1988), the 20- or 30-year mean accumulation rate can be cal- variations with time on ice stream B (McDonald and Whillans culated. This mean accumulation rate is integrated over the 1988). catchment area as obtained from the best available map (Shab- This research was supported by National Science Founda- taie, Whillans, and Bentley 1987). The output by flow is mea- tion grants DPP 83-17235, DPP 85-17590, and DPP 87-16447. sured by the repeat tracking of Transit (also called Doppler) satellites for ground control followed by repeat aerial photog- raphy and photogrammetry. On these controlled photographs References separate crevasses are traced from epoch to epoch to obtain velocity profiles across the ice stream. Together with data on MacAyeal, DR., R.A. Bindschadler, S. Shabtaie, S.N. Stephenson, ice thickness, the discharge is calculated. The result indicates and C.R. Bentley. 1987. Force, mass and energy budgets of the Crary that ice stream B and its catchment are slowly thinning. Ice Rise complex, . Journal of Glaciology, 33(114), 218-230. More detailed studies suggest that the thinning of ice stream McDonald, 1 . and I. Whillans. 1988. Comparison of results from B is not uniform but is especially large and irregular near the TRANSIT satellite tracking. Annals of Glaciology. 11, 83-88 transition from inland ice flow to streaming flow (Shabtaie et McDonald J . , and I.M. Whillans. 1988. Search for short-term velocity al. 1988; Whillans, Boizan, and Shabtaie 1987). In contrast, variation on ice stream "B," . Eos, (Abstract,) 69(16), 365. farther downstream, ice stream B appears to be thickening Shabtaie, S., C.R. Bentley, R.A. Bindschadler, and D.R. MacAyeal. (MacAyeal and others 1987). 1988. Mass-balance studies of ice streams A, B, and C, West Ant- The main portion of ice stream C is nearly stagnant (Mc- arctica, and possible surging behavior of ice stream B. Annals of Donald and Whillans 1988), as had been suspected. The in- Glaciology. 11, 137-149 terstream ridges are, in contrast, relatively steady in flow Shabtaie, S., 1. M. Whillans, and C. R. Bentley. 1987. Surface elevations (Whillans et al. 1987). on ice streams A, B, and C, West Antarctica, and their environs. The next step in the study of ice streams is to deduce the Journal of Geophysical Research, 92(139), 8865-8883. mechanics controlling their flow. Once this is understood, it Van der Veen, C.J., and I.M. Whillans. In press a. Force budget: Part may be possible to address more fully the causes for the on- I, general theory and numerical methods. Journal of Glaciology. going changes in the ice streams and ice sheet as a whole. To Van der Veen, C.J., and I.M. Whillans. In press b. Force budget, Part II, application to the Byrd Station Strain Network. Journal of Gla- this end, very complete surveys of the velocity field of ice ciology. stream B are being obtained from repeat aerial photogram- Vornberger, P.L., and I.M. Whillans. 1986. Surface features of ice metry. The results are just becoming available, but the tech- stream B, Marie Byrd Land, West Antarctica. Annals of Glaciology, niques for interpreting these data have been more fully 8, 168-170. developed through theory (Van der Veen and Whillans in press Whillans, O.M., and R.A. Bindschadler. 1988. Mass balance of ice a) and application to the Byrd Station strain network (Van der stream B, West Antarctica. Annals of Glaciology. 11, 187-193 Veen and Whillans in press b) and to Byrd Glacier (Whillans Whillans, I. M., and J . Bolzan. 1988. A method for computing shallow et al. in press). ice-core depths. Journal of Glaciology. 34(118), 355-357 Other major efforts have been the interpretation of crevasse Whillans, I. M., J . Bolzan, and S. Shabtaie. 1987. Velocity of ice streams shapes on remote imagery to infer velocity patterns (Vorn B and C, Antarctica. Journal of Geophysical Research, 92(B9), 8895- - 8902. berger and Whillans 1986), a careful study of the reproduci- Whillans, I.M., Y.H. Chen, C.J. Van der Veen, and T.J. Hughes. In bility of positions calculated using transit- satellite tracking- press. Force budget, Part III: Application to three-dimensional flow data (McDonald and Whillans 1988), and a search for velocity on Byrd Glacier. Journal of Glaciology.

Drilling on Crary Ice Rise, During the 1987-1988 field season, two holes were drilled through Crary Ice Rise (83°S 170°W) to install thermistor cables. Antarctica The hot-water drill, designed by the Polar Ice Coring Office melted a hole averaging 26 centimeters in diameter at an av- R.A. BINDSCHADLER erage drilling rate of 0.5 meters per minute. Instrumentation on the drill stem included inclinometers to measure the tilt of National Aeronautics and Space Administration the hole, thermistors to measure the water temperature and Goddard Space Flight Center heat loss, and calipers to measure the size of the hole. Greenbelt, Maryland 20771 After the holes were drilled, cables with thermistors were installed in the holes and allowed to freeze in. Freezing took B. Koci only a few days after which each thermistor continued cooling to a final equilibrium temperature. This cooling required many Polar Ice Coring Office weeks, so final temperatures will not be obtained until re- University of Nebraska measurement next field season. Lincoln, Nebraska 68588-0200 The temperature data is used to date the time since the ice A. IKEN rise grounded. The premise of this technique, first applied by Lyons, Ragle, and Tamburi (1972), is that the bases of ice rises VAW/ETH-Zentrum are colder than floating ice shelves. Thus, as an grounds, 8092 Zurich, Switzerland the basal ice must cool, a process requiring thousands of years

60 ANTARCTIC JOURNAL

168W 83.4S 170W 83.2S 172W 83S

Ow

11 2ZOU- 100 .0-100

83.2S 83S 168W 82.8S 170W

Figure 1. Surface elevation of Crary Ice Rise. Contours are in meters above mean sea level. The isolated dome and single ridge are evident. Data are from airborne radar sounding (Shabtaie personal communication) and optical leveling. Filled circles indicate drill sites. and affecting, eventually, the entire ice rise (MacAyeal and The ice thickness above buoyancy at this point is 70 meters— Thomas 1980). By numerically modeling this transient cooling, enough, we expect, to prevent warm sea water from seeping the time elapsed since grounding can be determined. under the ice rise. Thus, the warm basal ice implies an ice rise The first hole was 370 meters deep and located at highest which is very young and has only just begun to cool. We bedrock (using radio echo-sounding data collected by the Uni- estimate the time since grounding is only a century or two. versity of Wisconsin). This location corresponded to a local ice This estimate will be refined after remeasurement of the ther- dome on the ice rise (figure 1). We speculate that ice here has mistors in both holes next field season. been grounded longest and thus will provide a maximum age An ancillary, but no less significant, achievement of drilling for the ice rise. The second hole was located on the prominant the second hole (450 meters deep) was the unexpected recovery ridge southwest of the dome. This ridge is the highest feature of subglacial material. A rock 5 centimeters long and a mud of the ice rise, but radar sounding data indicate that it occurs clast 4 centimeters long were lodged in the caliper arms when on the side of a bedrock slope rather than a bedrock ridge. the drill stem was winched to the surface (figure 3). In addition, Temperature measurements in the first hole lasted for 11.5 approximately 1,000 cubic centimeters of sediment material days. Although this was not long enough for full recovery from the drilling to occur, there was a very clear indication that the basal ice is very close to pressure melting (figure 2). 4 8 q

0 LU cc

I- <-10 cc uJ

LU I- -15

_20o 100 200 300 TIME (hours)

Figure 2. Cooling curves in first hole at 100, 200, 300, and 370 meters below the surface. Data at the bottom of hole (370 meters) Figure 3. Photograph of rock recovered from bottom of second is from two independent thermistors. (m denotes meters.) hole (450 meters).

1988 REVIEW 61 was spread over the drill stem filling most of the ledges and This research was supported under National Science Foun- holes. The rock appears to be basaltic in composition and strongly dation grant DPP 86-14407. faceted indicating subglacial transport over a considerable dis- tance (Ridky personal communication). Thin sections of the rock will be prepared, and it will be examined by electron microscopy for evidence of micro-striations. References The clast and mud appear to be equivalent in composition: a mixture of fine and coarse gravels. The mud may well have Lyons, J.B., R.H. Ragle, and A.J. Tamburi. 1972. Growth and ground- been formed when the high-pressure hot water broke and ing of the Ellesmere Island ice rises. Journal of Glaciology, 11(61), 43- 52. dissolved numerous subglacial clasts. Analysis of the biogenic MacAyeal, D.R., and R.H. Thomas. 1980. Ice-shelf grounding: Ice and composition of the mud and clast is underway at the Byrd bedrock temperature changes. Journal of Glaciology, 25(93), 397-400. Polar Research Center at Ohio State University. No younger Ridky, R. 1988. Personal communication. than upper Miocene have been identified in the samples (Scherer Scherer, R. 1988. Personal communication. personal communication). Shabtaie, S. 1988. Personal communication.

Hot-water drilling on the Siple Coast with numerous difficulties. Several heater transformers burned up and a short length of hose was ruined. With repairs made and the system functioning properly, the drilling took place W. L. BOLLER and J. M. SONDERUP over the next 10 days. Drilling was conducted along a grid that Polar Ice Coring Office consisted of a straight line of 100 holes (360 meters between University of Nebraska holes), with four crosslines of 10 holes each, for a total of 140 Lincoln, Nebraska 68588-0640 holes. Besides this grid, the crew (W.L. Boller, W.A. Bachman, and S.R. Bretz) did an additional small grid for a students (G. Moline) project. This consisted of 20 holes in one line, and The Polar Ice Coring Offices (PICO) drilling this season brought the total number of shot holes for the season to 160. focused not on the traditional electromechanical drill- In the next few days, we filled the last 20 shot holes with ing but rather on hot-water drilling. The drilling activities in- salt water. Electrodes were lowered and frozen in as we went. volved two projects in support of investigations by the University The traditional hot-tub party was held that evening, then we of Wisconsin at Madison and the National Aeronautics and dismantled the system and loaded it on a pallet for the flight Space Administration. A record number of seismic shot holes out. were drilled on the Siple Coast, and a unique sample of glacial The second PICO project involved hot-water drilling at Crary till mud was retrieved from a deep access hole through the Ice Rise for R. A. Bindschadler, National Aeronautics and Space Crary Ice Rise. Administration (Bindschadler, Koci, and Iken, Antarctic Jour- At Downstream B, PICO was assigned the task of providing nal, this issue). Our office was assigned the task of drilling two a grid of hot water shot holes in support of C.R. Bentley, holes to bedrock for installation of thermistor cables. The PICO University of Wisconsin (Bentley, Anandakrishnan, and Roo- field team consisted of B.R. Koci, W.H. Hancock, and J.M. ney Antarctic Journal, this issue; Bentley, Blankenship, and Mo- Sonderup. R.A. Bindschadler and A. Iken, ETH-Zurich, per- line, Antarctic Journal, this issue). The PICO technicians arrived formed a survey of the area and assisted with the drilling. at the Downstream B camp on 21 November, 1987. Two days A new hot-water drill and winch were designed and built were spent setting up the equipment. An Air Force pallet had by PICO for this project. The winch was wrapped with the to be substituted for the Maudheim sled which did not show maximum 600 meters of hose. The pump produced 190 pounds up on the put-in flight. A Tucker Sno-Cat was used to tow the per square inch (13 bars) of pressure at a flow rate of 22 gallons pallet of drilling equipment which consisted of two 80-kilowatt (85 liters) per minute. This allowed a drill rate of approximately heaters, a high-pressure pump, a hose reel, a generator, a 150- 0.4 meters per minute, creating a hole diameter of 10 to 12 gallon (550-liter) storage tank, and several drums of antifreeze inches (26 to 28 centimeters). Water was recirculated from a and fuel. The two heaters were first used to generate water water well 40 meters below the surface, pumped to the surface on the surface in the 150-gallon (550-liter) storage tank, then by a submersible pump. later used to heat the water to 95°C on its way down the drilling Heat was provided by six heaters (2 Alladin and 4 Hotsy hose. The high-pressure pump and full-flow nozzle provided heaters, of 350,000 British thermal units each) connected in the drilling punch. A flow rate of 12 gallons (44 liters) per parallel. The inlet water temperature at the heaters was 20°C minute provided a 4-inch (10 centimeter) hole, 17 meters deep and the outlet temperature was 90°C. The water temperature in 6 to 8 minutes. Once a steady routine was established, a at the drill was approximately 86°C. complete cycle (melting the required amount of water, drilling The drill system, which contained an instrumentation pack- the shot hole, packing up to move, and moving 360 meters age designed and built by W.H. Hancock, would measure hole down the line), could be completed in 40 minutes. diameter, inclination, depth of drill, water temperature inside The line had been established and flagged prior to PICOs and outside the drill, and inlet water temperature. All mea- arrival by S.T. Rooney and D.D. Blankenship of the Wisconsin surements were displayed and recorded on a Compaq portable group. The actual shot hole drilling began on 23 November— computer. 62 ANTARCTIC JOURNAL