOLUME

CONTENTS

Page

III

VI B 3 3 4 12

Foreword ------------------------------------------------------------------- Preface ---------------------------------------------------------------------- About this volume --------------------------------------------------------- Abstract --------------------------------------------------------------------- Introduction ---------------------------------------------------------------

V

Geographic place - names -------------------------------------------- Definitions ------------------------------------------------------ Dimensions ------------------------------------------------------

FIGURE 1. Map showing extent of 1:250,000 - scale and larger scale mapping in Antarctica produced by aerial photo- grammetric and satellite - image map techniques - - - - 2

2

5

6 6

2. Apollo 17 photograph of the Earth and part of
3. Oblique aerial photograph of the ice front in Okuma

Antarctica -----------------------------------------

Bay Ross Ice Shelf ---------------------------------------- 4 - 5. Photograph of:

4. An ice front on the Brunt Ice Shelf, Coats Land - - - -
5. An ice wall, Dorian Bay, Graham Land - - - - - - - - - - - -
6. An ice wall, Cape Norvegia, Princess Martha
7. Gipps Ice Rise, Larsen Ice Shelf, Graham Land --------
8. Ice rises and ice rumples, Wordie Ice Shelf, Graham
9. McDonald Ice Rumples, Brunt Ice Shelf, Coats

6 - 10. Oblique aerial photograph of:

7 8

9

10 11

4 12

Coast -------------------------------

Land -----------------------------

Land ---------------------------------

10. An ice doline, Princess Astrid Coast---------------------
11. Frequency of coastal types around Antarctica -------------
12. Morphometric data for Antarctica ----------------------------

T ABLE

3. Regional ice data -------------------------------- (^) 12

The Transantarctic Mountains --------------------------------------- Western margin of Ross Ice Shelf -------------------------

The ‘dry valleys’ of Victoria Land, by

Northern Victoria Land - -------------------------------------------

13 13 32

39 41

McMurdo Sound area ----------------------------------------

Trevor J. Chinn ------------------------------------

FIGURE 11 - 12. Annotated NOAA 6 advanced very high resolution radiometer image of:

11. The McMurdo Sound area and environs -----------------
12. A part of the Transantarctic Mountains ------------------
13. Reedy Glacier at the eastern extremity of the
14. Scott Glacier, Queen Maud Mountains -----------------

16, Axel Heiberg Glacier, Queen Maud Mountains -----

17. The upper part of Liv Glacier, Queen Maud
18. Shackleton Glacier, Queen Maud Mountains ---------
19. The northwestern end of the Queen Maud Mountains bordering on Beardmore Glacier -------------------
20. The mouth of Beardmore Glacier^ ------------------------

14 15 13 - 22. Oblique aerial photograph of: Queen Maud Mountains --------------------------------- 16

18 19

15. Amundsen Glacier, Queen Maud Mountains ----------

Mountains ------------------------------------------------ 20 21

22 23

21. Nimrod Glacier -------------------------------- ------------------------ 24
22. Byrd Glacier ---------------------------- 25

CONTENTS VII

Page

52. Annotated Landsat 1 MSS image of the source of 53. Annotated Landsat 1 MSS digitally enhanced false - color

Lambert Glacier B 69

composite image mosaic of Lambert Glacier and

54. Annotated Landsat 1 MSS image of the left bank of 55. Uncontrolled Landsat MSS image mosaic of the Amery Ice Shelf and the terminus of the Lambert Glacier, East Antarctica ------------------------------------------- 47

76

78

80 81

Amery Ice Shelf --------------------------------------- 70

Amery Ice Shelf ------------------------------------ 73

56. Annotated Landsat 1 MSS image of Mac. Robertson Land 57. Annotated Landsat 1 and 2 MSS image mosaic of

at Mawson Station -------------------------------------

Enderby Land ---------------------------------------------- 58 - 59. Annotated Landsat 1 MSS image of:

58. Alasheyev Bight at Molodezhnaya Station ----------- 59. Lützow - Holm Bay at Station ----------- 60. Annotated Landsat 1 MSS digitally enhanced false - color composite image of ablation areas of the Queen 82

83

Fabiola Mountains---------------------------------------

The Atlantic Ocean sector ------------------------------------------

Princess Ragnhild Coast, Princess Astrid Coast, Borg Massif, and Fimbul Ice Shelf, Queen Maud Land -------------------------------------------------------- 83 Riiser - Larsen Ice Shelf and Shackleton Range ------------ 97 Filchner and Ronne Ice Shelves -------------------------- 101

84

85

87

88

89 90 91

FIGURE 61. Annotated Landsat 1 MSS image of the Sør - Rondane

62. Annotated Landsat 1 MSS false - color composite image of the Orvin and Wohlthat Mountains -------------------- 63. Annotated Landsat 2 MSS image of Lazarev Ice Shelf at

Mountains -----------------------------------------------------

Novolmarevskaya ------------------------------------------- 64 - 67. Oblique aerial photograph of:

64. The ablation area surrounding Schirmacher Hills ---- 65. The tidal sea lake at the western end of Schirmacher Hills ------------------------------------------------------ 66. Nunataks in Queen Maud Land -------------------------- 67. The Heimefront Range in Queen Maud Land -----------

radiometer three - image mosaic of New Schwaben -

68. Annotated NOAA 7 advanced very high resolution land, Queen Maud Land ---------------------------------- 93 69. Annotated Landsat 1 and 2 MSS image mosaic of Jutulstraumen Glacier and environs, Princess 94

image of the Jutulstraumen Glacier and environs ----- 95

96

96

98

74. The upper Slessor Glacier, Queen Maud Land -------- 99 75. Slessor Glacier and the Shackleton Range ------------- 100 76. Filchner Ice Shelf and the Grand Chasms -------------- 102 77. Ronne Ice Shelf and Korff Rise - - - - - - - - - - - - - - - - - 104

105

Martha Coast ------------------------------------------------

70. Landsat 2 MSS digitally enhanced false-color composite

71 - 72. Oblique aerial photograph of:

71. The Berg Massif --------------------------------------------- 72. Neumayer Cliffs, in the northeastern part of Kirwan Escarpment ------------------------------------------ 73 - 77. Annotated Landsat 1 MSS image of: 73. Stancomb - Wills Glacier ------------------------------------

The Antarctic Peninsula-------------------------------------------

FIGURE 78. Annotated Landsat 2 MSS image of the northern extremity of the Antarctic Peninsula ------------------- 106

79. Annotated Landsat 3 MSS image of Graham Land plateau and the Larsen Ice Shelf ------------------------- 108 80. Oblique aerial photograph of Doumer, Wiencke, and Anvers Islands ----------------------------------------------- 109

CONTENTS IX

Page 81 - 82. Annotated Landsat 3 MSS image of:

81. Marguerite Bay and the west coast of Graham 82. Northern Palmer Land and Wordie Ice Shelf --------- 83. Buffer Ice Rise and the mouth of Fleming Glacier, 84. Tidal sea lakes, George VI Ice Shelf ----------------- 85. Spartan Glacier, Alexander Island----------------------

Land ------------------------------- B 112 83 - 85. Oblique aerial photograph of: Graham Land ------------------------------------------ 113 114 115

.

86. Annotated Landsat 1 MSS image of Palmer Land 87. Annotated Landsat 3 MSS image of Alexander

and George VI Ice Shelf ------------------------------- 116

Island --------------------------------------------------------- 118 The Pacific Ocean sector------------------------------------------------ (^) 119 Ellsworth Land and Ellsworth Mountains--------------- 119 Marie Byrd Land -------------------------------------------- 124 Eastern Margin of R o s s Ice Shelf ------------------------- 135

FIGURE 88. Annotated Landsat 1 MSS digitally enhanced false - color composite image of the English Coast of Palmer 120

Carlson Inlet --------------------------- 121

Land -----------------------------------------------------------

89. Annotated Landsat 1 MSS image of Fowler Ice Rise and 90. Annotated Landsat 1 MSS digitally enhanced false- color composite image of the Sentinel Range, Ellsworth Mountains, and Rutford Ice Stream ---------- 91. Oblique aerial photograph of the Sentinel Range, Ellsworth Mountains --------------------------------------- 92. Annotated Landsat 1 MSS image of Pine Island Glacier 93. Annotated Landsat 1 MSS image mosaic of Thwaites 94. Annotated Landsat 2 MSS images of selected volcanoes 95. Annotated Landsat 1 MSS image of Mount Takahe --------

122

123

and the Walgreen Coast ------------------------- (^) 125

Glacier and Thwaites Iceberg Tongue, 1972 - 73 --------- 126 in Marie Byrd Land ------------------------- (^) 128 130

131 131

96 - 97. Oblique aerial photograph of:

96. Mount Takahe volcano ----------------------------- 97. Mount Hampton volcano ----------------------------------

X CONTENTS

SATELLITE IMAGE ATLAS OF GLACIERS OF THE WORLD

ANTARCTICA

By CHARLES SWITHINBANK 1

Abstract

Of all the world’s continents Antarctica is the coldest, the highest, and the least known. It is one and a half times the size of the United States, and on it lies 91 percent (30,109,800 km^3 ) of the estimated volume of all the ice on Earth. Because so little is known about Antarctic glaciers compared with what is known about glaciers in popu- lated countries, satellite imagery represents a great leap forward in the provision of basic data. From the coast of Antarctica to about 81°south latitude, there are 2,514 Landsat nominal scene centers (the fixed geographic position of the intersection of orbital paths and latitudinal rows). If there were cloud-free images for all these geographic centers, only about 520 Landsat images would be needed to provide complete coverage. Because of cloud cover, however, only about 70 percent of the Landsat imaging area, or 55 percent of the continent, is covered by good quality Landsat images. To date, only about 20 percent of Antarctica has been mapped at scales of 1:250,000 or larger, but these maps do include about half of the coastline. The area of Antarctica that could be planimetri- cally mapped at a scale of 1:250,000 would be tripled if the available Landsat images were used in image map production. This chapter contains brief descriptions and interpretations of features seen in 62 carefully selected Landsat images or image mosaics. Images were chosen on the basis of quality and interest; for this reason they are far from evenly spaced around the conti- nent. Space limitations allow less than 15 percent of the Landsat imaging area of Antarc- tica to be shown in the illustrations reproduced in this chapter. Unfortunately, a wealth of glaciological and other features of compelling interest is present in the many hundreds of images that could not be included. To help show some important features beyond the limit of Landsat coverage, and as an aid to the interpretation of certain features seen in the images, 38 oblique aerial photographs have been included. Again, these represent only a small fraction of the large number of aerial photographs now available in various national collections. The chapter is divided into five geographic sections. The first is the Transantarctic Mountains in the Ross Sea area. Some very large outlet glaciers flow from the East Antarctic ice sheet through the Transantarctic Mountains to the Ross Ice Shelf. Byrd Glacier, one ofthe largest in the world, drains an area of more than 1,000,000 km^2. Next, images from the Indian Ocean sector are discussed. These include the Lambert Glacier- Amery Ice Shelf system, so large that about 25 images must be mosaicked to cover its complex system of tributary glaciers. Shirase Glacier, a tidal outlet glacier in the sector, flows at a speed of 2.5 km a -l^. About 200 km inland and 200 km west of Shirase Glacier lie the Queen Fabiola (“Yamato”)Mountains, whose extensive exposures of ‘blue ice’ lay claim to being the world’s most important meteorite - collecting locality, with more than 4,700 meteorite fragments discovered since 1969. The Atlantic Ocean sector is fringed by ice shelves into which flow large ice streams like Jutulstraumen, Stancomb-Wills, Slessor, and Recovery Glaciers. Filchner and Ronne Ice Shelves together cover an area two-thirds the size of Texas. From the western margin of the Ronne Ice Shelf, the north-trending arc of the Antarctic Peninsula, with its fjord and alpine landscape and fringing ice shelves, stretches towards South America. The Pacific Ocean sector begins with the Ellsworth Mountains, which include the highest peaks (Vinson Massif at 4,897 m) in Antarctica. The area between the Ellsworth Moun- tains and the eastern margin of the Ross Ice Shelf is fringed with small ice shelves and some major outlet glaciers. One of these, Pine Island Glacier, was found from comparing 1973 and 1975 images to have an average ice-front velocity of 2.4 km a-l. This part of Antarctica contains many dormant volcanoes; the summits of several, such as Mount Takahe with its 8-km-wide summit caldera, protrude through the West Antarctic ice sheet. Five major ice streams, ‘A’ through ‘E,’ drain into the eastern margin of the Ross Ice Shelf. The orbital range of Landsat allows only the northernmost of these, Ice Stream ‘E,’ to be imaged. A final section of the chapter lists optimum Landsat images for each of the 2,514 nominal scene centers.

(^1) British Antarctic Survey.

ANTARCTICA B

Figure 1. - Extent of 1 :25O,OOO - -scale and larger scale mapping in Antarctica (shaded areas) produced by aerial photogrammetric and satellite-image map techniques.

Figure 2. - Apollo 17 color photograph of the Earth showing most of the continent of Antarc- tica. NASA photograph no. 72 - HC-928, courtesy of the NASA Public Information Of- fice, Washington, D.C.

B2 SATELLITE IMAGE ATLAS O F GLACIERS O F THE WORLD

Definitions

In contrast to other continents, there are few independent (separate)

local glaciers in Antarctica, that is to say glaciers having well-defined

boundaries. Thus it is important to bear in mind that the definition of

glacier used in this chapter includes ice sheets, ice shelves, ice rises, ice caps, ice piedmonts, outlet glaciers, and valley glaciers (Armstrong and others, 1973). In simple terms it can almost be said that there is only one glacier in Antarctica, although it is ten times the area of all

the rest of the world's glaciers put together. Glacier units are therefore

much harder to define here than in lower latitudes. It is for this reason

and also because of the lack of maps at a suitable scale that no glacier

inventory of Antarctica has yet been attempted (Swithinbank, 1980), except for an inventory of glaciers on James Ross Island and Vega

Island, which lie to the east of the Trinity Peninsula in the northern

part of the Antarctic Peninsula (Rabassa and others, 1982). There are similar unusual circumstances when discussing the Antarctic coastline. In other continents, except where glaciers extend into the ocean (for example, northeastern Canada, northwestern Greenland, or Svalbard) everyone knows what we mean by the term coastline. But in Antarctica there is more than one coastline (table 1 ).

TABLE 1.-Frequency of coastal types around Antarctica (from Drewry, 1983) Type Percent Ice shelf (ice front) ---------------------------------

Ice stream/outlet glacier (ice front or ice wall)- -

44 38 13 5 100

Ice walls - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Rock - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Total -----------------------------------

In the absence of sea ice, mariners would hold that the coastline is an

immovable barrier at the limit of navigation. There are, however, sev-

eral interpretations of this definition:

1. Almost half of the Antarctic coastline consists of ice front (ice

barrier), a vertical cliff from 2 to 50 m above sea level (figs. 3 and 4).

But the mariner will be surprised to find that at this coastline his

echosounder may show the depth of water to be between 100 m and

600 m. Here the ice sheet is afloat.

2. Approaching an ice wall, the mariner will see a vertical cliff re -

sembling an ice front. Here the ice sheet is aground. At this coastline

the echosounder may show the depth of water to be between 0 and

500 m. If the rock basement is at sea level the ice cliff is called a strand

ice wall (fig. 5); if below sea level it is called a neritic ice wall (fig. 6)

(Roberts and others, 1955).

3. Our mariner will have no difficulty in recognizing the coastline

where waves lap against a rocky shore. Only about 5 percent of the

Antarctic coast is like this.

4. When told that an ice-front coastline can retreat by 50 km in a

day by the calving of an iceberg, a lawyer might say that a floating

coastline is tantamount to a contradiction in terms. For legal purposes,

a coastline must be permanent; it is only permanent where the ice

sheet is grounded. Apart from definitions 2 and 3 above, the permanent coastline is represented by the inland boundary of ice shelves and

glacier tongues. It may be from 50 km to 800 km from the ice front, and

the lawyer will be disconcerted to learn that the depth of ice below sea

level there may be from 100 m to 2,000 m. But this coastline, like the

B4 SATELLITE IMAGE ATLAS OF GLACIERS OF THE WORLD

others, can generally be interpreted from Landsat images. On selected images (see figs. 47 and 63, for example) we have indicated with a dotted line the assumed position of the sub-ice coastline in order to draw attention to visible features we believe to be diagnostic. This coastline is referred to as the inland boundary of the ice shelves, or the grounding line, but it could with equal justification be called the flota - tion line. Some authors have called it the hinge line because tidal bending is taken up there.

5. If we find definitions 1,2, and 4 unsatisfactory on the ground that their coasts are ephemeral, we may favor the concept of a sub-ice coastline at which the rock rises up to sea level. But this coastline cannot be identified from satellite images, can only be found by radio - echosounding, and is unknown over 90 percent of its length.

Figure 3.-Oblique aerial photograph of the ice front in Okuma Bay, eastern edge of the Ross Ice Shelf and Shirase Coast, taken from an altitude of 1,500 m on 22 October 1961, looking west. The ice shelf flows from left to right at a speed of 350 m a-' (Personal com- mun. from Andre Flotron). The ice front is ap- proxjmately 20 m high. U. S. Navy trimetrogon aerial photograph no. 1 4 (TMA 822 F33) 2 from the Antarctic Map and photograph Li- brary, U.S. Geological Survey.

(^2) TMA is an abbreviation for Trimetrogon Antarctica. The number following TMA refers to the mission or sortie. A trimetrogon camera configuration includes three mapping cameras, a left oblique (F31). a vertical (F32), and a right oblique (F33), with reference to the flight path of the survey aircraft. Major post-World War II trimetrogon aerial survey operations in the Antarctic included U.S. Navy Operation Highjump (HJ), which used L, V, and R, and U.S. Navy Operation Deep Freeze (DF), which used 1, 2, and 3, for left oblique, vertical, and right oblique, respectively. Oblique aerial photographs have also been acquired during radio-echosounding surveys and are identified as RES (see figure 9, for example). In recent years, overlapping vertical aerial photographs have been ac - quired of specific field areas to support the preparation of conventional maps of such areas by stereophotogrammetric techniques. The U.S. Geological Survey's 1:50,000-scale topographic maps of the 'dry valleys' area are a good example of such modem maps.

as seen from a ship, Coats Land, on 5 January 1977. The cliff is generally 20 to 30 m high. Photograph by Charles Swithinbank, British Antarctic Survey.

The best pre - satellite description of the glaciers of Antarctica and the sub - Antarctic islands is that of Mercer (1967), who also reported on glacier variations (Mercer, 1962). Such is the size of Antarctica that the satellite imagery selected for reproduction in this chapter can only cover a very small proportion of the coastline and a few places of special interest inland. No usable scenes were found of the sub - Antarctic is- lands. By contrast, it was very difficult to select the best scenes of Antarctica from the hundreds available. A typical scene shows a fea- tureless expanse of snowy whiteness covering the whole frame. Bare rock, after all, covers a very small proportion of the surface area of the continent. However, many of the scenes contain a wealth of detail showing glaciological features that were unknown and unsuspected before the satellite images were studied. Certain glacier features are unique to the Antarctic and for this reason are inadequately treated in the “Illustrated Glossary of Snow and Ice” (Armstrong and others, 1973). Here we shall discuss in greater detail ice shelves, ice rises, ice rumples, and ice dolines. Nearly half of the coastline of Antarctica is fringed by ice shelves (see figs. 3 and 54). Ice shelves are floating ice sheets that rise and fall with the tide. Their thicknesses range from a minimum of about 10 m to a maximum of about 2,000 m, though most are in the 100 to 500 m range. They are nourished partly by the seaward extension of land glaciers, partly by the accumulation of snow on their upper surface, and partly by bottom freezing. They are dissipated mainly by the calving of icebergs from their seaward edges and by melting from their lower and, exception- ally, from their upper surfaces. Forward movement consists of one

Land, as seen from a ship on 13 December

1979. The ice wall is approximately 20 m high. Photograph by Charles Swithinbank, British Antarctic Survey.

Figure 6.-Annotated oblique aerial pho- tograph of an ice wall, Cape Norvegia, Princess Martha Coast, taken from an altitude of 2,500 m on 25 January 1951, looking south.

. The ice wall is approximately 30 m high. Pho- tograph no. DML^3 51 - 52 2323 by Sigvard Kjellberg, Norsk Polarinstituft, Oslo.

(^3) DML is an abbreviation for Dronning Maud Land (Queen Maud Land), the region of Antarctica most in - tensively studied by scientists of the Norsk Polarinsti- tutt.

ANTARCTICA B

component contributed by the seaward flow of land glaciers and an- other, increasing towards the ice front, provided by spreading in re - sponse to the local accumulation of snow (Swithinbank, 1955). An Antarctic ice shelf may carry no ice of land origin by the time it reaches the ice front; bottom melting has removed both it and the debris of glacial erosion. As the ice shelf moves forward, a thinning wedge of ice of land origin is progressively displaced by a thickening wedge of ice formed from locally accumulated snow. In some cases the land ice may be underlain in places by a variable thickness of sea ice (Morgan, 1972; Zotikov and others, 1979; Neal, 1979). In contrast to an ice shelf repre- senting the seaward extension of an inland ice sheet or a number of land glaciers, a glacier tongue represents the extension of a single land glacier. Most glacier tongues are composed of ice mainly of land origin; few are long enough to be substantially nourished by locally accumu - lated snow. We become progressively less certain of the principal component of ice shelves as we approach their northern (climatic) limit. In the Antarctic Peninsula, for example, Wilkins Ice Shelf (fig. 87), at latitude 70ºS. is the northernmost on the Pacific coast that is nourished princi - pally by local snow. Wordie Ice Shelf, at latitude 69ºS., consists essen - tially of coalescent glacier tongues. Two small ice shelves, Muller and Jones Ice Shelves, the northernmost on the west coast of the Antarctic Peninsula, are found in the fjord region between latitudes 67° and 68°S. (fig. 81). On the east coast of the peninsula, the thin but permanent floating ice in Prince Gustav Channel (latitude 64º 1 5 ' S. ) is nourished not by snowfall but instead by the freezing of seawater (Reece, 1950). Other parts of the Antarctic have their share of ice shelves of uncertain composition. Ice rises are dome-shaped ice caps grounded on shoals within or at the seaward edge of ice shelves (figs. 7 and 77). It is probable that most of them originate from localized grounding of areas of ice shelf. But being grounded, they are, by definition, not part of the ice shelf. Although nourished almost exclusively by local accumulation, many are to some

Figure7.—Oblique aerial photograph of Gipps Ice Rise, Larsen Ice Shelf, Graham Land, taken from an altitude of 7,000 m on 1 January 1972, looking east. The ice rise has dimensions of 9 x 18 km and is 300 m high. Photograph by Charles Swithinbank, British Antarctic Survey.

B8 SATELLITE IMAGE ATLAS O F GLACIERS OF THE WORLD