For several decades, CHS and GSC have carried out joint or independent mapping operations in four primary regions of the Canadian Arctic: (1) portions of the deep Arctic Ocean basin within Canada's 200 nautical miles limit; (2) the continental shelf and slope of the Beaufort Sea and north of the Canadian Arctic Archipelago; (3) the channels between the islands of the Canadian Arctic Archipelago; and (4) Baffin Bay.

A significant percentage of the observations in the first three regions consisted of point measurements taken through ice, with observers and instruments transported to the observation sites by helicopter. Remaining measurements in these regions, as well as all measurements in Baffin Bay, were acquired by surface vessels equipped with conventional echo sounders.

For the most part, observations were carried out systematically over rectangular grids or closely spaced survey lines, with the exception of Baffin Bay where the majority of soundings were acquired on an opportunity basis by vessels that were either in transit or deployed in other kinds of operations. Whether through-ice or shipborne, measurements were positioned for the most part with shore-based radio-location systems in the early years of the mapping program, but in later years these systems were phased out and replaced with GPS.

Significant portions of the CHS and GSC data bases are freely available in the public domain, and may be readily incorporated in the proposed Arctic compilation. Other portions will be released when their final processing is complete, and when they are published in chart form or in the scientific literature.

Bathymetry data base of the central Arctic region contains sea-floor depth measurements carried out in the course of Russian and foreign (J.K.Hall, 1970) field investigations. Point observation distance varies from 10x10 km to 40x40 km. Trackline measurements with distance of 5-10 km between observation points were acquired during high-latitudinal geotransect studies from De Long Islands to Makarov Basin. Celestial, radiogeodetic and satellite positioning provided maximal error in determination of site locations +/- 600 m. Sea-floor depths were measured using echosounding and seismic observations with an error not exceeding 2% of depth. For initial data processing original software (Korneva, 1994) and Autocad (AUTODESK Inc., 1992) were employed.

Sea-floor depth grid was calculated by gridding with continuous curvature spline in tensions (Smith & Wessel, 1990). Such digital bathymetry model is considered best approximation to initial depth field.

From calculated grid a coloured structural (pseudo-shadow) bathymetry map at 1:2,500,000 scale was compiled. Software "Potential fields data processing" (Blue Vajra Computing, GSC Atlantic, 1994), ER MAPPER (Earth Resource Mapping Pty Ltd., 1995) was used.

Presented bathymetry data significantly supplement the existing knowledge of the bathymetry of central Arctic region.

The Arctic Ocean is the least known of all the ocean basins. The Arctic has been explored from ice islands, icebreakers, airplanes and satellites. Every survey has revealed more of the Arctic Ocean basin, but operated under the restrictions imposed by ice and weather. Only a submarine can cruise below the ice, independent of surface conditions.

A nuclear-powered submarine can operate autonomously anywhere in the Arctic Ocean basin. A submarine can survey the seafloor, collecting co-registered data sets for mutual analysis. In principle, any of the underway data sets collected from surface ships can be gathered from a submarine. The speed, stability and silence of the submarine make it an ideal platform for underway geophysical measurements.

Three times since 1993, the US Navy has provided a Sturgeon class fast attack submarine for an unclassified science cruise. Under this program, a nuclear-powered submarine was deployed to the Arctic Ocean in 1993, 1995 and 1996. Approximately 100 science days in the Arctic Ocean operational area have yielded about 50,000 kilometers of continuous underway bathymetry and gravity data. Three additional cruises are scheduled for 1997, 1998 and 1999.

On the SSns PARGo, CAVALLA, POGY and ARCHERFISH (1997 cruise) cruises, geophysical instrumentation consisted of a narrow-beam bottom sounder (standard shipboard equipment) and a Bell BGM-3 gravimeter. Although these instruments have returned valuable data from unexplored areas, the information they provide on the morphology and structure of the sea floor is meager compared to data collected from a typical modern research vessel.

Development, fabrication and testing of sonar instrumentation for the remaining cruises is underway. Three components make up this instrumentation; two sonars; an optimized SeaMARC-type sidescan swath bathymetric sonar; a chirp-type high resolution sub-bottom profiler; and a data acquisition system. The transducers for the two sonars will be carried in two instrument pods attached to the underside of the submarine. Cables, routed through the ballast tanks, will deliver signals from the transducers to outboard processors in three pressure tight cases secured in a freeflood space. After initial processing, the signals will be brought in board, processed, logged and archived.

Initial preparations for SCAMP instalation on the SSN HAWKBILL (the submarine designated for 1998) were completed on schedule in early July in Honolulu. The mounting points that will hold the transducer pods were placed and welded to the hull. An internal cable was installed, the pod foundations were fitted to the mounting points and the divers, who will do the final installation, were familiarized with the hardware. The transducer pods and foundations will be installed dockside by divers with crane support in Spring 1998.

Seismic observations along the drift track of research stations "NP-21" - "NP-26" were carried out by specialists of Ministry of Geology - employees of VNIIOkeangeologia - in the course of expeditions conducted by AARI. Nearly 30,000 individual reflectionseismic soundings were implemented during this period.

Research methods were aimed to study regional features of the bottom topography and sedimentary cover structure along the drift track which crossed the major morphostructures of the Eurasian and Amerasian Basins, such as Amundsen, Podvodnikov and Makarov Basins, Lomonosov Ridge, Mendeleev Rise, etc. Satellite and celestial positioning systems were used for position control of observation sites. In addition to geological information, the initial analog seismic reflectiondata contain significant bathymetric component which is currently being digitized along with other information. The presentation demonstrates location of observation points and first examples of digital bathymetry data processing obtained by VNIIOkeangeologia by the time of the workshop.

SE PMGRE holds seismic data obtained in the course of Arctic expeditions during 1984 - 1992, including:

• Seismic reflection survey at drift stations North Pole (NP-26/northern part of drift/NP-28, NP-31);
• Aircraft-supported seismic reflection soundings on sea-ice acquired during TRANSARCTICA expeditions along lines of the geotransects;
• Base seismic reflection observations during TRANSARCTICA expeditions.

Investigations were mainly conducted in deep-water part of the Amerasian subbasin of the Arctic Oean (Chukchee Dome, Mendeleev Rise, Makarov Basin, Lomonosov Ridge).

The data are still mostly preserved in analog form, although the technologies for their digitization have already been worked out and successfully tested.

Over-ice streamers (12-24 channels of cross or angular configuration) and analog recorders SMOV-0-24 were used to obtain seismic data. Seismic impulse was initiated by explosion of 3-5 detonators at the depth of about 8 m. Recording time was 12 sed. Observation interval on drifing stations was about 1-2 km, during aircraft-supported trackline survey close to 5 km. Satellite positioning accuracy of coordinating observation points within 100 m.

In the nearest future PMGRE is planning to continue TRANSARCTICA expeditions along the geotransect crossing the Mendeleev Rise from Makarov Basin to Canadian Basin. Seismic reflection survey will constitute an important part of the program and allow to obtain accompanying bathymetry information.

Spherical form of seismic impulse is an important feature of seismic technology which puts certain constraints on use of seismic data for surveying sea-floor depths.

SE PMGRE encourages the idea to compile the Arctic bathymetry digital data base as an important contribution to geological-geophysical study of the region and also in connection with the need to approach delimitation of the coastal states' shelf zones on the basis of unified cartographic approach.

The US National Geophysical Data Center has accumulated and assimilated into its global trackline geophysical data base about 700,000 Arctic bathymetric soundings from 630,000 line km of ship track from 183 cruise legs of data collected by 16 oceanographic institutions located in eight countries. Most of these bathymetric data were collected from regions of the Arctic which are ice-free or periodically traversible by ship. Additional bathymetric data from several cruise legs are waiting to be assimilated. All these data were collected between 1961 and 1995 and the depth measurements are believed to be relatively accurate, ranging from earlier soundings digitized from precision depth recorder records, to more recent soundings collected by narrow beam and multi-beam systems. Navigation accuracy is that of earlier celestial navigation and/or transit satellite, and, more recently, the global positioning system.

In addition NCEI assimilated in separate data bases 1) an estimated 20 million depth soundings collected with a multi-beam bathymetric sounding system; 2) depth soundings digitized from Russian and Norwegian nautical charts; 3) depth soundings collected on Canadian gravimetric surveys from helicopter; and 4) depth soundings collected from a US station on an ice island.

Extensive bathymetry information has been accumulated in the course of geomorphological survey and sea-floor echosounding carried out by PINRPO and MMBI since early 60-ties until the present time. These data constituted the basis for compilation of series of bathymetry maps at scales from 1:200,000 to 1:2,000,000. including original bathymetry map of the Barents Sea at a scale of 1:1,500,000 compiled in 1975 and upgraded in 1992. Individual bathymetry maps of north-western and north-eastern Atlantic were published as well. Bathymetry map of Franz Josef Land at a scale of 1:5,000,000 was published in 19995 in cooperation with the US Geological Survey.

The maps are of significant importance in terms of problems relevant to history of Quaternary glaciation of the Arctic and Northern Atlantic and formation of specific category of morphostructures - glacial and periglacial shelves. In our opinion the maps contain information which proves existence in recent times of thick (1-2 km) glacial sheet on the Barents-Kara shelf.

The maps were compiled manually and can now be used in the planned IASC project in two ways: 1) digitizing isolines for developing grids for appropriate sea-floor areas; 2) selection of the most reliable depth values from initial data used for isoline compilation and incorporation of these values in a digital format in the International bathymetry data base.

Joint compilation by VNIIOkeangeologia and GUNiO of bathymetry map of the Arctic Basin (1:5,000,000 scale, stereographic projection, contour interval 200 m) is nearing completion. The map is based on all national bathymetry data obtained during several decades of regional investigations of the Arctic Basin bottom topography.

The level of detail in depicting the topography allows to state with confidence that the Gakkel Ridge occupies an isolated position in the Eurasian Basin and is not connected with mid-oceanic ridge system of the north-eastern Atlantic. Contour interval chosen for compilation emphasizes a distinct link between the topography of the central oceanic basin with that in adjacent continental margins, thus suggesting their morphostructural unity. At the same time the map helps to identify least studied areas where additional studies are necessary to obtain reliable topographic evidence.

The map is manually compiled but can subsequently be digitized and used for the purposes of proposed IASC project as background information which would supplement initial data grids and may help to control interpretation of gridded data during compilation of final maps.

The Naval Research Laboratory (NRL) holds over 21.5 million datapoints of single and multibeam trackline bathymetry in the northern Polar Regions.

These data include all research trackline bathymetry data held by the US National Geophysical Data Center, and many other US and non-US sources. The Laboratory has informal bilateral agreements with a number of non-US institutions, which allow us to use the data. However, under these agreements, we are unable to disseminate those data. Rather, the originator of the data is responsible for that task. In cases where bathymetric data come to NRL in raw form, i.e., on echosounding rolls with accompanying navigational files or lists, those data are hand-digitized. After completion of the digitization, error-checking and comparison with existing bathymetric data, the digital data and original materials are returned to the source.

Analysis of NRL Arctic bathymetry data base has resulted in the compilation and publication of five north polar region bathymetric charts: four have been published (after peer review) by the Geological Society of America in their Map and Chart series, and one has been used as the basemap in an atlas published by the Norwegian Polar Institute. The bathymetry is printed on the obverse, and the tracklines are registered to and printed on the reverse of the map. Some non-US sources of data have agreed to permit showing these tracklines, as long as the sounding data themselves remain held in a proprietary sense.

When the NRL science program dictates the necessity for up-to-date bathymetry of a specific area, the data are plotted at very large scales, e.g., 1:125,000, permitting all or almost all of the data points to be plotted in a legible scale. The data are then contoured in the traditional sense, i.e., by hand, by a qualified and experienced bathymetry specialist.

Digital bathymetry collected along transit tracks under the Arctic ice pack and marginal ice zone by US nuclear submarines between 1957 and 1982 are being readied for release into the public domain later this year. These bathymetric data will be available to the science community as a whole and will significantly enhance the Arctic bathymetry database.

* Unless otherwise stated, the expressed views are my own. They may not be the opinions of the US Navy, the Department of Defense, nor the US Government.

When calculating bathymetry grids by method of gridding with continuous curvature spline in tensions (Smith & Wessel, 1990), the results were correlated with digital data sets: Terrain Base Global 5-minute Both (NGDC, 1985), New Arctic Bathymetry-Topography (Macnab et al., 1995), GEBCO Digital Atlas (IOC & IHO, 1994); digital analogs of maps: Bathymetry of the Barents and Kara seas (Cherkis et al., 1995).

From calculated grid bathymetry maps of the Russian Arctic shelf seas at a scale of 1:6,000,000 were compiled using software "Potential fields data processing (Blue Vajra Computing, GSC Atlantic, 1994), ER MAPPER (Earth Resource Mapping Pty Ltd., 1995).

Presented bathymetry data significantly supplement the existing knowledge of the bathymetry of Russian Arctic shelf seas.

Archiving and digitizing bathymetry data is now underway in a consortium which incorporates sea flor laboratories of several RAS institutions. This provides opportunity for computer access to earlier data from the Arctic region and evaluation of their possible use in compilation of an international digital bathymetry data base (analysis of accuracy of positioning of observation point, depth measurements and other parameters characterizing the quality of available information and its suitability for the purposes of the project).

Recently adopted programs of future investigations in the Russian Arctic seas can provide significant contribution to accumulation of additional modern information relevant to studying the bathymetry and geomorphological mapping of the Arctic basin.

Since 1972 MAGE has been conducting regular surveys in the Arctic seas: Barents, Kara, Laptev, Spitsbergen shelf, Geological and geophysical observations were always accompanied by bathymetry survey of the sea bottom. Bathymetry survey and positioning were carried out in strict accordance with instructions of GUNiO acting for the time of survey implementation.

As a result of investigations the following data were obtained for the Arctic shelf:

• gravity survey at a scale of 1:1,000,000 with line spacing 10-20 km of virtually entire area of the Barents and Kara seas;
• gravity survey of the southern Barents Sea at a scale 1:200,000 with line spacing 2-3 km;
• regional seismic trackline network in nearly entire Barents Sea and partially Kara and Laptev Sea;
• multidisciplinary geological and geophysical data within the boundaries of State Geological map sheets at a scale 1:1,000,000 (R-35,36; R-37; R-38; S-38; S-39; S-40; T-39,40; S-41,42) including high resolution seismic profiling over the areas with line spacing about 20 km.

  All offshore surveys included continuous echosounding. The root-mean-square error of depth measurements accounts for 1-3% of the measured depth value depending on the type of applied echosounder. The root-mean-square error of coordinate determination by mid-80-ties accounted for up to +/-800 m, and now is reduced to +/-100 m.

  All echosounding data set is stored in form of analog records and partially, in table form with interval between measurements 10-20 min depending on type of geological and geophysical survey. Coordinates are given for the same time intervals.

  Given some financial support MAGE could participate in compilation of the international bathymetry digital data base for the Arctic basin and submit all information on bathymetry survey for use in the project on the understanding that reprocessing of the data and their conversion to international data base format will be carried out by MAGE itself, and MAGE will get the copies of final documents of joint work which will duly relfect participation of MAGE's specialists in the project.

In modern times, the Swedish Polar Secretariat has organized three marine expeditions to the central Arctic Ocean, Y mer-80, Arctic Ocean-91 and Arctic Ocean-96. The expeditions were carried out from Swedish ice-breakers and bathymetric data were collected more or less continuously during all three occasions using convential single-beam echo-sounding equipment.

The data fro Ymer-80 and Arctic Ocean-91 has been deposited at the National Geophysical and Solar-Terrestrial Data Center's (NGDSC) marine geophysical data base. The new bathymetric data collected during the Arctic Ocean-96 expedition show that the details of available published bathymetric charts are largely inaccurate inthe eastern part of the Lomonsov Ridge. For example, the bathymetric map compiled by Perry et al. (1986) indicates a ridge depth between 1000 and 1500 m at about 85 degrees 25 minutes N, 152 degrees E where we recorded a shoal with a minimum depth of 607 m. However, Perry's bathymetric map was used as reference to which the data collected during Arctic Ocean-96 were added. Public-domain data from the US Navy SCICEX program were also merged in order to make an update of the bathymetry in the eastern part of the Lomonsov Ridge between 85 degrees 20 minutes N, 135 degrees E and 87 degrees 40 minutes N, 155 degrees E. The compiled bathymetry suggests a somewhat narrower ridge crest than previously published charts and the minimum depth of 607 m is the shallowest depth of the Lomonosov Ridge recorded (in public domain) in the central Arctic Ocean. However, the bathymetric data are still widely spaced in this area and unknown topographic features are likely present.

In 1996, the Naval Research Laboratory funded the processing of bathymetric data originating from many thousand kilometers of lines of seismic reflection data from USSR sources (V. Gataullin). Contours at 25 m intervals are presented, and compared to contour intervals constructed for the whole Arctic Bathymetry Map produced at the Naval Research Laboratory (N. Cherkis). At the degraded NRL contour interval the fit with the USSR bathymetry is relatively good in the Barents Sea and less so in the Kara Sea. Without doubt, the USSR data have improved the detail coverage in the areas mentioned (see attached figures).

The German ice-breaking research vessel "Polarstern" has been operational since 1983. In general, the operation areas are the Arctic during the northern summer and the Antarctic during the austral summer. "Polarstern" was the first ice-breaking research vessel equipped with the Seabeam multibeam sonar system in order to perform high resolution bathymetric surveys in the ice-covered areas of the polar oceans.

Until 1989 an integrated navigation system with standard dead reckoning systems (Gyro, Doppler Sonar) and Transit Satellite System formed the primary navigation and positioning system.

The Global Positioning System (GPS) in high precision on-line Differential Mode is used since the full satellite constellation has been available. For operations in high latitudes, the ship's heading, which is used for the calculation of the beam co-ordinates, is determined using a multi-antenna ship's attitude measuring system.

In 1989 the Seabeam system on "Polarstern" was replaced by the more powerful Hydrosweep System that uses ice-strengthened transducers. The current Hydrosweep installation provides Sidescan Sonar and Backscatter analysis options, which allow recovery of small scale features at the sea floor. The multibeam data from the Hydrosweep system is used to compile large scale bathymetric charts in scales of 1:100,000 and smaller.

Since the summer 1983 "Polarstern" has carried out 35 cruises into the Arctic region. During 14 Legs multibeam surveys were performed in areas of special scientific interest (Fram Strait, Aegir Ridge) and also during transits. During all other cruises single beam sonar data was collected. However, single beam sonar data collected in the Arctic outside the special study areas never have been processed or checked for quality.

All data are archived together with navigation and time information.

Due to the low quality of the digitsing unit of the Honeywell-ELAC Narrow Beam Sonar System (NGS) on "Polarstern" the data contain large amounts of outliers and blunders. Thus, for scientific use, a detailed analysis of this data must be performed.

During the workshop detailed information about the technical conditions on "Polarstern" and the bathymetric programs of the Alfred-Wegener-Institut in the Arctic will be presented to the workshop in form of differentiated track plots and small scale bathymetric charts of the study areas.

New contour bathymetric maps for the Barents and Kara Seas (south of 76 degrees N and between 32 degrees - 70 degrees E) have been compiled in NIIMorgeo from mainly shallow seismic and borehole data. Shallow seismic data were acquired largely by analog sparker with record frequency varying from 80-300 Hz to 1-2.5 kHz, as well as by means of echosounding and Parasound records with frequency between 3.5 and 9 kHz. Total length of seismic lines obtained in this area by various FSU organizations (NIIMorgeo, AMIGE, Sojuzmorinzhgeologija", VNIIOkeangeologija, MAGE, PMGRE, VSEGEI, several individual profiles by IO RAS) is close to 100,000 km.

In compilation of the maps, data from more than 300 boreholes drilled by AMIGE and numerous gravity cores have been utilized as both spot observations and constraints on depth conversion of seismic evidence.

Continuous geological cross-sections at a horizontal scale 1:500,000 were constructed along all seismic profiles using 1460 m/s as sound velocity value in water for depth conversion. Next step was to plot these continuous geo-seismic cross-sections on bathymetric work maps and to draw lines of thalwegs and ridges. Only after thisinterpolation of contour lines (isobaths at 25 m interval) was performed with full account of information contained in marine navigation charts, expecially for shallow water. All work maps were compiled in Universal Transverse Mercator (UTM) projection at 1:500,000 scale, then digitized in the Naval Research Laboratory (Washington, DC) and reduced to a smaller scale in the process of plotting.

Compilation of bathymetric maps of the southwestern Kara Sea are as yet only half accomplished. The data base for the Kara Sea is by far less complete and includes only about 15,000-20,000 km of shallow seismic lines and 20 boreholes. On the other hand, some new detailed navigation charts released by CUNiO in 1993-1995 are now available in public domain and allow to construct additional bathymetric contour maps.

In general, sea floor topography in the eastern Barents Sea is very diverse. In the shallower southeasternmost area the prevailing depths are less than 100m, while in the Central Deep area they exceed 300 m. Between these two areas there is a series of shallow banks (Murmansk, South and North Kanin, Geese Bank, Moller Plato, etc.) separated by narrow deeps. At water depth more than 100-150 m (below the level of wave/storm erosion) the relief displays linear features, directed south- to north-westward from Novaya Zemlya. These features are believed to be caused by moving grounded ice. As opposed to this trend, the banks west of Novaya Zemlya bear transverse elongated lows and highs up to 200-300 km inlength and 100 m in relative relief. The major ridges are subparallel to the Navaya Zemlya coastline and are thought to mark the main stillstand inthe ice-sheet retreat.

No similar features related to ice movement are observed in the south-western Kara Sea. The only exception is the East Novaya Zemlya Trough where strongly marked linear orientation of relief reflects glacial movement along the Novaya Zemlya. The main part of the region, the West Kara Plain, shows chaotically oriented, intensively rugged hummocky relief withintricate, winding patterns of isobaths. The most important uncertainty is the existence of specific short and narrow incisions up to 100-200 m depth.