Equilibrium profile of ice shelves
Using expressions for ice-shelf creep derived by Weertman (1957) and Thomas (1973[b]) a general method is developed for calculating equilibrium thickness profiles, velocities, and strain-rates for any ice shelf. This is done first for an unconfined glacier tongue and the result agrees well with data for Erebus Glacier tongue (Holdsworth, 1974). Anomalies occur within the first 3 km after the hinge zone and these are too great to be the result of local bottom freezing; they are probably due to disturbance of the velocity field. Secondly, profiles are calculated for bay ice shelves. Thickness gradients are largely independent of melt-rate or flow parameters but are inversely proportional to the width of the bay. Data from Antarctic ice shelves agree with this result both qualitatively and quantitatively. The theory is readily extended to ice shelves in diverging and converging bays. An ice shelf in a diverging bay can only remain intact if it is thick enough and slow enough to creep sufficiently rapidly in the transverse direction. If it cannot, it will develop major rifts or will come adrift from the bay walls. It is then likely to break up. The presence of ice rises or areas of grounding towards the seaward margin can radically alter the size of the ice shelf which can form. The theory could be used as a starting point to study non-equilibrium behaviour.
Spectrograms of broad-band ELF/VLF goniometer data obtained from ground based measurements made at Halley, Antarctica (L = 4.3, conjugate near St. Anthony, Newfoundland) have shown the presence of discrete line radiation of magnetospheric origin, in the frequency range 1–4 kHz. The properties of this radiation are broadly similar to Power Line Harmonic Radiation (PLHR), studied from ground based observations made at Siple, Antarctica (L = 4.1, conjugate—Roberval, Quebec), although there are some interesting differences. Line radiation observed at Halley, is never regularly spaced in frequency by 120 Hz, as one may expect if signals from the Newfoundland power distribution system (60 Hz fundamental) are entering the magnetosphere, and being amplified. Instead, frequency spacings are widely distributed about mean values between 50 and 90 Hz. The lines are observed to trigger emissions and often exhibit 2 hop amplitude modulation, which demonstrates that they are of magnetospheric origin. Events occur mostly in quiet to moderate geomagnetic conditions, and during the late afternoon period of local time. Arrays of lines are often observed to drift upwards together in frequency. Line bandwidths are 20–30 Hz—much larger than the bandwidths of locally generated induction lines. We show that the line spacing of ∼80 Hz is too large to correspond to sideband separation for waves of equatorial field strength ∼10 pT, and we investigate the conditions required for effective particle trapping by the wave array, of the type described by Nunn, 1974. It is proposed that the line radiation either originates in the signals which enter the magnetosphere from Newfoundland, or is “naturally” generated, possibly by a linear instability which takes place if the electron distribution function has sharp localised gradients in pitch angle.
The continuum theory of mixtures is used as the mathematical framework for a four-constituent model of a natural snowpack. The general conservation equations in point form are derived from appropriate integral balances and constitutive requirements are identified. In particular, constitutive postulates are made for the interaction terms due to phase change in the momentum and energy equations. The conservation equations are written in terms of partial variables whereas material constitutive laws are given in terms of intrinsic variables. Generalising Morland’s theory* enables these two types of variable to be related when mass transfer due to phase change is included. A reduced model is proposed which assumes linear hypo-thermoelastic response for the ice and linearly viscous fluid response for the water, water-vapour and air.
The feeding activity of four benthic suspension-feeding groups (bryozoans, hydroids, polychaetes and holothurians) was monitored in situ every month for a 2-year period at Signy Island in the maritime Antarctic. The bryozoans were monitored at species level, whereas the other taxa could be differentiated only to genus. A marked seasonal variation in feeding activity was observed in most taxa. Although environmental parameters such as sea water temperature, fastice duration and water column chlorophyll concentrations suggested that winter in the maritime Antarctic lasts for about 6 months, many animals ceased feeding only for a short period of 2 or 3 months around the middle of the austral winter (June/July). These suspension feeders must therefore be efficient at utilising the low concentration of the microplankton existing in the water column for much of the year. Comparison with environmental variables suggested several possible cues for changes in feeding activity, but these cues may differ between taxa. Photoperiod and changes in disturbance by water movement (both mediated by ice), and food concentration are likely to be important environmental cues for polar suspension feeders.
Ice melts when it is in contact with ocean waters that have temperatures above the in situ freezing point. The product is a mixture of meltwater and seawater having properties intermediate between those of the two components. Density is one of the properties that is affected, and this has important implications for how the melt-induced changes are eventually manifested. Although the direct impact of melting is to cool and dilute the ocean, subsequent convection can carry the products of melting to parts of the water column where they are comparatively warm and salty. These principles are illustrated with a set of observations from the continental shelf of the Amundsen Sea. Measurements made near a floating glacier are used to calculate the concentration of meltwater in the water column. Concentrations approaching 2% are associated with comparatively high temperatures, low dissolved oxygen concentrations, and negligible stable isotope anomalies. The impact of drifting icebergs on the Southern Ocean is discussed. Over most of the area to the south of the Polar Front, melting effects a transfer of heat from the Circumpolar Deep Water to the overlying winter water. The resultant net heat flux over the entire area is small, but locally it may exceed 100 W m−2.
Biological research in Antarctica has made considerable progress in science over recent decades. As little as 50 years ago, there was scant knowledge even of the species inhabiting the region. Since then, understanding has developed rapidly, across diverse disciplines including physiology, biochemistry, ecology and biogeography. Some dramatic global-scale discoveries and advances have been made, including the characterisation of antifreeze proteins from notothenioid fish and the finding that some fish lack a heat shock response, the identification of microbial communities living within the surface layers of rocks and description of the simplest faunal communities known, the identification that possibly the fastest environmental and ecological change on earth is occurring in Antarctic lakes, and that the biodiversity of the Southern Ocean is much greater than previously thought. Findings such as these have made biology in cold extreme environments one of the most stimulating areas for research in recent decades. Now, the advent and widespread applicability of the novel genomic technologies promise to move us into a period of equally, or possibly even more, rapid advance. At present, genomic information on Antarctic species is limited mainly to a number of fish species and microbes. However, an increasing number of Antarctic genomics projects are being funded and will significantly increase the amount of molecular information available on a much wider range of species in the near future. Hence it is timely to review progress so far in the use of genomic methods in Antarctic research and identify exciting prospects for dramatic future advances.
Murray Levick is best known for being one of the surgeons on Scott’s Terra Nova Antarctic expedition (1910–1913) and, as a member of the Northern Party of that expedition, spending a winter living in a snow hole when the ship was unable to collect the men. However, his career encompassed much more than that. He served in the Royal Navy during both World Wars and was a pioneer in physical medicine and rehabilitation. He also founded the British Schools Exploring Society.
Glaciers in the Himalaya–Karakoram mountain ranges harbour approximately half of the ice volume in High-mountain Asia and modulate the flow of freshwater to almost 869 million people within the Indus, Tarim, Ganges and Brahmaputra river basins. Since the mid-twentieth century, rising temperatures have led to unsustainably high melting rates for many glaciers, particularly in the Himalaya, temporarily increasing summer meltwater run-off but continuously reducing the ice-storage volume. In this Review, we discuss how and why glaciers and meltwater supplies have changed, how they will likely evolve in the future and how these changes impact water resources and water-related hazards. Heterogeneous glacier retreat is changing streamflow patterns, in turn, affecting the incidence of glacial-lake outburst floods and exacerbating the risk of flooding and water shortages associated with future climate change. These changes could negatively impact downstream populations and infrastructure, including the thriving hydropower sector and some of the world’s largest irrigated agriculture systems, by making water flow more extreme and unpredictable. An improved in situ monitoring network for weather, hydrology and glacier change is a crucial requirement for predicting the future of this resource and associated hazards, and their impact on regional water, energy and food security.
FacebookTwitterLinkedInEmailScott Olson/Getty Images(CHICAGO) — Tucker Speckman was in for a surprise at the Chicago Cubs home opener on Wednesday.The fourth-grader had skipped school to attend the game, bringing a sign with him that read: “Skipping School. Shh! Don’t tell Principal Versluis.”Tucker hoped his sign would make it on TV, but it reached even more people when the Major League Baseball Twitter page tweeted out a photo of Speckman and his sign, captioned, “We got you,” to its over 8 million followers.What came as even more of a surprise was when Tucker’s principal, Patrick Versluis, spotted him at the game after apparently skipping out on school himself.“I kind of hollered, ‘Hey, you’re skipping school’ … and they popped that sign up and it was just complete humor,” Versluis told ABC Chicago station WLS.Tucker said he wasn’t worried about running into Versluis. The two even posed for a picture as Tucker held the sign.“I wasn’t nervous because I know he’s such a great principal he wouldn’t be mad or anything,” Tucker told WLS.Copyright © 2018, ABC Radio. All rights reserved. Beau Lund Written by
April 12, 2018 /Sports News – National 4th-grader skips school for baseball game, runs into principal
Beau Lund Written by May 2, 2018 /Sports News – National Scoreboard roundup — 5/3/18
FacebookTwitterLinkedInEmailiStock/Thinkstock(NEW YORK) — Here are the latest scores from today’s sports events:INTERLEAGUESt. Louis 3 Chi White Sox 2AMERICAN LEAGUEBoston 5 Kansas City 4Cleveland 12 Texas 4Detroit 3 Tampa Bay 2, 12 InningsMinnesota 4 Toronto 0N.Y. Yankees 4 Houston 0L.A. Angels 10 Baltimore 7Oakland 3 Seattle 2NATIONAL LEAGUEColorado 11 Chi Cubs 2San Francisco 9 San Diego 4Washington 9 Pittsburgh 3Atlanta 7 N.Y. Mets 0Philadelphia 6 Miami 0Milwaukee 3 Cincinnati 1L.A. Dodgers 2 Arizona 1NATIONAL BASKETBALL ASSOCIATION PLAYOFFSUtah 116 Houston 108NATIONAL HOCKEY LEAGUE PLAYOFFSTampa Bay 4 Boston 1San Jose 4 Vegas 0Copyright © 2018, ABC Radio. All rights reserved.