Showing papers on "Antarctic sea ice published in 1971"

The Origin of Massive Icy Beds in Permafrost, Western Arctic Coast, Canada

Abstract: Massive beds of ground ice are shown to exist along the arctic coastal plain east of the Alaska–Yukon boundary for a distance of at least 500 km. The massive ground ice can be seen in both undisturbed and glacially disturbed Pleistocene sediments. An examination of several thousand seismic shot hole logs, from drill holes of 15 to 35 m in depth, also corroborates the widespread occurrence of ground ice. The icy beds typically have an ice content, defined in terms of the weight of ice to dry soil, in excess of 200% for sections as much as 35 m thick. A theory is presented which suggests that: the ice is of segregation origin; the source of excess water was from the expulsion of ground water during the freezing of sands; and high pore water pressures, favorable to ice segregation, developed beneath an aggrading impermeable permafrost cover. Permafrost aggradation may have occurred either on an exposed sea floor during a period of sea level lowering which would have accompanied a glacier advance, or followin...

Albedo of melting sea ice in the southern Beaufort Sea

Abstract: Two Kipp hemispherical radiometers mounted back to back and suspended by an 18 m cable from a helicopter flying at an altitude of about 90 m were used to make measurements of incident and reflected short-wave radiation. The helicopter was brought to a hovering position at the instant of measurement to ensure that the radiometers were in the proper attitude and a photograph of the ice cover was taken at the same time. The observations were made in 1969 during 16 flights out of Tuktoyaktuk, Northwest Territories (lat. 69° 26’N., long. 133° 02’W.) over the fast ice extending 80 km north of Tuktoyaktuk. Values of albedo of the ice cover were found to decrease during the melting period according to the equation A = 0.59 —0.32P where P is the degree of puddling of the surface.

Pressure ridge characteristics in the arctic coastal environment

Abstract: Pressure ridges and hummocks, which are the largest of the ice relief features, present formidable problems to design of off-shore facilities and to the operation of surface and subsurface shipping. The mechanics of ridge and hummock formation are reviewed and it is shown that several distinct types of ice formation features occur depending upon whether the formation mechanism is marginal crushing, overthrusting or shearing. Between 1969 and the present a number of both free-floating and grounded ridges have been examined by the authors in the Bering, Chukchi and Beaufort Seas. Profiles of the upper and lower surfaces of the ridges were determined by leveling and by drilling and sonar, respectively, and the internal structure of the ridges was investigated by coring. Ice temperatures, salinities, and densities were obtained and brine volumes were computed from the temperatures and salinities. Representative profiles are presented. The present results of this program are: 1. The degree of bonding between ice blocks and, therefore, the overall structural integrity of ridge keels would appear to be variable, presumably changing with the age of the ridge and the initial temperature of the ice being incorporated into the ridge. It can be shown that during the winter the cold reserve of ice blocks being incorporated into a ridge can be sufficient to cause significant inter-block ice growth. 2. Lack of local isostatic adjustment is common in ridges. In new ridges a significant portion of the surface load is supported by the surrounding plate ice resulting in its deflection. When ridges form by thrusting, their upper and lower portions may be laterally separated by tens of meters. This obviously results in a nonisostatic condition which is compensated by deflections of the local plate ice. 3. A representative salinity for the ice in the ridges we examined was 4 percent. Temperature profiles were reasonably linear except in the lower parts of ridges with pronounced keels where temperatures were roughly constant at near freezing values. The brine volume of the ice blocks in the keels varied between 40 and 120 percent. 4. Present information indicates that the average slope angle of the above-water portion of a ridge (24 degrees) is less than that of the underwater portion (33 degrees). 5. Ridges act as effective snow fences, causing large amounts of snow to accumulate both in and around their upper parts. 6. It appears doubtful that the cross-section profiles of all ridges can adequately be represented by any one geometric model. Current data bearing on the general distribution of deformation features in time and space over the Arctic Ocean are also summarized. The data sources include the Birdseye flights, recent special laser profilometer flights, and sonar traces of the lower ice surface. Prime attention is paid to the ridging characteristics in the Coastal and Offshore Sea Ice Provinces where the ice is clearly more highly deformed than the ice in the Central Arctic Basin Province. Winter and summer distributions of both sail heights and keel depths as well as the number of ridges per nautical mile are presented.

Use of side‐looking air‐borne radar for sea ice identification

Abstract: An experiment was conducted to assess the performance of side-looking air-borne radar (SLAR) in mapping and identifying sea ice parameters. A Philco-Ford AN/DPD-2 (Modified) SLAR was installed on a Coast Guard C-130 aircraft and flown on an experimental basis during September 1969 in conjunction with the S.S. MANHATTAN's transit of the Northwest Passage. In addition to the research effort to determine its feasibility as an ice observational technique, the SLAR was also used as a routing aid to the MANHATTAN. The results of this experiment indicate that SLAR can readily be used to detect ice concentrations, floe size and number, and water openings, and to identify through careful image interpretation, ice age, ice drift, surface topography, fractures, and pressure characteristics. SLAR's broad areal coverage, all weather, day and night capability make it an effective means of observing sea ice and for many purposes it provides observations superior to information obtained by a visual ice observer. SLAR imagery can be used in research efforts to study the formation, growth, and decay of sea ice and can be used operationally for ship routing and ice forecasting. It will be necessary to conduct similar experiments during other seasons of the year to determine whether there is a seasonal influence on the imaged appearance of sea ice. (Author)

Wind stress over ice and over water in the Beaufort Sea

Abstract: A sonic anemometer-thermometer has been used in a study of Reynolds stress, sensible heat flux, and velocity and temperature spectra over ice and over water in the Beaufort Sea. The wind-drag coefficient over ice for stable conditions is C10=0.0026, and over water for unstable conditions C10=0.0014.

Circulation and hydrology under the seasonal ice in McMurdo Sound, Antarctica

Abstract: Results are presented here of measurements of current velocity, temperature and salinity made at seven positions in McMurdo Sound (77° 50’ S, 166° 30’ E): four near the seasonal ice/fast ice boundary, two along the seasonal ice/sea boundary, and one in a channel in the sea ice. Current velocities were strongly influenced by tides with speeds greatest during periods of high tidal range. Current velocities changed rapidly in the upper 100 m and current speeds generally increased with depth to within 200 m of the bottom. In the lower 200 m current speed decreased towards the bottom. The mean circulation near the seasonal ice/fast ice boundary, found by eliminating the tidal variation, appears to consist of an inflow of water towards the fast ice at positions further than a mile (1.3 km) from Ross Island and a nett outflow from under the fast ice at positions closer than a mile (1.3 km) from Ross Island.

Some Effects of Ice on a River Bed

Abstract: Morphological activity of ice on the bed of the Tana River of Finnmark, Norway, during the Spring flood is concentrated into a short period of time when water stage is changing rapidly. Ice affects the bed in four ways. 1) Actual contact of the ice with the bed gouges grooves if the ice is still moving or flattens the micro-relief of the surface if the velocity is low. 2) Grounded blocks in a strong flow generate separation eddies which cause local depositional and erosional irregularity. 3) Blocks of ice melting on a subaerially exposed sediment surface disturb the surface as they collapse. 4) Depressions are thought to be due to the melting of buried ice blocks. probably frozen to the sediment surface. The preservation potential of these structures is low but they might, in exceptio al circumstances, be found in fluviatile sandstones.

Flow Law for Antarctic Ice Shelves

Abstract: ICE shelves are floating glaciers which are attached to an inland ice sheet or to land. They creep under their own weight, the creep rates being dependent on the ice flow law at low stresses.

Observations of ice stalactites in McMurdo Sound, Antarctica

Abstract: Observations have been made of ice stalactites with lengths of 1.5–6.0 meters and diameters of 10–25 cm growing under pack ice in Antarctica. The possible physical significance of the stalactites to the natural desalination of sea ice and to the formation of the antarctic bottom water is discussed.

Method and apparatus for forming ice island for drilling or the like

Abstract: A method and apparatus for forming an ice island in cold geographical regions to recover resources such as oil from areas normally covered with ice, frozen muskeg or the like in the winter. In one embodiment an oil drilling barge is moved to an offshore drill site during a thaw period and allowed to be frozen in at the onset of winter. Concentric, spaced apart walls are constructed about the barge and water is pumped into the area between the walls, frozen, and the cycle repeated a number of times until the weight of built-up ice causes the walls to sink gradually through the pack ice and eventually to the ocean bottom. The barge is next secured to the inner wall to serve as a drilling platform. Ice and water within the inner wall is removed and drilling proceeds. During seasonal thaws refrigeration equipment is utilized to keep the ice island in a frozen condition. When the ice island is to be moved to another drill site, air is introduced beneath the ice island, and the upper layers of ice are thawed, scraped away and dumped over the side during a thaw period unitl the lightened, buoyed island floats off the ocean bottom. It is towed to the new drill site, built up again, and sunk as before.

Sea ice and supercooled water

Abstract: The existence of supercooled water below growing sea ice has been postulated in the past to explain anomalous temperature and salinity values in the water column. In addition supercooling has been invoked to explain ice-crystal production in the water that is tens of meters below the ice sheet and on the sea bed near the shore. From a study of the literature and the laboratory experiments we conclude that the postulate is unnecessary and that supercooling of the water mass, if it exists at all, is transitory.

Observations on the Glacial History of Livingston Island

Abstract: Livingston Island, one of the South Shetland Islands, Antarctica, has recorded at least three glacial events. During the oldest event, all areas of the island below 200 m were covered by an expanded island ice cap. At that time Livingston Island ice probably joined that of adjacent islands. A second, less extensive event, is recorded by deposits of both the inland ice cap and cirque glaciers. Between these two glacial events, a higher stand of sea level produced beaches and terraces at 10.6 m to 12 m above the present sea level. Following the second glacial event, a higher sea level produced beaches 6.1 m above the present sea level. A third, minor and probably relatively recent glacial event is recorded by push moraines in some cirques from which the ice has now receded.

Transport of ice nuclei over the north pacific ocean

Abstract: Simultaneous measurements have been made over extended periods of time of the relative concentrations of ice nuclei in the air at stations in Alaska, Hawaii and Washington State. On occasions large increases in ice nucleus counts lasting for a week or more (“ice nucleus storms”) were observed. The ice nucleus storms sometimes occurred in close proximity in time at different stations and it is shown that in some cases this can be explained by the advection of particles in the lower troposphere between stations. On other occasions the ice nucleus storms appeared to be of local origin. DOI: 10.1111/j.2153-3490.1971.tb00544.x

The interaction between ice and coastal structures

Abstract: Two subjects are dealt with. One is piling up of ice on shores and coastal structures. The other is the influence of ice floating in front of the structures on spray caused by wind wave action. Field data were secured from Scandinavia, Canada, and United States. The collected material consists of photos and measurements of extreme ice situations together with drawings of the actual structures. Based upon the field data, following general conclusion may be drawn: 1) Sloping shores and structures favour ice piling. As a result of wind and current forces, ice may pile up to elevations of 10-15 m above still water level. A berm or platform incorporated in the structure caused somewhat less ice piling than a corresponding straight rubble mound, mainly due to the "delay" obtained in filling up the platform with ice. 2) Vertical walls do not favour ice piling. If the depth in front of the structure is sufficient, the ice does not climb, but is rather forced down. When depth in front of the structure including any filling i.e. in the form of a rock mound was above 5 m, no piling up took place in most cases. But with 4 m depth (including a rock mound), piling occurred at one lighthouse (Hals Barre, Denmark). This does not allow the conclusion that 4 to 5 m is a "critical depth". Such depth must depend upon the actual exposure and ice conditions. Cases mentioned in this paper are examples on medium to heavy situations.

Determination of sea ice drift using side-looking airborne radar

Abstract: Side-Looking Airborne Radar (SLAR) has been used experimentally to map sea ice conditions since the early 1960's. In conjunction with the MANHATTAN tanker test, the U.S. Coast Guard equipped a C-130 aircraft with a Philco-Ford AN/DPD-2 Side-Looking Radar (Ku band) and conducted ice mapping experiments in the Northwest Passage during September 1969. In addition to observing the overall ice conditions, individual ice floes were identified on SLAR imagery by their size, shape, and surface characteristics. The results of this experiment revealed that single ice floes, as well as general ice masses, could be tracked to an accuracy of nearly one nautical mile. Also, water currents appear to have dominant long term influence on ice drift in this area. By assuming that one can obtain measures of the wind stress, Coriolis force, and pressure gradient force, one may be able to ascertain approximate values of the surface ocean currents in the vicinity of a given floe. (Author)

Ground-Wave Propagation over Arctic Sea Ice

Abstract: Radio ground-wave propagation in the Arctic Ocean occurs over mixed paths. The mixed paths include layered or homogeneous sea ice and sea water. Amplitude and phase variations occurring as "dropoff" or "recovery" effects at the ice-sea-water boundaries provide a technique for sea-ice mapping and an explanation for anomalous radio reception. The phase variations are more sensitive over short distances from the mixed path boundaries. Center for Research in Engineering Science

Cold Regions Science and Engineering Monograph 3, Section B1a: Winter Regime of Rivers and Lakes,

Abstract: : The monograph summarizes existing knowledge of river and lake ice surveys, heat balance on open water in winter, frazil, ice cover formation, ice breakup and ice control. (Author)

Climate and Energy Exchange on a Sub-Polar Ice Cap in Summer. Part A. Physical Climatology,

Abstract: : The analysis is based on climatological and micro-meteorological measurements made mainly at an elevated observation-place (Ice Cap Station, 1.3 km above M.S.L.) in the area of superimposed ice formation on the northwest slope of the ice cap. Comparative measurements were temporarily made in different parts of the ice cap. The structure of the wind-field over the ice cap, especially in situations with katabatic winds, was investigated by means of pilot balloons. In the middle of the summer the low-lying parts of the ice cap and the outlet glaciers are invaded by air of temperatures above freezing. Since the temperature of the ice cannot rise further than to melting-point, an advection inversion develops above the surface. Over the high-lying parts of the ice cap the air temperature in general stays well below freezing. Here the radiation climate is the factor which dominates the temperature stratification in the surface layer. At Ice Cap Station the conditions are intermediate in this respect; air temperatures above freezing were obtained in about 40% of all temperature readings at screen level in July. (Author)

Skallhultsplatån, en Supraakvatisk Deltayta Bildad Innanför Inlandsisens Rand under Isavsmältningen i Vätterbäckenet

Abstract: The Skallhult plateau is situated in an cast-westerly pass of Hokensas, a mountain ridge that separates the Vatter and Tida basins on the northern border of the South Swedish Highlands. The plateau has formerly been interpreted as an ice marginal delta built up in the Baltic Ice Lake (Munthe 1940) or in a local ice lake which covered the Vatter and Tida basins south of the ice margin (cf. Munthe 1910 and Nilsson 1939, 1953, 1968). These interpretations have been forwarded without any descriptions or proofs as regards morphology and stratification. According to results of morphological investigations presented in this paper the Skallhult plateau was formed by subglacial flow which penetrated the ice surface during deglaciation and built up a supraaquatic delta or outwash plain surrounded by ice. Meltwater flowed westwards over this plain from the Vatter basin to the Tida basin and was probably drained into crevasses of stagnated ice masses. A deposit of the same type has also been found ca. 30 km ...

Ice thickness observations, north american arctic and subarctic, 1966-67, 1967-68

Abstract: : The paper is a fifth in a series of reports on lake and river ice and land-fast sea ice, records ice thicknesses observed throughout the North American arctic and subarctic during the 1966-67 and 1967-68 seasons. Information on ice surface conditions, dates of first ice, freeze-over and breakup, and detailed measurements of ice thickness across Alaskan rivers are also included. Continued reports from the Alaska National Guard Network on ice thickness measurements on lakes and rivers in the remote regions of interior Alaska are presented. Analyses on maximum observed ice thicknesses reported during the two winters in North America and deviations from the mean ice thickness amounts measured across Alaska rivers between 1965 and 1968 were conducted. (Author)

On ice and snow and rock

Abstract: Interestingly, on ice and snow and rock that you really wait for now is coming. It's significant to wait for the representative and beneficial books to read. Every book that is provided in better way and utterance will be expected by many peoples. Even you are a good reader or not, feeling to read this book will always appear when you find it. But, when you feel hard to find it as yours, what to do? Borrow to your friends and don't know when to give back it to her or him.

Annual report no. 3

Abstract: : The report summarizes research performed during the year 1 October 1970 - 30 September 1971. Research topics include: sea ice dynamics, heat and mass budget of arctic sea ice, atmospheric turbulence in the arctic, thermal and mechanical stresses in sea ice, radiation in ice, and bearing capacity of floating ice sheets. (Author)

Sea ice characteristics in bering sea

Abstract: Sea ice samples collected from the NORTHWIND icebreaker cruise Jan.-Feb. 1970 extending from Cape Newenham to the Russian coast were studied onboard ship. Large blocks of sea ice were obtained for their section petrofabric examination and the collection of ice-sediments. The Bering Sea ice consisted of three layers: a thick horizontal C axis layer bounded by thin vertical C axis layers at the top and the bottom. The maximum sediment concentration in Bering sea ice was observed near the lower boundary of horizontal C axis layer. The unusual bottom vertical C axis ice layer in Bering Sea may be due to several sea ice forming phenomena. However, extreme cold weather accompanied by severe storm in this area is suggested for this ice-layer. Bering Sea throughout the region displayed a consistent crystallographic structure. Sea ice was layered, with a bubbly, milky, fine-grained layer on the top and a layer of clear, dense, bubble-free ice near the bottom. The ice near the top contained a layer with vertically oriented crystals. This layer underlain by a thick layer of clear, dense ice consisting of long, tapered crystals with horizontal C-axis. This particular crystal fabric is quite common in lake ice and stream ice. A layer of clear, very fine grained dense, bubbly milky ice was observed at the bottom. Beside crystal orientation the vertical layering of the Bering sea ice can also be differentiated on the basis of crystallinity. Maximum of five layers were observed in some samples. These layers were characterized by primarily the crystal orientation, size and shape of individual crystal, air bubbles, salt pockets and sediment or phytoplankton content in the ice. The freezing of seawater and the resulting sea is a complex process in which the rate of cooling, salinity and the rate of loading play a significant role. Theoretical as well as experimental work to elucidate the formation of sea ice has been conducted by Anderson and Weeks (1958), and Weeks (1962). Field observations on sea ice have been made by several investigators and these studies were conducted primarily to evaluate the mechanical properties of sea ice, better icebreaker design, sea ice landing strips, offshore drilling platforms, dredging facilities and other related structures. The petrofabric studies of sea ice have been made and described insofar as to explain the mechanical properties such as strength of sea ice etc.

Historical Reference to Ice Islands

Abstract: Some years ago M. Dunbar gave a detailed account of earlier ice reports which could refer to ice islands, as distinguished by G. Hattersley-Smith from other ice in the polar sea by their great unit area, thickness, structural strength and rolling relief. Among the old descriptions of 'floebergs' and 'palaeocrystic ice' some of Greely's come closest to a description of an ice island. Another early report might be worth mentioning: Franz Boas, the German-born anthropologist and later professor at Columbia University states that in October 1883 a huge iceberg drifted into Cumberland Sound, Baffin Island. It had a height of 15 m to 20 m, a length of 14 km and a width of 5 km. The total thickness of 100 m to 150 m could be seen when the ice broke into pieces. The estimated volume was 13 cu km. Similar ice formations of smaller size had been repeatedly encountered when approaching Cumberland Sound. The upper surface consisted of long low rounded parallel rolls with a wavelength of about 150 m and extending over 1 km to 3 km. The surface and the uppermost 2 m of the ice contained stones; no stratification or crevasses were visible. The description fits that of a typical ice island. That ice islands from the northern coast of Ellesmere Island can reach Baffin Bay and Cumberland Sound is shown by the recent drift of ice island WH55; a segment of at least 14 sq km passed through southern Davis Strait.