Decadal Ocean Forcing and Antarctic Ice Sheet Response: Lessons from the Amundsen Sea

first_imgMass loss from the Antarctic Ice Sheet is driven by changes at the marine margins. In the Amundsen Sea, thinning of the ice shelves has allowed the outlet glaciers to accelerate and thin, resulting in inland migration of their grounding lines. The ultimate driver is often assumed to be ocean warming, but the recent record of ocean temperature is dominated by decadal variability rather than a trend. The distribution of water masses on the Amundsen Sea continental shelf is particularly sensitive to atmospheric forcing, while the regional atmospheric circulation is highly variable, at least in part because of the impact of tropical variability. Changes in atmospheric circulation force changes in ice shelf melting, which drive step-wise movement of the grounding line between localized high points on the bed. When the grounding line is located on a high point, outlet glacier flow is sensitive to atmosphere-ocean variability, but once retreat or advance to the next high point has been triggered, ocean circulation and melt rate changes associated with the evolution in geometry of the sub-ice-shelf cavity dominate, and the sensitivity to atmospheric forcing is greatly reduced.last_img read more

Evidence of marine ice-cliff instability in Pine Island Bay from iceberg-keel plough marks

first_imgMarine ice-cliff instability (MICI) processes could accelerate future retreat of the Antarctic Ice Sheet if ice shelves that buttress grounding lines more than 800 metres below sea level are lost1, 2. The present-day grounding zones of the Pine Island and Thwaites glaciers in West Antarctica need to retreat only short distances before they reach extensive retrograde slopes3, 4. When grounding zones of glaciers retreat onto such slopes, theoretical considerations and modelling results indicate that the retreat becomes unstable (marine ice-sheet instability) and thus accelerates5. It is thought1, 2 that MICI is triggered when this retreat produces ice cliffs above the water line with heights approaching about 90 metres. However, observational evidence confirming the action of MICI has not previously been reported. Here we present observational evidence that rapid deglacial ice-sheet retreat into Pine Island Bay proceeded in a similar manner to that simulated in a recent modelling study1, driven by MICI. Iceberg-keel plough marks on the sea-floor provide geological evidence of past and present iceberg morphology, keel depth6 and drift direction7. From the planform shape and cross-sectional morphologies of iceberg-keel plough marks, we find that iceberg calving during the most recent deglaciation was not characterized by small numbers of large, tabular icebergs as is observed today8, 9, which would produce wide, flat-based plough marks10 or toothcomb-like multi-keeled plough marks11, 12. Instead, it was characterized by large numbers of smaller icebergs with V-shaped keels. Geological evidence of the form and water-depth distribution of the plough marks indicates calving-margin thicknesses equivalent to the threshold that is predicted to trigger ice-cliff structural collapse as a result of MICI13. We infer rapid and sustained ice-sheet retreat driven by MICI, commencing around 12,300 years ago and terminating before about 11,200 years ago, which produced large numbers of icebergs smaller than the typical tabular icebergs produced today. Our findings demonstrate the effective operation of MICI in the past, and highlight its potential contribution to accelerated future retreat of the Antarctic Ice Sheet.last_img read more

A 2018 Horizon Scan of Emerging Issues for Global Conservation and Biological Diversity

first_imgThis is our ninth annual horizon scan to identify emerging issues that we believe could affect global biological diversity, natural capital and ecosystem services, and conservation efforts. Our diverse and international team, with expertise in horizon scanning, science communication, as well as conservation science, practice, and policy, reviewed 117 potential issues. We identified the 15 that may have the greatest positive or negative effects but are not yet well recognised by the global conservation community. Themes among these topics include new mechanisms driving the emergence and geographic expansion of diseases, innovative biotechnologies, reassessments of global change, and the development of strategic infrastructure to facilitate global economic priorities.last_img read more

Pan-Arctic surface ozone: modelling vs. measurements

first_imgWithin the framework of the International Arctic Systems for Observing the Atmosphere (IASOA), we report a modelling-based study on surface ozone across the Arctic. We use surface ozone from six sites – Summit (Greenland), Pallas (Finland), Barrow (USA), Alert (Canada), Tiksi (Russia), and Villum Research Station (VRS) at Station Nord (North Greenland, Danish realm) – and ozone-sonde data from three Canadian sites: Resolute, Eureka, and Alert. Two global chemistry models – a global chemistry transport model (parallelised-Tropospheric Offline Model of Chemistry and Transport, p-TOMCAT) and a global chemistry climate model (United Kingdom Chemistry and Aerosol, UKCA) – are used for model data comparisons. Remotely sensed data of BrO from the GOME-2 satellite instrument and ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) at Eureka, Canada, are used for model validation. The observed climatology data show that spring surface ozone at coastal sites is heavily depleted, making ozone seasonality at Arctic coastal sites distinctly different from that at inland sites. Model simulations show that surface ozone can be greatly reduced by bromine chemistry. In April, bromine chemistry can cause a net ozone loss (monthly mean) of 10–20 ppbv, with almost half attributable to open-ocean-sourced bromine and the rest to sea-ice-sourced bromine. However, the open-ocean-sourced bromine, via sea spray bromide depletion, cannot by itself produce ozone depletion events (ODEs; defined as ozone volume mixing ratios, VMRs, < 10 ppbv). In contrast, sea-ice-sourced bromine, via sea salt aerosol (SSA) production from blowing snow, can produce ODEs even without bromine from sea spray, highlighting the importance of sea ice surface in polar boundary layer chemistry. Modelled total inorganic bromine (BrY) over the Arctic sea ice is sensitive to model configuration; e.g. under the same bromine loading, BrY in the Arctic spring boundary layer in the p-TOMCAT control run (i.e. with all bromine emissions) can be 2 times that in the UKCA control run. Despite the model differences, both model control runs can successfully reproduce large bromine explosion events (BEEs) and ODEs in polar spring. Model-integrated tropospheric-column BrO generally matches GOME-2 tropospheric columns within ∼ 50 % in UKCA and a factor of 2 in p-TOMCAT. The success of the models in reproducing both ODEs and BEEs in the Arctic indicates that the relevant parameterizations implemented in the models work reasonably well, which supports the proposed mechanism of SSA production and bromide release on sea ice. Given that sea ice is a large source of SSA and halogens, changes in sea ice type and extent in a warming climate will influence Arctic boundary layer chemistry, including the oxidation of atmospheric elemental mercury. Note that this work dose not necessary rule out other possibilities that may act as a source of reactive bromine from the sea ice zone.last_img read more

Resilience in Greenland intertidal Mytilus: The hidden stress defense

first_imgThe Arctic is experiencing particularly rapid rates of warming, consequently invasive boreal species are now able to survive the less extreme Arctic winter temperatures. Whilst persistence of intertidal and terrestrial species in the Arctic is primarily determined by their ability to tolerate the freezing winters, air temperatures in the Arctic summer can reach 36 °C in the intertidal, which is beyond the upper thermal limits of many marine species. This is normally lethal for the conspicuous ecosystem engineer Mytilus edulis. Transcriptomic analyses were undertaken on both in situ collected and experimentally warmed animals to understand whether M. edulis is able to tolerate these very high summer temperatures. Surprisingly there was no significant enrichment for Gene Ontology terms (GO) when comparing the inner and outer fjord intertidal animals with outer fjord subtidal (control) animals, representing animals collected at 27 °C, 19 °C and 3 °C respectively. This lack of differentiation indicated a wide acclimation ability in this species. Conversely, significant enrichment for processes such as signal transduction, cytoskeleton and cellular protein modification was identified in the expression profiles of the 22 °C and 32 °C experimentally heated animals. This difference in gene expression between in situ collected and experimentally warmed animals was almost certainly due to the former being acclimated to a fluctuating, but predictable, temperature regime, which has increased their thermal tolerances. Interestingly, there was no evidence for enrichment of the classical cellular stress response in any of the animals sampled. Identification of a massive expansion of the HSPA12 heat shock protein 70 kDa gene family presented the possibility of these genes acting as intertidal regulators underpinning thermal resilience. This expansion has resulted in a modified cellular stress response, as an evolutionary adaptation to the rigour of the invasive intertidal life style. Thus, M. edulis appear to have considerable capacity to withstand the current rates of Arctic warming, and the very large attendant thermal variation.last_img read more

US women’s soccer team honors Stoneman Douglas victim

first_img FacebookTwitterLinkedInEmailABC News(ORLANDO, Fla.) — By everyone’s account, Alyssa Alhadeff, a 14-year-old student and member of the Marjory Stoneman Douglas High girls soccer team, was bound for great things in life, on and off the field.“Alyssa took every second of her life and did something with it,” her mother, Lori Alhadeff, said. “She had the fire to fight. She had the spirit.”Alyssa Alhadeff was one of 17 students and teachers gunned down Feb. 14 at the Parkland, Florida, school. A former student was indicted this week on 34 counts in the massacre, including first-degree premeditated murder.According to Lori Alhadeff, a soccer player herself, Alyssa Alhadeff started playing soccer at the age of 3 and by age 8, was playing competitively.She said her daughter, who played center mid, was on track to play soccer in college and had dreamed of one day being on the U.S. women’s national soccer team.“She loved the sport. … I always thought someday that she would be on the women’s national soccer team,” Lori Alhadeff said. “She aspired for that greatness. … She was probably one of the smallest on the team but the fiestiest.”She said Alyssa Alhadeff was also a huge fan of Alex Morgan, a forward on the U.S. women’s national soccer team. The two had even met six years ago, Lori Alhadeff said, and Morgan had signed not only Alyssa Alhadeff’s book but also her cellphone.Her father, Ilan Alhadeff, said that after her death, her friend Jamie Morris tweeted Morgan to let her know how much Alyssa Alhadeff had loved her and the women’s soccer team. Morgan reached out to the friend, Ilan Alhadeff said, and invited the family and the school’s team to a game.On Wednesday, the Alhadeffs and the Stoneman Douglas girls soccer team traveled to Orlando to watch the U.S. women’s national soccer team play against England. Before the game, a moment of silence was held for Alyssa Alhadeff and her picture was posted on the Jumbotron. Her teammates stood in the stands, holding posters bearing her pictures and messages of friendship.The family and team were also each presented with a national team jersey, complete with Alyssa Alhadeff’s name on it and her number: 8. After the game, members of the U.S. soccer team signed the jerseys for the girls.Laurie Thomas, the girls’ soccer team coach, said that after the shootings, the team had gotten together for days, focused on keeping the memory of their friend and team captain alive.“She was the voice of our team,” Thomas said of Alyssa Alhadeff. “She was a leader, not just by what she said, but also by the character. She lead the team on and off the field.”Lori Alhadeff said the school team as well as her sons had felt the love, compassion and strength from the U.S. women’s team.“It has literally taken my breath away,” she said of the day and experience. “Alyssa would be ecstatic. She would’ve been just jumping for joy, crying and laughing.”Ilan Alhadeff said his daughter would have loved to share the moment with her family, friends and teammates.“It would have been the best day ever,” he said. “It’s just amazing, the overwhelming support. … Helping not just us, but our entire city heal.”Copyright © 2018, ABC Radio. All rights reserved. Beau Lund Written bycenter_img March 9, 2018 /Sports News – National US women’s soccer team honors Stoneman Douglas victimlast_img read more

Runnin’ Utes Add Lahat Thioune to 2018-19 Roster

first_img Written by Tags: Lahat Thioune/Men’s Basketball/Utah Utes FacebookTwitterLinkedInEmailSALT LAKE CITY – Utah head men’s basketball coach Larry Krystkowiak announced today that Lahat Thioune has signed a national letter of intent to play for the Runnin’ Utes beginning in the fall of 2018.Thioune joins a 2017-18 recruiting class that included the additions of Timmy Allen (Mesa, Ariz.), Riley Battin (Oak Park, Calif.), Naseem Gaskin (Oakland, Calif.) and Charles Jones, Jr. (Portland, Ore.), which all signed national letters of intent this past November.“We are excited to have Lahat join our program,” said Krystkowiak. “With his ability to run the floor, block shots and rebound, he brings a great deal of balance to this year’s class. Lahat has a motor and upside that we are excited to coach, but more importantly he’s a phenomenal young man with a great attitude that our fans and community will enjoy.”Thioune, who originally hails from Dekar, Senegal, will attend the U after playing high school basketball at Florida Prep (Melbourne, Fla.). A 6-10, 210 pound forward, Thioune helped lead his high school squad to a 25-6 overall record and a perfect 13-0 mark in division play, while also guiding the team to the FHSAA Class 2A state semifinals. He went on to average 14 points and eight rebounds per game this past season. Robert Lovell April 11, 2018 /Sports News – Local Runnin’ Utes Add Lahat Thioune to 2018-19 Rosterlast_img read more

Utah’s Tomlinson Holds His Own After Day 1 of competition

first_imgMay 15, 2018 /Sports News – Local Utah’s Tomlinson Holds His Own After Day 1 of competition Tags: Blake Tomlinson/Ryan Han/UC Davis/Utah Golf Written by Brad James FacebookTwitterLinkedInEmailSTOCKTON, Calif.-Monday, as the NCAA Stockton men’s golf regional commenced at the University of Pacific, the lone Ute to qualify for postseason play fared well all things considered.Utah men’s golf freshman phenom Blake Tomlinson is currently tied for 13th place headed into Tuesday competition.The prodigious freshman posted three birdies and only one bogey Monday, shooting 1-under par on the front nine and then another 1-under par on the back nine holes.Tomlinson also netted the fourth-lowest score of the 10 individuals in action this week. He trails UC Davis’ Ryan Han by three strokes. Han carded a 5-under par (67) to lead in individual competition overall.Tomlinson will play another 18 holes during second-round play and is scheduled to tee off at 10:42 am MDT Tuesday.last_img read more

New UVU Men’s Soccer Recruit Named As Gatorade Player of the Year

first_img Written by Brad James Tags: Carter Johnson/Gatorade/Lucas Cawley/Thomas Loomis/UVU Men’s Soccer June 11, 2018 /Sports News – Local New UVU Men’s Soccer Recruit Named As Gatorade Player of the Year FacebookTwitterLinkedInEmailCHICAGO-Per an announcement Monday, incoming Utah Valley men’s soccer player Carter Johnson has been named as Gatorade’s Utah Boys Soccer Player of the year, which is in its 33rd year of honoring the best high school athletes in the nation.Johnson, a product of Herriman High School, received an award honoring outstanding athletic excellence as well as high standards of academic achievement and exemplary character demonstrated both on and off the field.The 5’11” 165-pound senior amassed 21 goals and 22 assists this past season as he led the Mustangs to the Class 6-A state finals. Johnson was named Mr. Soccer by the Deseret News and is a two-time first team all-state and all-region selection.Johnson maintained a 4.0 GPA in the classroom and was named as his graduating class’s valedictorian.Other Wolverines on the roster to be named as Gatorade Boys Soccer player of the year recipients include Lucas Cawley and Thomas Loomis.last_img read more

Utah Men’s Tennis Announces 2018-19 Schedule

first_img FacebookTwitterLinkedInEmailSALT LAKE CITY-Friday, Utah men’s tennis announced its schedule for 2018-19. This is highlighted by 15 home matches at the Eccles Tennis Center.The Utes’ fall season consists of three tournaments, commencing in October. These are match-ups at the ITA Regionals October 15-19 at Las Vegas, The Gopher Invitational November 2-4 at Minneapolis and the Loyola Marymount Invitational November 9-11 at Los Angeles.In 2019, the Utes will face off against bitter rival Brigham Young January 12 at Provo with their home opener occurring January 19 as they host Weber State and Montana State.Pac-12 play commences March 8 and 9 as they host UCLA and USC respectively.The Utes’ home schedule concludes April 6 and 7 as they square off against California and Stanford.The regular season concludes with the Utes visiting Tucson, Ariz. and Tempe, Ariz. April 12 and 13 against Arizona and Arizona State, respectively.The Pac-12 tournament runs from April 23-27 at Ojai, Calif. as the NCAA regionals commence May 10. Tags: Arizona/Arizona State/BYU/California/Eccles Tennis Center/Montana State/Stanford/UCLA/USC/Utah Men’s Tennis/Weber State August 10, 2018 /Sports News – Local Utah Men’s Tennis Announces 2018-19 Schedule Written by Brad Jameslast_img read more

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