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Continued decline of total ozone over Halley, Antarctica, since 1985

first_imgIN 1985, Farman et al.1 announced that a dramatic reduction in total ozone was occurring in the atmosphere over Halley, Antarctica, during the polar spring. Analysis of satellite data revealed that this ozone depletion was an Antarctic-wide phenomenon2. Combined theoretical3á¤-5, observational6,7 and laboratory8 work has shown that chlorine radicals derived from the photolysis of chlorofluorocarbons were the dominant cause of the ozone loss9á¤-11. Ten years later, we review here the status of the ‘ozone hole’ based on the continued total-ozone measurements at Halley. The springtime ᤘozone holeᤙ continues to deepen, with both the October mean and minimum total ozone persistently decreasing. The ozone loss extends into January and February, so that significant increases in ultraviolet-B radiation can be expected at the surface over Antarctica during the summer. A signal of ozone loss is now apparent in the spring and summer temperature records, with recent temperatures at the 100-mbar level consistently close to, or colder than, the historical (1957á¤-72) minima for the period October to January. These low temperatures may well enable the maintenance of springtime ozone-loss mechanisms until later in the year.last_img read more

Numerical simulation of VLF risers, fallers, and hooks observed in Antarctica

first_imgThe VLF database from Halley station, Antarctica, has been searched, and prominent examples of discrete emissions are presented. Risers, fallers, quasiconstant tones, and upward and downward hooks are all common. Also observed are risers and fallers triggered from the tops of hiss bands. A one-dimensional Vlasov VHS code has been used to simulate the main types of events observed. Using realistic plasma parameters, the code successfully reproduces the main kinds of events observed, in good qualitative agreement with observations. Distinct generation region structures are found to be associated with risers and fallers. Hook formation is interpreted as being a spontaneous transition between these two quasi-stable generation region structures.last_img read more

Late Pleistocene record of elevated UV radiation in an Antarctic lake

first_imgElevated ultraviolet irradiance (UVR, 280–400 nm) damages DNA and induces reorganisation within biological communities at the Earth’s surface. Southern high latitude aquatic ecosystems may be particularly susceptible because of low stratospheric ozone levels and extremely low contents of photoprotective dissolved organic matter (DOM). Surveys of shallow lakes and ponds in eastern Antarctica show that cyanobacteria survive elevated UVR exposure by increasing extra-cellular concentrations of photoprotective compounds, which are preserved in sediments together with photosynthetic pigments. Thus, reconstruction of long-term changes in biological UVR receipt, to provide a context for evaluating the long-term significance of recent changes in ozone column depth, is feasible in Antarctic settings. The sediment in Lake Reid (69° 23′ S, 76° 53′ E), Antarctica, spans the late-Pleistocene and contains UVR-absorbing pigments from benthic cyanobacteria. Here we show that mean exposure of these benthic cyanobacteria to UVR during the last glacial was more than three times higher than during the Holocene, likely due to short periods of photosynthetic activity coinciding with relatively high UVR fluxes, or due to increased UVR transmission to the Earth’s surface resulting from changes in external factors such as stratospheric ozone levels, cloud cover and surface albedo.last_img read more

QBO modulation of traveling planetary waves during northern winter

first_imgThis study analyzes geopotential height data from the ERA-40 and ERA-Interim reanalyses for the period of 1958–2009 to provide some new insights on the stratospheric Quasi-Biennial Oscillation (QBO) modulation of traveling planetary waves during Northern Hemisphere (NH) winter. In the stratosphere, the zonal wave number 1–3 waves with periods of 22.5–30 days and 45–60 days are found to be significantly stronger at midlatitudes when the QBO at 50 hPa is in its westerly phase than when it is in its easterly phase. The modulation is stronger for eastward propagating and standing waves and weaker for westward propagating waves. A QBO modulation of 11–13 day planetary waves is also found but the effect is dominated by post-satellite data. In the troposphere, significant QBO modulation is only detected in westward propagating waves at zonal wave number 2 with periods of 22.5–30 days in early winter (Oct-Dec). Consistent results in the stratosphere are obtained using the temperature data from SABER/TIMED. The SABER data also show that the QBO effect on the eastward propagating 23-day waves extends into the mesosphere (∼70 km) for wave number 1 and only up to the stratopause (∼45 km) for wave numbers 2 and 3. We suggest that the 22.5–30 day planetary waves are secondary waves generated by a nonlinear coupling between zonal-mean intraseasonal oscillations (ISO) and the well-known 16-day planetary waves. The QBO modulation of those planetary waves is due to a QBO-ISO interaction. Further studies are needed to prove this hypothesis.last_img read more

Feather mercury concentration in streaked shearwaters wintering in separate areas of southeast Asia

first_imgWe measured mercury concentration ([Hg]) and nitrogen stable isotope values (δ15N) in tail feathers that were replaced during the non-breeding period of streaked shearwaters Calonectris leucomelas that bred on 3 islands in Japan. The birds’ year-round movements were tracked and their breeding status was monitored. [Hg] was greater in males than in females, and was greatest in those birds spending their non-breeding period in the South China Sea (3.1 ± 1.5 µg g-1 dry weight), moderate in birds in the Arafura Sea (1.5 ± 0.7 µg g-1), and lowest in birds in the Pacific Ocean north of New Guinea (0.8 ± 0.4 µg g-1). Adverse effects of feather [Hg] on breeding status were not observed. This regional variation in feather [Hg] might partly reflect differences in the intake of Hg between these non-breeding areas in addition to accumulation during the late breeding period and the southward migration periodlast_img read more

Modelling present-day basal melt rates for Antarctic ice shelves using a parametrization of buoyant meltwater plumes

first_imgBasal melting below ice shelves is a major factorin mass loss from the Antarctic Ice Sheet, which can contributesignificantly to possible future sea-level rise. Therefore,it is important to have an adequate description of thebasal melt rates for use in ice-dynamical models. Most currentice models use rather simple parametrizations based onthe local balance of heat between ice and ocean. In thiswork, however, we use a recently derived parametrization ofthe melt rates based on a buoyant meltwater plume travellingupward beneath an ice shelf. This plume parametrizationcombines a non-linear ocean temperature sensitivity with aninherent geometry dependence, which is mainly describedby the grounding-line depth and the local slope of the iceshelfbase. For the first time, this type of parametrizationis evaluated on a two-dimensional grid covering the entireAntarctic continent. In order to apply the essentially onedimensionalparametrization to realistic ice-shelf geometries,we present an algorithm that determines effective values forthe grounding-line depth and basal slope in any point beneathan ice shelf. Furthermore, since detailed knowledge oftemperatures and circulation patterns in the ice-shelf cavitiesis sparse or absent, we construct an effective ocean temperaturefield from observational data with the purpose ofmatching (area-averaged) melt rates from the model with observedpresent-day melt rates. Our results qualitatively replicatelarge-scale observed features in basal melt rates aroundAntarctica, not only in terms of average values, but also interms of the spatial pattern, with high melt rates typically occurringnear the grounding line. The plume parametrizationand the effective temperature field presented here are thereforepromising tools for future simulations of the AntarcticIce Sheet requiring a more realistic oceanic forcing.last_img read more

Gulden Homers as Utah Baseball Falls to Arizona State, 7-4

first_img Robert Lovell FacebookTwitterLinkedInEmailTEMPE, Ariz. – The Utah baseball team opened a three-game series against Arizona State with a 7-4 loss to the Sun Devils on Friday evening.ASU broke a 4-4 tie with three runs in the bottom of the eighth for the win.Rykker Tom went 2-for-4 on the night at the plate while Wade Gulden hit a two-run home run for the Utes.Utah used five pitchers, with starter Josh Tedeschi pitching two innings, allowing four runs (three earned) on eight hits with a strikeout. Justin Kelly pitched two scoreless innings with two strikeouts before leaving the game with an injury. Jacob Rebar, who earned the loss, pitched 3 2/3 innings and allowed three runs on three hits with two walks and a strikeout. Trenton Stoltz pitched the final 1/3 of an inning, allowing one hit.Utah stranded two on base in the first inning, but it was ASU that broke through first with two runs in the bottom of the first, as the Sun Devils left the bases loaded to end the inning. Arizona State also scored two runs on four hits in the second for a 4-0 lead.The Utes rallied back in the third as Chris Rowan walked to lead off the inning and Keirsey doubled, leading to Rowan scoring on a ground out. Keirsey scored the second run of the inning on a wild pitch.Davis Delorefice walked to lead off the fourth and set up Gulden’s two-run home run, tying the game at 4-4.Utah got out of a jam in the fifth, forcing ASU into leaving bases loaded, and both teams kept runners off the bases in the late innings before the Sun Devils broke through in the eighth for the win.Utah and ASU play game two of the series on Saturday, April 21, at 7:30 p.m. MDT (6:30 p.m. PT/MST). Tags: Baseball/Pac 12/Utah Utes Written by April 21, 2018 /Sports News – Local Gulden Homers as Utah Baseball Falls to Arizona State, 7-4last_img read more

Kringlen, Hale and Clawson back Wood’s gem in 9-1 win over San Diego

first_img FacebookTwitterLinkedInEmailPROVO, Utah – Keaton Kringlen’s two-run homer and Jordan Wood’s excellent outing helped BYU baseball to a 9-1 win over San Diego Thursday night at Larry H. Miller Field.“Tonight felt like Cougar baseball,” BYU head coach Mike Littlewood said. “Wood did a great job and we had quality at-bats. We played great defense with a couple double-plays and didn’t make mistakes.”In addition to Kringlen’s first dinger this season, Brock Hale and David Clawson had three hits apiece as Wood (3-4) threw eight innings and allowed just one run on three hits, with six strikeouts.The Cougars got back to .500 in the league (8-8 West Coast Conference, 19-17 overall) while the Toreros fell to 18-24, 7-12 (WCC).The BYU bats produced a first-inning run, with Brennon Anderson scoring from second on Hale’s single up the middle. Anderson reached with a single through the 5.5 hole and advanced to second on a wild pitch.In the third, the Toreros drilled a triple and a double to tie the game at 1-1. Kringlen erased the tie with a two-run bomb on a first-pitch curveball in the bottom half. His shot cleared the left-center fence and plated Hale, who singled.Nate Favero and Clawson drove in a run each in the fifth to extend BYU’s lead to 5-1. Favero lined a single through the left side to plate Kringlen and Clawson brought him around with a triple down the right field line.Hale’s third single up the middle scored Daniel Schneemann in the sixth to give the Cougars a 6-1 lead. Kringlen bunted runners to second and third, and a throwing error from the San Diego first baseman allowed Brian Hsu to hustle home. Kyle Dean added to the damage with a double into the left field corner to score two more, and BYU led 9-1.Blake Inouye closed the game on the mound for the Cougars, firing one scoreless inning.BYU plays Friday (6 p.m., Harry Potter Night) and Saturday to finish the series against San Diego.​ Written by April 26, 2018 /Sports News – Local Kringlen, Hale and Clawson back Wood’s gem in 9-1 win over San Diego Tags: Baseball/BYU Cougars/WCC Robert Lovelllast_img read more

Scoreboard roundup — 7/6/18

first_imgJuly 7, 2018 /Sports News – National Scoreboard roundup — 7/6/18 Written by FacebookTwitterLinkedInEmailiStock/Thinkstock(NEW YORK) — Here are the scores from Friday’s sports events:INTERLEAGUEN.Y. Mets 5, Tampa Bay 1L.A. Angels 3, L.A. Dodgers 2Colorado 7, Seattle 1AMERICAN LEAGUEToronto 6, N.Y. Yankees 2Detroit 3, Texas 1Cleveland 10, Oakland 4Houston 11, Chicago White Sox 4Minnesota 6, Baltimore 2Boston 10, Kansas City 5NATIONAL LEAGUECincinnati 3, Chicago Cubs 2Washington 3, Miami 2Philadelphia 17, Pittsburgh 5Milwaukee 5, Atlanta 4Arizona 3, San Diego 1San Francisco 3, St. Louis 2WOMEN’S NATIONAL BASKETBALL ASSOCIATIONSeattle 95, Atlanta 86Copyright © 2018, ABC Radio. All rights reserved.center_img Beau Lundlast_img read more

Colorado State-Pueblo Routs Dixie State in Season Opener

first_img Brad James FacebookTwitterLinkedInEmailPUEBLO, Colo.-The Colorado State-Pueblo Thunderwolves looked every bit the Rocky Mountain Athletic Conference champion favorites that coaches around the league thought they were in a 56-14 rout of Dixie State Saturday in RMAC football action.The Thunderwolves amassed 573 yards of offense, including 496 on the ground as they built a 21-0 lead early in the 2nd Quarter and never looked back.CSU-Pueblo star tailbacks Austin Micci (7 car, 177 yards, 3 TD’s) and Marche Dennard (5 car, 132 yards, 2 TD’s) helped the Thunderwolves average an astounding 11.3 yards per carry on the evening.Additionally, receiver Cole Forsgren (2 rec, 75 yards, TD) helped the Thunderwolves have some modicum of balance offensively.In defeat, the Trailblazers were led by Xavier Smith (3 rec, 76 yards, TD) who hauled in a 23-yard scoring pass from quarterback Trent Darms. Shiloh Pritchard also returned an interception 36 yards for a score for Dixie State. Tags: Austin Micci/Cole Forsgren/CSU-Pueblo Football/Marche Dennard/RMAC/Shiloh Pritchard/Trent Darms/Xavier Smith September 1, 2018 /Sports News – Local Colorado State-Pueblo Routs Dixie State in Season Opener Written bylast_img read more