The lengths of 9 421 Antarctic krill, Euphausia superba Dana, from 144 net samples from 4 depth ranges at the same location (north east of South Georgia) were measured over a period of 6 d. While the mean lengths showed differences between each depth range in each time period of each day, the only consistent difference occurred in the period 00.00 to 04.00 hrs local time, when the mean lengths of krill were up to 2 mm greater than those found at other times. While vertical migration may have contributed to this nocturnal change in mean length, differences in measurement techniques between observers were also implicated. Controlled laboratory experiments confirmed that there were significant differences between measurements of the same krill analysed by six different observers while there were no significant differences in replicate measurements made by a single observer. These results have important implications for future studies involving length and length-frequency analysis, and suitable precautions and experimental protocols are suggested.
New multifold seismic‐reflection and wide‐angle reflection/refraction data across George VI Sound, Antarctic Peninsula, show the presence of graben and horst structures indicating an extensional origin. The data suggest that rocks of an accretionary complex and fore‐arc basin underlie the Sound and are in faulted contact along its eastern boundary with volcanic and plutonic rocks of the associated Mesozoic arc of western Palmer Land. A cover of possible syn‐ and postglacial Cenozoic deposits drapes the structures. The combination of new seismic, synthetic‐aperture radar and previously acquired data suggests subduction‐related rifting in the Sound was segmented, with opening in the south predominately by normal extension whilst in the north, dextral transtension predominated.
Ice cores have provided many of the key pieces of evidence about past changes in climate and in forcing factors for climate. In particular, the core from Vostok (Antarctica) shows how climate and greenhouse gases have been intimately linked over the last 400,000 years. The European Project for Ice Coring in Antarctica (EPICA) is a consortium of scientists from 10 European countries that has set out to drill two new cores: one giving an even longer record, the other giving far more detail about the last climatic cycle. In a major publication, the team have presented data extending nearly 800,000 years in the past, with more to come. Future plans by the international ice coring community include ideas to extend the record in both Antarctica and Greenland yet further into the past, and to understand the spatial variability of polar climate on different timescales.
We compare the present and last interglacial periods as recorded in Antarctic water stable isotope records now available at various temporal resolutions from six East Antarctic ice cores: Vostok, Taylor Dome, EPICA Dome C (EDC), EPICA Dronning Maud Land (EDML), Dome Fuji and the recent TALDICE ice core from Talos Dome. We first review the different modern site characteristics in terms of ice flow, meteorological conditions, precipitation intermittency and moisture origin, as depicted by meteorological data, atmospheric reanalyses and Lagrangian moisture source diagnostics. These different factors can indeed alter the relationships between temperature and water stable isotopes. Using five records with sufficient resolution on the EDC3 age scale, common features are quantified through principal component analyses. Consistent with instrumental records and atmospheric model results, the ice core data depict rather coherent and homogenous patterns in East Antarctica during the last two interglacials. Across the East Antarctic plateau, regional differences, with respect to the common East Antarctic signal, appear to have similar patterns during the current and last interglacials. We identify two abrupt shifts in isotopic records during the glacial inception at TALDICE and EDML, likely caused by regional sea ice expansion. These regional differences are discussed in terms of moisture origin and in terms of past changes in local elevation histories, which are compared to ice sheet model results. Our results suggest that elevation changes may contribute significantly to inter-site differences. These elevation changes may be underestimated by current ice sheet models.
A mesospheric front was observed with an allskyairglow imager on the night of 9–10 July 2007 at FerrazStation (62 degrees S, 58 degrees W), located on King George island on the Antarctic Peninsula. The observed wave propagated from southwest to northeast with a well defined wave front and a series of crests behind the main front. The wave parameters were obtained via a 2-D Fourier transform of the imager data providing a horizontal wavelength of 33 km, an observed period of 6 min, and a horizontal phase speed of 92ms−1. Simultaneous mesospheric winds were measured with a medium frequency (MF) radar at Rothera Station (68degree S, 68degrees W) and temperature profiles were obtained from the SABER instrument on the TIMED satellite. These wind and temperature profiles were used to estimate the propagation environment of the wave event. A wavelet technique was applied to the wind in the plane of wave propagation at the OH emission height spanning three days centered on the front event to define the dominant periodicities. Results revealed a dominance of near-inertial periods, and semi-diurnal and terdiurnal tides suggesting that the ducting structure enabling mesospheric front propagation occurred on large spatial scales. The observed tidal motions were used to reconstruct the winds employing a least-squares method, which were then compared to the observed ducting environment.Results suggest an important contribution of largescalewinds to the ducting structure, but with buoyancy frequencyvariations in the vertical also expected to be important.These results allow us to conclude that the wave frontevent was supported by a duct including contributions fromboth winds and temperature.
One of the most remarkable features of contemporary oceanic climate change is the warming and contraction of Antarctic Bottom Water over much of global ocean abyss. These signatures represent changes in ventilation mediated by mixing and entrainment processes that may be location-specific. Here we use available data to document, as best possible, those mixing processes as Weddell Sea Deep and Bottom Waters flow along the South Orkney Plateau, exit the Weddell Sea via Orkney Passage and fill the abyssal Scotia Sea. First, we find that an abrupt transition in topography upstream of Orkney Passage delimits the extent of the coldest waters along the Plateau’s flanks and may indicate a region of especially intense mixing. Second, we revisit a control volume budget by Heywood et al. (Nature, 2002) for waters trapped within the Scotia Sea after entering through Orkney Passage. This budget requires extremely vigorous water mass transformations with a diapycnal transfer coefficient of 39(±10) × 10-4 m2 s–1. Evidence for such intense diapycnal mixing is not found in the abyssal Scotia Sea interior and, while we do find large rates of diapycnal mixing in conjunction with a downwelling Ekman layer on the western side of Orkney Passage, it is insufficient to close the budget. This leads us to hypothesize that the Heywood budget is closed by a boundary mixing process in which the Ekman layer associated with the Weddell Sea Deep Water boundary current experiences relatively large-vertical-scale overturning associated with tidal forcing along the southern boundary of the Scotia Sea. This article is protected by copyright. All rights reserved.
Sub-Antarctic South Georgia is a key region for studying climate variability in the Southern Hemisphere, because of its position at the core of the Southern Hemisphere Westerly Wind belt and between the Antarctic Circumpolar Current and the Polar Frontal Zone. Here, we present a 5.8-m long high-resolution pollen record from Fan Lake on Annenkov Island dominated by local sub-polar vegetation, with Acaena and Poaceae being present throughout the last 7000 years. Palynological and sedimentological analyses revealed a warm late Holocene ‘climate optimum’ between 3790 and 2750 cal. yr BP, which was followed by a gradual transition to cool and wet conditions. This cooling was interrupted by slightly warmer environmental conditions between 1670 and 710 cal. yr BP that partly overlap with the Northern Hemisphere ‘Medieval Climate Anomaly’. Increases in non-native and long-distance pollen grains transported from South America (e.g. Nothofagus, Podocarpus) indicate that stronger Southern Hemisphere Westerly Winds over South Georgia possibly occurred during some ‘colder’ phases of the late Holocene, most notably between c. 2210 and 1670 cal. yr BP and after 710 cal. yr BP.
Accurate measurements of sea ice thickness are critical to better understand climate change, to provide situational awareness in ice-covered waters, and to reduce risks for communities that rely on sea ice. Nonetheless, remotely measuring the thickness of sea ice is difficult. The only regularly employed technique that accurately measures the full ice thickness involves drilling a hole through the ice. Other presently used methods are either embedded in or through the ice (e.g., ice mass balance buoys) or calculate thickness from indirect measurements (e.g., ice freeboard from altimetry; ice draft using sonars; total snow and ice thickness using electromagnetic techniques). Acoustic techniques, however, may provide an alternative approach to measure the total ice thickness. Here laboratory-grown sea ice thicknesses, estimated by inverting the time delay between echoes from the water-ice and ice-air interfaces, are compared to those measured using ice cores. A time-domain model capturing the dominant scattering mechanisms is developed to explore the viability of broadband acoustic techniques for measuring sea ice thickness, to compare with experimental measurements, and to investigate optimal frequencies for in situ applications. This approach decouples ice thickness estimates from water column properties and does not preclude ice draft measurements using the same data.
September 11, 2018 /Sports News – Local USU-Eastern Utah Women’s Soccer To Host Special Fundraiser Written by Tags: Ammon Bennett/leukemia/Maeser Prep/Otero Junior College/Sophie Cannon/USU Eastern Utah Women’s Soccer FacebookTwitterLinkedInEmailPRICE, Utah-Tuesday, USU-Eastern Utah’s women’s soccer program announced a special fundraiser to raise money for their teammate, Sophie Cannon, who has been diagnosed with leukemia.This will be during the September 22 home game against Otero Junior College.Cannon, a product out of Lindon, Utah and Maeser Prep Academy, is still a part of the team, but unable to play after her 2017 diagnosis.For more information, please contact head coach Ammon Bennett at [email protected] Brad James
Tags: Basketball/Donovan Mitchell/NBA/Utah Jazz FacebookTwitterLinkedInEmailSALT LAKE CITY (AP) — Donovan Mitchell scored 21 points and Derrick Favors had 17 to help the Utah Jazz romp over the short-handed Miami Heat 111-84 on Wednesday night.“It started from the tip,” Mitchell said after the Jazz led by as many as 42. “We came out strong and didn’t let up.”Playing against one of his basketball idols probably for the final time, Mitchell unleashed a variety of moves — the crossovers and misdirection dribbles that have prompted comparisons to a young Dwyane Wade. Mitchell has acknowledged he studies film of Wade to develop his own offensive repertoire.On Tuesday night, Mitchell took Wade to dinner in downtown Salt Lake City and gifted him a rocking chair. Then, the second-year guard, who said he calls Wade on the phone often and picks his brain, matched up and scored on the 12-time All-Star at least a few times in the blowout.Rodney McGruder paced the Heat with 16 points and Kelly Olynyk had 14 as Miami played without Hassan Whiteside and Goran Dragic. Wade, set to retire after the season, scored six points.Less than two weeks ago, the Jazz also went up big in the first quarter against the Heat, leading by as many as 19 before allowing a 20-0 run and watching Wade sink two free throws to win it in Miami, 102-100.This time, there was no such drama.The Jazz sprinted out to a 34-10 lead on hot shooting and tenacious defense that denied the Heat any easy looks early.Favors went 7 of 8 and had eight boards in 19 minutes, while Rudy Gobert had 10 points and 11 rebounds. Kyle Korver, who has opened up the floor for the Jazz since arriving via trade from Cleveland, made four more 3-pointers and scored 16 points.The Jazz have had an up-and-down year by any measure. This win marked Utah’s second by 27 points or more in eight days, but the Jazz have also lost games by 33 and 50 points and have yet to reach the .500 mark at home (now 5-6).Even within the same game, the Jazz were nearly unstoppable in the first quarter — shooting 70 percent — but went through long stretches later in the game when they couldn’t generate any offense and had a spate of turnovers. They ended up shooting 52.6 percent, including 16 of 32 from 3-point range, with 17 turnovers.The Heat have been riding their own rollercoaster. They led by 31 in the second quarter of a win against New Orleans on Nov. 30 and then trailed by 31 — and more — in the second quarter to the Jazz less than two weeks later.MISSING YOUWhiteside, who left the court for the locker room during the fourth quarter of a home loss to Orlando last week, is still not with the team for personal reasons. He later said he just needed to go to the bathroom, but Miami coach Erik Spoelstra was upset and said the Heat “handled it as a team.” Whiteside is expected back with the club on Friday.Dragic, who has battled a sore right knee for the last six weeks and had it drained in mid-November, missed the game — his 12th scratch of the season. Fellow guard Dion Waiters hasn’t played at all since having ankle surgery in January.TIP-INSHeat: Wade, making his last regular-season appearance in Salt Lake City, got a standing ovation when he checked in midway through the first quarter and another when exited the court after the game. … The Heat’s 15 points were a season low in the first quarter for a Jazz opponent.Jazz: Raul Neto missed the game with a sore right leg. … The win snapped a four-game skid against Miami.UP NEXTHeat: Visit the Memphis Grizzlies on Friday night.Jazz: At the Orlando Magic on Saturday. Written by Associated Press December 12, 2018 /Sports News – Local Mitchell, Jazz roll over short-handed Heat 111-84