Summer and winter concentrations of sodium, potassium and calcium in some maritime Antarctic cryptogams

first_img(1) The source and availability of nutrients to the predominantly non-vascular cryptogam vegetation of Signy Island. South Orkney Islands, in the maritime Antarctic, are briefly discussed. (2) The concentrations of total Na, K and Ca were determined for fifteen species of moss, one species of liverwort, one species of alga and nine species of lichen growing in a wide range of habitats. (3) In all species examined the concentration of Na was considerably higher in summer than in winter, the difference being least in the lichens. Species occupying wet habitats or habitats near the shore had the highest Na concentrations (up to 0.53% of dry weight). There was a strong correlation between Na content in the plants and the distance both vertically and horizontally from the sea. (4) Potassium concentrations were higher than those of Na, but the concentration in summer was frequently less than that in winter, particularly in those mosses and lichens growing in relatively dry rock habitats. As with Na, the higher K concentrations appeared to be correlated with increased moisture availability, with the highest K values (up to 1.41% of dry weight) in species growing on wet rocks. (5) The concentrations of Ca varied considerably and showed little conformity in fluctuation in all groups of species. The highest concentrations of the element (up to 2.29% of dry weight) were in species associated with mineral substrata and a high Ca content. There was a strong correlation between the Ca concentration in the plant material and the pH of the substratum. (6) The difference between summer and winter concentrations of the three cations suggests the probability of an annual cycle of mineral elements within the plants, with relatively high spring to early summer levels and winter minima. However, this cycle may not be complementary with the seasonal trends in soil elements. (7) The mineral-ion concentration within the plants varied considerably, not so much in relation to species but to environment, and to some extent to growth form which is strongly correlated with environment. Different species associated with a particular habitat tended to have similar concentrations of specific mineral elements, whereas the same species growing in a variety of habitats tended to have a range of mineral-ion concentrations. (8) The simple mechanism of uptake and storage of mineral-ions in these non-vascular species is considered to be a response to the moisture regime of the habitat and to the concentration of the elements in the substratum or in precipitation. The concentrations within the plants tend to be proportional to those occurring in the substratum, although some degree of accumulation, despite the absence of specialized storage tissues, is suspected.last_img read more

The Antarctic climate of the UKMO Unified Model

first_imgWe examine some aspects of the performance of the United Kingdom Meteorological Office’s new climate model over Antarctica. Pressure and temperature fields are presented as a basic check on the model climate. The gradient of pressure between mid-latitudes and high southern latitudes is too great, resulting in an Antarctic trough that is too deep by 4–6 hPa. Temperature is well modelled though the interior is slightly too cold in winter. Precipitation is interesting because of its relevance to mass balance and therefore changes in sea level. The simulation of the pattern of accumulation is good despite somewhat high values at places in the coastal areas, with an areally-averaged value of 182 mm y−1. We also look at the phenomena of the coreless winter and the katabatic winds which are a consequence of the intense radiative cooling. These two effects may provide a useful diagnostic of the model performance.last_img read more

Forearc tectonic evolution of the South Shetland Margin, Antarctic Peninsula

first_imgThe main provinces of the South Shetland margin, Antarctic Peninsula characterized on the basis of multichannel seismic, long-range side scan sonar and swath bathymetry data, include from northwest to southeast (1) the oceanic crust of the former Phoenix Plate, flexed down toward the margin and affected by normal faulting in the upper crust; (2) a narrow trench, with a horizontally layered sediment fill which onlaps the thin sedimentary cover on the oceanic crust and shows incipient deformation near its landward edge; (3) an accretionary prism with a complex internal structure, the toe of which is overthrust above the youngest trench deposits; (4) a midslope forearc basin, with an asymmetric synformal structure; and (5) the continental shelf, which includes two distinct tectonic provinces. Calculations of the late Cenozoic convergence history at the trench indicate a rapid decrease in convergence rate after 6.7 Ma from about 60 mm/yr, resulting from the slowing and eventual cessation of spreading on the Antarctic-Phoenix ridge. Once spreading had completely ceased (3.5–2.4 Ma), the convergence rate at the trench equalled the rate of extension in Bransfield Strait, which was probably less than 10 mm/yr at first but may have increased since 1.3 Ma, and this, in turn, would imply a corresponding increase in convergence rate. Above the basal detachment the toe of the accretionary prism is composed of a stack of thrust fault bounded wedges, laterally and vertically segmented by normal faults. Most of the trench fill sediments are overthrust by the toe of the accretionary prism and subducted beneath it for as far as they can be traced on the seismic profiles. This suggests that there may be tectonic erosion of the forearc since a large part of the trench sediment appears to be derived from erosion on the forearc slope. The forearc basin records a long history of subsidence, during which the depocenter migrated landward, paralleling retrogradational erosion of the distal margin of the basin. Subduction of the Hero Fracture Zone at approximately the same location since 10 Ma may have enhanced tectonic erosion of the accretionary prism. In the forearc basin a synform is coincident with a bathymetric reentrant, but its axis is oblique to the trends of both the basin and the fracture zone. The origin of this synform and the final phase of uplift of the blueschist facies terrane on which Smith Island stands are probably related to their position above the subducting fracture zone ridge. The present elevation of Smith Island is thought to result from uplift which followed a ridge crest-trench collision directly southwest of the Hero Fracture Zone at 5.5 Ma. The northwestern edge of the Mesozoic to early Cenozoic arc batholith, trending northeast–southwest on the shelf, is proposed to have acted as a backstop to the accretionary prism during Cenozoic subduction.last_img read more

In-situ quantification of ice rheology and direct measurement of the Raymond Effect at Summit, Greenland using a phase-sensitive radar

first_imgThe Glen exponent ncharacterizes the stress-dependence of ice deformation, directly influencing the rate at which ice masses respond to external forcing. The slow deformation in large ice-sheets makes laboratory rheometry at representative strain-rates difficult. We develop a new technique to estimaten in-situ, deploying a phase-sensitive radar to measure vertical strain rates of around 10−4 yr−1within the top 1000 m of ice across ice divides at Summit and NEEM, Greenland. A fluid-dynamical feature, the Raymond Effect, predicts strong vertical strain-rate variation across divides over distances of a few ice-thicknesses. We achieve sufficient resolution to show this pattern, enabling us to estimaten= 4.5 by inverting our observations with flow modelling. This is higher than values previously used but consistent with other indirect measurements, implying laboratory measurements do not explore the full range of ice rheology and the consequent possibility of a greater sensitivity and responsiveness in ice-sheet dynamics.last_img read more

Feeding ecology, isotopic niche, and ingestion of fishery-related items of the wandering albatross Diomedea exulans at Kerguelen and Crozet Islands

first_imgFeeding ecology and isotopic niche of the wandering albatross Diomedea exulans were investigated in the poorly studied population on the Kerguelen Islands and compared to that on the Crozet Islands. Fish (48% by mass) and cephalopods (46%) were similarly important in chick food at Kerguelen, while cephalopods (87%) dominated the diet at Crozet. Fish prey included mainly deep-sea species, with the Patagonian toothfish Dissostichus eleginoides being the main item. Cephalopod beaks were identified, most of which were from adult oceanic squids. Albatrosses preyed upon the same taxa at both localities, but in different proportions. Histioteuthis atlantica (30% by number), Galiteuthis glacialis (13%), and Kondakovia longimana (10%) were the main squid prey at Kerguelen, while K. longimana (35%) and H. eltaninae (23%) dominated at Crozet. Chick feather δ15N values were higher in wandering albatrosses than in other oceanic seabirds of the 2 communities, indicating that the wandering albatross is an apex consumer together with the sperm whale and sleeper shark that have similar δ15N values. Satellite-tracked wandering albatrosses foraged in local subantarctic waters and farther north, with some Crozet birds overlapping with those from the Kerguelen population in western Kerguelen waters. Anthropogenic items (e.g. plastic fragments, hooks) were found in half the food samples. All fishery-related items were from the local toothfish fishery. The high number of hooks from Crozet indicated the presence of a fairly large number of illegal longliners in the area during the Austral winter 1998. A review of the feeding habits of Diomedea spp. highlights the need for more dietary investigations to achieve effective conservation and management of this endangered group of charismatic seabirds.last_img read more

Jazz GM Lindsey Addresses Future

first_imgMay 25, 2018 /Sports News – Local Jazz GM Lindsey Addresses Future Robert Lovell FacebookTwitterLinkedInEmail(Salt Lake City, UT)  —  Jazz general manager Dennis Lindsey believes the team can retain both Derrick Favors and Dante Exum as free agents this summer.Lindsey also hopes Royce O’Neal will continue to develop and expects Ricky Rubio to have a productive summer. Written by Tags: Dante Exum/Dennis Lindsey/Derrick Favors/Ricky Rubio/Royce O’Neal/Utah Jazzlast_img read more

Report: Texans to cut Demaryius Thomas

first_img Written by Beau Lund February 12, 2019 /Sports News – National Report: Texans to cut Demaryius Thomascenter_img FacebookTwitterLinkedInEmail33ft/iStock(HOUSTON) — The Houston Texans are reportedly parting ways with Demaryius Thomas.ESPN reports the team will release the 31-year-old wide receiver on Tuesday. The news comes nearly two months after Thomas tore his Achilles tendon on Dec. 23 in a game against the Philadelphia Eagles.Houston acquired Thomas from the Denver Broncos last October. Following the trade, he appeared in seven games for the Texans, catching 23 passes for 275 yards and scoring two touchdowns.Copyright © 2019, ABC Radio. All rights reserved.last_img read more

Scoreboard roundup — 6/25/19

first_img Beau Lund FacebookTwitterLinkedInEmailiStock(NEW YORK) — Here are the scores from Tuesday’s sports events:MAJOR LEAGUE BASEBALLINTERLEAGUESan Diego 8, Baltimore 3Houston 5, Pittsburgh 1Seattle 8, Milwaukee 3Oakland 7, St. Louis 3LA Angels 5, Cincinnati 1AMERICAN LEAGUENY Yankees 4, Toronto 3Boston 6, Chi White Sox 3Texas 5, Detroit 3Kansas City 8, Cleveland 6Minnesota 9, Tampa Bay 4NATIONAL LEAGUEPhiladelphia 7, NY Mets 5Washington 6, Miami 1Atlanta 3, Chi Cubs 2LA Dodgers 3, Arizona 2San Francisco 4, Colorado 2WOMEN’S NATIONAL BASKETBALL ASSOCIATION PLAYOFFSMinnesota 78, Indiana 74Las Vegas 60, Seattle 56Copyright © 2019, ABC Radio. All rights reserved. June 26, 2019 /Sports News – National Scoreboard roundup — 6/25/19center_img Written bylast_img read more

Anderson named player of the week; Badgers hold steady at No. 6

first_img Brad James September 24, 2019 /Sports News – Local Anderson named player of the week; Badgers hold steady at No. 6 Written by Tags: Central Wyoming/Ellee Anderson/Southern Nevada/SWAC FacebookTwitterLinkedInEmailEPHRAIM, Utah-Snow College volleyball standout, freshman Ellee Anderson has been named the Scenic West Athletic Conference Player of the Week after leading her squad to three wins this past week.The Morgan, Utah native posted 75 assists in this span, averaging 8.3 assists per set. Under Anderson’s direction, the Snow College offense registered a 66.5 side-out percentage through three matches on the week, including a 67.7 side-out percentage against Central Wyoming.Anderson racked up seven more aces this past weekend, adding to her team leading total of 45. Anderson currently ranks fourth nationally in total aces.NATIONAL RANKINGFor the third straight week, the Snow College women’s volleyball team has been ranked No. 6 in the NJCAA Division-I Volleyball Rankings. The Badgers posted three wins this past week, including a 3-0 win over Northwest College and a pair of back-to-back, straight-set victories over Central Wyoming. At 19-2 on the season, the Badgers have won more matches than any team currently ranked in the top-10 of the nation.This week’s national rankings mark the 32nd straight week the Badgers have been ranked in the Top 20.Furthermore, this is the 28th time during that stretch the team has been ranked No. 10 or higher. Snow has won a total of 14 matches in three straight sets, including seven of its last eight matches.Snow College will next travel to Las Vegas to take on Southern Nevada on Saturday, Sept. 28. The Scenic West Conference opener for both teams will begin at 1 p.m. PDT.last_img read more