Organochlorine residues in Antarctic snow

first_imgDDT is a useful model compound for studying the circulation of a toxic pollutant in the global environment1,2. An understanding of this process could in future be related to potentially more hazardous materials. Present models of the dynamics of DDT circulation can account for only a small fraction of the amounts of DDT and DDE which are known to have been released into the environment. Major unknowns include the extent to which the atmosphere and oceans act as reservoirs and the transfer rate of these residues from the atmosphere to the oceans where, according to present ideas, they may be removed from circulation by transfer to the abyss3. Such atmospheric and oceanic transport mechanisms may carry pollutants into the ecologically protected area of Antarctica and it is necessary to assess the extent to which this is occurring and the relative importance of alternative input routes. The atmosphere has been assumed to play the major role in the transport cycle but there is a lack of supporting data. We report here levels of DDT and metabolites in Antarctic snow which suggest that the role of the atmosphere in the transport of DDT may have been overemphasised.last_img read more

Layers of Antarctic krill, Euphausia superba  : are they just long krill swarms?

first_imgAntarctic krill, Euphausia superba Dana, a major component in the southern ocean food web, typically occur in aggregations that range from small, discrete swarms and schools through to layers and superswarms that extend horizontally for several kilometres. A large Longhurst–Hardy plankton recorder has been used to obtain high-resolution serial samples from within two layers (up to 4 km in length) that were found near Elephant Island, north of the Antarctic Peninsula. Krill length, sex and maturity stage, net and acoustic estimates of number density are shown to vary significantly within these large layers. The variation occurring within a single layer is comparable with that occurring in a set of 38 swarms sampled contemporaneously with the layers. Thus, unlike a krill swarm, a whole krill layer may account for a substantial amount of the variation in the local krill population, although individual parts of the layer cannot be considered in this way. The layers play an important role in the ecology of the krill within the area. Firstly, these large layers may contain a significant proportion of the biomass within an area. Secondly, the structure of the layers gives some insight into the ways in which krill swarm formation and dispersal may be occurring.last_img read more

An appraisal of NCEP/NCAR reanalysis MSLP data viability for climate studies in the South Pacific

first_imgFifty years of monthly mean sea level pressure (MSLP) data from the NCEP/NCAR reanalysis (hereinafter NNR) are validated against station observations in the extratropical South Pacific and West Antarctica. The period for which the NNR may be considered reliable differs markedly between regions. It is only realistic from ∼1970 across West Antarctica. A lack of surface observations entering the model causes the NNR to be poorly constrained prior to the availability of GTS‐based data in 1967: the latter coincides with a significant improvement in the NNR MSLP across the eastern South Pacific. Substantial spurious negative trends occur within the NNR MSLP at high latitudes; although the decrease is greatest prior to the advent of satellite sounder data it continues into the 1990s south of 60°S. In addition, widely used tropical and extra‐tropical circulation indices are poorly represented in the NNR data prior to the 1960s.last_img read more

Provisioning behaviour of macaroni penguins Eudyptes chrysolophus

first_imgUnderstanding how parental expenditure reflects food availability and influences reproductive output is a key part of studies of breeding performance. Provisioning behaviour is an important aspect of parental expenditure. We show that Macaroni Penguins Eudyptes chrysolophus have clear sex-specific differences in provisioning behaviour. Females provision chicks throughout rearing and at higher rates than males, which only participate in the later stages. Female provisioning is consistent throughout chick-rearing and appears to relate to a threshold rate governing whether or not chicks survive. The additional expenditure by males (but not females) during the creche period influenced chick growth and fledging mass of survivors. We suggest a very simple model to account for these sex-specific differences and effects. Interannual variation in parental expenditure resulted in differences in reproductive output between years. Years of lowest expenditure resulted in lowest growth rate of chicks, Sex-specific differences in provisioning were similar among years, however, with a consistent proportion of expenditure by males.last_img read more

West Antarctic Ice Sheet collapse – the fall and riseof a paradigm

first_imgIt is now almost 30 years since John Mercer (1978) first presented the idea that climate change could eventually cause a rapid deglaciation, or “collapse”, of a large part of the West Antarctic ice sheet (WAIS), raising world sea levels by 5 metres and causing untold economic and social impacts. This idea, apparently simple and scientifically plausible, created a vision of the future, sufficiently alarming that it became a paradigm for a generation of researchers and provided an icon for the green movement. Through the 1990s, however, a lack of observational evidence for ongoing retreat in WAIS and improved understanding of the complex dynamics of ice streams meant that estimates of likelihood of collapse seemed to be diminishing. In the last few years, however, satellite studies over the apparently inaccessible Amundsen Sea sector of West Antarctica have shown clear evidence of ice sheet retreat showing all the features that might have been predicted for emergent collapse. These studies are re-invigorating the paradigm, albeit in a modified form, and debate about the future stability of WAIS. Since much of WAIS appears to be stable, it may, no longer be reasonable to suggest there is an imminent threat of a 5-m rise in sea level resulting from complete collapse of the West Antarctic ice sheet, but there is strong evidence that the Amundsen Sea embayment is changing rapidly. This area alone, contains the potential to raise sea level by around ~1.5 m, but more importantly it seems likely that it could, alter rapidly enough, to make a significant addition to the rate of sea-level rise over coming two centuries. Furthermore, a plausible connection between contemporary climate change and the fate of the ice sheet appears to be developing. The return of the paradigm presents a dilemma for policy-makers, and establishes a renewed set of priorities for the glaciological community. In particular, we must establish whether the hypothesized instability in WAIS is real, or simply an oversimplification resulting from inadequate understanding of the feedbacks that allow ice sheets to achieve equilibrium: and whether there is any likelihood that contemporary climate change could initiate collapse.last_img read more

Jurassic high heat production granites associated with the Weddell Sea rift system, Antarctica.

first_imgThe distribution of heat flow in Antarctic continental crust is critical to understanding continental tectonics, ice sheet growth and subglacial hydrology. We identify a group of High Heat Production granites, intruded into upper crustal Palaeozoic metasedimentary sequences, which may contribute to locally high heat flow beneath the West Antarctic Ice Sheet. Four of the granite plutons are exposed above ice sheet level at Pagano Nunatak, Pirrit Hills, Nash Hills and Whitmore Mountains. A new Usingle bondPb zircon age from Pirrit Hills of 178.0 ± 3.5 Ma confirms earlier Rbsingle bondSr and Usingle bondPb dating and that the granites were emplaced approximately coincident with the first stage of Gondwana break-up and the developing Weddell rift, and ~ 5 m.y. after eruption of the Karoo-Ferrar large igneous province. Aerogeophysical data indicate that the plutons are distributed unevenly over 40,000 km2 with one intruded into the transtensional Pagano Shear Zone, while the others were emplaced within the more stable Ellsworth-Whitmore mountains continental block. The granites are weakly peraluminous A-types and have Th and U abundances up to 60.7 and 28.6 ppm respectively. Measured heat production of the granite samples is 2.96–9.06 μW/m3 (mean 5.35 W/m3), significantly higher than average upper continental crust and contemporaneous silicic rocks in the Antarctic Peninsula. Heat flow associated with the granite intrusions is predicted to be in the range 70–95 mW/m2 depending on the thickness of the high heat production granite layer and the regional heat flow value. Analysis of detrital zircon compositions and ages indicates that the high Th and U abundances are related to enrichment of the lower-mid crust that dates back to 200–299 Ma at the time of the formation of the Gondwanide fold belt and its post-orogenic collapse and extension.last_img read more

An updated seabed bathymetry beneath Larsen C Ice Shelf, Antarctic Peninsula

first_imgIn recent decades, rapid ice-shelf disintegration along the Antarctic Peninsula has had a global impact through enhancing outlet glacier flow, and hence sea level rise, and the freshening of Antarctic Bottom Water. Ice shelf thinning due to basal melting results from the circulation of relatively warm water in the underlying ocean cavity. However, the effect of sub-shelf circulation on future ice-shelf stability cannot be predicted accurately with computer simulations if the geometry of the ice-shelf cavity is unknown. To address this deficit for Larsen C Ice Shelf, west Antarctica, we integrate new water-column thickness measurements with existing observations. We present these new data here along with an updated bathymetry grid of the ocean cavity. Key findings include relatively deep seabed to the south-east of the Kenyon Peninsula, along the grounding line and around the key ice shelf pinning point of Bawden Ice Rise. In addition, we can confirm that the cavity’s southern trough stretches from Mobiloil Inlet to the open ocean. These areas of deep seabed will influence ocean circulation and tidal mixing, and will therefore affect the basal-melt distribution. These results will help constrain models of ice-shelf cavity circulation with the aim of improving our understanding of sub-shelf processes and their potential influence on ice shelf stability. The data set comprises all point measurements of seabed depth and a gridded data product, derived using additional measurements of both offshore seabed depth and the thickness of grounded ice. We present all new depth measurements here as well as a compilation of previously published measurements used in the gridding process. The gridded data product is included in the supplementary material.last_img read more

Scoreboard roundup — 7/17/18

first_img Beau Lund Written by FacebookTwitterLinkedInEmailiStock/Thinkstock(NEW YORK) —      Here are the scores from yesterday’s sports events:    ALL-STAR GAME Final  AL   8  NL   6, 10 Innings  Copyright © 2018, ABC Radio. All rights reserved.center_img July 18, 2018 /Sports News – National Scoreboard roundup — 7/17/18last_img

UFC’s Conor McGregor pleads guilty to Barclays incident

first_img FacebookTwitterLinkedInEmailSteve Marcus/Getty Images(NEW YORK) — UFC star Conor McGregor pleaded guilty Thursday to a misdemeanor count of disorderly conduct three months after his arrest following a melee in the loading dock of Barclays Center.The Brooklyn District Attorney’s Office agreed to drop the felony charge that McGregor, 29, had faced for throwing a dolly at a bus full of other MMA fighters, three of whom were injured.In exchange for his plea, the judge imposed a sentence of community service and anger management. He had already paid for the damage to the bus.“I just want to say I’m thankful to the DA and the judge for allowing me to move forward,” McGregor said. “I want to say to my friends, my family, my fans — thank you for the support.”    McGregor was ordered to stay away from the three UFC stars injured by broken glass for the next two years.Cian Cowley, a fighter who trains with McGregor, was also charged in the attack.Last year, McGregor boxed Floyd Mayweather, losing by technical knockout in the 10th round. He hasn’t fought for UFC since November 2016.Copyright © 2018, ABC Radio. All rights reserved. Written by July 26, 2018 /Sports News – National UFC’s Conor McGregor pleads guilty to Barclays incidentcenter_img Beau Lundlast_img read more

Utah Women’s Tennis To Host 12 Matches

first_img Tags: Boise State/California/Chicagoland/Colorado/Las Vegas/Loyola Marymount/Mat Iandolo/New Mexico/Pac 12/Southern Utah/Stanford/Texas A&M/Utah State/Utah Women’s Tennis/Washington/Washington State August 22, 2018 /Sports News – Local Utah Women’s Tennis To Host 12 Matches Written by FacebookTwitterLinkedInEmailSALT LAKE CITY-Wednesday, Utah women’s tennis announced its 2018-19 schedule per a statement from head coach Mat Iandolo.This features 12 home matches but the season starts October 5-7 in the Chicagoland area for the Northwestern Invitational.The Utes then compete at the ITA Regionals October 10-15 at Las Vegas. The fall play for Utah concludes at the San Diego State Invitational November 9-11.Dual match play commences January 12 at Newport Beach, Calif. against Texas A&M before they make their home debut on the season.January 19, the Utes will host Southern Utah and Utah State and then New Mexico and Boise State visit Salt Lake City February 8 and 10, respectively.Pac-12 play commences for the Utes March 8 and 10 against Washington State and Washington, respectively at Salt Lake City.The regular season also concludes at home for the Utes from April 11-20 as they host Loyola Marymount April 11, Stanford April 12, California April 14 and Colorado April 20.The Pac-12 championships will run from April 24-28 at Ojai, Calif. Brad Jameslast_img read more

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