Stability of ice rises and uncoupled marine ice sheets

first_imgAn analysis of the linear stability of marine ice sheets uncoupled from associated ice shelves is presented. The principal feature is a zero eigenvalue associated with infinitesimal shifts along the line of neutral equilibrium in phase space, termed the “equilibrium manifold”. A finite-difference scheme is constructed which respects this stability property. The zero eigenvalue appears to allow modelling errors to accumulate rather than dissipate as occurs in land-based ice sheets. The practical significance of this is that even rather fine spatial grids may allow substantial numerical error to accumulate.last_img

Topographic and hydrological controls on Subglacial Lake Ellsworth, West Antarctica

first_imgSubglacial Lake Ellsworth (SLE) was identified using reconnaissance data collected in the 1970s, here we present more detailed surveys. SLE lies beneath 3.2 km of ice in a subglacial valley in West Antarctica. It has an area of only similar to 18 km(2), is dissimilar to the large tectonically-controlled lakes beneath East Antarctica and is a strong candidate for in situ exploration. Our analysis indicates that the ice above SLE is floating on a fluid whose density is 950-1013 kg m(-3). This could indicate freshwater, but certainly precludes seawater, or high salt, acid, or clathrate content. The water in the lake is unlikely to be produced solely by local melt; it is more likely delivered via subglacial drainage. Our surveys show no identifiable hydrological barrier to outflow, meaning SLE is effectively full; new water entering the lake is likely balanced by outflow, which would drain into another lake that we have also identified.last_img read more

Individual variation in migratory movements and winter behaviour of Iberian Lesser Kestrels Falco naumanni revealed by geolocators

first_imgThe population decline of the Lesser Kestrel Falco naumanni has been the subject of studies across its Western Palaearctic breeding range, but little is known about its use of pre-migratory areas or African wintering quarters. We used geolocators to describe the temporal and spatial patterns of Portuguese Lesser Kestrel migration and wintering behaviour. Data on the complete migration were obtained from four individuals and another three provided further information. Prior to southward migration, Lesser Kestrels showed two different behaviours: northward-orientated movements to Spain and movements in the proximity of the breeding area. Autumn migration took place mostly in late September; spring departures occurred mainly in the first half of February. Wintering grounds included Senegal, Mauritania and Mali, with individuals overlapping considerably in Senegal. Movements registered within the wintering grounds suggest itinerant behaviour in relation to local flushes of prey. During spring migration, birds crossed the Sahara Desert through Mauritania, Western Sahara and Morocco before passing over the Mediterranean to reach Portugal. Autumn migration lasted 4.8 ± 1.1 days, and spring migration lasted 4.1 ± 0.3 days. The mean daily flight range varied between approximately 300 and 850 km for an entire journey of around 2500 km. Effective protection of roosting sites in both pre-migratory and wintering areas and maintaining grasshopper populations in Sahelian wintering quarters appear crucial in preserving this threatened migratory raptor across its African–Eurasian flyway. There was no evidence of any deleterious effects of fitting birds with loggers.last_img read more

The Southern Ocean ecosystem under multiple climate change stresses – an integrated circumpolar assessment

first_imgA quantitative assessment of observed and projected environmental changes in the Southern Ocean (SO) with a potential impact on the marine ecosystem shows: (1) large proportions of the SO are and will be affected by one or more climate change processes; areas projected to be affected in the future are larger than areas that are already under environmental stress, (2) areas affected by changes in sea-ice in the past and likely in the future are much larger than areas affected by ocean warming. The smallest areas (<1% area of the SO) are affected by glacier retreat and warming in the deeper euphotic layer. In the future, decrease in the sea-ice is expected to be widespread. Changes in iceberg impact resulting from further collapse of ice-shelves can potentially affect large parts of shelf and ephemerally in the off-shore regions. However, aragonite undersaturation (acidification) might become one of the biggest problems for the Antarctic marine ecosystem by affecting almost the entire SO. Direct and indirect impacts of various environmental changes to the three major habitats, sea-ice, pelagic and benthos and their biota are complex. The areas affected by environmental stressors range from 33% of the SO for a single stressor, 11% for two and 2% for three, to <1% for four and five overlapping factors. In the future, areas expected to be affected by 2 and 3 overlapping factors are equally large, including potential iceberg changes, and together cover almost 86% of the SO ecosystem.last_img read more

Impact of abrupt sea ice loss on Greenland water isotopes during the last glacial period

first_imgGreenland ice cores provide excellent evidence of past abrupt climate changes. However, there is no universally accepted theory of how and why these Dansgaard–Oeschger (DO) events occur. Several mechanisms have been proposed to explain DO events, including sea ice, ice shelf buildup, ice sheets, atmospheric circulation, and meltwater changes. DO event temperature reconstructions depend on the stable water isotope (δ18O) and nitrogen isotope measurements from Greenland ice cores: interpretation of these measurements holds the key to understanding the nature of DO events. Here, we demonstrate the primary importance of sea ice as a control on Greenland ice core δ18O: 95% of the variability in δ18O in southern Greenland is explained by DO event sea ice changes. Our suite of DO events, simulated using a general circulation model, accurately captures the amplitude of δ18O enrichment during the abrupt DO event onsets. Simulated geographical variability is broadly consistent with available ice core evidence. We find an hitherto unknown sensitivity of the δ18O paleothermometer to the magnitude of DO event temperature increase: the change in δ18O per Kelvin temperature increase reduces with DO event amplitude. We show that this effect is controlled by precipitation seasonality.last_img read more

Invasive non‐native species likely to threaten biodiversity and ecosystems in the Antarctic Peninsula region

first_imgThe Antarctic is considered to be a pristine environment relative to other regions of the Earth, but it is increasingly vulnerable to invasions by marine, freshwater and terrestrial non‐native species. The Antarctic Peninsula region (APR), which encompasses the Antarctic Peninsula, South Shetland Islands and South Orkney Islands, is by far the most invaded part of the Antarctica continent. The risk of introduction of invasive non‐native species to the APR is likely to increase with predicted increases in the intensity, diversity and distribution of human activities. Parties that are signatories to the Antarctic Treaty have called for regional assessments of non‐native species risk. In response, taxonomic and Antarctic experts undertook a horizon scanning exercise using expert opinion and consensus approaches to identify the species that are likely to present the highest risk to biodiversity and ecosystems within the APR over the next 10 years. One hundred and three species, currently absent in the APR, were identified as relevant for review, with 13 species identified as presenting a high risk of invading the APR. Marine invertebrates dominated the list of highest risk species, with flowering plants and terrestrial invertebrates also represented; however, vertebrate species were thought unlikely to establish in the APR within the 10 year timeframe. We recommend (a) the further development and application of biosecurity measures by all stakeholders active in the APR, including surveillance for species such as those identified during this horizon scanning exercise, and (b) use of this methodology across the other regions of Antarctica. Without the application of appropriate biosecurity measures, rates of introductions and invasions within the APR are likely to increase, resulting in negative consequences for the biodiversity of the whole continent, as introduced species establish and spread further due to climate change and increasing human activity.last_img read more

Storm Chasers Edge Bees

first_img FacebookTwitterLinkedInEmail(Omaha, NE)  —  The Bees fell to the Storm Chasers 5-4 last night in a rain-shortened game in Omaha.The Bees scored three times in the second inning but couldn’t keep pace.  The series continues tonight in Omaha. Written by Tags: Baseball/PCL/Salt Lake Bees Robert Lovell August 7, 2018 /Sports News – Local Storm Chasers Edge Beeslast_img

There’s really not much proof probiotics work: Study

first_img Written by September 6, 2018 /Sports News – National There’s really not much proof probiotics work: Study Beau Lundcenter_img FacebookTwitterLinkedInEmailiStock/ThinkstockBY: DR. NICKY MEHTANI(NEW YORK) — Over the past decade, probiotic dietary supplements have turned into a multi-million dollar industry, taken by almost 4 million adults and prescribed by up to 60 percent of health care providers. Yet the scientific community has known little about whether or not they actually work.But this is likely to change, thanks to two back-to-back studies published Thursday in Cell, which cast further doubt on the benefits of the highly-commercialized probiotic products.“People have thrown a lot of support to probiotics, even though the literature underlying our understanding of them is very controversial,” Eran Elinav, senior author and an immunologist at the Weizmann Institute of Science in Israel, said in a press release, “we wanted to determine whether probiotics such as the ones you buy in the supermarket do colonize the gastrointestinal tract like they’re supposed to, and then whether these probiotics are having any impact on the human host.”What are probiotics?Probiotics are live microorganisms, often marketed and sold in foods (such as yogurt) and dietary supplements. While most people think of bacteria as “bad” (causing disease), many bacteria serve vital roles in keeping us alive. Count among them the bacteria that line our digestive tracts and help break down and absorb food — actually fighting off infections.Probiotics are intended to mimic and strengthen the effects of these “good” bacteria, touted as bacteria that can “rebalance” your system. Claims from the probiotic industry range run from preventing the common cold to treating allergic disorders such as atopic dermatitis. Since they are marketed as dietary supplements, not drugs, probiotics have never been approved for the prevention or treatment of any health conditions by the U.S. Food and Drug Administration (FDA) — they don’t need to be, by law.Based on these new studies, the road to health claims seems rockierWhile the vast majority of prior studies on probiotics have relied on analyzing stool to get an idea of the person’s gut microbiome, Elinav’s research team actually looked, with an endoscope, at bacteria present in the colon itself — both in mice and in humans.After 25 healthy volunteers ate a generic probiotic with 11 strains of “good” bacteria, they all had probiotic bacteria in their stool, which the research team expected. But when doctors did the endoscopy to evaluate their intestines, they found that probiotics had only actually “stuck” and grown in a few people.“Although all of our probiotic-consuming volunteers showed probiotics in their stool, only some of them showed them in their gut, which is where they need to be,” Eran Segal, a computational biologist at the Weizmann Institute, said in a press release.If the probiotics aren’t in the colon, it’s hard to argue that they are doing any good.One of the most common uses of probiotics is to counteract diarrhea that sometimes comes after antibiotic use. Antibiotics do kill off disease-causing “bad” bacteria, but in the process, many “good” bacteria in the colon are sacrificed as well — thus diarrhea and poor absorption of key nutrients from food. That’s why some doctors tell their patients to take probiotics with a course of antibiotics or right afterward, to prevent the complete loss of “good bacteria.” These providers believe that, while not always 100 percent effective, the use of probiotics in healthy adults is at least relatively risk-free.The researchers asked volunteers to finish a course of broad-spectrum antibiotics and looked at their intestines after they’d also taken probiotics. The probiotics did effectively “colonize” their gastrointestinal tracts, but they did so at the expense of the normal gut microbiome, delaying the return to its normal, pre-antibiotic state by several months.It’s not proof of harm, but it is known that lower microbial diversity after antibiotics can lead to increased susceptibility to a myriad of chronic and infectious diseases. Thus, the low level of diversity permitted by probiotic colonization and the ensuing delay they cause in returning a person’s gut microbiome to the pre-antibiotic state suggests that probiotics may not be harmless, as most seem to think.Dr. Nicky Mehtani is an internal medicine physician and part of the ABC News Medical Unit.Copyright © 2018, ABC Radio. All rights reserved.last_img read more

Southern Utah uses 2nd-half run to beat San Jose State 66-59

first_img Associated Press Written by Tags: SUU Thunderbirds Basketball FacebookTwitterLinkedInEmailSAN JOSE, Calif. (AP) — Cameron Oluyitan scored 15 points, Dwayne Morgan added 13 and Southern Utah rallied with 12 straight points to beat San Jose State 66-59 on Saturday night.The Thunderbirds (2-0) trailed 51-44 before going on a 12-0 run to lead 56-51 with 6:05 to go. Southern Utah pushed to lead to 61-53 on Ivan Madunic’s dunk with 2:47 to go and led by no less than six from there.The first half had 10 lead changes and ended with a 31-all tie. The Spartans (1-1) took control early in the second half and led 48-41 after a 14-4 run.Craig LeCesne had 15 points and Seneca Knight added 10 for San Jose State.Southern Utah made just 3 of 18 from 3-point range but made 25 of 50 from inside the arc. The Thunderbirds had a 22-2 edge in points off turnovers, committing only 10 turnovers to San Jose State’s 19. November 10, 2018 /Sports News – Local Southern Utah uses 2nd-half run to beat San Jose State 66-59last_img read more

Merrill’s 23 lifts Utah St. over Lobos 91-83 in MWC tourney

first_img FacebookTwitterLinkedInEmailLAS VEGAS (AP) — Sam Merrill had 23 points as Utah State beat New Mexico 91-83 in the quarterfinals of the Mountain West Conference Tournament on Thursday night. Tags: Mountain West/Mountain West Tournament/Sam Merrill/Utah State Aggies Basketball The second-seeded Aggies will now play No. 3 seed Fresno State in the Mountain West semifinals Friday at 9:30 PM MDT in Las Vegas. Merrill shot 11 for 12 from the foul line. He added nine assists. Neemias Queta had 16 points and six blocks for Utah State (26-6). Justin Bean added 14 points and 15 rebounds. Diogo Brito had 14 points for Utah State. Written by Vance Jackson had 25 points for the Lobos (14-18). Corey Manigault added 16 points. Anthony Mathis had 14 points and five steals. March 14, 2019 /Sports News – Local Merrill’s 23 lifts Utah St. over Lobos 91-83 in MWC tourney Associated Presslast_img read more