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The anthropogenic chlorofluoro-methanes CCl3F (F-11) and CCl2F2 (F-12) have been measured to depths of 1800 m in the Canada Basin of the Arctic Ocean (approximate position 85°50′N, 108°50′W). The measurements were made as part of the Canadian Expedition to Study the Alpha Ridge (CESAR) during April 1983. Surface layer concentrations beneath the ice were 4.79×10−12 mol/kg (F-11) and 2.11×10−12 mol/kg (F-12). Both profiles exhibit a rapid concentration decrease with depth through the halocline and very low, but detectable, concentrations at depths of 350–900 m in the Atlantic Layer. In the Arctic Ocean Deep Water (900–1800 m), concentrations are at or below our practical detection limit of 0.01×10−12 mol/kg. The profiles have been interpreted using two “extreme-case” lateral ventilation models in order to place bounds on the water column ventilation rates. The “Ventilation age” of the upper portion of the halocline (60–150 m) increases with depth from 4 to 14 years. The core of the Atlantic Layer at this location appears to have been isolated from the surface for at least 30 years.

Gamma‐gamma logs were used to study the density of sedimentary rocks and formations in the Western Canada basin. The frequency distributions of density of all the main rock types have negative skewness, a characteristic that seems to be a general feature of density distributions of rocks based on well logging. The frequency distributions of density for sandstone and limestone were not found to be different from those of shale and dolomite, respectively, at the 0.01 level of significance. Several density‐depth functions were applied to the shale samples. Athy's (1930) exponential function provided the best fit to observed values. Using this function, the average thickness of sediments removed by denudation in south and central Alberta was calculated to be 4400 or 3600 ft on the assumption that the density of the original surface clay was 1.4 or [Formula: see text], respectively. Maps of average density for six formations in Alberta and Saskatchewan indicate only a partial correlation with lithology and depth. A large scattering of density with depth was found in the case of four Cretaceous formations in which density was observed to be independent of the sandstone/shale ratio. In the case of one formation containing predominantly shale, no obvious dependence on depth was found. Also, no relationship between density and the occurrence of oil and gas fields was apparent.

The USS Nautilus (SSN-571) was the first vessel to cross the Arctic Basin via the north pole in early August 1958. During this expedition, almost continuous acoustic under-ice thickness profiles were recorded. In August 1970 USS Queenfish (SSN-651) retraced Nautilus' route, yielding the only duplicate transect of under-ice topography across the Arctic Basin. Comparisons of the statistical analysis of the under-ice draft measurements obtained through use of wide-beam and narrow-beam and narrow-beam only acoustic profilers by Nautilus and Queenfish, respectively, along the coincidental route are presented. Geographic areas found to have distinct under-ice characteristics and ice composition are identified. The under-ice statistics of both cruises are considered in relation to representative field observations and modeling results of other researchers. Principal findings are (1) Nautilus recorded generally more severe ice conditions within the Canada Basin than did Queenfish 12 years later; overall mean drafts were 3.08 and 2.39 m, respectively, (2) the under-ice topography becomes progressively more severe when proceeding from the Canadian to the Eurasian side of the Arctic Basin, (3) the Canada Basin may contain the most moderate under-ice topography and the greatest number of open water and refrozen polynyas and leads within the central Arctic Basin, (4) the Makarov and Amundsen basins and the Arctic mid-ocean ridge may contain some of the most severe under-ice topography within the Arctic Basin, and (5) the present study indicates an overall Arctic Basin mean of 3–4% open water/new ice (less than 30 cm) in summer.

Application of mass balances of 18O, tritium and salt, plus 14C data show that the deep Eurasian Basin exchanges water with the subarctic Atlantic Ocean on a time scale of 10 to 100 years, while the deep Canada Basin has an exchange time scale of about 700 years. Only small fractions, less than 10 to 15% of the deep waters, originate from the shelves. The deep Canada Basin cannot consist of fossil water from glacial time or from the latest cool climate spell, just 100 to 300 years ago.

The time function of bomb tritium concentrations in river runoff to the Arctic Ocean has been reconstructed from published data on tritium in precipitation 1959–1975. Tritium measurements on oceanic samples through the halocline exhibit strong linear relationships between tritium concentrations (TU values) and salinity. These waters thus look like binary mixtures of Atlantic source water and freshwater runoff. Combining these data, the vintage of the freshwater component in the Arctic Basin has been determined assuming no other major tritium source. The relation indicates the average age of the freshwater component to be 11±1 years in the Nansen Basin and the outflow and somewhat higher in the Canada Basin. According to tritium/salinity data, a surface layer of 10–60 m is affected by sea ice melting and freezing in the Nansen Basin, and the thickness of this layer increases to 150–170 m toward the Canada Basin. There is tritium also in the deeper waters, the unmixed Atlantic water, which points at residence times for that water not to exceed 17 years. The appendix is available with the entire article on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, D.C. 20009. Document J81-012; $1.00, payment must accompany order.

Atmospheric dust fallout and ice-rafted glacial detritus are significant factors for the Arctic Ocean sediment budget. Atmospheric dust amounting to .09 mm/1,000 yrs is being delivered to the Canada Basin, Chukchi Plain and Alpha Cordillera areas today. This is 10 percent of the sedimentation rate for some parts of the Arctic Ocean during the past 2 to 3 m.y. Clay mineralogy of the modern atmospheric dust and of the Arctic Ocean sediment is approximately 40 percent illite with almost equal amounts of chlorite and kaolinite. Ice-rafted detritus is widespread on the Arctic Ocean floor today. In addition, erratics greater than 8 mm and less than 40 mm have been found in 44 of almost 100 cores studied to date. These erratics are carbonates and sandstones in large part; metamorphics and cherts are less abundant. No pattern of lithologic and vertical distribution correlation of erratics among the cores is present. The oldest erratic occurs in sediment approximately 3.5 m.y. old. In excess of 30 percent by weight of some Arctic sediment consists of greater than 62 μ material. This is largely ice-rafted material. Together with the atmospheric dust fallout, this is a significant part of the average 2 to 3 mm/1,000 yrs sedimentation rate determined from magnetic stratigraphy.

The SSN Nautilus obtained the first continuously recorded echo-sounder profile across the center of the Arctic Basin during its 1958 cruise from Point Barrow to the North Pole and then to the Atlantic Ocean. The sounding lines, supplemented by lines from SSN SKATE reveal the following geomorphic features: (1) the Alaskan continental terrace and continental rise; (2) Canada Basin, a flat abyssal plain at the depth of 3850 m; (3) Chukchi Cap, a projection from the Chukchi Shelf with a summit elevation of about 900 m; (4) a continuation of Canada Basin, interrupted by a few sea knolls and having a depth of 3900 m; (5) Central Arctic Rise, a region of smoothly undulatory topography at depths between 2000 and 3700 m, with relief not exceeding 900 m; (6) Central Arctic Basin, an abyssal plain at 3940 m; (7) Lomonosov Ridge, rising abruptly from the basin to a summit at 1290 m: (8) beginning almost at the North Pole, the Eurasia Basin, an abyssal plain sloping south with a depth gradually increasing from 4090 m to 4500 m; (9) a region of rough topography containing numerous sharp peaks and having relief of as much as 1100 m and containing the deepest sounding of the Arctic Basin, 5335 m; (10) Nansen Ridge, a smoothly undulatory ridge rising to 1280 m where crossed.