The Antarctic Zone Flux Experiment

The article of record as published may be found at https://doi.org/10.1175/1520-0477(1996)0772.0.CO;2In winter the eastern Weddell Sea in the Atlantic sector of the Southern Ocean hosts some of the most dynamic air-ice-sea interactions found on earth. Sea ice in the region is kept relatively thin by heat flux from below, maintained by upper-ocean stirring associated with the passage of intense, fast-moving cyclones. Ocean stratification is so weak that the possibility of deep convection exists, and indeed, satellite imagery from the Weddell Sea in the 1970s shows a large expanse of open water (the Weddell Polynya) that persisted through several seasons and may have significantly altered global deep-water production. Understanding what environmental conditions could again trigger widespread oceanic overturn may thus be an important key in determining the role of high latitudes in deep-ocean ventilation and global atmospheric warming. During the Antarctic Zone Flux Experiment in July and August 1994, response of the upper ocean and its ice cover to a series of storms was measured at two drifting stations supported by the National Science Foundation research icebreaker Nathaniel B. Palmer. This article describes the experiment, in which fluxes of heat, mass, and momentum were measured in the upper ocean, sea ice, and lower-atmospheric boundary layer. Initial results illustrate the importance of oceanic heat flux at the ice undersurface for determining the character of the sea ice cover. They also show how the heat flux depends both on high levels of turbulent mixing during intermittent storm events and on large variability in the stratified upper ocean below the mixed layer. 39 refs., 8 figs

The influence of an Antarctic glacier tongue on near-field ocean circulation and mixing

The article of record as published may be located at http://dx.doi.org/10.1002/2013JC009070In situ measurements of flow and stratification in the vicinity of the Erebus Glacier Tongue, a 12 km long floating Antarctic glacier, show the significant influence of the glacier. Three ADCPs (75, 300, and 600 kHz) were deployed close (<50 m) to the sidewall of the glacier in order to capture near-field flow distortion. Scalar (temperature and conductivity) and shear microstructure profiling captured small-scale vertical variability. Flow magnitudes exceeded 0.3 m s21 through a combination of tidal flow ( 8 cm s21) and a background/residual flow ( 4–10 cm s21) flowing to the NW. Turbulence was dominated by deeper mixing during spring tide, likely indicative of the role of bathymetric variation which locally forms an obstacle as great as the glacier. During the neap tide, near-surface mixing was as energetic as that seen in the spring tide, suggesting the presence of buoyancy-driven near-surface flows. Estimates of integrated dissipation rate suggest that these floating extensions of the Antarctic ice sheet alter energy budgets through enhanced dissipation, and thus influence coastal near-surface circulation.The work was funded by The New Zealand Royal Society administered Marsden Fund, and US NSF support to Stanton and McPhee. Logistic support was provided by Antarctica New Zealand and travel funding from Air New Zealand

The effects of selection for lean growth and the halothane allele on growth performance and mortality of pigs in a tropical environment

The effects of the halothane allele and other genes for rapid lean growth were examined in pigs grown in an environment of high temperature/transport stress. The halothane allele n was segregating with its normal alternative N in a line which had been selected for rapid lean growth and in an unselected control line. Pigs of the three halothane segregants, NN, Nn and nn from both lines were grown on ad lib. feeding from 25 to 90 kg liveweight. Relative to the control, the selected line had faster, more efficient growth with lower 90 kg backfat thickness. Least square means in the selected and control lines were 0.87 and 0.77 ± 0.01 kg for daily liveweight gain, 2.63 and 2.98 ± 0.03 for food conversion ratio and 13.1 and 18.7 ± 0.3 mm for backfat. The halothane allele reduced appetite, growth rate, food conversion ratio and backfat. Means of the NN, Nn and nn segregants were 2.46, 2.31 and 2.10 ± 0.04 kg for daily food intake, 0.86, 0.84 and 0.78 ± 0.01 kg for daily liveweight gain, 2.89, 2.77 and 2.74 ± 0.03 for food conversion ratio and 16.7, 15.8 and 15.1 ± 0.4 mm for backfat. The average effect of the n allele on food intake and growth rate was higher in the selected than the control line. Mortality rates were increased by the halothane allele. Its effect on mortality was greatest in the selected line in summer while pigs were on road to the abattoir. Mean mortality rates were 1.4 ± 0.4, 2.6 ± 0.4 and 13.7 ± 1.1% for the NN, Nn and nn segregants

The effects of selection for lean growth and the halothane allele on growth performance and mortality of pigs in a tropical environment

The effects of the halothane allele and other genes for rapid lean growth were examined in pigs grown in an environment of high temperature/transport stress. The halothane allele n was segregating with its normal alternative N in a line which had been selected for rapid lean growth and in an unselected control line. Pigs of the three halothane segregants, NN, Nn and nn from both lines were grown on ad lib. feeding from 25 to 90 kg liveweight. Relative to the control, the selected line had faster, more efficient growth with lower 90 kg backfat thickness. Least square means in the selected and control lines were 0.87 and 0.77 ± 0.01 kg for daily liveweight gain, 2.63 and 2.98 ± 0.03 for food conversion ratio and 13.1 and 18.7 ± 0.3 mm for backfat. The halothane allele reduced appetite, growth rate, food conversion ratio and backfat. Means of the NN, Nn and nn segregants were 2.46, 2.31 and 2.10 ± 0.04 kg for daily food intake, 0.86, 0.84 and 0.78 ± 0.01 kg for daily liveweight gain, 2.89, 2.77 and 2.74 ± 0.03 for food conversion ratio and 16.7, 15.8 and 15.1 ± 0.4 mm for backfat. The average effect of the n allele on food intake and growth rate was higher in the selected than the control line. Mortality rates were increased by the halothane allele. Its effect on mortality was greatest in the selected line in summer while pigs were on road to the abattoir. Mean mortality rates were 1.4 ± 0.4, 2.6 ± 0.4 and 13.7 ± 1.1% for the NN, Nn and nn segregants

The first megatheropod tracks from the Lower Jurassic upper Elliot Formation, Karoo Basin, Lesotho

A palaeosurface with one megatheropod trackway and several theropod tracks and trackways from the Lower Jurassic upper Elliot Formation (Stormberg Group, Karoo Supergroup) in western Lesotho is described. The majority of the theropod tracks are referable to either Eubrontes or Kayentapus based on their morphological characteristics. The larger megatheropod tracks are 57 cm long and have no Southern Hemisphere equivalent. Morphologically, they are more similar to the Early Jurassic Kayentapus, as well as the much younger Upper Cretaceous ichnogenus Irenesauripus, than to other contemporaneous ichnogenera in southern Africa. Herein they have been placed within the ichnogenus Kayentapus and described as a new ichnospecies (Kayentapus ambrokholohali). The tracks are preserved on ripple marked, very fine-grained sandstone of the Lower Jurassic upper Elliot Formation, and thus were made after the end-Triassic mass extinction event (ETE). This new megatheropod trackway site marks the first occurrence of very large carnivorous dinosaurs (estimated body length >8-9 meters) in the Early Jurassic of southern Gondwana, an evolutionary strategy that was repeatedly pursued and amplified in the following ~135 million years, until the next major biotic crisis at the end-Cretaceous