Opportunities and Priorities in Arctic Geoscience (1991)

The types of investigations attempted and the volume of data acquired in arctic geoscience studies have been hindered by the remoteness and harshness of the environment. There has been an inability, in part technological and in part fiscal, to apply to the Arctic Ocean the full range of geological and geophysical techniques that are available to research in marine geoscience at lower latitudes. The committee believes that the technological constraints, although still severe, are no longer paramount. With adequate funding, scientific platforms and technology capable of revolutionizing our knowledge of the solid earth beneath the Arctic Ocean could be mobilized.

The overriding problem for solid-earth geoscience in the Arctic Ocean Basin has, of course, been its inaccessibility to standard marine research vessels and drill ships. Recent cruises of icebreakers to high latitudes within the arctic ice pack and of Soviet nuclear icebreakers to the North Pole suggest that this barrier will soon be broken. Other technologies, discussed in more detail below, will soon be available to arctic science. The degree to which the scientific community can mobilize these latent technological resources will determine the extent of its contribution to both arctic and global science in the decade of the 1990s.

There are two philosophies regarding support arrangements for arctic research. One is the concept that investigators with all levels of sophistication and preparedness for arctic conditions should utilize large, federally-supported facilities to acquire arctic data; the other is the concept that each program and their parties should secure their own logistic platforms and support.

In Alaska, the large facility concept was used by the U.S. Navy at its year-round Naval Arctic Research Laboratory at Point Barrow, which was decommissioned in 1980 owing to changing Navy priorities. It has since been refurbished by the North Slope Borough but has only limited facilities for support of large-scale investigations. On a smaller scale, the University of Alaska operates a seasonal camp at Toolik Lake, just north of the Brooks Range, that could support small-scale, local projects in the geosciences. With the development of the Prudhoe Bay and Kuparuk oil fields, it is now possible to drive motor vehicles to the coast; helicopters, fixed-wing aircraft, and small boats can be chartered for fieldwork at Barrow, Prudhoe Bay, and Kaktovik, where living accommodations are also available.

The Canadian government is heavily involved in multidisciplinary transects across the Canadian arctic continental shelf and supports these activities with airborne logistics and major camps for mobilizing field parties. Sizable camps are maintained at Inuvik, in the Mackenzie Delta,

and at Alert, on northern Ellesmere Island. The program is of finite duration, however, and has limited value for long-term baseline studies.

Recent events demonstrate possible Soviet interest in opening of the Soviet Arctic to researchers from other nations. For example, the Soviets recently solicited western geoscientists for collaborative or contract work on a Soviet research vessel operating on the Siberian Shelf. Such a development would be of great utility to the arctic geoscience community because the Soviet Union, with a well-developed network of coastal settlements with scheduled air service that are visited regularly by freighters along the northern sea route as well as by established air routes, is relatively accessible to arctic research.

Also, the recent return of the USSR to the group of countries jointly participating in the Ocean Drilling Program is another encouraging sign of potential Soviet participation in international oceanographic research programs. In addition, the USSR is a signatory to the newly formed International Arctic Science Committee, a non-governmental organization established to facilitate coordination and cooperation in all fields of arctic science.

Scandinavia, like Alaska, has a number of arctic settlements, including those on Spitzbergen, from which arctic field studies could be staged. Of these, Longyearbyen, at 78°N, is the northernmost, with regular airline service and commercial facilities. The situation in Greenland is somewhat different in that the relevant facilities there are military. Denmark maintains an airfield at Station Nord (80°30'N) on east Greenland that can be used as a stepping-stone for research in the high Arctic.

The committee believes that existing commercial and government facilities in North America and northern Europe can support most of the field investigations recommended in this report. Suitable fixed wing and rotor craft and a variety of ice-reinforced ships operated by companies with arctic experience are widely available for hire, and an extensive, if not particularly dense, network of airfields and living accommodations is available for logistical base camps. Because most of the research proposed in this report requires nonrepetitive measurements and sampling, the committee recommends that arctic geoscience research funds not support permanent logistic facilities. Such facilities are costly to build, maintain, and staff; they could support only some of the logistic platforms required by the proposed research; and they would represent an impost on all geoscience research projects in the Arctic. Such facilities would also create an additional bureaucracy that might grow and drain significant funds from arctic research. Where long-term facilities are required for a particular investigation (e.g., seismograph stations) or program (e.g., coastal process studies), that investigation or program should budget the full cost. We believe that such a policy would be most cost effective and that it would also remove the influence that subsidized (and expensive) research facilities would inevitably have on where and how arctic geoscience would be conducted.

The recent development of new geophysical instruments and the continuing reduction in size and weight of others will greatly advance solid-earth geoscience research in the Arctic. Important examples of such instruments are small digital recorders that can be deployed in long seismic refraction arrays on sea ice in late winter and spring, digital recorders capable of recording and processing 16 or more channels of seismic reflection data that are sufficiently rugged and compact to operate on sleds during field operations in the Arctic, gravity systems that can achieve accuracies of 3 or 4 mgals from airplanes or helicopters, and long-range side-scan imaging and digital bathymetric mapping systems that can image and map the seafloor from submarines. Many measurements that could not be made, or at least could not be made efficiently and economically, in the 1980s will be routine observations in the 1990s.

Satellites have proven to be of great value in studying the character and motion of polar sea ice and glaciers and in imaging structural lineaments, lithologic contrasts, and morphologic and

textural features of geologic interest on the circum-arctic landmass. Many of the newer satellites, particularly the Synthetic Aperture Radar (SAR) satellites, also carry radar altimeters. Analysis of the radar altimeter data on SEASAT produced pseudo-gravity maps of most of the world's oceans because the mean sea level measured by these instruments is a good approximation to the geoid. Pseudo-gravity maps are available only below about 70° latitude, however, because none of the original satellites with radar altimeters covered the polar regions. The new SAR satellites will extend the coverage to about 80°N.

Thus, the radar altimeter data collected by SAR satellites could produce a pseudo-gravity map of the Arctic Ocean Basin to 80°N. However, this would depend on the development of an algorithm to correct the differences between the returns from the sea-ice surface to sea level of the Arctic Ocean using radar altimetry. In order to obtain coverage above 80°N and to fill the data gap quickly, the committee recommends conducting a combined aerogravity/aeromagnetic survey of the Arctic Ocean Basin. Such a survey could record the near surface, short-wavelength components of the earth's gravity and magnetic fields that are beyond the reach of satellite-borne instruments. Instruments deployed in orbiting satellites, on the other hand, could provide better definition of the long-wavelength components of the gravity and magnetic fields and would provide the best means for removing the earth's main magnetic and gravity field from the airborne geopotential field measurements. Satellite data would also place the arctic data in a global context and would provide a means of relating it to areas of the circum-arctic landmasses where potential field data are sparse or of uncertain quality.

The anticipated deployment of the full complement of GPS satellites by the United States in 1992 will bring round-the-clock decimeter-level, three-dimensional satellite navigation to the entire Arctic Ocean Basin. With careful recording and processing of the satellite data, subcentimeter estimates of relative horizontal position and about 2 cm estimates of relative vertical position can be achieved for suitably founded stations (Bock and Leppard, 1990). A similar system (GLONASS) is operated by the Soviet Union. Combined with ever smaller and more sophisticated receivers, GPS and GLONASS enable the acquisition of positioning data for scientific observations in the Arctic. The levels of achievable GPS resolution are useful for measuring a number of active geological phenomena in the Arctic, such as the tectonic strain of the earth's surface; geomorphoiogic processes; and vertical and horizontal motions and ablation rates of glaciers, ice caps, and snow fields; and it can make these measurements with unprecedented ease. Satellites have proven less satisfactory for the transmission of field data from high latitudes because much of the Arctic is above the latitude at which geostationary satellites (approximately 79°N for a satellite on the same longitude) can be seen reliably from earth-based relay stations. For experiments requiring low data-transmission rates, it is possible to transmit the data during the times when available satellites, such as those of the National Oceanic and Atmospheric Administration, are visible. More data-intensive experiments, such as seismic data acquisition, require more capable satellite data relay systems. Such systems are in fact deployed, but they are not available to civilian users. Access to these or to other near real-time data transmission links would allow active geophysical experiments to be deployed in the high Arctic.

Airplanes have been central to Arctic Ocean Basin research ever since personnel of the Soviet All-Union Arctic Institute, led by I.D. Papanin, used airplanes to establish a drifting scientific station on sea ice at the North Pole in 1937. The simplified logistics, lower costs, and mobility provided by airplanes have since been the principal means by which high-latitude arctic ice stations have been established. In conjunction with helicopters, they have supported seismic refraction, seismic reflection, potential field, sea-ice sediment studies, and bathymetric surveys in ice-covered areas of the Arctic Ocean.

Configurations of the earth's magnetic and gravity fields over the Arctic Ocean are most efficiently and economically investigated from aircraft because of the remoteness of the region, the perennial sea ice, and the commonly large and irregular perturbations of the magnetic field caused by magnetic storms. Submarines would be effective platforms for arctic magnetic and gravity surveys, but their cost would be much higher unless shared with other scientific or surveying missions. Correction for external field variations, however, would be more of a problem with submarines.

Total magnetic field measurements from aircraft are now routine and economical, and the equipment and algorithms to measure, record, and process the data are widely available. Acquisition of gravity data adequate for geologic interpretation has, until recently, been possible only on land, sea ice, or moving ships and submarines. This limitation has been overcome by recently developed aerogravity systems that can operate from airplanes or helicopters. Such surveys are presently available from three commercial companies in North America, and a system is also being developed by the U.S. Naval Research Laboratory (NRL). In the NRL system, GPS provides accurate positions and velocities for determination of the Eotvos correction and, by use of interferometry, can track motions of the aircraft in three dimensions with an accuracy of about 10 cm. The ability to track aircraft motion eliminates the need for radar altimeters to determine vertical motions of the aircraft. Polar elevations above sea level are especially difficult to obtain over sea ice. It is estimated that an accuracy of 3 to 4 mgals is obtainable with the NRL system.

Scientific observations within perennially ice-covered regions of the Arctic Ocean Basin were first made from ships that entered and were frozen into the polar ice pack. The earliest observations of record were made from the ill-fated Jeannette, on which Lieutenant George W. DeLong and his party drifted from near Wrangel Island, in the Chukchi Sea, to north of the New Siberian Islands in 1879–81. This expedition was followed by the epochal drift of Nansen's Fram from the New Siberian Islands to the North Atlantic in 1893–1896, during which a large body of oceanographic, geophysical, and other scientific data were acquired.

A number of proposals to emulate the drift of the Fram by inserting overage icebreakers or floating concrete drilling platforms into the transpolar drift as a base for oceanographic and geoscience observations—and for shallow drilling—have been made in recent years. The Norwegian Nansen Centennial Program, for example, is planning to insert a vessel in the ice pack in the Eurasia Basin for a two-year drift to gather data in several scientific disciplines. Despite vigorous advocacy by segments of the arctic scientific community, these proposals have not as yet been funded. Because of the high cost and large staffing requirements of the proposed drifting platforms and because of their slow, erratic, and unpredictable drift paths, it is the consensus of the committee that more efficient and cost-effective alternative methods are available for gathering solid-earth geoscience data in the Arctic Ocean Basin. Such methods include icebreakers, ice stations, over-ice surveys with helicopters and surface vehicles, and data buoys.

Ice stations on ice floes, especially on ice islands (tabular icebergs with high freeboard that are of glacial origin), are ideal facilities for long-term oceanographic and weather observations in the central Arctic Ocean Basin. First used in 1918 by Storker Storkerson of Vilhjalmur Stefansson's Canadian Arctic Expedition, ice-floe or ice-island stations became the mainstay of central arctic scientific exploration by the USSR beginning in 1937, the United States beginning

in 1952, and Canada beginning in 1967. Most of our current knowledge of the geophysics, geology, and oceanography of the Arctic Ocean Basin has been gathered from these floating camps. Ice stations, however, are not well suited for gathering some types of geoscience data. Thus, although they are effective platforms for seismic refraction and local potential field surveys and sea-ice observations, their progress across the seabed is uncontrolled and too slow and erratic for the efficient collection of seismic reflection data and subseafloor rock and sediment samples. For these purposes, active platforms, which can expeditiously occupy a series of preselected survey lines and sample sites, are preferable. Stations on ice floes are also vulnerable to damage or destruction by sea-ice pressure ridging or fissuring and can be considered only temporary establishments. Large ice islands, which are much more stable platforms, are scarce in the Arctic Ocean.

Over-ice travel by man-hauled boats equipped with sled runners was employed by the Edward Parry party to explore the fringes of the Arctic Ocean Basin north of Svalbard as early as 1827, and dog sleds were used by the Charles F. Hall party to explore north of Greenland as early as 1871. These and a few other expeditions dependent on ''mammal power'' brought back significant scientific data from the central Arctic Ocean Basin during the heroic age of arctic exploration in the 19th and early 20th centuries, but mammal power experienced instant obsolescence with the arrival of aircraft in the Arctic in the 1920s.

The development of reliable lightweight gasoline-or diesel-driven vehicles for over-ice transportation after the Second World War promises a revival of over-ice logistic systems for some types of scientific studies in the central Arctic. Snowmobiles and conventional-tracked vehicles are now commonly used for scientific research and other activities in the fast-ice zone of the arctic ice pack in winter and spring, but more important opportunities lie in operations that can now be conducted beyond the fast-ice zone.

It has been proposed that lightweight gasoline-driven snow vehicles deployed by aircraft may be an efficient means of acquiring on-ice multichannel seismic reflection data in late winter and spring. It is estimated that about 15 to 20 km of profiles could be recorded in this manner per day through use of a snow streamer with geophones and explosive sources. If the DeHaviland Twin Otter aircraft is used for deployment, such surveys could be conducted as far as 500 to 600 km from airfield bases and farther if on-ice fuel dumps are established. Snow vehicles are not practical, however, for independent over-ice travel for useful distances during the late summer and early fall when the smoothing snow cover is minimal, the ice surface is pitted with melt ponds, and there are many open leads between ice floes. In this season, when the ice pack reaches its annual minimum position and icebreakers can penetrate it most easily, air cushion vehicles or amphibious craft that can traverse both open water and rough sea ice may be able to provide logistic support for seismic reflection, seismic refraction, and other geoscience studies from sea ice. Such vehicles, of which the amphibious ARKTOS, developed by Watercraft Offshore Canada, Ltd. of Richmond, British Columbia is an example, would have to be deployed from icebreakers because they are too large for aircraft capable of landing on summer and fall sea ice.

From the first recorded voyage of western man to the Arctic, that of Pytheas of the Greek colony of Massilia in 320 B.C., until the Jeannette and the Fram were inserted in the main ice pack in the late 19th century, exploration of the Arctic Ocean by ship extended only as far north as the marginal ice zone. Ships contributed little to our knowledge of the solid earth beneath the Arctic Ocean Basin itself until the development of ice-reinforced steel-hulled marine research vessels with diesel propulsion and large icebreakers with diesel and nuclear power plants during and following the Second World War.

Ice-reinforced research vessels operating as far north as the marginal ice zone in late summer

and early fall have obtained valuable geophysical and oceanographic data over the continental shelf, slope, and rise at the margins of the Arctic Ocean Basin in the Beaufort Sea and the vicinity of Svalbard and on the outer shelf in the Laptev Sea. Because sea-ice forecasting is an inexact science, however, operations are inefficient when data are sought in areas of the Arctic Ocean that are only occasionally ice free.

The advent of large, powerful diesel-electric-and nuclear-powered icebreakers able to negotiate the main polar ice pack has made it possible to acquire geological, geophysical, and other scientific data in the central Arctic Ocean Basin. The Polar class icebreakers in the United States and the Ermak class diesel and the Arktika class nuclear icebreakers in the USSR allow scientific investigation of the central Arctic Ocean Basin, whereas the earlier vessel classes could work only in the basin margins. Harbingers of this revolution are the cruise of the West German polar research vessel Polarstern to 86°22'N in 1987 to conduct multidisciplinary research; the voyages of the Arktika and Sibir to the North Pole in 1977 and 1987, during which geophysical data were collected; and the cruise of the Polar Star to the Northwind Ridge in 1988 to collect geophysical data and cores. As additional experience is acquired in deep penetration of the polar ice pack, and especially when two icebreakers can work together, complex multidisciplinary expeditions will be possible in most areas of the Arctic Ocean. However, icebreaker operations may be difficult or severely curtailed in areas of the Arctic Ocean such as the vicinity of the Queen Elizabeth Islands, where heavy concentrations of pressure-ridged sea ice are commonly found.

The advantages that icebreakers bring to arctic solid-earth geoscience are their ability to carry researchers and bulky or heavy equipment to or near areas of specific scientific interest in sea ice, to support a wide variety of scientific investigations concurrently, and to carry helicopters and over-ice vehicles that can conduct collateral research 100 km or more beyond the ship. Gravity, piston, and box coring are now routine from icebreakers, and these ships can be adapted to deploy the longer piston cores and shallow drills that are under development in a number of institutions. Seismic refraction, seismic reflection, gravity field and bathymetric measurements, and sea-ice and oceanographic observations are also routinely conducted from icebreakers. A prime advantage of icebreakers over-ice stations is their ability to move relatively quickly to successive sites or traverses of interest along predetermined tracklines. Drifting stations lack this mobility and can be moved from point to point only by relocation, which is cumbersome and time consuming. Suitable campsites may also not be available in all areas of interest.

Experience on the Polar Star in 1988 suggests that under certain conditions, seismic reflection studies can be conducted from icebreakers in multiyear pack ice. These conditions are sea-ice concentrations of about seven-tenths or less, or the presence of open leads or polynas, when only one ship is used for reflection profiling. Further development, especially the use of two ships working in tandem, may allow profiling in higher ice concentrations. Limiting factors are ice floes and pressure ridges too thick to be broken semicontinuously and ice concentrations too high to allow a small area behind the advancing ship to remain free of large pieces of ice during profiling. Conditions that would permit seismic reflection profiling in areas of sea ice are not widespread, but they can be found locally in many areas of the central Arctic in summer. Targets for seismic reflection profiling in the central Arctic can, however, be defined only broadly. The specific location of profiles across features of interest will depend on locating suitable ice conditions from satellite images and airborne reconnaissance. If these restrictions are accommodated, it appears that 6-and even 12-channel seismic reflection surveys employing air gun or water gun sources can be conducted in many areas of the Arctic Ocean from icebreakers.

The only icebreakers capable of operating in the central Arctic Ocean Basin today are the Soviet Arktika class nuclear-powered icebreakers, the Soviet Ermak class diesel-powered ice-breakers, and the two U.S. Polar class vessels. Only the Arktika class icebreakers, however, are truly capable of sustained operations in far northern waters. Although highly ice capable, the Ermak class icebreakers are fuel limited. The Polarstern cannot routinely operate alone at these high latitudes, and it was at the limit of its operational capabilities when it attained 86°22'N in 1987. The Canadian Coast Guard's St. Laurent and the U.S. Coast Guard's Polar class ships working in pairs might be able to work in parts of the central Arctic, but they are unreliable for

sustained solo operations at such high latitudes. The Soviet heavy icebreakers, which can work more or less routinely in the central Arctic Ocean Basin, are employed along the northern sea route and may become available for charter in late summer and early fall of years with mild sea-ice conditions, when they would be largely idle. Employment of one of these ships for a tourist cruise to the North Pole in 1990 and solicitations for passengers for a second cruise in 1991 suggests that Soviet nuclear icebreakers will be available for charter by western scientists seeking research platforms in the Arctic Ocean Basin.

With the cancellation of the Canadian Polar 8 icebreaker, there will be no existing or prospective North American ship that alone can routinely support scientific work in the central Arctic Ocean Basin. The U.S. Coast Guard is planning a new icebreaker with extensive research facilities, but the proposed design indicates that this ship will be less ice capable than the Polar class vessels (4-foot versus 6-foot continuous level icebreaking capability). In 1988, the Polar Research Board issued a report on "Evaluation of the U.S. Coast Guard's 'Preliminary Design Document' for the Proposed Next Generation of Polar Class Icebreakers" that provides recommendations on specifications for redesign, including features necessary for supporting geophysical research and for acquiring "...cores and dredge samples from the deep Arctic Basin." (NRC, 1988a). The committee reaffirms these recommendations, particularly because although there are already several U.S. and Canadian icebreakers capable of working in the marginal ice zone, there are none that can work independently in the central Arctic Ocean Basin.

If the new U.S. Coast Guard icebreaker is not capable of routine work in the high Arctic, the North American scientific community will have to turn to the Soviet icebreaker fleet for support in geoscience research in the central Arctic Ocean Basin. If the Soviet icebreakers are not available to western scientists and if the Polar class vessels prove too fragile for sustained high-latitude operations, the United States will be severely limited in its ability to conduct solid-earth geoscience research in this region.

Thus, the scientific interests of the United States in the Arctic Ocean demand that a much more ice-capable vessel (e.g., able to operate routinely in the central Arctic Ocean) be added to the U.S. icebreaker fleet. Previous Polar Research Board reports have recommended procurement of such a vessel based on the requirements of the arctic marine science community (NRC, 1988b). The arctic geoscience community reaffirms this need.

Submarine exploration of the Arctic Ocean Basin was first attempted by Sir Hubert Wilkins in 1931, when he cruised a short distance beneath the polar ice pack in Fram Strait in a secondhand diesel-and battery-powered submarine. Deep penetrations of the ice pack, however, awaited the development of nuclear submarines in the 1950s. The U.S. submarine Nautilus brought the nuclear age to the Arctic when it sailed north through Fram Strait in 1957, followed by its epochal crossing of the Arctic Ocean from the Bering Strait to the Greenland Sea in 1958. Since then, nuclear submarines of the United States, the Soviet Union, and the United Kingdom have operated extensively in the Arctic Ocean Basin, gathering large quantities of classified bathymetric and sea-ice data and demonstrating the feasibility of routine under-ice operations. The potential usefulness of nuclear submarines for scientific studies of the Arctic Ocean Basin is widely recognized, but the priorities of the Cold War and high operating costs have until now precluded the employment of these vessels for nonmilitary purposes. The apparent end of the Cold War and the renewed interest in the Arctic, however, may be creating opportunities for the use of nuclear submarines for arctic geoscience research.

Bathymetric, gravity, magnetic, and side-scan seabed imaging data can now be collected from nuclear submarines, and it appears likely that high-frequency, shallow-penetration seismic reflection data can also be acquired. Although the engineering and fabrication costs will be high, acquisition of medium-or low-frequency seismic reflection data using sparker, exploder, or water gun sources and single channel or multichannel streamers is probably also feasible from nuclear submarines. Electrical and electromagnetic methods for studying the solid earth are not viable from submarines because of the conductivity of seawater.

Proposals for using nuclear submarines for solid-earth geoscience would, of course, have to consider both their total cost and the relative cost of alternative platforms for particular applications. We lack the data for assessing these costs, but it appears that regional magnetic and gravity fields in the Arctic can be mapped more cheaply with aircraft unless the operating expenses of the submarines were subsidized or shared with other projects. Submarines are uniquely suited, however, for acquiring regional bathymetric, side-scan sonar and probably high-frequency, shallow-penetration seismic reflection data beneath the polar ice pack. Furthermore, there are no alternative platforms for acquiring such data uniformly over the entire Arctic Ocean Basin or even large subregions thereof, although ships may be more cost-effective for research in certain areas of the basin. The first use of submarines for solid-earth geoscience in the Arctic would probably be to gather regional bathymetric, side-scan sonar, and probably high-frequency seismic reflection data. Suitably equipped submarines can also deploy and recover ocean bottom instruments such as ocean-bottom seismometers year-round in the Arctic. Recovering such instruments from surface vessels in sea ice is feasible mainly in summer and fall and commonly requires high-risk under-ice operations by divers.

A regional bathymetric, side-scan sonar and high-frequency seismic reflection survey from a submarine would improve understanding of the physiography and shallow structure and stratigraphy of the Arctic Ocean Basin. An even greater advance in knowledge of the earth's crust beneath the Arctic Ocean would follow, however, from a regional submarine seismic reflection survey. Installing and operating such a system would certainly be expensive, but in the committee's view, based on the analysis of current and planned facilities, the scientific reward would be worth the cost and technological risk. A submarine seismic reflection survey would in a relatively short period, provide detailed knowledge of the structure and seismic stratigraphy of the Arctic Ocean Basin and its margins. It would create a data set from which the geologic framework and tectonic history of the entire Arctic Ocean Basin could be inferred. Also, it would define the optimum sites for further geological sampling to determine the paleoclimatic and paleoceanographic history of the region. In addition, it would provide the data to evaluate the nonrenewable resource potential of perennially ice-covered areas of the Arctic Ocean Basin and of its continental shelves.

The committee believes that within a few years, submarines will become the mainstay of geophysical data acquisition in the Arctic, and it strongly recommends that a national program to acquire multisensor geophysical data beneath the arctic ice pack be considered. The suggested program would create a special niche for the United States in arctic solid-earth geoscience and produce major breakthroughs in scientific knowledge as well as economic returns to the United States.

Manned deep-diving submersibles have led to advances in understanding of mid-ocean ridges, oceanic hydrothermal systems, submarine erosion and depositional systems, and many other features of the world ocean. Their application to Arctic Ocean Basin solid-earth geoscience does not appear imminent, however, because of the prohibitive logistic difficulties and substantial risks in operating such vehicles beneath the polar ice pack. Moreover, many of the topics such vehicles would study are usually defined at a more mature stage of scientific exploration than now exists in the Arctic Ocean Basin. Unmanned deep-diving submersibles would remove some of the risk and expense associated with manned submersibles, but they are nevertheless costly. Therefore, the committee believes that regional geophysical studies and subseabed sampling, both utilizing other facilities, have a higher priority.

Buoys that transmit data via satellites are important systems for gathering oceanographic and meteorological data in the Arctic Ocean, and they may be important for collecting and studying fine-grained particulate and organic matter in the water column. Such data are important for

determining sedimentation in the Arctic Ocean and therefore can contribute to evaluation of the underlying sediment column. As with submersibles, however, the committee believes that sediment buoys have a lower priority than the acquisition of regional geophysical data and subseabottom rock and sediment samples.

Four piston cores and a dredge haul from drifting ice stations and three piston cores from icebreakers have recovered pre-Pliocene sediments or rocks from slopes on Alpha and Northwind Ridges in the Amerasia Basin. In addition, more than 600 samples of Plio-Pleistocene and Quaternary sediment have been recovered by random sampling of ridges and basin plains by piston cores lowered from drifting ice stations and icebreakers in the Amerasia Basin. Study of these samples constitutes only the first step toward understanding the stratigraphy and environmental history of the Amerasia Basin, but it suggests that a fairly complete lithostratigraphic and biostratigraphic history of the basin from its origin in Cretaceous time to the present can be pieced together from suitably placed piston cores.

Piston coring with 10-m core barrels is now routine from ice stations and icebreakers. Experience on Polar Star in 1988 and 1989 showed that as many as five piston cores per day, with lengths to 28 feet, can be collected routinely in 1,000 to 4,000 m of water covered by high concentrations of multiyear pack ice with no loss of equipment. More time was spent identifying and occupying sample sites than in coring operations. Improvements under development at a number of institutions, including longer core barrels, air-pressure devices to drive core barrels into the bottom sediment, and water lubrication systems to facilitate the injection and extraction of piston corers in the subbottom may permit even longer cores to be recovered routinely. Lightweight rotary drills and piston coring systems that may be deployable on ice floes from aircraft as small as the ubiquitous DeHaviland Twin Otter are also under development.

Field experience suggests that the ratio of Cretaceous and Tertiary to Quaternary cores in the Arctic would increase significantly if piston core sites were chosen on ridge crests and slopes on the basis of bathymetric criteria or seismic reflection profiles, if ships or air-mobile coring stations were placed over specific stratigraphic targets, and if the improved coring devices now under development were able to obtain deeper subbottom penetrations. High-resolution seismic reflection data would be invaluable for achieving deeper stratigraphic penetration by identifying sampling sites where Quaternary sediment, which almost everywhere mantles bedrock in the Arctic Ocean Basin, is thin. Given careful site selection and improved coring equipment, we believe that most of the stratigraphic section in the ridge systems of the Arctic Ocean Basin can be sampled in sufficient detail to construct a stratigraphic framework for the region.

The stratigraphic record obtained by piston cores can be supplemented by dredging from ice stations and by drilling with lightweight coring systems placed on the seabed. Dredging from an ice station has recovered the only sample of the volcanic rocks inferred to underlie Alpha Ridge, but the near ubiquitous mantle of Quaternary deposits nevertheless places older sediment and rock beyond the reach of dredges almost everywhere in the basin. Dredging from ships in pack ice is time consuming and difficult and would ordinarily be tried only where high-resolution seismic reflection data indicate that hard rocks crop out at the seabed.

Coring with tethered lightweight rotary drills placed on the seabed is a technology with considerable promise that is under development in Finland, Canada, and the United States. These systems have yet to be proven reliable and practical, however, and they may be better suited for sampling hard rock than soft sediment. When their development reaches the stage at which they can be used routinely from ice stations and icebreakers, they will provide an important tool for piecing together a pre-Quaternary stratigraphy of the Arctic Ocean Basin.

A number of proposals for deep drilling in the Arctic Ocean Basin have been made in recent years. Their objectives have ranged from Quaternary stratigraphy of the continental shelves to continuous sampling of the entire sedimentary column in the basin. Thanks to the infrastructure that was created for petroleum exploration in the Beaufort, Chukchi, and Barents Seas, coring of Quaternary and deeper targets on arctic shelves from specialized drill ships or bottom-founded

platforms can be contracted from commercial companies experienced in both the European and North American Arctic. Contract drilling from shorefast and bottomfast ice on arctic shelves—especially the shallow inner shelves—is available in the Beaufort and Chukchi Seas and perhaps in the Barents and Kara Seas. Although these services are costly, they are available on relatively short notice. The real technological challenge in arctic drilling is the acquisition of continuous deep cores from off-shelf, deep-water sites.

Cost-effective off-shelf core drilling within areas of perennial sea ice must overcome a number of natural conditions that appear to be beyond the capability of current technology. Even with icebreaker support, existing drill ships—including the Ocean Drilling Program's JOIDES Resolution—are not sufficiently ice strengthened to maneuver safely within the main polar ice pack. Sedimentary fill in the Canada and Makarov Basins ranges from 6 to 12 km or more, and its upper part is inferred to consist of Late Cenozoic turbidites that are of secondary interest for determining the environmental history of these basins. Drilling such targets in deep water is at the limits of petroleum industry technology in areas free of sea ice, and it is enormously costly. The semicontinuous movement of the mainly wind-driven ice pack will not permit such deep bores to be drilled, especially because continuous coring would be required, without some method of holding position against the drift of the ice pack. Such methods have been developed for shallow areas of arctic shelves, but none is in prospect for the deep-water areas of the basin.

Because there are more than 600 cores in the Plio-Pleistocene and Quaternary section of the Arctic Ocean Basin, principal targets for future stratigraphic coring are the Cretaceous and Tertiary beds that lie at shallow depth beneath the crests and slopes of the submarine ridges of the basin. The first phase of sampling should be by piston coring, dredging, and possibly shallow coring with tethered drills deployed on the seabed. Coring sites should be pre-selected from high-resolution seismic reflection or bathymetric profiles or side-scan sonar images, and the coring should be conducted from icebreakers or ice stations deployed by aircraft, which can be positioned over selected sites. After a preliminary stratigraphy and more precise targets have been defined by these methods, a more sophisticated program of coring to somewhat greater depths might be instigated. A realistic program might attempt a series of 50 to 100-m core holes from a specially modified icebreaker that could occupy preselected sample sites at a late stage of a coring program. A large, randomly drifting commercial drilling platform has been proposed recently to obtain cores from the Arctic Ocean Basin. Such platforms are costly (estimated cost about $40 million per year) and have essentially no prospect of acquiring a comprehensive suite of pre-Quaternary samples from the Arctic Ocean Basin.