Ross Ice Shelf Project

Drilling in and below ice will reveal physical, chemical, biological features

JAMES H. ZUMBERGE

College of Earth SciencesUniversity of Arizona

The Ross Ice Shelf Project as presently conceivedwill involve the drilling of a hole in the Ross IceShelf to investigate the shelf ice, the underlying seawater, and the ocean floor.

It is difficult to trace the origin of the idea for thismultidisciplinary project to an individual or group ofindividuals, but ever since the Ross Ice Shelf waspenetrated at Little America in 1958 (Ragle et al.,1960), a number of scientists have speculated on thevalue of future ice-core drilling in the shelf. In 1968,A. P. Crary suggested in his address to the Interna-tional Symposium on Antarctic Glaciological Ex-ploration that a number of scientific problems couldbe solved if a hole drilled several hundred kilometersback of the Ross Ice Shelf barrier could be used tosample the underlying water column and bottomsediments (Crary, 1970).

One of the original authors of the Ross Ice ShelfProject may have been the late Harry Wexler. Dr.J . W. Brodie, director of the New Zealand Oceano-graphic Institute, reported in a letter to G. 0. Hem-men (May 15, 1969) that "many years ago" he haddiscussed with Wexler the proposition of drilling ahole through the Ross Ice Shelf to sample animalsand sediments in the water column and at the bot-tom; to measure current velocity and direction, tem-perature, and salinity in the water column; to measureheat flow through the bottom; and to install suchpermanent monitoring equipment as current metersand thermographs. Brodie recommended in his letterto Hemmen that the site of the hole be over a sub-stantial depth of water and several hundred kilome-ters from the ice front.

The National Academy of Sciences' Committee onPolar Research (1970) made a number of formalrecommendations that relate directly to the scientificgoals of the Ross Ice Shelf Project and established anad hoc planning group to look into the matter. Dr.

Sayed Z. El-Sayed of Texas A&M University, chair-man, convened the group in Washington, D.C., orMarch 27 and 28, 1970, at which time a number oideas were presented and some recommendationwere made.

Scientific objectives

As a result of the March 1970 meeting, the scien-tific objectives of the Ross Ice Shelf Project haveemerged. Physical, chemical, biological, and geolog-ical conditions within and beneath the Ross Ice Shelfwill be investigated to determine how they relate tothe ice itself, the water mass, the ocean floor, and thesubsea sediments. More specifically, answers will besought to these and other questions:

1. What is the thermal regime (melting or freezing)at the base of the Ross Ice Shelf several hundredkilometers from the ice front?

2. What do the physical and chemical aspects othe water mass reveal about the origin, age, and circulation of sea water beneath the Ross Ice Shelf? Ithis water mass (or part of it) stagnant with respectto the Ross Sea, or is there continuous interchangeof water between them?

3. What are the biological inhabitants of the watermass? Does a living biome exist as a separate anisolated entity with its own nutrient cycle? Are alor some of the organisms beneath the shelf immigrantfrom the Ross Sea?

4. What are the conditions of sedimentation on thsea floor beneath the Ross Ice Shelf and how do the)differ from the sedimentary environment of the Ross'Sea at varying distances from the ice front? Are thesediments on the floor of the Ross Sea and the oceanbottom beneath the Ross Ice Shelf diagnostic of theabsence, or presence, of shelf ice conditions?

5. What can be learned from sedimentary coretaken beneath and beyond the Ross Ice Shelf aboutthe waxing and waning of the antarctic ice sheet anthe preglacial geologic history of the Ross basin?

This list is by no means exhaustive, but it gives aidea of the intriguing scientific questions that mighbe answered from the project.

258 ANTARCTIC JOURNAL

SCAR group of specialists

On February 27, 1970, Scientific Committee onAntarctic Research (SCAR) Circular 248 reportedon progress in the United States toward formulatinga plan to drill through the Ross Ice Shelf and invitedthe SCAR nations to indicate their interests in sucha project in preparation for discussions at the 11thSCAR meeting in Oslo in August 1970.

Considerable interest in the Ross Ice Shelf Projectwas voiced by a number of scientists at the Oslo meet-ing. A paper outlining the plan was presented to theopening plenary session, to a special meeting ofSCAR delegates and observers, and to the joint meet-ihg of the SCAR working groups on geology and solidearth geophysics (Zumberge, 1970). The Oslo dis-cussions were reported by the International Union ofGeodesy and Geophysics (1970) and the ScientificCommittee on Antarctic Research (1971).

As a result of these discussions, the SCAR executiveappointed a specialist group on ice shelf drilling proj-ects to offer guidance and advice to the Ross Ice Shelfsteering group of the U.S. Committee on Polar Re-search (discussed below) and to other groups that

ight develop future ice shelf drilling projects. De-tails on the specialist group are given in ScientificCommittee on Antarctic Research (1971, p. 797).Members of the specialist group are R. D. Adams(New Zealand), C. R. Bentley (U.S.A.), J . W.Brodie (New Zealand), W. F. Budd (Australia), M.

rosval'd (Soviet Union), B. L. Hansen (U.S.A.),Ishida (Japan), C. C. Langway (U.S.A.),

R. Radok (Australia), G. de Q . Robin (Unitedingdom), C. M. Swithinbank (U.K.), E. Seibold

(West Germany, liaison with the Scientific Commit-te on Oceanographic Research), and J . H. Zum-brge (U.S.A., convenor). The specialist group planst6 meet at the twelfth SCAR meeting in Canberra,4ugust 1972.

Committee on Polar Research steering groupTo follow up the work of the ad hoc planning

g oup, Dr. L. M. Gould, chairman of the Committeeo Polar Research, appointed a Ross Ice Shelf Projectsl eering group consisting of C. R. Bentley (Universityo 1 Wisconsin), D. H. Elliot (Ohio State University),S Z. El-Sayed (Texas A&M University), A. L. Gor-d n (Lamont-Doherty Geological Observatory), B.L. Hansen (U.S. Army Cold Regions Research andEngineering Laboratory). D. E. Hayes (Lamont-

oherty), C. C. Langway (CRREL), R. P. Southard(U.S. Geological Survey), N. Untersteiner (Univer-sity of Washington), J . Weertman (NorthwesternUniversity), and J . H. Zumberge (University ofArizona; chairman). P. M. Smith (National ScienceFoundation) and L. DeGoes (Committee on PolarResearch, executive secretary) are ex officio members.

The steering group met in Washington, D.C., onApril 16, 1971, to discuss the scientific objectives ofthe Ross Ice Shelf Project and to review the status ofthe planning. The following remarks are based onthe deliberations at that meeting.

General plan

It was decided to divide the Ross Ice Shelf Projectinto two phases: a pilot hole project and a main drill-ing project. The objective of the pilot hole projectwill be to test the feasibility of drilling a hole in theshelf and of keeping it unfrozen long enough to con-duct a limited scientific program. During the drillingof the pilot hole, the diameter of which has not yetbeen determined, a complete ice core will be recov-ered. The water column will be sampled for biologicand inorganic content, and other parameters of thewater mass will be measured. Samples of the bottomsediment will be retrieved, and shallow gravity coringwill be attempted. Underwater television may betried, and bottom photography may be used. Thetentative site of the pilot hole is about 450 km fromthe ice front, at 82.5 0 S. 166 0 W., where the ice isabout 500 m thick and the underlying water column100 to 200 rn thick (see map on page 261).

The main drilling project will include all experi-ments attempted in the pilot hole plus a capabilityfor core drilling in the ocean floor. Additional experi-ments arising out of experience gained in the pilothole project may also be conducted. The site for themain drilling project will be selected after adequateseismic soundings through the shelf have been made.The start of the main drilling project is planned for1 year after the pilot hole is started. The ability tomeet this schedule will depend on the experiencegained in the pilot hole project and on such otherfactors as the need for specially designed equipment,funding, and logistics.

The Ross Ice Shelf Project will be augmented bythe deep-sea coring program of Glomar Challengerif plans by the National Science Foundation to fundseveral legs into antarctic waters materialize.

Details of the pilot hole project and some aspectsof the main drilling project follow.

Planning map

The U.S. Geological Survey is preparing a plani-metric map of the Ross Ice Shelf and environs at ascale of I : 1,000,000. The map will cover the areafrom 77° to 88'S. between 150°W. and the Trans-antarctic Mountains and will include all available in-formation from International Geophysical Yeartraverses, recent air photographs, radio-echo soundingdata on ice thickness, and newly published shadedrelief maps of the Transantarctic Mountains. Themap will be drafted on a stable base and will be re-

November—December 1971 259

from the ice front, was selected in part to test thebottom freezing hypothesis.

Physical oceanography

tamed at the Survey's Branch of Special Maps, wherenew information will be added as it becomes avail-able. Film positives or paper prints will be availableto Ross Ice Shelf Project scientists.

Drilling technique

The U.S. Army Cold Regions Research and Engi-neering Laboratory will design, fabricate, and test adrill rig under the direction of B. L. Hansen. The rigwill be of the compressed-air, reverse-rotary type andwill use a wire-line coring device for obtaining icecores. The hole diameter has not been established, butit will be in the 30- to 100-cm range. The upper sec-tion of the hole will be cased because of the perme-ability of the firn. A heated wire suspended in thehole will prevent sea water that enters the hole atthe base of the shelf from freezing. Drilling time willbe about 30 days in ice that is 500 m thick.

Glaciology

Considerable experience has been gained in theanalysis of ice cores from the 1,391-rn core taken atCamp Century in Greenland and the 2,164-rn coretaken at Byrd Station in Antarctica. Analytical tech-niques established by Langway (1970) on those coreswill be used on the Ross Ice Shelf cores. In addition,volcanic ash will be sought in the cores. Gow (1963,p. 277) identified ash horizons in the Little Americacore at the 172-, 219.4-, and 222.8-rn depths. Dis-covery of these volcanic ash inclusions in other icecores from the Ross Ice Shelf would not only providea means of correlation but also be of great value inanalyzing the dynamics of shelf movement.

The basal shelf ice will be examined for evidenceof sea ice accretion. Swithinbank and Zumberge(1965, p. 210) inferred bottom melting of the iceshelf near the barrier and bottom accretion of seaice near the land margin of the shelf. In their massbalance equation for the Ross Ice Shelf, Giovinettoand Zumberge (1968) used a value of 12 g per sqcm per yr as the mean rate of sea ice accretion at thebase of the Ross Ice Shelf south of a line about 150km south of the barrier. This value was based onprevious work (Zumberge, 1964), which has beenquestioned by Robin (Giovinetto and Zumberge,1968, p. 265). Oceanographic studies in the RossSea show high salinities (34.60 to 34.90 per mill) inthe bottom water (Jacobs et al., 1970), and Gordon(1969, p. 183) has suggested that the highly salinewaters originate beneath the ice shelf, where brine isreleased during the freezing of sea water to the shelfbottom. The thermal regime at the shelf-water inter-face some hundreds of kilometers south of the barrierwill be of obvious interest to glaciologists and ocean-ographers. The planned site of the pilot hole, 450 km

In addition to questions of freezing and melting atthe bottom of the ice shelf, other questions about thewaters below the shelf will be answered by directsampling and measurements through the open hole inthe shelf. The oceanographic aspects of the projeclwill include measuring salinity, temperature, oxygen,and the density-depth relationship; sampling waterfor turbidity, carbon-14, and chemical analyses; andmeasuring current. This work will be done overa few hours to a few days rather than over severalweeks or months. However, a self-contained recordingpackage may be left on the ocean bottom, or one ormore units may be suspended beneath the shelf; icethat forms in the hole can be melted for retrieval ofthe recorders. The extent to which existing samplingand measuring devices can be used will depend onthe stable diameter of the open hole.

Marine biology

The cold, dark waters beneath the Ross Ice Shelfwill be sampled carefully for pelagic or benthic life,.Because these forms may be microscopic, large vol-umes of sea water will be pumped from differentdepths and filtered to recover planktonic forms.Microscopic bottom dwellers will be sought in thebottom sediments. Underwater television and

photog

raphy will be used in the search for larger specieContamination of the hole will be kept to a minimuto protect the integrity of the biological samp1in.While there has been no speculation on the life formsthat might exist in isolation beneath the ice shelf,the occurrence of highly specialized forms of lifein aquatic caves suggests that marine life beneaththe Ross Ice Shelf is possible.

Bottom sediments

The pilot hole project will include the sampling ofbottom sediments and the retrieval of shallow gravitycores. These samples will be compared with samplesfrom the Ross Sea in the hope that a subshelf faci scan be distinguished from a Ross Sea facies. Th sdistinction is necessary in the interpretation of cor sfrom either beneath the shelf or the Ross Sea.

The main drilling project will include the capabi -ity of lowering the drill stem to the sea floor and re-trieving cores with a wire-line coring device. Thedepth of penetration will depend on the nature ofthe sediments encountered and on the time availablefor coring. The latter is a function of water depthand movement of the shelf. For example, with a waterdepth of 200 m and a shelf movement of about 1 rn

260 ANTARCTIC JOURNAL

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Ice thicknesses and depth soundings are in meters.After this paper was in press, the Scott Polar Research Institute (SPRI) released a draft version of a new ice thickness map

for the entire Ross Ice Shelf based on radio-echo soundings. The SPRI map shows greater detail in shelf ice thicknesses asa Fected by ice streams from Marie Byrd Land and by outlet glaciers from the Transantarctic Mountains.

November-December 1971 261

per day, we can drill for 10 days---assuming that cor-ing can continue until the hole in the shelf moveshorizontally 5 percent of the length of the watercolumn from the hole in the ocean floor. Because thelocation of the main drilling site will not be deter-mined until after the pilot hole project has been con-cluded, the time available for bottom coring cannotbe determined. It is assumed, however, that sufficienttime will be available at the main drilling site formoderate-depth coring.

Deep coringSince the early planning stages of the Ross Ice

Shelf Project, the National Science Foundation hasconsidered the possibility of extending Glomar Chal-lenger's drilling program to Antarctica. Plans for thisextension include the drilling of a number of sites inantarctic waters. The planning committee of the JointOceanographic Institutions for Deep Earth Sampling(JOIDES) has been advised of the desirability ofdeep coring in the Ross Sea to augment Ross IceShelf Project objectives. A JOIDES advisory panelon the antarctic ocean, established this year, hasidentified three sites in the Ross Sea that should beput on Glomar Challenger's schedule if core drillingin antarctic waters becomes a reality. These sites areat 78 0 S. 172 0 W. 1 77 0 S. 171 0 W., and 75.5°S.170°W. (see map). The points fall on the trajectoryof a projected ice flow line passing through the pilothole site and the edge of the continental shelf. Theseproposed drilling sites would have been covered bythe Ross Ice Shelf at an assumed earlier stage whenthe ice front stood along a line from Cape Colbeckon the Edward VII Peninsula to Cape Adare in Vic-toria Land, some 400 km north of the present front.

Even if these sites are approved by the JOIDESplanning committee, there is no guarantee that coringwill be done at those exact coordinates. The final de-cision can be made only after extensive seismic pro-filing in that region of the Ross Sea. Houtz andMeijer (1970) have shown that anticlinal structuresexist beneath the Ross Sea (see map). For obviousreasons, the penetration of a subocean anticline con-taining fluid hydrocarbons is to be avoided.

Seismic soundingsIn addition to seismic profiling in the Ross Sea,

seismic soundings at a number of places on the RossIce Shelf will be necessary to more clearly definewater depths, bottom topography, and geologicalstructures beneath the sea floor. The only informationon water depths beneath the shelf is based on tra-verses made during the International GeophysicalYear (Crary et al., 1962). An airborne seismic sound-ing program covering selected segments of the shelfwill provide information on the parts of the shelf not

covered by the IGY traverses and will be vital to theselection of the drilling sites.

Tentative scheduleThe magnitude of the Ross Ice Shelf Project, the

multidisciplinary range of the experiments, and theParticipation of non-U.S. scientists demand carefulplanning and skillful execution of the field program.At this writing, planning for the field activities isstill in a state of flux. Costs for various aspects of theproject have not been estimated; not all project lead-ers for the specific elements of the program have beenidentified; the exact means of involving foreign sci-entists have not been worked out; and the overallmanagerial assignment has not been made. Decisionsbearing on these questions need to be made soon.

Meanwhile, the Committee on Polar Researchsteering group for the Ross Ice Shelf Project has sug-gested a tentative timetable.

The Ross Ice Shelf planning map, in preparatioiby the U.S. Geological Survey, will be completed iiearly 1972.

Preliminary design and engineering for the drillingequipment is being undertaken by the U.S. ArmyCold Regions Research and Engineering Laboratory.Drilling of the pilot hole could commence in October1972 depending on the time needed for engineeringdesign, procurement, and testing at the CRREL drilltest facility in New Hampshire and in Greenland.Funding constraints could delay the pilot hole untilOctober 1973.

Seismic work on the shelf could be started in theaustral spring of 1972 and carried out over two su-cessive seasons. Because the pilot hole will not invohedrill-coring into the sea floor, seismic soundings a needed at the pilot hole site to establish only watE rdepth and ice thickness.

The main drilling project could take place in the1973-1974 austral summer, synoptically with drillingin the Ross Sea by Gloniar Challenger. If the manproject is delayed a year, the Glomar schedule willnot be affected because there is no compelling reasonto have the main drilling project coincide with coringin the Ross Sea.

When the diameter of the pilot hole is establisheequipment that will be lowered through the hole canbe procured by selecting from among existing iterr. s,by modifying present equipment, or by designing i -struments specifically for through-the-ice samplir gand measuring. This task should get under way ear yin 1972 so that all components will be ready for thepilot hole operation should it begin in the 1972-1973austral summer.

The success of the Ross Ice Shelf Project will de -pend on how carefully all of the component activ-ities can be fitted into a single operational schedule.If humanly possible, all participants should adhere

262 ANTARCTIC JOURNAL

to the master plan once it is established. However,unforeseen delays may arise, and each scientist mustbe prepared to adjust to a new situation on shortnotice. Scientists who possess this capability have

een the most successful in past antarctic operations.he Ross Ice Shelf Project is not likely to alter this

bservation.

References

mmittee on Polar Research. 1970. Polar Research—ASurvey. Washington, D. C., National Academy of Sciences,National Rsearch Council. 204 p.

(ary, A. P. 1970. Presidential address. International Sym-posium on Antarctic Glaciological Exploration (ISAGE),Hanover, New Hampshire, 3-7 September 1968. Interna-tional Association of Scientific Hydrology. Publication, 86:x—xvi.

(ary, 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: 2791-2807.

(Iovinetto, M. B., and J . H. Zumberge. 1968. The ice re-gime of the eastern part of the Ross Ice Shelf drainagesystem. International Association of Scientific Hydrology.Publication, 79: 255-266.

(ordon, A. L. 1969. Physical oceanography on EltaninCruises 32-37. Antarctic Journal of the U.S., IV(5)183-184.

Gow, A. 1963. The inner structure of the Ross Ice Shelf atLittle America V, Antarctica, as revealed by deep coredrilling. International Association of Scientific Hydrology.Publication, 61: 272-284.

Houtz, R., and R. Meijer. 1970. Structure of the Ross Seashelf from profiler data. Journal of Geophysical Research,75(32): 6592-97.

International Union of Geodesy and Geophysics. 1970. RossIce Shelf Project. Its Chronicle, 81: 169-170.

Jacobs, S. S., F. M. Amos, and P. M. Bruchhausen. 1970.Ross Sea oceanography and Antarctic Bottom Water for-mation. Deep-Sea Research, 17: 935-962.

Langway, C. C. 1970. Stratigraphic analysis of a deep icecore from Greenland. Geological Society of America. Spe-cial Paper, 125. 186 p.

Ragle, R. H., B. L. Hansen, and A. Gow. 1960. Deep coredrilling in the Ross Ice Shelf, Little America V, Antarc-tica. U.S. Army Snow, Ice, and Permafrost ResearchEstablishment. Technical Report, 70. 10 p.

Scientific Committee on Antarctic Research. 1971. SCARBulletin, 37: 796-797. Polar Record, 15: 648-649.

Swithinbank, C. W. M., and J . H. Zumberge. 1965. The iceshelves. Antarctica. New York, Frederick A. Praeger.p. 199-220.

Zumberge, J . H. 1964. Horizontal strain and absolute move-ment of the Ross Ice Shelf between Ross Island and Roose-velt Island, Antarctica. Antarctic Research Series, 2:65-81.

Zumberge, J . H. 1970. The Ross Ice Shelf Drilling Project.Washington, D. C., National Academy of Sciences, Com-mittee on Polar Research. 9 p. Mimeographed.

RIV Hero Cruise 71-2 to Isla de los Estados

OLIVER S. FLINT

Department of EntomologySmithsonian institution

The objective of R/V Hero Cruise 71-2 was tosurvey the vertebrate, arthropod, and marine biotasof Isla de los Estados and adjacent areas of Tierra

ci Fuego, Argentina. Much of Tierra del Fuego hasbeen studied, and its fauna is fairly well known. How-ever, aside from incidental observations and collec-tions, mostly of birds (Saivadori, 1900; Castellanos,935, 1937; and Beaglehole, 1961), the fauna ofsla de los Estados has not been surveyed previously.

^he island

Isla de los Estados is roughly 60 km long on anapproximate east–west axis and is situated across the

Estrecho de la Maire from the eastern tip of Tierradel Fuego (see map). The north and south sides arecut by many fjords, some of which almost bisect theisland. The topography is generally very rugged,reaching to 823 in in the Montes Bove. The north -eastern corner of the island and Islas Aflo Nuevo aremuch flatter, however. The shoreline is generallysteel), often precipitous, although there are a fewbays with sand or cobble beaches.

The lower slopes are covered with a dense ever-green forest of southern beech (Not hof agus) andwinter's bark (Drim),$), often with a dense under-growth of shrubs and bryophytes. On level areas withsaturated soil or at high elevations, the land is cov-ered with a moorland-type flora, sometimes hip-deepwith rushes. Bedrock is evident everywhere, with thepeaks generally barren rock.

Streams and ponds are numerous. The latter oc-cupy glacial basins, some of which (Lago Louisato,

&ovember–December 1971 263