Glaciological research in the Antarctic Peninsula

first_imgThe Antarctic Peninsula is a good place for studies that take advantage of its wide range of latitude. Other worthwhile investigations are those that set in context the glacier/climate relationships and provide a framework of basic glaciological data. In order to speed reconnaissance mapping a series of seven 1:250 000 map sheets was published which used satellite imagery as the only source for planimetric detail. In preparation for intermediate depth ice core drilling for glaciological and palaeoclimatic investigations a wide-ranging programme of radio echo sounding has been pursued since 1963; flight tracks now total 80000 km. Experimental results are presented for an area at the base of the peninsula between latitudes 73° S and 80° S. Track plotting was controlled by relating observed subglacial topographic features with the surface expression of the same features revealed in a Landsat image mosaic. Thus navigation was not subject to the cumulative position errors generally encountered on long flights far from fixed points (nunataks). Redefinition of the earlier speculative boundary of the inland ice sheet added 38000 km2 to the land area of Antarctica while reducing the area of Ronne Ice Shelf by 11%. An unmapped nunatak was found 187 km from the nearest known outcrop. Three major inlets contained the thickest floating ice ever measured. Floating ice 1860 m thick was identified at a point only 17 km from the Ellsworth Mountains; thus within 60 km of the highest mountain in Antarctica (5140 m) there is a trench reaching 1600 m below sea level. Subglacially, there is potentially a channel well below sea level that connects the Bellingshausen Sea with the Weddell Sea. A radio echo sounder was adapted to measure the surface velocity of glaciers by reference to the spatial fading pattern of the bottom echo. Checks on Fleming Glacier with optical survey instruments showed that the true rate of movement was 44% faster than indicated by the fading pattern. It was concluded that the sounder had measured surface velocity with reference to a reflecting horizon which itself was deforming or sliding over the glacier bed. Experiments on ice shelves have been used to extend the flow law of ice to stresses lower than can be studied in the laboratory. At least down to the lowest stress considered (0.04 MN m-2) the results supported a power law with a stress exponent of 3 as found in the laboratory for higher stresses. Ultra-clean sampling techniques were developed for detecting extremely low levels of impurities in snow (3 x 10-14g g-1). Thus DDT concentrations were found to be 40-100 times smaller than earlier reported for snow from central Antarctica. An extensive reconnaissance programme of 10 m ice core drilling has been pursued with the object of studying relationships between oxygen isotope fractionation and ice and air temperatures. The ice, water, and energy balances of two representative local glaciers have been studied as a contribution to the International Hydrological Decade.last_img read more

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Extreme adaptive life-cycle in a high arctic aphid, Acyrthosiphon svalbardicum

first_img1 The year-round biology of a high arctic aphid is described for the first time. 2 The life-cycle is shown to be genetically determined, and thus markedly different to temperate species where the observed polymorphism is governed primarily by external environmental cues. 3 The fundatrix, which emerges from the overwintering egg, gives birth directly to sexual morphs, a phenomenon previously undescribed in the Aphidinae. This process is essentially prevented in temperate aphids by an endogenous mechanism, the interval timer. 4 In addition to the sexual morphs, the fundatrix produces a small number of parthenogenetic individuals (viviparae) that give rise to a third generation. This last generation consists exclusively of oviparae and males that would increase the number of overwintering eggs provided there is sufficient thermal budget for them to mature and oviposit before conditions become adverse. 5 The position of particular morphs in the birth sequences of the second and third generations maximize the chances of survival in harsh conditions, whilst enhancing the likelihood that individuals from the third generation will add to the number of overwintering eggs. 6 Guaranteed egg production combined with an in-built flexibility to produce an extra generation in particularly favourable seasons, confer adaptations to the high arctic environment, and ideally suit this aphid to exploit elevated temperatures in an era of climate change.last_img read more

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Late Cambrian stratigraphy of the Heritage Range, Ellsworth Mountains: implications for basin evolution

first_imgDeposition of the Upper Cambrian succession of the Ellsworth Mountains was influenced by major, episodic tectonically-driven changes to the depositional basin geometry. We subdivide the succession into four stratigraphical sequences based on the recognition of three sequence-bounding unconformities. The upper part of Sequence 1 is composed of the laterally equivalent Liberty Hills, Springer Peak and Frazier Ridge formations, a siliciclastic fluvial to marine deltaic association displaying NW-directed palaeocurrents. A switch in the position of the Late Cambrian depocentre from the north-west to the south coincided with cessation of terrigenous clastic deposition and accumulation of Sequence 2, the limestones of the Minaret Formation. Previously unreported talus breccias from the Independence Hills provide important clues to basin configuration at this time. A brief period of emergence of the Minaret Formation is inferred, prior to rapid subsidence and disconformable deposition of Sequence 3 (the ‘transition beds’) in outer-inner shelf environments. Localized intra-basinal uplift occurred prior to the deposition of Sequence 4 (the lower Crashsite Group), the base of which is locally an erosive unconformity, with a correlative conformity exposed elsewhere. We interpret the Upper Cambrian succession as representing the ‘rift-drift’ transition from initial rifting (preceded by Middle Cambrian volcanism) to thermal subsidence along the South African sector of the palaeo-Pacific margin of Gondwana.last_img read more

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Orbitally induced oscillations in the East Antarctic ice sheet at the Oligocene/Miocene boundary

first_imgBetween 34 and 15 million years (Myr) ago, when planetary temperatures were 3–4 °C warmer than at present and atmospheric CO2 concentrations were twice as high as today1, the Antarctic ice sheets may have been unstable2, 3, 4, 5, 6, 7. Oxygen isotope records from deep-sea sediment cores suggest that during this time fluctuations in global temperatures and high-latitude continental ice volumes were influenced by orbital cycles8, 9, 10. But it has hitherto not been possible to calibrate the inferred changes in ice volume with direct evidence for oscillations of the Antarctic ice sheets11. Here we present sediment data from shallow marine cores in the western Ross Sea that exhibit well dated cyclic variations, and which link the extent of the East Antarctic ice sheet directly to orbital cycles during the Oligocene/Miocene transition (24.1–23.7 Myr ago). Three rapidly deposited glacimarine sequences are constrained to a period of less than 450 kyr by our age model, suggesting that orbital influences at the frequencies of obliquity (40 kyr) and eccentricity (125 kyr) controlled the oscillations of the ice margin at that time. An erosional hiatus covering 250 kyr provides direct evidence for a major episode of global cooling and ice-sheet expansion about 23.7 Myr ago, which had previously been inferred from oxygen isotope data (Mi1 event5).last_img read more

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Population abundance, structure and turnover estimates for leopard seals during winter dispersal combining tagging and photo-identification data

first_imgWinter dispersal in leopard seals is poorly understood because of its low density in most of its range. By combining photo-identification and tagging data from Bird Island, South Georgia, in mark-recapture models, leopard seal abundance over the winter of 2005 was estimated as 118 (95% CI: 78–179). Seasonal residents arrived earlier and stayed longer around the island (27 days; 95% CI: 23–32) and their numbers were low and stable over the winter Most of the seals (81; 95% CI: 31–130) were young transients, stayed only 1–7 days, and arrived later in the season. This suggests (1) very low predatory pressure upon the locally abundant prey populations; (2) two different patterns of winter movements: a winter migration in adult seals with long-term site fidelity, and large numbers of juveniles in dispersal possibly attracted by locally abundant prey colonies, and potentially influenced by increased environmental stress.last_img read more

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On the formulation of snow thermal conductivity in large-scale sea ice models

first_imgAn assessment of the performance of a state-of-the-art large-scale coupled sea ice – ocean model, including a new snow multilayer thermodynamic scheme, is performed. Four 29-years-long simulations are compared against each other and against sea ice thickness and extent observations. Each simulation uses a separate parameterization for snow thermo-physical properties. The first simulation uses a constant thermal conductivity and prescribed density profiles. The second and third parameterizations use typical power-law relationships linking thermal conductivity directly to density (prescribed as in the first simulation). The fourth parameterization is newly developed and consists of a set of two linear equations relating the snow thermal conductivity and density to the mean seasonal wind speed. Results show that simulation 1 leads to a significant overestimation of the sea ice thickness due to overestimated thermal conductivity, particularly in the Northern Hemisphere. Parameterizations 2 and 4 lead to a realistic simulation of the Arctic sea ice mean state. Simulation 3 results in the underestimation of the sea ice basal growth in both hemispheres, but is partly compensated by lateral growth and snow ice formation in the Southern Hemisphere. Finally, parameterization 4 improves the simulated snow depth distributions by including snow packing by wind, and shows potential for being used in future works. The intercomparison of all simulations suggests that the sea ice model is more sensitive to the snow representation in the Arctic than it is in the Southern Ocean, where the sea ice thickness is not driven by temperature profiles in the snow.last_img read more

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Downward wave reflection as a mechanism for the stratosphere-troposphere response to the 11-year Solar Cycle

first_imgThe effects of solar activity on the stratospheric waveguides and downward reflection of planetary waves during northern early to mid- winter are examined. Under high solar (HS) conditions enhanced westerly winds in the subtropical upper stratosphere and the associated changes in the zonal wind curvature led to an altered waveguide geometry across the winter period in the upper stratosphere. In particular, the condition for barotropic instability was more frequently met at 1 hPa near the polar night jet centred at ~55°N. In early winter the corresponding change in wave forcing was characterized by a vertical dipole pattern of the Eliassen-Palm (E-P) flux divergent anomalies in the high-latitude upper stratosphere accompanied by poleward E-P flux anomalies. These wave forcing anomalies corresponded with negative vertical shear of zonal mean winds and the formation of a vertical reflecting surface. Enhanced downward E-P flux anomalies appeared below the negative shear zone; they coincided with more frequent occurrence of negative daily heat fluxes and associated with eastward acceleration and downward group velocity. These downward reflected wave anomalies had a detectable effect on the vertical structure of planetary waves during November to January. The associated changes in tropospheric geopotential height contributed to a more positive phase of the North Atlantic Oscillation in January and February. These results suggest that downward reflection may act as a ‘top-down’ pathway by which the effects of solar ultraviolet (UV) radiation in the upper stratosphere can be transmitted to the troposphere.last_img read more

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Fatty acid profiles of Antarctic cyanobacteria Leptolyngbya

first_imgAntarctic cyanobacteria may represent a potential resource of new and unique compounds with interesting capabilities. Profiling of fatty acids in Antarctic cyanobacteria can provide an overview of potential fatty acids present in them, that can be utilised in future applications.last_img

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Scoreboard roundup — 4/2/18

first_img Written by April 3, 2018 /Sports News – National Scoreboard roundup — 4/2/18 FacebookTwitterLinkedInEmailiStock/Thinkstock(NEW YORK) Here are the scores from yesterday’s sports events:       INTERLEAGUE Final  Pittsburgh   5  Minnesota   4 Final  Boston       7  Miami       3       AMERICAN LEAGUE Final  Detroit     6  Kansas City     1 Final  Toronto     4  Chi White Sox   2 Final  Houston     6  Baltimore       1 Final  Oakland     3  Texas           1 Final  Cleveland   6  L-A Angels      0Tampa Bay  at  N-Y Yankees   1:05 p.m., postponed       NATIONAL LEAGUE Final  St. Louis    8  Milwaukee   4 Final  Cincinnati   1  Chi Cubs    0 Final  Washington   8  Atlanta     1 Final  Colorado     7  San Diego   4 L-A Dodgers   7  Arizona   8  , 15 innings Philadelphia  at  N-Y Mets   7:10 p.m., postponed       NATIONAL HOCKEY LEAGUE Final  Toronto      5  Buffalo     2 Final  Florida      3  Carolina    2 Final  Winnipeg     6  Ottawa      5 Final  Minnesota    3  Edmonton    0 Final  Washington   4  St. Louis   2 Final  L.A. Kings   3  Colorado    1       TOP-25 COLLEGE BASKETBALL Final  (2) Villanova   79  (7) Michigan   62Copyright © 2018, ABC Radio. All rights reserved.center_img Beau Lundlast_img read more

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Jamal Aytes Signs with Basel Star Wings

first_imgJune 5, 2018 /Sports News – Local Jamal Aytes Signs with Basel Star Wings Tags: Basel Star Wings/Jamal Aytes/SUU Men’s Basketball/Swiss Basketball League/Todd Simon Brad James FacebookTwitterLinkedInEmailBASEL, Switzerland-Per the official Twitter account of Southern Utah University men’s basketball coach Todd Simon, one of his standout former Thunderbirds has signed a pro contract overseas.Simon confirms that Jamal Aytes, a 6’6″ 225-pound forward, has signed with the Basel Star Wings, a Swiss professional basketball club that competes in the Swiss Basketball League, the highest level of competition in Switzerland.Aytes, who played at UNLV (2013-14), BYU (2015-17) and Southern Utah (2017-18) averaged 6.4 points and 2.8 rebounds a game while shooting 57.6 percent from the field as a collegian.Simon called Aytes, a San Diego native, ” a great leader, teammate and student here [at SUU].”The Starwings have one Swiss Cup championship in their history, won in 2010, while their history dates back to 2002. Written bylast_img read more

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