Download or read book Sea Ice on Mcmurdo Sound Antarctica Deep Freeze 67 Thickness and Temperature Studies written by Russell A. Paige and published by . This book was released on 1967 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt: The annual sea ice on McMurdo Sound, Antarctica, is extensively used as a runway by heavy cargo aircraft. Safe utilization requires a better understanding of thickness, temperature, and strength - basic properties affecting the load-carrying capacity of ice sheets. Thickness and temperature are the two parameters required to use load-carrying curves being developed by the Naval Civil Engineering Laboratory (NCEL). Annual sea-ice thickness varies seasonally between 8 and 11 feet by the end of the growth period. Thinning by bottom melting starts about mid-December and continues until breakout in late January or early February. The average ice-sheet temperature has increased each season since Deep Freeze 65 (DF-65), and becomes essentially isothermal about the same time bottom melting begins. For operational safety, the ice sheet should be monitored for thickness and temperature as described in this report. The surface temperature, T sub s, measured at a depth below the influence of diurnal air temperature fluctuations, is needed to select the correct NCEL load-carrying curve. A depth of 24 inches is beyond the influence of this fluctuation and is suitable for determining T sub s on a daily or weekly basis. The average ice-sheet temperature, based on the freezing point of seawater, is (T sub s + 1.8)/2. Both the surface temperature and the average ice-sheet temperature gradually change with time. (Author).
Download or read book Sea Ice Studies on Mcmurdo Sound During Deep Freeze 65 written by Russell A. Paige and published by . This book was released on 1965 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: The sea ice adjacent to McMurdo Station, Antarctica, has been used extensively since 1956 for aircraft operations, travel, freight hauling, and loading and unloading ships. A study of some factors affecting the safety and efficiency of these operations was made during the summer of 1964-65. The factors included cracks, seal holes, pressure ridges, and breakout of the ice in this area at the end of the 1964-65 summer season. It was found that cracks which did not penetrate the ice sheet, and seal holes in thick ice did not seriously affect the bearing capacity of the ice; however, flooding in pressure zones and around seal holes on the ice sheet created a hazard to travel where the ice was covered with snow. In addition, it was observed that breakout of the ice south of McMurdo Station began about 3 weeks after the ice exhibited minimum strength, maximum temperature, and a rapid decrease in thickness, and 4 to 6 weeks after maximum daily air temperatures were observed at McMurdo Station. It was concluded that additional research is needed to provide adequate knowledge on the influence of those factors affecting the safe and efficient utilization of sea ice in Antarctica.
Download or read book Strength Studies on Antarctic Sea Ice written by George Hendrickson and published by . This book was released on 1965 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Sea Ice Studies on McMurdo Sound During Deep Freeze 63 written by N. S. Stehle and published by . This book was released on 1963 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: Studies of one-year-old sea ice and very young sea ice were conducted during the austral summer of 1962-63 at McMurdo Station, Antarctica. During the observation period on the one-year-old sea ice approximately 18 inches of ice were lost solely on the bottom surface. Average salinities and densities of the total ice thickness decreased slightly with time. Average shear strength values for the total ice thickness changed very little with time; however, a decrease in shear strength was noted in the middle p rtion of the ice sheet. This corresponded closely with the level at which drainage of brine was noted. The very young sea ice was observed in a 6-1/2- by 7-foot well in the one-year-old ice. Ice growth and salinity of the newly accreted ice, older ice, and the well water were checked every 2 to 3 days. Although sampling was done primarily during January, the well study of very young ice appears to be very promising and further studies of this type are planned. (Author).
Download or read book SEA ICE ON McMURDO SOUND ANTARCTICA PRELIMINARY THICKNESS written by R. A. Paige and published by . This book was released on 1966 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: The thickness of sea ice in McMurdo Sound, Antarctica, and its variations throughout the season and from year to year affects the safety and efficiency of travel and air operations by the U.S. Navy Antarctic Support Activities. The annual sea ice growth stages are: (1) youth - the ice sheet is actively growing in thickness and extent; (2) maturity - growth ceases, maximum thickness is attained; (3) old age - the ice sheet is nearly isothermal and begins to thin rapidly by bottom melting. Growth rate and ultimate thickness varies locally depending mainly upon snow cover and proximity to land or the ice shelf. Bottom melting begins in mid-December and progresses rapidly until breakout. Thinning is differential depending upon location; the Cape Armitage sea ice area becomes dangerously thin when most of the sea ice in McMurdo Sound remains thick enough for safe travel. Measurements of thickness, air, ice and water temperature, and snow cover during the entire season are needed for correlation with accumulative degree-days to develop load-carrying curves and to predict thickness. (Author).
Download or read book Technical Abstract Bulletin written by and published by . This book was released on with total page 912 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Sea Ice Studies on Mcmurdo Sound During Deep Freeze 64 written by Nancy S. Stehle and published by . This book was released on 1964 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: Studies of 1- and 2-year-old ice were conducted during the austral summer of 1963-64 at McMurdo Station, Antarctica. Approximately 75 cores were taken. During the observation period, approximately 3-1/2 feet of ice were lost from the bottom surface of the 2-year ice, which was found to be very irregular. Observations of the 1-year ice sheet were concluded halfway through the test season due to breakup. The average salinity of both ice ages decreased, with the salinity of the 1-year ice approaching that of the 2-year ice by mid-January. Deterioration of the upper region of the ice sheet, as evidenced by low density and salinity values, did not begin until after mid-November. The initial high salinity of the upper region of the young sea-ice sheet was noted to have migrated to the middle of the 2-year ice sheet, leaving a low salinity ice at the surface. Shear values were about 100 psi higher in the 2-year ice than in the 1-year; both decreased during the period of observation. Maximum density values did not coincide with maximum strength values. (Author).
Download or read book Sea Ice Studies on McMurdo Sound During Deep Freeze 62 written by Naval Civil Engineering Laboratory (Port Hueneme, Calif.) and published by . This book was released on 1963 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Western Ross Sea and McMurdo Sound Ice Forecasting Guide written by R. J. Perchal and published by . This book was released on 1975 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt: Procedures for preparing short-range (48-hour) forecasts and long-range (15- and 30-day) estimates of austral summer sea ice conditions in the western Ross Sea and McMurdo Sound are given. Magnitude and direction of short-period ice drift are related to pack concentration, topography, and thickness, surface currents, and forecasted surface wind velocities. Long-period ice estimates are based on analog techniques relating various environmental factors to pack growth, extent, and disintegration as well as using the progression of ice melt indicated by selected historical data. Examples of short-range ice forecasts and long-range estimates are given. Techniques are included for interpreting sea ice from satellite imagery.
Download or read book Sea Ice Strength Studies on Mcmurdo Sound During the Austral Summer 1964 65 written by R. A. Paige and published by . This book was released on 1966 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: During the austral summer of 1964-65, a study of some of the physical properties of sea ice was made near McMurdo Station, Antarctica, where the sea ice is used extensively for aircraft operations, travel, freight hauling, and docking facilities. Tests of specimens showed that both shear and ring-tensile strengths increased almost linearly as specimen temperature decreased; the strength decreased as the ice sheet became warmer and more nearly isothermal. Average shear strength decreased from 140 psi in late October to a low of 90 psi in late January and then increased to 115 psi by 10 February just before breakup; average ring-tensile strength similarly decreased from 190 psi in mid-December to a low of 145 psi in early February, and then increased to 170 psi by 10 February. Internal deterioration and decrease in strength, thickness, salinity of brine, and temperature gradient are all related to rising temperatures and increased solar radiation during the summer. Development of a reliable method of predicting the bearing capacity of sea ice depends upon more detailed knowledge of the effects of loads, the history of the ice, danger zones and safety factors, and other features to insure safe operation on the ice. (Author).
Download or read book Guide to Technical Documents written by Naval Civil Engineering Laboratory (Port Hueneme, Calif.) and published by . This book was released on 1974 with total page 374 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mcmurdo Ice Wharf Surface and Subsurface Observations During Deep Freeze 67 written by Russell A. Paige and published by . This book was released on 1967 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: The wharf at McMurdo Station, Antarctica, consists of a limited area of fast ice, or old sea ice, that has accumulated along the western shore of Winter Quarters Bay. This facility is critically needed for safe, efficient unloading of cargo ships for Operation Deep Freeze. Since Deep Freeze 64 (DF-64) when the fast ice was first used as a wharf, surface erosion, undercutting of the vertical ice face by wave action, and the caving off of large slabs of the surface during summer have damaged and deteriorated the usable wharf area. Observations during DF-67 showed that wave action is the primary cause of undercutting and indicates that surface erosion has been essentially eliminated by proper drainage control. Twelve-inch-diameter cores from a depth of 38 feet show that the ice wharf consists of 20 feet of white, slightly saline, bubbly ice underlain by 30 to 40 feet of dense, grey ice containing layers and lenses of basaltic rock debris. Additional subsurface exploration with a tricone bit defines the approximate size and shape of the ice wharf and indicates that the amount of fast ice available for the wharf is definitely limited and rapidly disappearing. It is concluded that measures are urgently needed to protect the wharf from further loss of surface area. (Author).
Download or read book Antarctic Journal of the United States written by and published by . This book was released on 1967 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Oceanography written by Defense Documentation Center (U.S.) and published by . This book was released on 1969 with total page 896 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Crystallographic Studies of Sea Ice in Mcmurdo Sound Antarctica written by Russell A. Paige and published by . This book was released on 1966 with total page 37 pages. Available in PDF, EPUB and Kindle. Book excerpt: The sea ice in McMurdo Sound is used extensively for aircraft operations, travel, and docking areas. The safety and efficiency of utilizing the sea ice depends upon many factors affecting its physical properties throughout the season. Sea ice is a crystalline solid with physical properties that are highly temperature dependent between -1.8 C and -10 C. This dependence becomes less with decreasing temperatures. A study of various crystal parameters and structure is essential for a better understanding of their relationship with strength properties. Horizontal banding in the ice sheet was studied to determine the effect of temperature fluctuations on band frequency. Various crystal parameters such as subcrystal platelet width, crystal length-to-width ratios, and crystal size were measured from photographs of thin sections. Subcrystal platelet width increased with depth from about 0.5 mm at the surface to about 1 mm at 2.8 meters. The length-width ratio of single crystals increased from 2 to 1 near the surface to more than 5 to 1 at depths greater than 2 meters. Thenumber of crystals per unit area decreased with depth. Strained ice from a pressure ridge showed preferred c-axis orientation and wavy extinction similar to that observed in strained quartz. There is apparently no correlation between strength and crystal structure in a mature isothermal ice sheet. (Author).
Download or read book Observations Within and Beneath Antarctic Sea Ice in McMurdo Sound and the Weddell Sea 1967 1968 written by and published by . This book was released on 1969 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Operation Deep Freeze 1959 1960 McMurdo Byrd Pole Hallett written by and published by U.S. Navy Seabee Museum. This book was released on with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt:
