An intercomparison of Antarctic sea ice extent datasets from the US Joint Ice Center (JIC) and satellite passive microwave observations for 1979–88

first_imgUS Joint Ice Center (JIC) Antarctic sea ice extent data, the longest continuous series of its kind for this part of the world, are compared with direct passive microwave-based estimates to assess their overall consistency both spatially and temporally in the period 1979–88. Using ice edge position as a proxy for ice extent, the comparison reveals close agreement in most years, in monthly averaged ice edge positions in all Antarctic regions at the time of maximum ice extent, and also in autumn and spring in the Ross and Weddell Seas. Unexpectedly, JIC relative overestimation prevails during both autumn and spring in some other areas. Previously noted differences in JIC and passive microwave total Antarctic extent in 1979–80 result mainly from problems in the Ross Sea. Reasons for the various discrepancies may lie in differences in the methods used to produce the datasets especially in spring but those in autumn seem to often arise for other reasons. It is found that the prevalent discrepancies in the Ross Sea in 1979–80 as well as those in spring in other regions from 1981 coincide with periods of ice extent change and the evolution/intensification of ice extent anomalies.last_img read more

The influence of seasonal environmental variables on the distribution of presumptive fecal coliforms around an Antarctic research station

first_imgFactors affecting fecal microorganism survival and distribution in the Antarctic marine environment include solar radiation, water salinity, temperature, sea ice conditions, and fecal input by humans and local wildlife populations. This study assessed the influence of these factors on the distribution of presumptive fecal coliforms around Rothera Point, Adelaide Island, Antarctic Peninsula during the austral summer and winter of February 1999 to September 1999. Each factor had a different degree of influence depending on the time of year. In summer (February), although the station population was high, presumptive fecal coliform concentrations were low, probably due to the biologically damaging effects of solar radiation. However, summer algal blooms reduced penetration of solar radiation into the water column. By early winter (April), fecal coliform concentrations were high, due to increased fecal input by migrant wildlife, while solar radiation doses were low. By late winter (September), fecal coliform concentrations were high near the station sewage outfall, as sea ice formation limited solar radiation penetration into the sea and prevented wind-driven water circulation near the outfall. During this study, environmental factors masked the effect of station population numbers on sewage plume size. If sewage production increases throughout the Antarctic, environmental factors may become less significant and effective sewage waste management will become increasingly important. These findings highlight the need for year-round monitoring of fecal coliform distribution in Antarctic waters near research stations to produce realistic evaluations of sewage pollution persistence and dispersal.last_img read more

Studies of substorm on March 12, 1991: 2. Auroral electrons. Acceleration, injection, and dynamics

first_imgIn the first part of this study of the substorm of March 12, 1991, the space-time structure of substrorm disturbance and dynamics of auroral ions were considered. This second part presents an analysis of measurements of auroral electrons onboard the CRRES satellite. It is demonstrated that enhancements of the electron flux (injections) during large-scale and local dipolarizations of the magnetic field are determined by a combination of field-aligned, induction, and betatron mechanisms of acceleration with an effect of displacement of the drift shells of particles. The relative contributions of these mechanisms in relation to the energy of auroral electrons are determined.last_img

A space oddity: Geographic and specific modulation of migration in Eudyptes penguins

first_imgPost-breeding migration in land-based marine animals is thought to offset seasonal deterioration in foraging or other important environmental conditions at the breeding site. However the inter-breeding distribution of such animals may reflect not only their optimal habitat, but more subtle influences on an individual’s migration path, including such factors as the intrinsic influence of each locality’s paleoenvironment, thereby influencing animals’ wintering distribution. In this study we investigated the influence of the regional marine environment on the migration patterns of a poorly known, but important seabird group. We studied the inter-breeding migration patterns in three species of Eudyptes penguins (E. chrysolophus, E. filholi and E. moseleyi), the main marine prey consumers amongst the World’s seabirds. Using ultra-miniaturized logging devices (light-based geolocators) and satellite tags, we tracked 87 migrating individuals originating from 4 sites in the southern Indian Ocean (Marion, Crozet, Kerguelen and Amsterdam Islands) and modelled their wintering habitat using the MADIFA niche modelling technique. For each site, sympatric species followed a similar compass bearing during migration with consistent species-specific latitudinal shifts. Within each species, individuals breeding on different islands showed contrasting migration patterns but similar winter habitat preferences driven by sea-surface temperatures. Our results show that inter-breeding migration patterns in sibling penguin species depend primarily on the site of origin and secondly on the species. Such site-specific migration bearings, together with similar wintering habitat used by parapatrics, support the hypothesis that migration behaviour is affected by the intrinsic characteristics of each site. The paleo-oceanographic conditions (primarily, sea-surface temperatures) when the populations first colonized each of these sites may have been an important determinant of subsequent migration patterns. Based on previous chronological schemes of taxonomic radiation and geographical expansion of the genus Eudyptes, we propose a simple scenario to depict the chronological onset of contrasting migration patterns within this penguin group.last_img read more

Variability and trends in the Southern Hemisphere high latitude, quasi-stationary planetary waves

first_imgWe investigate variability and trends of the Southern Hemisphere quasi-stationary planetary waves over 1979–2013 using the European Centre for Medium-range Weather Forecasts (ECMWF) Interim reanalyses. The effects of tropical and extra-tropical forcing factors on the phase and amplitude of the planetary waves are identified. The amplitudes of wave numbers 1–3 exhibit an annual cycle with a minimum in summer and maximum over the extended austral winter period. The phase of wave number 1 has a semi-annual cycle, moving east in austral spring/autumn and west in summer/winter as a result of differences in the phase of the semi-annual oscillation across the Pacific sector of the Southern Ocean. The phase of wave number 3 has an annual cycle, being more eastward (westward) in summer (winter). Year-to-year variability of the amplitude of wave number 1 is found to be strongly associated with the Amundsen Sea Low, which in turn is known to be strongly influenced by the El Niño–Southern Oscillation, with the consequence that the amplitude of wave number 1 is larger during the El Niño phase of the cycle. Regarding trends for the year as a whole, the amplitude of wave number 1 has decreased since 1979 (p < 0.1), while the amplitudes of wave numbers 2 and 3 have increased. These changes are consistent with the warming trends in sea surface temperatures across much of the tropical oceans. However, the factors associated with longer-term trends are less clear than for year-to-year variability.last_img read more

Multi-colony tracking reveals spatio-temporal variation in carry-over effects between breeding success and winter movements in a pelagic seabird

first_imgCarry-over effects, whereby events in one season have consequences in subsequent seasons, have important demographic implications. Although most studies examine carry-over effects across 2 seasons in single populations, the effects may persist beyond the following season and vary across a species’ range. To assess potential carry-over effects across the annual cycle and among populations, we deployed geolocation loggers on black-legged kittiwakes Rissa tridactyla at 10 colonies in the north-east Atlantic and examined relationships between the timing and destination of migratory movements and breeding success in the year of deployment and subsequent season. Both successful and unsuccessful breeders wintered primarily in the north-west Atlantic. Breeding success affected the timing of migration, whereby unsuccessful breedersdeparted the colony earlier, arrived at the post-breeding and main wintering areas sooner, and departed later the following spring. However, these patterns were only apparent in colonies in the south-west of the study region. Furthermore, the effect of breeding success was stronger onmigration timing in the first part of the winter than later. Timing of migratory movements was weakly linked to subsequent breeding success, and there was no detectable association between breeding success in the 2 seasons. Our results indicate temporal structure and spatial hetero -geneity in the strength of seasonal interactions among kittiwakes breeding in the north-east Atlantic. Variable fitness consequences for individuals from different colonies could have important implications for population processes across the species’ range and suggest that thespatio-temporal dynamics of carry-over effects warrant further study.last_img read more

Physical properties of shallow ice cores from Antarctic and sub-Antarctic islands

first_imgThe sub-Antarctic is one of the most data-sparse regions on earth. A number of glaciated Antarctic and sub-Antarctic islands have the potential to provide unique ice core records of past climate, atmospheric circulation, and sea ice. However, very little is known about the glaciology of these remote islands or their vulnerability to warming atmospheric temperature. Here we present melt histories and density profiles from shallow ice (firn) cores (14 to 24 m) drilled on three sub-Antarctic islands and two Antarctic coastal domes. Additionally, complementary ground-penetrating radar (GPR) data were collected to further characterize each site and assess the spatial distribution of the observed melt layers. This study includes the first ever firn cores from Bouvet Island (54∘25′19′′ S, 03∘23′27′′ E) in the South Atlantic, from Peter I Island (68∘51′05′′ S, 90∘30′35′′ W) in the Bellingshausen Sea, and from Young Island (66∘31′44′′ S, 162∘33′21′′ E) in the Ross Sea sector’s Balleny island chain. Despite their sub-Antarctic location, surface melt is low at most sites (melt layers account for ∼ 10 % of total core), with undisturbed ice layers in the upper ∼ 40 m, suggesting minimal impact of meltwater percolation. The exception is Young Island, where melt layers account for 47 % of the firn core. Surface snow densities range from 0.47 to 0.52 kg m−3, with close-off depths ranging from 21 to 51 m. Based on the measured density, we estimate that the bottom ages of a 100 m ice core drilled on Peter 1 Island would reach ∼ 1856 CE and ∼ 1874 CE at Young Island.last_img read more

NFL suspends Patriots wide receiver Josh Gordon indefinitely

first_img Written by FacebookTwitterLinkedInEmailMichael Reaves/Getty Images(NEW YORK) — New England Patriots wide receiver Josh Gordon was suspended indefinitely on Thursday for violating the terms of his conditional reinstatement under the NFL’s substance abuse policy.“Effective today, Josh Gordon has been returned to the Reserve/Commissioner Suspended list indefinitely for violating the terms of his conditional reinstatement under the Policy and Program for Substances of Abuse,” the NFL said in a statement Thursday.The announcement came after Gordon, 27, tweeted that he was “stepping away from the football field for a bit to focus on my mental health.”pic.twitter.com/omiQgO8IjE— Flash Gordon (@JOSH_GORDONXII) December 20, 2018The Patriots chimed in afterwards, saying they “support Josh Gordon in his continued efforts to focus on his health.”Copyright © 2018, ABC Radio. All rights reserved. Beau Lundcenter_img December 21, 2018 /Sports News – National NFL suspends Patriots wide receiver Josh Gordon indefinitelylast_img read more

Utah dominates Washington State for 88-70 victory

first_imgJanuary 12, 2019 /Sports News – Local Utah dominates Washington State for 88-70 victory Utah took a 11-5 lead on back-to-back layups from Gach after Washington State went nearly six minutes without scoring a basket. Wade ended the drought with a jumper and added a layup to punctuate a 6-0 run that tied it at 11. Charles Jones, Jr. and Riley Battin each added 11 points while Sedrick Barefield and Parker Van Dyke chipped in 10 apiece for the Utes. Barefield also dished out seven assists. UP NEXT Utah hosts Colorado on Jan. 20. Utah came out on fire after halftime to completely pull away from the Cougars. The Utes scored baskets on seven straight possessions, culminating in a dunk from Jayce Johnson, to take a 62-32 lead with 13:19 remaining. All seven baskets were layups or dunks. Washington State hosts California on Thursday. Washington State opened a door for the decisive run by missing eight straight shots and committing three turnovers over a 4½ minute stretch. THE BIG PICTURE Washington State’s leading scorer Robert Franks missed his fourth consecutive game while recovering from a hip contusion. The senior forward did not travel with the Cougars to Boulder or Salt Lake City this week. Franks is averaging 22.1 points and 7.9 rebounds per game for this season. C.J. Elleby scored 21 points and Isaiah Wade added 12 to lead Washington State. The Cougars (7-9, 0-3) have lost all eight games they have played outside Pullman this season.center_img Without Franks in the lineup, the Cougars looked lost on offense and fell victim to multiple prolonged shooting and scoring droughts. Van Dyke kept the Cougars from actually taking the lead. He drained a 3-pointer to put Utah back in front. Then the senior guard stole the ball and took it in for a dunk. Van Dyke’s two baskets sparked a 15-0 run that gave the Utes a 26-11 lead. Tags: Pac 12/Utah Runnin’ Utes Basketball Utah: The Utes bounced back from a ragged offensive performance against Washington by driving into the paint and getting out in transition. Utah finished with 48 points in the paint and tallied 24 fast break points against Washington State after scoring 26 in the paint and 12 in transition against the Huskies. It helped the Utes overcome 16 turnovers that led to 22 points for the Cougars. FacebookTwitterLinkedInEmailSALT LAKE CITY (AP) — Timmy Allen scored 15 points and collected nine rebounds while Both Gach added 14 points to lead Utah to an 88-70 victory over Washington State on Saturday night. Utah (8-8, 2-2 Pac-12) snapped a two-game losing streak and beat the Cougars for the 17th consecutive time in Salt Lake City, dating back to 1946. Washington State: Turnovers and poor perimeter shooting doomed the Cougars on offense for the second straight game. Washington State coughed up 13 turnovers, leading to 21 points for Utah and averaged 12.5 turnovers per game on its road trip this week. The Cougars also shot just 5 of 24 from 3-point range after going 2 of 18 from the perimeter against Colorado. Written by Associated Presslast_img read more

Huggins hits 3 in final seconds, Fresno State wins 78-77

first_img FacebookTwitterLinkedInEmailLOGAN, Utah (AP) — Braxton Huggins poured in a career-high 33 points, and with five seconds left nailed a straightaway 3-pointer after shaking a defender and Fresno State pulled out a 78-77 win over Utah State on Wednesday night. January 9, 2019 /Sports News – Local Huggins hits 3 in final seconds, Fresno State wins 78-77 Merrill launched a 3 as time was winding down, but it was partially blocked. Quinn Taylor grabbed the rebound while going out of bounds and his putback missed. Written by Merrill scored 16 points and but was held to 3 of 10 from the floor. He was 9 of 11 at the foul line. Neemias Queta also scored 16 on 6-of-6 shooting and grabbed nine rebounds for Utah State (11-5, 1-2). Tags: Mountain West/Utah State Aggies Basketball Fresno State (12-3, 3-0 Mountain West) had trailed the entire game until Huggins launched his winning 3 . He broke right, then cut left to get defender Sam Merrill on the wrong foot. Braxton was 8 of 13 from behind the arc and the Bulldogs made 15 3-pointers — half their made field goals (30 of 66). Fresno State faces No. 10 Nevada on Saturday. Associated Presslast_img read more