May 9, 2021 | |Post a Comment

first_imgAptian to Pliocene time-series of X-ray fluorescence data from the Antarctic Peninsula are used to assess the degree of chemical weathering and maturity of sediments deposited prior, and subsequent to the establishment of glaciation in West Antarctica. A continuous palaeoclimatic signal is inferred from comparing the results with previously published palaeotemperature and palaeobotanical data. Aptian–Cenomanian (warm/cool), and Santonian–Early Paleocene (warm/cold) cycles were followed by the global Late Paleocene–Early Eocene climatic optimum. Subsequent steady decline in temperatures resulted in glacial conditions in the northern Antarctic Peninsula by Early Oligocene time. Under alternating Cenozoic frigid/cold climates and in sedimentary regimes dominated by physical weathering, geochemical signatures were primarily indicative of provenance. The development of Cretaceous arboreal vegetation in the northern Antarctic Peninsula can be correlated with the major climatic cycles.last_img read more

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first_imgBryum argenteum, B. pseudotriquetrum and Ceratodon purpureus are the predominant mosses in Victoria Land, continental Antarctica. All have cosmopolitan distributions and are widespread throughout Antarctica with wide ecological amplitudes resulting in considerable morphological variation. They are well adapted to tolerate the physiological stresses imposed by the severe environment. This study investigates aspects of their growth, physiology and survival in response to habitat constraints, especially hydrology. Their distribution is controlled almost exclusively by moisture availability. Each species tends to predominate in a specific zone along hydrological gradients, with B. pseudotriquetrum on moist soil, C. purpureus on drier soil, and B. argenteum on unstable stream margins, fluvial deposits and the marginal capillary zone. Where conditions are optimal, each species can form a turf 6–10 cm thick. Nutrient status of the soil does not appear to be an important determinant in the distribution pattern within communities. The thermal regime of the moss turf varies according to its moisture content; for a period of ca. six weeks during the summer, with the frequent long spells of 24-h sunshine, temperatures remain above 0 °C for much of the time even though air temperatures are frequently below the freezing point. This allows growth and metabolic activity to proceed continuously at a relatively rapid rate for quite long periods. Annual shoot incremental growth can exceed 3.5 mm in each species. Growth of B. argenteum may be inhibited by UV- B radiation. The optimal temperature for photosynthesis in each species is around 15 °C, but significant carbon fixation occurs at 5 °C. Photosynthetic rates at 5, 10 and 20 °C were B. argenteum > B. pseudotriquetrum > C. purpureus.last_img read more

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first_imgA total of 138 scientific publications and theses on Antarctic and sub-Antarctic birds for 1999 is listed by author.This annual list is produced on behalf of the Bird Biology Subcommittee of the Scientific Committee on AntarcticResearch (SCAR) Working Group on Biology as a service to marine ornithologists.last_img

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first_imgA total of 183 scientific publications and theses on Antarctic and sub-Antarctic birds for 2000 is listed by author. This annual list is produced on behalf of the Group of Experts on Birds of the Scientific Committee on Antarctic Research (SCAR) Life Sciences Standing Scientific Group (formerly the Bird Biology Subcommittee of the SCAR Working Group on Biology) as a service to marine ornithologists.last_img

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first_imgThe Jurassic Latady Basin (southern Antarctic Peninsula) developed in a broad rift zone associated with the early stages of Gondwana extension. Early Jurassic sedimentation (~185 Ma) occurred in small, isolated terrestrial to lacustrine rift basins in the present-day northwest and west and became shallow marine by the early Middle Jurassic. Quantitative modal analysis reveals a high proportion of mature, quartzose sandstone derived from cratonic and quartzose recycled-orogen provenances, most likely in the direction of the Ellsworth–Whitmore Mountains in the Gondwana interior. Sandstones with a more volcanolithic provenance probably represent an influx of sands from a Permian volcanic source in West Antarctica. The Early Jurassic Latady sequence contains abundant volcanic quartz and rhyodacite grains, locally derived from the nearby ignimbrites of the rift-related Mount Poster Formation (~185 Ma). Between the Middle and Late Jurassic (?160–150 Ma), there was a dramatic change throughout the Latady Basin to higher-energy conditions with marked lateral facies variations. Sandstones contain abundant fresh volcanic detritus and plot in the transitional arc field. Their source was a nearby, active continental margin arc, but there is no outcrop of arc material on the Antarctic Peninsula from this time. A possible source area is preserved on the Thurston Island block to the southwest. However, some fluvial systems still had access to areas of uplifted metamorphic/plutonic basement and quartzose, cratonic sources. Evidence of mixing of fluvial systems from different provenances and the lack of mixing of other fluvial systems suggest a complex topography of variably uplifted fault blocks with fluvial systems constrained in narrow valleys. The change from continental rift- to arc-related sources illustrates the shift from plume- (continental provenances) to continental margin arc-dominated tectonics. Thermal relaxation in the Late Jurassic led to the final phase of deposition in anoxic, deep-water conditions in a sediment-starved marine basin stretching from Ellsworth northward into southern South America.last_img read more

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first_imgWe present a new 150-year, high-resolution, stable isotope record (delta O-18) from the Gomez ice core, drilled on the data sparse south western Antarctic Peninsula, revealing a similar to 2.7 degrees C rise in surface temperatures since the 1950s. The record is highly correlated with satellite-derived temperature reconstructions and instrumental records from Faraday station on the north west coast, thus making it a robust proxy for local and regional temperatures since the 1850s. We conclude that the exceptional 50-year warming, previously only observed in the northern Peninsula, is not just a local phenomena but part of a statistically significant 100-year regional warming trend that began around 1900. A suite of coupled climate models are employed to demonstrate that the 50 and 100 year temperature trends are outside of the expected range of variability from pre-industrial control runs, indicating that the warming is likely the result of external climate forcing. Citation: Thomas, E. R., P. F. Dennis, T. J. Bracegirdle, and C. Franzke (2009), Ice core evidence for significant 100-year regional warming on the Antarctic Peninsula, Geophys. Res. Lett., 36, L20704, doi: 10.1029/2009GL040104.last_img read more

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first_imgWe present a finite difference implementation ofa three-dimensional higher-order ice sheet model. In comparison to a conventional centred difference discretisation it enhances both numerical stability and convergence. In order to achieve these benefits the discretisation of the governing force balance equation makes extensive use of information on staggered grid points. Using the same iterative solver, a centred difference discretisation that operates exclusivelyon the regular grid serves as a reference. The repriseof the ISMIP-HOM experiments indicates that both discretisations are capable of reproducing the higher-order model inter-comparison results. This setup allows a direct comparison of the two numerical implementations also with respect to their convergence behaviour. First and foremost, the new finite difference scheme facilitates convergence by a factor of up to 7 and 2.6 in average. In addition to this decrease in computational costs, the accuracy for the resultant velocity field can be chosen higher in the novel finite difference implementation. Changing the discretisation also prevents build-up of local field irregularites that occasionally cause divergence of the solution for the reference discretisation. The improved behaviour makes the new discretisation more reliable for extensive application to real ice geometries.Higher accuracy and robust numerics are crucial intime dependent applications since numerical oscillations inthe velocity field of subsequent time steps are attenuated and divergence of the solution is prevented.last_img read more

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first_imgFatty acid biomarkers analysis was performed on juvenile and adult northern krill (Meganyctiphanes norvegica) to determine variability in diet between individuals and the consequences for their growth rates. Animals were sampled from Gullmarsfjorden, western Sweden during September 2004 and incubated for 4 days to measure instantaneous growth rate (IGR) before subsequent fatty acid analysis. We found positive linear relationships between IGR and certain fatty acid concentrations within adult specimens. In particular, highest growth was seen in individuals containing high concentrations of 18:2(n-6) and 18:3(n-6), indicative of filamentous algae and/or terrestrial carbon dietary sources, and 16:4(n-1), a biomarker fatty acid for diatoms. Similar relationships were not evident for juvenile krill. In an accompanying study, stomach content analyses established that adult krill had been feeding on a diverse range of red, brown and green benthic filamentous algae, which contain fatty acids of the (n-6) series. Incidence of filamentous algae in the stomachs of juvenile krill was much lower, possibly reflecting the shallower water depths inhabited by this maturity stage. Although a benthic feeding mode has previously been observed for M. norvegica, this is the first direct evidence to indicate that benthic food sources can be important in supporting the growth of this euphausiid. Furthermore, high variability in growth rates and fatty acid concentrations between individuals suggest a diversity of feeding strategies within this fjordic population.last_img read more

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first_imgThe Southern Ocean exerts a profound influence on the functioning of the Earth System, in part because its location and unique bathymetric configuration enable direct linkages to the other major ocean basins (Ganachaud and Wunsch, 2000 and Lumpkin and Speer, 2007). It is the site of the world׳s largest current system, the Antarctic Circumpolar Current (ACC), which transfers waters and climatically/ecologically-important tracers between the Atlantic, Indian and Pacific Oceans (Rintoul et al., 2001). In addition to the strong horizontal connectivity, the ACC is also characterized by a vigorous overturning circulation, which upwells warm, nutrient-rich waters from intermediate depth to the surface, where they are modified by interactions with the atmosphere and cryosphere to form new water masses, some of which are lighter and others more dense (Marshall and Speer, 2012). This overturning circulation structures the Southern Ocean both horizontally and vertically, dictates the levels of its communication with the rest of the global ocean, and is a fundamental control on the sequestration of carbon from the atmosphere into the ocean interior (Sallée et al., 2012). In some locations, the upwelled waters can intrude onto the Antarctic shelves, supplying heat and nutrients to the shallower regions. This is believed to be especially effective in west Antarctica, where the southern edge of the ACC moves close to the shelf break (Martinson, 2011, Orsi et al., 1995 and Thoma et al., 2008).last_img read more

May 8, 2021 | |Post a Comment

first_imgMay 29, 2018 /Sports News – National Steph Curry and 5-year-old daughter celebrate big win in the cutest way Written by FacebookTwitterLinkedInEmailRonald Martinez/Getty Images(SAN FRANCISCO) — NBA star Stephen Curry and his 5-year-old daughter, Riley, celebrated the Golden State Warriors’ Game 7 win in the cutest way.News cameras captured the daddy-daughter duo celebrating with a special handshake on Monday, just moments after the Warriors beat the Houston Rockets in Game 7 of the Western Conference Finals, securing a spot in this year’s NBA Finals.ABC San Francisco station KGO shared a clip of the precious exchange on Twitter late Monday, calling it the “cutest celebration ever.”The Warriors came back from a first-half deficit during the third quarter, when Curry scored more than half of his 27 points.Curry — with his wife, Riley and her 3-year-old sister, Ryan, by his side — said he was just happy to put the “stressful but fun” night behind him.“For us to have the firepower to kind of turn the momentum to our side pretty quickly, you know, get some stops, make some shots, and start to feel a little bit better about ourselves, it was a fun night all the way around,” Curry told ESPN after the game. “You have to have endurance, you’ve got to have resiliency, you’ve got to have confidence in yourself, no matter how the game’s going up until that point, that you can turn it around.”The Warriors are scheduled to host LeBron James and the Cleveland Cavaliers in Game 1 on Thursday, the fourth straight Finals matchup between the two teams.Copyright © 2018, ABC Radio. All rights reserved.center_img Beau Lundlast_img read more