Antarctic ice core recovery
Ross Ice Shelf Project stations (see figure 2). 'I
.2 0 . .
.2 V
V 0.
0
V
.
V
-0V V
a V c50._ v
0-11 11°S.l o w. 30-31 December 1977 X X X X X X 0-19 100 S.30 E. 19-20January 1978 X X X X X X P-18 10.60 S.2.60 E. 23 January 1978 X X X P-19 l0.70 S.3.00 E. 24 January 1978 X X X Q-16 11.2°S.1.50 E. 24 January 1978 X X X Q-17 11.1 0 S.2.1 0 E. 24 January 1978 X X X Q-18 11.0°S.2.60 E. 23 January 1978 X X X R-16 11 1120S. I 112°E. 27-28 December 1977 X X X X X R-17 11 1/20 S.20 E. 26 December 1977 X X X R-18 11.4 0 S.2.60 E. 22 January 1978 X X X S-16 120 S.1 1/20 E. 27 December 1977 X X X S-17 120 S.20 E. 26 December 1977 X X X
This is University of Wisconsin, Geophysical and Polar &esearch Center, Contribution 355.
References
Bentley, C. R. 1971. Secular increase of gravity at South Pole Station. In: Antarctic Snow and Ice Studies 2 (American Geophysical Union Antarctic Research Series, 16, A. P. Crary, ed.). p. 191. Bentley, C. R. 1976. Analysis of Ross Ice Shelf geophysics. Antarctic Journal of the U.S., 11(4): 276-277. Bentley, C. R,J. W. Clough, andJ. D. Robertson. 1974. Geophysical work of the Ross Ice Shelf Geophysical and Glaciological Survey (RIGGS) in 1973-74. Antarctic Journal of the U.S., 9(4): 157-159. Bentley, C. R, and K. C. Jezek. 1977. Ross Ice Shelf geophysical survey, 1976-1977. Antarctic Journal of the US., 12(4): 142-144. Clough,J. W., andJ. D. Robertson. 1975. RISP geophysical survey. Antarctic Journal of the U.S., 10(4): 153. Crary, A. P., E. S. Robinson, H. F. Bennett, and W. W. Boyd, Jr. 1962. Glaciological regime of the Ross Ice Shelf. Journal of Geophysical Research, 67(7): 2791-2807.
Bibliography
Albert, D. G., C. R. Bentley, and L. L. Greischar. 1978. Submarine topography of the Ross Embayment from the continental shelf to the Byrd subglacial basin. Transactions, (American Geophysical Union), 59(4): 308. (Abstract) Bentley, C. R., j. D. Robertson, and L. L. Greischar. 1977. Isostatic gravity anomalies on the Ross Ice Shelf, Antarctica. Proceedings of Symposium on Antarctic Geology and Geophysics, Madison, Wisconsin, August 1977. Bentley, C. R., and S. Shabtaie. 1978. Geophysical evidence for the mass balance at the ice/water boundary beneath the Ross Ice Shelf. Transactions (American Geophysical Union), 54(4): 309. (Abstract) October 1978
Greischar, L. L., and C. R. Bentley. 1978. Isostatic rebound and the configuration of the grounding line between the Ross Ice Shelf and the West Antarctic ice sheet. Transactions (American Geophysical Union), 54(4): 309. (Abstract) Robertson,J. D., C. R. Bentley,J. W. Clough, and L. L. Greischar. 1977. Sea bottom topography and crustal structure below the Ross Ice Shelf, Antarctica. Proceedings of Symposium on Antarctic Geology and Geophysics, Madison, Wisconsin, August 1977.
Antarctic ice core recovery ERICK CHIANG and CHESTER C. LANGwAY,JR Department of Geological Sciences State University of New York at Buffalo Amherst, New York 14226
As part of the Polar Ice Core Analysis Program (Langway and Herron, 1977), ice cores were obtained from sites Q-13 (78°57'24.4"S. and 179"55'22.3"E.), C-16 (81°!! '36.6"S. and 170°29'52.2"E.),J-9 (82°22'S. and 168°40'W.), on the Ross Ice Shelf, and South Pole (90°S.). These cores and other samples were collected to permit further investigation of the seasonal variation in sea salt concentrations (Herron and Langway, 1978), delineation of aerosol sources by chemical analysis, and assessment of the factors influencing the variations in the physical characteristics of the ice at these and other selected sites. In addition to the ice cores, snow and ice samples were collected from the ice towers near the summit of Mt. Erebus and also on the Ross Ice Shelf for preliminary investigations of the dispersion of aerosols emitted in the Mt. Erebus plume toward the shelf. All phases of the field activities were completed between 16 November 1977 and 26 January 1978. Between 16 November and 2 December the field team (E. Chiang, field leader;J. Cragin; G. Klouda) collected samples at the summit of Mt. Erebus and, in a complementary sampling effort, recovered nine five-meter hand-augered firn cores at radially increasing distances from Ross Island. Several samples of condensed vapor from the plume were collected from the inner rim of the Mt. Erebus crater, and a small ice tower (2.5 meters high x 1.5 meters in diameter) approximately 30 meters from the crater rim was sectioned for laboratory analysis of chemical composition and physical properties. The radial sampling was conducted with helicopter support out of McMurdo along three flight lines. The maximum distance of each line from Mt. Erebus varied from 75-85 nautical miles. The field team was supported in the shallow drilling operations by the Polar Ice Coring Office (Pico), which provided the drill crews (T. Clark, S. Atwood, R. Tilsson, and P. Marshall) and the Army Cold Regions Research and Engineering Laboratory (CRREL) shallow drill (Rand, 1976). Coring operations were initiated on 2 December 1977 and were completed by 15 January 1978. The drilling operations at Q-13, and South Pole proceeded smoothly and, in general, the quality of the core obtained is excellent. Although 100 59
g/cm3 .300 .500 .700
-51.5 -505 -49.5 -48.5 I I I I I
0
I-I-I-I-
C
o. K
1978 Core Hole
I_
0'co
20
Close Off - Zone 004
•:C16 40 '&--S-Pole 0:Q13
P 20 40-
1974 Core Hole
0II
II II I:
-
60-
.-'
South Pole Core Hole Temperatures
60o
at
80
Core Densities
II -ci 4
100-b
-I
Figure 3. South Pole core hole temperatures.
I'
120'-
Figure 1. South Pole, C-16, and 0-13 core densities.
-290
OC
-270 -250 -230 -21.0
re Me
80
Figure 2. 0-13 and C-16 temperature profiles.
60
meters of core could be obtained in 4 to 5 days site time (actual drilling time decreased as the drillers gained experience, from about 28 hours at Q-13 to 14 1/2 hours at the South Pole), considerations for surface-to-core tie-in studies and down-borehole measurements suggest that a minimum of 7 to 10 days is required to complete future shallow-drilling operations with this drill. Because of the rapid rate of core recovery by the USA CRREL shallow drill, field measurements on the core were restricted to: (a) careful logging of each section with respect to depth and container number, (b) recording of the major stratigraphic features, and (c) measurements for the determination of bulk density from selected sections of the core prior to packaging and crating in preparation for the return to the Ice Core Laboratory at SUNY/Buffalo. The density measurements obtained at those sites are presented in figure 1. At C-16 and Q-13 the pore close-off zone was reached at a depth of about 45 meters, which is comparable to that atJ-9 (Chiang and Langway, 1976) but shallower than the 52 meters measured at Little America V (Gow, 1968). The extension of the South Pole density profile (Langway, 1975) indicates that pore close-off has not yet been reached by 111.49 meters. Further detailed hydrostatic densities of the impermeable ice will be conducted in the laboratory. Surface chemical sampling and surface-to-core tie-in studies were conducted in the vicinity of each of these Sites following the core-recovery operations. Two adjacent pits were excavated 5-6 kilometers from the main camp. Ultraclean, 4çailed collections were made in one pit for further laboratory investigations of seasonal variations (Herron and Langway, 1978) and horizontal variations (Klouda, 1977) in chemical constituents, and for further characterization of the glaciochemical regimes represented on the Ross
ANTARCTIC JOURNAL
Ice Shelf (Herron and Langway, 1976). Detailed density and stratigraphic measurements were conducted in the adjacent pit, located downwind of the chemical-sampling pit, to obtain an approximation of the recent rates of surface accumulation. Corehole temperatures were measured using a thermistor in conjunction with a Wheatstone Bridge (figures 2 and 3). At the South Pole, measurements were obtained from the 100meter corehole drilled under the dome in 1974 (Rand, 1975) as well as from the 111-meter corehole drilled during austral summer 1978 (figure 3). The comparison of the two temperature profiles from the South Pole suggests that there is a signficant (0.2° C) influence on the more recent temperature profile resulting from heat from the drill. This is especially apparent between 90 and 110 meters in the new hole where the penetration rate was considerably slower because of the denser firn. Coincident with the South Pole drilling operations was the core recovery at J-9 5-14 January 1978. Core processing was done by James Cragin. While there was some difficulty with the chip removal system, core recovery was rapid and core quality improved with depth. The corehole was fluid-filled at approximately 100 meters, and the final depth was 170.76 meters. This work was supported by National Science Foundation grant DPP 78-04412.
References
Chiang, E., and C. C. Langway, Jr. 1976. Physical properties of the 100 meters deep ice core from J-9, Ross Ice Shelf, Antarctica, Discussed at Symposium of SCAR-Specialist Group on Ice Shelf Drilling Projects, Mendoza, Argentina. Draft documents of XIV meeting of SCAR, October 18-23, 1976 (Abstract). p. 211. Gow, A.J. 1968. Deep core studies of the accumulation and densification of snow at Byrd Station and Little America V, Antarctica. US. Army Cold Regions Research and Engineering Laboratory. Research
Report, 197. Hanover, New Hampshire. Herron, M. M., and C. C. Langway, Jr. 1976. Glaciochemical regimes of the Ross Ice Shelf, Antarctica. Discussed at Symposium of SCAR-Specialist Group on Ice Shelf Drilling Projects, Mendoza, Argentina. Draft documents of XIV meeting of SCAR, October 18-23, 1976 (Abstract). p. 212. Herron, M. M., and C. C. Langway,Jr. 1978. Seasonal variations in Ross Ice Shelf precipitation chemistry. EOS Transactions, American Geophysical Union, 59(4): 308. (Abstract) Klouda, G. A. 1977. An investigation of the geochemical uniformity of an ice sheet. Unpublished master's thesis, State University of New York at Buffalo. Langway, C. C.,Jr., and M. M. Herron. 1977. Polar ice core analysis. Antarctic Journal of the US., 12(4): 152-154. Langway, C. C.,Jr. 1975. Antarctic ice core studies. AntarcticJournal of the US., 10 (4): 152-153. Rand, J. H. 1976. The USA CRREL Shallow Drill. In: Ice Core Drilling U. F. Splettstoesser, ed.). University of Nebraska Press, Lincoln. pp. 133-137. Rand,J. H. 1975. 100-meter ice cores from the South Pole and the Ross Ice Shelf. Antarctic Journal of the US., 10 (4): 150-15 1.
October 1978
Erebus Glacier Tongue movement G. HOLDSWORTH Environment Canada Ottawa, Canada
R. HOLDSWORTH University of Waikato Hamilton, New Zealand
Ice deformation measurements were made on the Erebus Glacier Tongue (77°40'N.166 0 40'E.), McMurdo Sound, in an attempt to support the hypothesis that, as a result of ocean wave excitation, a floating glacier may oscillate at a frequency that corresponds to one of its higher modes (Holdsworth and Glynn, in press). Under storm conditions with open water, the amplitude and duration of vertical oscillations may be caused by the bending stresses in the resonant-like motion, that cause fatigue failure in the ice. A field camp on the glacier (figure 1) was occupied continuously from 21 December 1977 until 26 January 1978. Because of the degree of crevassing all over the glacier surface, travel was by skis and equipment was moved by sled. The water depth at the glacier's edge was measured at 15 points by sounding line. Either a hole was drilled through the sea ice (3 to 3.8 meters thick) with a SIPRE corer or existing cracks or seal holes were used. Figure 2 shows the bottom profiles along the north and south edges of the glacier. Although no measurement of water depths directly under the glacier could be obtained, the data suggest that the glacier is free-floating except for a section of the north edge at the fixed end. On 15 February a hydrographic survey was made by USCGC Burton Island, but only near the terminus (figure 3) because fast sea ice remained in Erebus Bay and north of the glacier. Deformation of the glacier was measured by continuously recording wire strain meters (Goodman and Holdsworth, 1978) and a Schaevitz LSOC ( 1 0 ) servo-inclinometer. The direct current output of the latter instrument was fed to a portable strip-chart recorder. The unprocessed results obtained for tow of the stations reveal oscillations with periods of about ito 1 minutes and about 30 seconds occurring alternately as if there were "beating" between the two frequencies. Waves with a period of roughly 15 seconds are also evident. Pronounced oscillations exist with a period of 16 ( 1) seconds, which correlates well with the peak in the frequency spectrum for the sea ice (Goodman, personal communication, May 1978) although waves with a longer period (about 2 minutes) also are present in the glacier motion, at the same point. Personnel from the Scott Polar Research Institute, in cooperation with the U.S. Navy, surveyed ice thickness along the canterline of the glacier by air. The provisional glacier thickness profile is shown in figure 2. Other measurements included density and temperature in the upper 11 meters of firn at station number EGO 0. Density varied irregularly from 0.463 to 0.64 million grams per cubic
61
.2 0 . .
.2 V
V 0.
0
V
.
V
-0V V
a V c50._ v
0-11 11°S.l o w. 30-31 December 1977 X X X X X X 0-19 100 S.30 E. 19-20January 1978 X X X X X X P-18 10.60 S.2.60 E. 23 January 1978 X X X P-19 l0.70 S.3.00 E. 24 January 1978 X X X Q-16 11.2°S.1.50 E. 24 January 1978 X X X Q-17 11.1 0 S.2.1 0 E. 24 January 1978 X X X Q-18 11.0°S.2.60 E. 23 January 1978 X X X R-16 11 1120S. I 112°E. 27-28 December 1977 X X X X X R-17 11 1/20 S.20 E. 26 December 1977 X X X R-18 11.4 0 S.2.60 E. 22 January 1978 X X X S-16 120 S.1 1/20 E. 27 December 1977 X X X S-17 120 S.20 E. 26 December 1977 X X X
This is University of Wisconsin, Geophysical and Polar &esearch Center, Contribution 355.
References
Bentley, C. R. 1971. Secular increase of gravity at South Pole Station. In: Antarctic Snow and Ice Studies 2 (American Geophysical Union Antarctic Research Series, 16, A. P. Crary, ed.). p. 191. Bentley, C. R. 1976. Analysis of Ross Ice Shelf geophysics. Antarctic Journal of the U.S., 11(4): 276-277. Bentley, C. R,J. W. Clough, andJ. D. Robertson. 1974. Geophysical work of the Ross Ice Shelf Geophysical and Glaciological Survey (RIGGS) in 1973-74. Antarctic Journal of the U.S., 9(4): 157-159. Bentley, C. R, and K. C. Jezek. 1977. Ross Ice Shelf geophysical survey, 1976-1977. Antarctic Journal of the US., 12(4): 142-144. Clough,J. W., andJ. D. Robertson. 1975. RISP geophysical survey. Antarctic Journal of the U.S., 10(4): 153. Crary, A. P., E. S. Robinson, H. F. Bennett, and W. W. Boyd, Jr. 1962. Glaciological regime of the Ross Ice Shelf. Journal of Geophysical Research, 67(7): 2791-2807.
Bibliography
Albert, D. G., C. R. Bentley, and L. L. Greischar. 1978. Submarine topography of the Ross Embayment from the continental shelf to the Byrd subglacial basin. Transactions, (American Geophysical Union), 59(4): 308. (Abstract) Bentley, C. R., j. D. Robertson, and L. L. Greischar. 1977. Isostatic gravity anomalies on the Ross Ice Shelf, Antarctica. Proceedings of Symposium on Antarctic Geology and Geophysics, Madison, Wisconsin, August 1977. Bentley, C. R., and S. Shabtaie. 1978. Geophysical evidence for the mass balance at the ice/water boundary beneath the Ross Ice Shelf. Transactions (American Geophysical Union), 54(4): 309. (Abstract) October 1978
Greischar, L. L., and C. R. Bentley. 1978. Isostatic rebound and the configuration of the grounding line between the Ross Ice Shelf and the West Antarctic ice sheet. Transactions (American Geophysical Union), 54(4): 309. (Abstract) Robertson,J. D., C. R. Bentley,J. W. Clough, and L. L. Greischar. 1977. Sea bottom topography and crustal structure below the Ross Ice Shelf, Antarctica. Proceedings of Symposium on Antarctic Geology and Geophysics, Madison, Wisconsin, August 1977.
Antarctic ice core recovery ERICK CHIANG and CHESTER C. LANGwAY,JR Department of Geological Sciences State University of New York at Buffalo Amherst, New York 14226
As part of the Polar Ice Core Analysis Program (Langway and Herron, 1977), ice cores were obtained from sites Q-13 (78°57'24.4"S. and 179"55'22.3"E.), C-16 (81°!! '36.6"S. and 170°29'52.2"E.),J-9 (82°22'S. and 168°40'W.), on the Ross Ice Shelf, and South Pole (90°S.). These cores and other samples were collected to permit further investigation of the seasonal variation in sea salt concentrations (Herron and Langway, 1978), delineation of aerosol sources by chemical analysis, and assessment of the factors influencing the variations in the physical characteristics of the ice at these and other selected sites. In addition to the ice cores, snow and ice samples were collected from the ice towers near the summit of Mt. Erebus and also on the Ross Ice Shelf for preliminary investigations of the dispersion of aerosols emitted in the Mt. Erebus plume toward the shelf. All phases of the field activities were completed between 16 November 1977 and 26 January 1978. Between 16 November and 2 December the field team (E. Chiang, field leader;J. Cragin; G. Klouda) collected samples at the summit of Mt. Erebus and, in a complementary sampling effort, recovered nine five-meter hand-augered firn cores at radially increasing distances from Ross Island. Several samples of condensed vapor from the plume were collected from the inner rim of the Mt. Erebus crater, and a small ice tower (2.5 meters high x 1.5 meters in diameter) approximately 30 meters from the crater rim was sectioned for laboratory analysis of chemical composition and physical properties. The radial sampling was conducted with helicopter support out of McMurdo along three flight lines. The maximum distance of each line from Mt. Erebus varied from 75-85 nautical miles. The field team was supported in the shallow drilling operations by the Polar Ice Coring Office (Pico), which provided the drill crews (T. Clark, S. Atwood, R. Tilsson, and P. Marshall) and the Army Cold Regions Research and Engineering Laboratory (CRREL) shallow drill (Rand, 1976). Coring operations were initiated on 2 December 1977 and were completed by 15 January 1978. The drilling operations at Q-13, and South Pole proceeded smoothly and, in general, the quality of the core obtained is excellent. Although 100 59
g/cm3 .300 .500 .700
-51.5 -505 -49.5 -48.5 I I I I I
0
I-I-I-I-
C
o. K
1978 Core Hole
I_
0'co
20
Close Off - Zone 004
•:C16 40 '&--S-Pole 0:Q13
P 20 40-
1974 Core Hole
0II
II II I:
-
60-
.-'
South Pole Core Hole Temperatures
60o
at
80
Core Densities
II -ci 4
100-b
-I
Figure 3. South Pole core hole temperatures.
I'
120'-
Figure 1. South Pole, C-16, and 0-13 core densities.
-290
OC
-270 -250 -230 -21.0
re Me
80
Figure 2. 0-13 and C-16 temperature profiles.
60
meters of core could be obtained in 4 to 5 days site time (actual drilling time decreased as the drillers gained experience, from about 28 hours at Q-13 to 14 1/2 hours at the South Pole), considerations for surface-to-core tie-in studies and down-borehole measurements suggest that a minimum of 7 to 10 days is required to complete future shallow-drilling operations with this drill. Because of the rapid rate of core recovery by the USA CRREL shallow drill, field measurements on the core were restricted to: (a) careful logging of each section with respect to depth and container number, (b) recording of the major stratigraphic features, and (c) measurements for the determination of bulk density from selected sections of the core prior to packaging and crating in preparation for the return to the Ice Core Laboratory at SUNY/Buffalo. The density measurements obtained at those sites are presented in figure 1. At C-16 and Q-13 the pore close-off zone was reached at a depth of about 45 meters, which is comparable to that atJ-9 (Chiang and Langway, 1976) but shallower than the 52 meters measured at Little America V (Gow, 1968). The extension of the South Pole density profile (Langway, 1975) indicates that pore close-off has not yet been reached by 111.49 meters. Further detailed hydrostatic densities of the impermeable ice will be conducted in the laboratory. Surface chemical sampling and surface-to-core tie-in studies were conducted in the vicinity of each of these Sites following the core-recovery operations. Two adjacent pits were excavated 5-6 kilometers from the main camp. Ultraclean, 4çailed collections were made in one pit for further laboratory investigations of seasonal variations (Herron and Langway, 1978) and horizontal variations (Klouda, 1977) in chemical constituents, and for further characterization of the glaciochemical regimes represented on the Ross
ANTARCTIC JOURNAL
Ice Shelf (Herron and Langway, 1976). Detailed density and stratigraphic measurements were conducted in the adjacent pit, located downwind of the chemical-sampling pit, to obtain an approximation of the recent rates of surface accumulation. Corehole temperatures were measured using a thermistor in conjunction with a Wheatstone Bridge (figures 2 and 3). At the South Pole, measurements were obtained from the 100meter corehole drilled under the dome in 1974 (Rand, 1975) as well as from the 111-meter corehole drilled during austral summer 1978 (figure 3). The comparison of the two temperature profiles from the South Pole suggests that there is a signficant (0.2° C) influence on the more recent temperature profile resulting from heat from the drill. This is especially apparent between 90 and 110 meters in the new hole where the penetration rate was considerably slower because of the denser firn. Coincident with the South Pole drilling operations was the core recovery at J-9 5-14 January 1978. Core processing was done by James Cragin. While there was some difficulty with the chip removal system, core recovery was rapid and core quality improved with depth. The corehole was fluid-filled at approximately 100 meters, and the final depth was 170.76 meters. This work was supported by National Science Foundation grant DPP 78-04412.
References
Chiang, E., and C. C. Langway, Jr. 1976. Physical properties of the 100 meters deep ice core from J-9, Ross Ice Shelf, Antarctica, Discussed at Symposium of SCAR-Specialist Group on Ice Shelf Drilling Projects, Mendoza, Argentina. Draft documents of XIV meeting of SCAR, October 18-23, 1976 (Abstract). p. 211. Gow, A.J. 1968. Deep core studies of the accumulation and densification of snow at Byrd Station and Little America V, Antarctica. US. Army Cold Regions Research and Engineering Laboratory. Research
Report, 197. Hanover, New Hampshire. Herron, M. M., and C. C. Langway, Jr. 1976. Glaciochemical regimes of the Ross Ice Shelf, Antarctica. Discussed at Symposium of SCAR-Specialist Group on Ice Shelf Drilling Projects, Mendoza, Argentina. Draft documents of XIV meeting of SCAR, October 18-23, 1976 (Abstract). p. 212. Herron, M. M., and C. C. Langway,Jr. 1978. Seasonal variations in Ross Ice Shelf precipitation chemistry. EOS Transactions, American Geophysical Union, 59(4): 308. (Abstract) Klouda, G. A. 1977. An investigation of the geochemical uniformity of an ice sheet. Unpublished master's thesis, State University of New York at Buffalo. Langway, C. C.,Jr., and M. M. Herron. 1977. Polar ice core analysis. Antarctic Journal of the US., 12(4): 152-154. Langway, C. C.,Jr. 1975. Antarctic ice core studies. AntarcticJournal of the US., 10 (4): 152-153. Rand, J. H. 1976. The USA CRREL Shallow Drill. In: Ice Core Drilling U. F. Splettstoesser, ed.). University of Nebraska Press, Lincoln. pp. 133-137. Rand,J. H. 1975. 100-meter ice cores from the South Pole and the Ross Ice Shelf. Antarctic Journal of the US., 10 (4): 150-15 1.
October 1978
Erebus Glacier Tongue movement G. HOLDSWORTH Environment Canada Ottawa, Canada
R. HOLDSWORTH University of Waikato Hamilton, New Zealand
Ice deformation measurements were made on the Erebus Glacier Tongue (77°40'N.166 0 40'E.), McMurdo Sound, in an attempt to support the hypothesis that, as a result of ocean wave excitation, a floating glacier may oscillate at a frequency that corresponds to one of its higher modes (Holdsworth and Glynn, in press). Under storm conditions with open water, the amplitude and duration of vertical oscillations may be caused by the bending stresses in the resonant-like motion, that cause fatigue failure in the ice. A field camp on the glacier (figure 1) was occupied continuously from 21 December 1977 until 26 January 1978. Because of the degree of crevassing all over the glacier surface, travel was by skis and equipment was moved by sled. The water depth at the glacier's edge was measured at 15 points by sounding line. Either a hole was drilled through the sea ice (3 to 3.8 meters thick) with a SIPRE corer or existing cracks or seal holes were used. Figure 2 shows the bottom profiles along the north and south edges of the glacier. Although no measurement of water depths directly under the glacier could be obtained, the data suggest that the glacier is free-floating except for a section of the north edge at the fixed end. On 15 February a hydrographic survey was made by USCGC Burton Island, but only near the terminus (figure 3) because fast sea ice remained in Erebus Bay and north of the glacier. Deformation of the glacier was measured by continuously recording wire strain meters (Goodman and Holdsworth, 1978) and a Schaevitz LSOC ( 1 0 ) servo-inclinometer. The direct current output of the latter instrument was fed to a portable strip-chart recorder. The unprocessed results obtained for tow of the stations reveal oscillations with periods of about ito 1 minutes and about 30 seconds occurring alternately as if there were "beating" between the two frequencies. Waves with a period of roughly 15 seconds are also evident. Pronounced oscillations exist with a period of 16 ( 1) seconds, which correlates well with the peak in the frequency spectrum for the sea ice (Goodman, personal communication, May 1978) although waves with a longer period (about 2 minutes) also are present in the glacier motion, at the same point. Personnel from the Scott Polar Research Institute, in cooperation with the U.S. Navy, surveyed ice thickness along the canterline of the glacier by air. The provisional glacier thickness profile is shown in figure 2. Other measurements included density and temperature in the upper 11 meters of firn at station number EGO 0. Density varied irregularly from 0.463 to 0.64 million grams per cubic
61
