Byrd Glacier Research Articles

The Surface Topography of Large Ice Masses from Landsat Imagery

AbstractApparent ice-surface topography is observed at several scales on Landsat multi-spectral scanner (MSS) imagery. Digitally enhanced MSS scenes from Antarctica and Nordaustlandet, Svalbard, are compared with ice-surface elevations from aircraft altimetry (relative accuracy 2–3 m) to show that this apparent topography is real. Apparent ice divides on Landsat images fit closely with divides on altimetric records. Ice-surface irregularities within drainage basins are also shown to be real. On Byrd Glacier, Antarctica, apparent “flow lines” coincide with ridges on altimetric records. Synoptic Landsat data, calibrated by information from aircraft altimetric flight lines, are used to classify the surface roughness of the ice caps on Nordaustlandet and 40% of the Antarctic ice sheet. On Nordaustlandet, the roughest ice is of amplitude 15–25 m and wavelength 3–4.5 km. Drainage basins with such rough surface characteristics may be associated with ice streams or possibly past surge activity. The most rough Antarctic terrain is up to 60 m in amplitude, with wavelengths of <10 km. The roughness of the Antarctic ice sheet increases with distance from ice divides, reflecting changes in the parameters affecting the transfer of basal stresses to the ice surface.

The Surface Topography of Large Ice Masses from Landsat Imagery

AbstractApparent ice-surface topography is observed at several scales on Landsat multi-spectral scanner (MSS) imagery. Digitally enhanced MSS scenes from Antarctica and Nordaustlandet, Svalbard, are compared with ice-surface elevations from aircraft altimetry (relative accuracy 2–3 m) to show that this apparent topography is real. Apparent ice divides on Landsat images fit closely with divides on altimetric records. Ice-surface irregularities within drainage basins are also shown to be real. On Byrd Glacier, Antarctica, apparent “flow lines” coincide with ridges on altimetric records. Synoptic Landsat data, calibrated by information from aircraft altimetric flight lines, are used to classify the surface roughness of the ice caps on Nordaustlandet and 40% of the Antarctic ice sheet. On Nordaustlandet, the roughest ice is of amplitude 15–25 m and wavelength 3–4.5 km. Drainage basins with such rough surface characteristics may be associated with ice streams or possibly past surge activity. The most rough Antarctic terrain is up to 60 m in amplitude, with wavelengths of <10 km. The roughness of the Antarctic ice sheet increases with distance from ice divides, reflecting changes in the parameters affecting the transfer of basal stresses to the ice surface.

Multi-Spectral Landsat Image Maps of Antarctica (Abstract)

The US Geological Survey is conducting a program to prepare digitally enhanced Multispectral Scanner (MSS) Landsat images of Antarctica. The goal is to furnish accurate planimetric, false-colour composite image maps in Lambert conformal conic projection for the following purposes: (1) to locate and delineate blue-ice areas for the collection of meteorites; (2) to produce special purpose maps showing selected features; (3) to provide synoptic views that aid in the detection and interpretation of glaciological features associated with the inland ice sheet, outlet glaciers, ice streams, and ice shelves; (4) to monitor changes in coastline and glacial features; (5) to enable the superposition and correlation of different types of digital cartographic data; and (6) to furnish spectral and (or) structural information in areas of limited bedrock outcrop to aid in regional geologic interpretation. Only the first four of these objectives are addressed here.About 170 Landsat computer-compatible tapes covering Victoria Land, the coastline of West Antarctica, the Antarctic Peninsula, and other selected areas were assembled into false-color, multi-spectral, digital composites of band 4 (0.5 to 0.6 μm, green), band 5 (0.6 to 0.7 μm, red) and band 7 (0.8 to 1.1 μm, near infra-red). The tapes were subjected to routine image-processing procedures, such as noise removal and radiometric and geometric corrections. Further processing included haze removal and enhancement by linear stretching of individual MSS bands based on inspection of gray-value (digital-number) histograms. Saturation of snow-covered scenes in bands 4, 5, and 6 is a severe problem in Landsat MSS images of Antarctica and makes many images unsuitable for multi-spectral work. We have developed special techniques to restore the saturated snow-and-ice information in these bands to overcome this problem.The Landsat image maps have different formats, depending on their planned applications. An example of a planimetric image map is the one of the McMurdo Sound area; it is based on excellent ground control and processed at full spatial resolution. It comprises five complete and three partial 1 : 250 000 scale topographic quadrangles. One of these is the Convoy Range quadrangle which includes the Allan Hills meteorite-collection site. Blue-ice areas show exceptionally well on this quadrangle, and new information on blue-ice locations and delineations was obtained from it.Thematic maps prepared for the Byrd Glacier area selectively show only rock or ice areas, thus depicting the location of desired features. Synoptic-view maps and mosaics provide information on flow lines associated with ice streams, the location of ice rises, ice rumples, and other possible grounded areas, and the location and extent of buried mountain ranges. Image maps which cover the same area at different times do show changes: a 10-year interval between Landsat images obtained in the Byrd Glacier area shows that crevasses had opened and rifts had drifted within the floating part of the glacier; measurements of the changed positions have yielded average velocities for glacier and ice-shelf movements in that area. The ease with which the dynamics of the coastline can be monitored on Landsat images is particularly useful, because such changes have implications for variations in world climate.

Multi-Spectral Landsat Image Maps of Antarctica (Abstract)

The US Geological Survey is conducting a program to prepare digitally enhanced Multispectral Scanner (MSS) Landsat images of Antarctica. The goal is to furnish accurate planimetric, false-colour composite image maps in Lambert conformal conic projection for the following purposes: (1) to locate and delineate blue-ice areas for the collection of meteorites; (2) to produce special purpose maps showing selected features; (3) to provide synoptic views that aid in the detection and interpretation of glaciological features associated with the inland ice sheet, outlet glaciers, ice streams, and ice shelves; (4) to monitor changes in coastline and glacial features; (5) to enable the superposition and correlation of different types of digital cartographic data; and (6) to furnish spectral and (or) structural information in areas of limited bedrock outcrop to aid in regional geologic interpretation. Only the first four of these objectives are addressed here. About 170 Landsat computer-compatible tapes covering Victoria Land, the coastline of West Antarctica, the Antarctic Peninsula, and other selected areas were assembled into false-color, multi-spectral, digital composites of band 4 (0.5 to 0.6 μm, green), band 5 (0.6 to 0.7 μm, red) and band 7 (0.8 to 1.1 μm, near infra-red). The tapes were subjected to routine image-processing procedures, such as noise removal and radiometric and geometric corrections. Further processing included haze removal and enhancement by linear stretching of individual MSS bands based on inspection of gray-value (digital-number) histograms. Saturation of snow-covered scenes in bands 4, 5, and 6 is a severe problem in Landsat MSS images of Antarctica and makes many images unsuitable for multi-spectral work. We have developed special techniques to restore the saturated snow-and-ice information in these bands to overcome this problem. The Landsat image maps have different formats, depending on their planned applications. An example of a planimetric image map is the one of the McMurdo Sound area; it is based on excellent ground control and processed at full spatial resolution. It comprises five complete and three partial 1 : 250 000 scale topographic quadrangles. One of these is the Convoy Range quadrangle which includes the Allan Hills meteorite-collection site. Blue-ice areas show exceptionally well on this quadrangle, and new information on blue-ice locations and delineations was obtained from it. Thematic maps prepared for the Byrd Glacier area selectively show only rock or ice areas, thus depicting the location of desired features. Synoptic-view maps and mosaics provide information on flow lines associated with ice streams, the location of ice rises, ice rumples, and other possible grounded areas, and the location and extent of buried mountain ranges. Image maps which cover the same area at different times do show changes: a 10-year interval between Landsat images obtained in the Byrd Glacier area shows that crevasses had opened and rifts had drifted within the floating part of the glacier; measurements of the changed positions have yielded average velocities for glacier and ice-shelf movements in that area. The ease with which the dynamics of the coastline can be monitored on Landsat images is particularly useful, because such changes have implications for variations in world climate.

Surface Velocity Determination on Large Polar Glaciers by Aerial Photogrammetry

Aerial photogrammetric block triangulation, a standard and well-developed technique for extending accurate control for mapping into the interior of a region from a few points of known position on its perimeter, can be readily adapted to determine surface velocities on bodies of ice which are too large, and often too crevassed, to be studied effectively by conventional ground surveying. Velocities are calculated from the changes in positions of the same natural surface features determined from photography of two (or more) epochs and the elapsed time. This method is capable of providing many uniformly-spaced measurements over the whole, moving, ice surface, thus allowing the production of maps of velocity and strain-rate, which are valuable in analyzing the ice-flow regime. Results from measurements completed some years ago on Byrd Glacier, one of the largest outlet glaciers from the East Antarctic plateau, are presented as an example of what the method can yield. By means of Doppler satellite surveying, relative positions of control points for each photography epoch can be determined with sub-meter accuracy, making the technique suitable also in regions where no fixed land features exist. A brief description of a project under way in such an area, on Ice Stream B in West Antarctica, is given.

Surface Velocity Determination on Large Polar Glaciers by Aerial Photogrammetry

Aerial photogrammetric block triangulation, a standard and well-developed technique for extending accurate control for mapping into the interior of a region from a few points of known position on its perimeter, can be readily adapted to determine surface velocities on bodies of ice which are too large, and often too crevassed, to be studied effectively by conventional ground surveying. Velocities are calculated from the changes in positions of the same natural surface features determined from photography of two (or more) epochs and the elapsed time. This method is capable of providing many uniformly-spaced measurements over the whole, moving, ice surface, thus allowing the production of maps of velocity and strain-rate, which are valuable in analyzing the ice-flow regime. Results from measurements completed some years ago on Byrd Glacier, one of the largest outlet glaciers from the East Antarctic plateau, are presented as an example of what the method can yield. By means of Doppler satellite surveying, relative positions of control points for each photography epoch can be determined with sub-meter accuracy, making the technique suitable also in regions where no fixed land features exist. A brief description of a project under way in such an area, on Ice Stream B in West Antarctica, is given.

Antarctica: Measuring Glacier Velocity from Satellite Images

Many Landsat images of Antarctica show distinctive flow and crevasse features in the floating part of ice streams and outlet glaciers immediately below their grounding zones. Some of the features, which move with the glacier or ice stream, remain visible over many years and thus allow time-lapse measurements of ice velocities. Measurements taken from Landsat images of features on Byrd Glacier agree well with detailed ground and aerial observations. The satellite-image technique thus offers a rapid and cost-effective method of obtaining average velocities, to a first order of accuracy, of many ice streams and outlet glaciers near their termini.

Shackleton Limestone archaeocyaths

The Shackleton Limestone is a thick unit of bedded and allochthonous limestone, with minor dolostone, quartzite, sandstone and siltstone, spanning the central portion of the Transantarctic Mountains. It is a record of Early Cambrian shelf and peri-platform carbonate deposition on the margin of the East Antarctic craton. Slope, shallow marine and intertidal-supratidal conditions prevailed during deposition. Thirty-one species of archaeocyaths described from measured sections in the northern Holyoake Range (Nimrod Glacier area) and at Crackling Cwm (Byrd Glacier area) confirm earlier correlations of Shackleton Limestone faunas with the Botomian stage of Siberia. Archaeocyaths from a section at Mt Egerton (Byrd Glacier area) are of either Botomian or Toyonian age. Ten further archaeocyath species are added to the six species already known to be common to both Antarctica and Australia, confirming the existence of a Gondwana supercontinent in the Early Palaeozoic. New taxa described are the genera Kymbecyathus...

Photogrammetric Investigation of Byrd Glacier Surface Lowering (Abstract only)

While carrying out photogrammetric measurements to provide surface velocities and elevations for use in studies of the equilibrium and dynamics of Byrd Glacier, I noted that comparison of elevations obtained by ground surveys in 1978-79 with US Geological Survey topographic maps made from 1960-62 aerial photography indicated a very large apparent lowering of the glacier surface in this short timeinterval. The apparent lowering varied between 50 and 150 m along a 60 km section of the glacier for which data were available (Brecher 1980). The ground measurements were estimated to be in error by no more than 3 in but the accuracy of elevations on the maps was unknown. Because these are reconnaissance maps, however, substantial errors would not be unexpected. It was therefore necessary to obtain more accurate glacier surface elevations for 1960–62 in order to determine whether the lowering is real. Photogrammetric strip triangulations of three individual strips of photography, two taken in November 1960 and the third in February 1963, which cover the region of the greatest apparent lowering, have now been completed. The old strips were oriented to fixed points on the two “banks” of the glacier derived for this purpose from the 1978–79 photogrammetric work, thus bringing the measurements from the old and new photography into a common coordinate system. The glacier surface elevations for 1960–62 are the same as those obtained from the 1978–79 ground survey and photogrammetry. While it is difficult to give measures of accuracy of the results since no independent data are available for comparison, internal evidence indicates that precision higher than the expected 10 m has been achieved in the measurements. It can thus be stated unambiguously that no detectable surface lowering has occurred on any of the parts of the glacier which have been investigated.

The Effect of Crevassing on The Radiative Absorptance of a Glacier Surface (Abstract only)

Surface melting has been observed on the lower, floating half of Byrd Glacier, Antarctica, during the height of the summer ablation season, in spite of regional air temperatures consistently below 0°C. The thickness of ice in this area is about 2 500 m, but surface crevasses penetrate to a depth of about 20 m, and bottom crevasses, being water-filled, may extend all the way up to sea-level. This leaves a zone of uncrevassed ice between which is of the order of 200 m in thickness, across which lateral shear stress due to drag against fjord walls will be concentrated. Variations in the mechanical properties of ice in this zone, specifically variations in hardness due to temperature changes, will obviously have a significant effect on the dynamics of the ice stream. A model of the rough ice surface has been constructed, in which large crevasse furrows are represented by cylindrical V-grooves. These form the upper boundary of a solid conduction region which is semiinfinite below, and whose transient temperature distribution is calculated using the finite element method. The free surface boundary condition, that of sunlight warming the rough ice surface, is calculated by the construction and solution of coupled Fredholm integral equations of the second kind; these represent the energy absorbed at a point on the V-groove surface as being due to (1) energy directly incident from the sun, if the point is not in shadow, and (2) indirect radiation reflected from the opposite wall of the V-groove. This formulation takes into account all multiple reflections of radiation between the walls of the V-groove cavity. Additionally, the reflectivity of the ice surface is not given a constant value, but is allowed to vary, increasing as the angle of incidence departs from the surface normal. The purpose of the model is to compare temperature distributions with a rough surface to the same model with a smooth surface. Due to the many simplifications made with regard to surface heat transfer, it is imprudent to make assertions about actual temperature distributions based on the model results, but the difference between the rough and smooth model results will provide a lower bound on the actual enhancement effect of surface roughness, i.e. future, more comprehensive, modeling of energy exchange at an ice surface will be in error by at least the predicted amount if the surface is treated as if it were flat. The major effects of the surface roughness are greater absorptive capacity and non-uniform distribution of the absorbed energy. The greater absorptive capacity of a V-groove cavity is well known from studies in radiation heat transfer. Non-uniform distribution is due to two mechanisms: (1) the cavity effect is most pronounced at the apex of the V-groove, and (2) when surface melting occurs, energy is transported in the form of latent heat of melting from wherever the melting occurs to below the apex of the V-groove where the melt water refreezes. The possibility that lateral shear stress is concentrated in a zone only 200 m thick means that temperature perturbations due to surface roughness need only penetrate on the order of 200 m, or possibly even less, to have a significant effect on the mechanical properties of the ice, and in turn on the dynamics of the ice stream.

Photogrammetric Investigation of Byrd Glacier Surface Lowering (Abstract only)

While carrying out photogrammetric measurements to provide surface velocities and elevations for use in studies of the equilibrium and dynamics of Byrd Glacier, I noted that comparison of elevations obtained by ground surveys in 1978-79 with US Geological Survey topographic maps made from 1960-62 aerial photography indicated a very large apparent lowering of the glacier surface in this short timeinterval. The apparent lowering varied between 50 and 150 m along a 60 km section of the glacier for which data were available (Brecher 1980).The ground measurements were estimated to be in error by no more than 3 in but the accuracy of elevations on the maps was unknown. Because these are reconnaissance maps, however, substantial errors would not be unexpected. It was therefore necessary to obtain more accurate glacier surface elevations for 1960–62 in order to determine whether the lowering is real. Photogrammetric strip triangulations of three individual strips of photography, two taken in November 1960 and the third in February 1963, which cover the region of the greatest apparent lowering, have now been completed. The old strips were oriented to fixed points on the two “banks” of the glacier derived for this purpose from the 1978–79 photogrammetric work, thus bringing the measurements from the old and new photography into a common coordinate system.The glacier surface elevations for 1960–62 are the same as those obtained from the 1978–79 ground survey and photogrammetry. While it is difficult to give measures of accuracy of the results since no independent data are available for comparison, internal evidence indicates that precision higher than the expected 10 m has been achieved in the measurements. It can thus be stated unambiguously that no detectable surface lowering has occurred on any of the parts of the glacier which have been investigated.

The Effect of Crevassing on The Radiative Absorptance of a Glacier Surface (Abstract only)

Surface melting has been observed on the lower, floating half of Byrd Glacier, Antarctica, during the height of the summer ablation season, in spite of regional air temperatures consistently below 0°C. The thickness of ice in this area is about 2 500 m, but surface crevasses penetrate to a depth of about 20 m, and bottom crevasses, being water-filled, may extend all the way up to sea-level. This leaves a zone of uncrevassed ice between which is of the order of 200 m in thickness, across which lateral shear stress due to drag against fjord walls will be concentrated. Variations in the mechanical properties of ice in this zone, specifically variations in hardness due to temperature changes, will obviously have a significant effect on the dynamics of the ice stream.A model of the rough ice surface has been constructed, in which large crevasse furrows are represented by cylindrical V-grooves. These form the upper boundary of a solid conduction region which is semiinfinite below, and whose transient temperature distribution is calculated using the finite element method. The free surface boundary condition, that of sunlight warming the rough ice surface, is calculated by the construction and solution of coupled Fredholm integral equations of the second kind; these represent the energy absorbed at a point on the V-groove surface as being due to (1) energy directly incident from the sun, if the point is not in shadow, and (2) indirect radiation reflected from the opposite wall of the V-groove. This formulation takes into account all multiple reflections of radiation between the walls of the V-groove cavity. Additionally, the reflectivity of the ice surface is not given a constant value, but is allowed to vary, increasing as the angle of incidence departs from the surface normal.The purpose of the model is to compare temperature distributions with a rough surface to the same model with a smooth surface. Due to the many simplifications made with regard to surface heat transfer, it is imprudent to make assertions about actual temperature distributions based on the model results, but the difference between the rough and smooth model results will provide a lower bound on the actual enhancement effect of surface roughness, i.e. future, more comprehensive, modeling of energy exchange at an ice surface will be in error by at least the predicted amount if the surface is treated as if it were flat.The major effects of the surface roughness are greater absorptive capacity and non-uniform distribution of the absorbed energy. The greater absorptive capacity of a V-groove cavity is well known from studies in radiation heat transfer. Non-uniform distribution is due to two mechanisms: (1) the cavity effect is most pronounced at the apex of the V-groove, and (2) when surface melting occurs, energy is transported in the form of latent heat of melting from wherever the melting occurs to below the apex of the V-groove where the melt water refreezes.The possibility that lateral shear stress is concentrated in a zone only 200 m thick means that temperature perturbations due to surface roughness need only penetrate on the order of 200 m, or possibly even less, to have a significant effect on the mechanical properties of the ice, and in turn on the dynamics of the ice stream.

Provenance of some glacial deposits in the Transantarctic Mountains based on Rb/1bSr dating of feldspars

Till deposits of Cenozoic age, formerly referred to the Sirius Formation, occur in the Transantarctic Mountains at numerous scattered localities. Many of the known occurrences are at high elevations and were deposited on old erosion surfaces that pre-date the dissection of the present Transantarctic Mountains. The most extensive deposits have been found along the walls of valleys presently occupied by outlet glaciers that flow from the East Antarctic ice sheet to the Ross Ice Shelf. The origin of these tills is the subject of conflicting hypotheses. The most plausible alternatives include deposition by local mountain glaciers and ice caps and/or by ancestral outlet glaciers that drained the East Antarctic ice sheet in Cenozoic time while uplift of the Transantarctic Mountains was taking place. Size fractions of feldspar in till of possible Cenozoic age in the valleys of the Byrd and Hatherton glaciers and on the summit plateau of Table Mountain have been analyzed for dating by the Rb/1bSr method. The results are interpretable in terms of a model based on two-component mixtures of feldspar grains of differing ages. One component is derived from the igneous rocks of the local basement complex that crystallized ∼ 500 Ma ago. The other component is Precambrian in age and may have originated from the East Antarctic shield. The results indicate that till in the valleys of the Byrd and Hatherton glaciers contain a component of Precambrian feldspar and were probably deposited by outlet glaciers draining the ice sheet of East Antarctica. The till on Table Mountain (elevation 1700 m) does not contain Precambrian feldspar and was probably deposited by a local ice cap. Till of Quaternary-Recent age along the Byrd Glacier and in the coastal moraine of the Brown Hills has a local provenance.

VLF Ground‐Based Measurements in Antarctica: Their Relationship to Stratifications in the Subsurface Terrain

The phase and amplitude characteristics of the near‐field broadside to a long horizontal dipole operated close to ground level at very low frequencies can be used to obtain useful information about the nature of the subsurface media. This study is about antarctic glacial terrain and makes use of data collected recently in the Byrd glacier area to draw tentative conclusions about the nature of the glacial ice and underlying earth. Data obtained by use of this method suggest that the depth of the ice layer is in the neighborhood of 2250 meters, that the bulk relative complex dielectric constant of the ice may be approximated by the value 6.0‐j14 at 12.8 kHz, and that the conductivity of the underlying earth approaches 0.10 mho meter−1. A reflection coefficient of approximately 0.60 is indicated when plane waves arrive at vertical incidence at the surface of the ice. These figures are shown to be reasonable when compared with available data from other sources.

Some Photogrammetric and Geodetic Aspects of Measurement of Glacier Surface Movement as Function of Time

AbstractThe ice movement on the Byrd Glacier, Antarctica, was measured as function of time, on the basis of aerial photography. The method of aero-levelling strip triangulation with a minimum of geodetic control was applied. The methods and procedures were verified over Laufen-Bauma test area.

Some Photogrammetric and Geodetic Aspects of Measurement of Glacier Surface Movement as Function of Time

Abstract The ice movement on the Byrd Glacier, Antarctica, was measured as function of time, on the basis of aerial photography. The method of aero-levelling strip triangulation with a minimum of geodetic control was applied. The methods and procedures were verified over Laufen-Bauma test area.

Ice Movement of Valley Glaciers Flowing into the Ross Ice Shelf, Antarctica

Seven glaciers from 9 to 26 kilometers in width move 0.3 to 2.3 meters per day. Byrd Glacier is the fastest moving of the known valley glaciers in Antarctica.