Large losses of total ozone in Antarctica reveal seasonal ClOx/NOx interaction

first_imgRecent attempts1,2 to consolidate assessments of the effect of human activities on stratospheric ozone (O3) using one-dimensional models for 30° N have suggested that perturbations of total O3 will remain small for at least the next decade. Results from such models are often accepted by default as global estimates3. The inadequacy of this approach is here made evident by observations that the spring values of total O3 in Antarctica have now fallen considerably. The circulation in the lower stratosphere is apparently unchanged, and possible chemical causes must be considered. We suggest that the very low temperatures which prevail from midwinter until several weeks after the spring equinox make the Antarctic stratosphere uniquely sensitive to growth of inorganic chlorine, ClX, primarily by the effect of this growth on the NO2/NO ratio. This, with the height distribution of UV irradiation peculiar to the polar stratosphere, could account for the O3 losses observed.last_img read more

Muscle fibre types and metabolism in post-larval and adult stages of notothenioid fish

first_imgA histochemical study was carried out on muscle fibre types in the myotomes of post-larval and adult stages of seven species of notothenioid fish. There was little interspecific variation in the distribution of muscle fibre types in post-larvae. Slow fibres (diameter range 15–60 μm) which stained darkly for succinic dehydrogenase activity (SDHase) formed a superficial layer 1–2 fibres thick around the entire lateral surface of the trunk. In all species a narrow band of very small diameter fibres (diameter range 5–62 μm), with only weak staining activity, occurred between the skin and slow fibre layer. These have the characteristics of tonic fibres found in other teleosts. The remainder of the myotome was composed of fast muscle fibres (diameter range 9–75 μm), which stain weakly for SDHase, α-glycerophosphate dehydrogenase, glycogen and lipid. Slow muscle fibres were only a minor component of the trunk muscles of adult stages of the pelagic species Champsocephalus gunnari and Pseudochaenichthys georgianus, consistent with a reliance on pectoral fin swimming during sustained activity. Of the other species examined only Psilodraco breviceps and Notothenia gibberifrons had more than a few percent of slow muscle in the trunk (20%–30% in posterior myotomes), suggesting a greater involvement of sub-carangiform swimming at cruising speeds. The ultrastructure of slow fibres from the pectoral fin adductor and myotomal muscles of a haemoglobinless (P. georgianus) and red-blooded species (P. breviceps), both active swimmers, were compared. Fibres contained loosely packed, and regularly shaped myofibrils numerous mitochondria, glycogen granules and occasional lipid droplets. Mitochondria occupied >50% of fibre volume in the haemoglobinless species P. georgianus, each myofibril was surrounded by one or more mitochondria with densely packed cristae. No significant differences, however, were found in mean diameter between fibres from red-blooded and haemoglobinless species. The activities of key enzymes of energy metabolism were determined in the slow (pectoral) and fast (myotomal) muscles of N. gibberifrons. In contrast to other demersal Antarctic fish examined, much higher glycolytic activities were found in fast muscle fibres, probably reflecting greater endurance during burst swimming.last_img read more

Thermomechanical coupling of ice flow with the bedrock

first_imgTwo aspects of thermal coupling with bedrock are considered: the coupled time-dependent problem of co-evolving temperatures in lithosphere and ice; and the influence of basal topography on steady temperature distribution within the ice. The nature of the time-dependent coupling is found to depend on the horizontal velocity. As has been suggested, there is a cooling of steady temperatures on bedrock highs, but this is phase-shifted downstream when horizontal velocities increase. This observation may have consequences for geomorphological processes such as plucking and protection. The effect of bedrock channelling on steady temperature is considered. The positive anomaly of basal temperature due to channelling increases as the transverse wavelength decreases, but not monotonically, reaching a plateau when both the wavelengths of the basal topography are around 100 km.last_img read more

Global climate drives southern right whale (Eubalaena australis) population dynamics

first_imgSea surface temperature (SST) time-series from the southwest Atlantic and the El Niño 4 region in the western Pacific were compared to an index of annual calving success of the southern right whale (Eubalaena australis) breeding in Argentina. There was a strong relationship between right whale calving output and SST anomalies at South Georgia in the autumn of the previous year and also with mean El Niño 4 SST anomalies delayed by 6 years. These results extend similar observations from other krill predators and show clear linkages between global climate signals and the biological processes affecting whale population dynamics.last_img

Modeling polar ionospheric effects during the October-November 2003 solar proton events

first_imgAt Ny Ålesund, Svalbard (78°54′N, 11°53′E, L ∼ 18), a narrowband VLF receiver was used to monitor the behavior of the amplitude of several high-power transmitters located in the Northern Hemisphere under the influence of the solar proton events (SPE) of October/November 2003. We have used Sodankylä ion chemistry (SIC) atmospheric model profiles calculated at the midpoint location of the propagation paths in the northern wintertime polar region to investigate the radio propagation properties of several high-latitude paths. Different paths showed different responses to the proton precipitation, but propagation modeling was broadly able to account for most of the positive and negative responses observed. Using the SIC-based electron density profiles, we have been able to develop models of ionospheric effective height (h′) and sharpness (β) in order to describe the D region behavior as a function of proton flux, extending previous work which reported β and h′ values as functions of the X-ray flux from solar flares. As a result of these models, our understanding of VLF propagation influenced by SPEs is such that VLF observations might be used to predict changes in the ionospheric D region electron density profiles during other particle precipitation events.last_img read more

UK-HiGEM: The New U.K. High Resolution Global Environment Model – Model description and basic evaluation

first_imgThis article describes the development and evaluation of the U.K.’s new High-Resolution Global Environmental Model (HiGEM), which is based on the latest climate configuration of the Met Office Unified Model, known as the Hadley Centre Global Environmental Model, version 1 (HadGEM1). In HiGEM, the horizontal resolution has been increased to 0.83° latitude × 1.25° longitude for the atmosphere, and 1/3° × 1/3° globally for the ocean. Multidecadal integrations of HiGEM, and the lower-resolution HadGEM, are used to explore the impact of resolution on the fidelity of climate simulations. Generally, SST errors are reduced in HiGEM. Cold SST errors associated with the path of the North Atlantic drift improve, and warm SST errors are reduced in upwelling stratocumulus regions where the simulation of low-level cloud is better at higher resolution. The ocean model in HiGEM allows ocean eddies to be partially resolved, which dramatically improves the representation of sea surface height variability. In the Southern Ocean, most of the heat transports in HiGEM is achieved by resolved eddy motions, which replaces the parameterized eddy heat transport in the lower-resolution model. HiGEM is also able to more realistically simulate small-scale features in the wind stress curl around islands and oceanic SST fronts, which may have implications for oceanic upwelling and ocean biology. Higher resolution in both the atmosphere and the ocean allows coupling to occur on small spatial scales. In particular, the small-scale interaction recently seen in satellite imagery between the atmosphere and tropical instability waves in the tropical Pacific Ocean is realistically captured in HiGEM. Tropical instability waves play a role in improving the simulation of the mean state of the tropical Pacific, which has important implications for climate variability. In particular, all aspects of the simulation of ENSO (spatial patterns, the time scales at which ENSO occurs, and global teleconnections) are much improved in HiGEM.last_img read more

RNA preservation of Antarctic marine invertebrates

first_imgFifteen species of marine invertebrate commonlyoccurring in the near-shore environment of Rotherabase, Antarctica, were used to test tissue sample storageprotocols with regard to preservation of RNA integrity.After animal collection, the tissues were either immediatelyextracted for RNA or stored at -80C after havingbeen, either directly flash frozen in liquid nitrogen orpreserved in a commercial RNA storage solution, forextraction in the UK. In four cases, direct flash freezingproduced enhanced RNA integrity compared with samplesin the commercial storage solution. A subset of sampleswere further tested for the preferred temperature of storagein the commercial reagent. RNA integrity was well preservedat both ?4 and -20C over periods of 2 months,but degradation was rapid in tissues stored at room temperature.Eight out of the fifteen species only produced asingle ribosomal band on gel electrophoresis. This surveyprovides a guide for tissue transport of Polar cold watermarine invertebrates.Keywords Tissue preservation Tissue transport28 s ribosomal RNA Echinoderms MolluscsIntroductionRNA preservation is sometimes problematic in non-modelspecies but this is particularly the case when dealing withenvironmental species. Logistical issues often surround theability to effectively preserve field-collected samples forRNA analyses. Whilst rapid flash freezing in liquid nitrogengenerally solves this problem, it is not often availablebecause of the remote nature of the work. Even when sucha facility is available on site at a field station, it usuallycannot be transported to the actual, more remote specimencollection site. Also, -80C storage may not be possibleduring transportation from the field site to the mainresearch institute, often thousands of miles away. Antarcticspecimens have the additional issue of operating at temperatures that most species would consider cold and hencecool stow is less effective at reducing tissue degradationthan with, for example, those taken from mammalianspecies. Hence, we decided to carry out a study of effectivestorage protocols for the most common invertebrates foundin the near-shore marine environment in Marguerite Bayclose to Rothera research station, Antarctica.last_img read more

Latitudinal and bathymetric patterns in the distribution and abundance of mesopelagic fish in the Scotia Sea

first_imgMesopelagic fish are a key component of the pelagic ecosystem throughout the world’s oceans. Opening and closing nets were used to investigate patterns in the distribution and abundance of mesopelagic fish from the surface to 1000 m on a series of transects across the Scotia Sea from the ice-edge to the Antarctic Polar Front. A total of 141 non-target net hauls were undertaken during three cruises (Nov 2006, Jan 2008 and Mar 2009), with 7852 teleost fish captured, representing 43 species in 17 families. A further 1517 fish were caught in targeted net hauls. The dominant families were the Myctophidae (6961 specimens; 21 species) and Bathylagidae (1467 specimens; 4 species). Few fish were caught in the upper 400 m during daylight, which was attributed to a combination of net avoidance and diurnal vertical migration. Species composition was linked to depth and location and was closely associated with oceanographic features. Diversity was lowest in cold water at the most southerly stations, which were dominated by Electrona antarctica, Gymnoscopelus braueri and Bathylagus antarcticus. Further north, diversity increased with the addition of species such as Krefftichthys anderssoni, Protomyctophum bolini and Electrona carlsbergi. The depth integrated biomass of myctophids was similar across the latitudinal transect and produced an estimate of 4.5 million tonnes in the Scotia Sea. Bathylagids were patchily distributed, but were abundant in the lower mesopelagic zone (>400 m) and are potentially significant zooplankton consumers. Given the biomass of the myctophids and bathylagids coupled with the vertical migrations of many species, these fish are likely to play a significant role in carbon export from the surface waters to the deep ocean.last_img read more

Experimental protocol for sea level projections from ISMIP6 stand-alone ice sheet models

first_imgProjection of the contribution of ice sheets to sea level change as part of the Coupled Model Intercomparison Project Phase 6 (CMIP6) takes the form of simulations from coupled ice sheet–climate models and stand-alone ice sheet models, overseen by the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6). This paper describes the experimental setup for process-based sea level change projections to be performed with stand-alone Greenland and Antarctic ice sheet models in the context of ISMIP6. The ISMIP6 protocol relies on a suite of polar atmospheric and oceanic CMIP-based forcing for ice sheet models, in order to explore the uncertainty in projected sea level change due to future emissions scenarios, CMIP models, ice sheet models, and parameterizations for ice–ocean interactions. We describe here the approach taken for defining the suite of ISMIP6 stand-alone ice sheet simulations, document the experimental framework and implementation, and present an overview of the ISMIP6 forcing to be used by participating ice sheet modeling groups.last_img read more

Utah Baseball Falls 6-3 to No. 17 UCLA

first_img FacebookTwitterLinkedInEmailSALT LAKE CITY – A late rally by UCLA doomed the Utah baseball team on Saturday afternoon, falling to the 17th-ranked Bruins, 6-3.Utah led 3-2 before UCLA tied the game with a run in the eighth and took the lead with three runs in the top of the ninth.Oliver Dunn went 2-for-3 with two runs scored, including a home run, and two RBI to lead Utah at the plate.Tanner Thomas pitched five innings for the Utes, allowing two runs on five hits with four strikeouts and six walks. Justin Kelly allowed one run on two hits with two walks while Trenton Stoltz surrendered three runs on four hits with three walks and a strikeout in the loss.Utah took a quick 1-0 lead in the first inning on a solo home run from Dunn. UCLA quickly replied in the second inning, scoring two runs on four hits to take a 2-1 lead before Utah got out of the inning with UCLA leaving the bases loaded.The Utes came back to re-take the lead in the third inning. Matt Richardson reached on an error and scored on an RBI double from Dunn that was just fair, landing on the chalk line. Rykker Tom drove in Dunn to give the Utes a 3-2 lead.UCLA left runners on base in several innings as the game continued before breaking through to tie it at 3-3 with a run on two hits and a walk in the top of the eighth. The Bruins took the lead in the top of the ninth with three runs on three hits.Davis Delorefice led off the ninth with an infield single for Utah but three-straight fly outs clinched the win for UCLA.Utah and UCLA close out the series on Sunday, April 15, at 1:00 p.m. at Smith’s Ballpark. Written by April 14, 2018 /Sports News – Local Utah Baseball Falls 6-3 to No. 17 UCLA Tags: Baseball/Pac 12/Utah Utes Robert Lovelllast_img read more