Aspects of Scotia Sea zooplankton

first_imgInformation on small scale distributions of three species of Antarctic zooplankton is reviewed. Aggregations of the euphausiid Euphausia superba, the tunicate Salpa thompsoni, and the amphipod Parathemisto gaudichaudii are compared, and the manner in which such aggregations mav arise is discussed. A possible relationship between swarming and feeding activity in E. superba is suggested in which krill are thought to be dispersed whilst feeding but that on repletion they swarm. It is thought that this may account for this species’ irregular spatial distribution as recorded bv previous expeditions. A further consequence of this theory is that during the Winter swarming will be minimal.last_img

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Southern hemisphere thermospheric dynamics: A review

first_imgThe dynamics of the upper thermosphere in the southern polar cap, auroral, and mid‐latitude zones is reviewed. Information has been drawn from published measurements from the DE 2 and AE‐C spacecraft and from ground‐based stations and interpreted using the latest thermospheric general circulation models. Necessarily, frequent reference is made to the F region of the ionosphere, which permeates the upper thermosphere. Great emphasis is placed on the coupling and feedback mechanisms which exist between these interpenetrating fluids. It is shown that to obtain close approximation to observation, a complex model is required which incorporates these mechanisms in a self‐consistent way. Published results from general circulation models show that there is a broad measure of agreement at both high and middle latitudes between simulation and observation over a wide range of geomagnetic activity for the sunlit southern middle and high latitudes near solar maximum. However, there are comparatively few data for a full investigation to be made, and present conclusions must be regarded as strictly interim. Strong driving forces in the auroral zones and polar caps cause a wind regime which is distinctly different from that observed at middle latitudes. Geomagnetic activity has been shown to have a strong effect on the extent of the high‐latitude wind field, its strength, and its penetration to middle latitudes. The orientation of the interplanetary magnetic field has also been shown to be important. The coupling mechanisms between ions and neutrals heat the thermosphere and drive its circulation using energy from magnetospheric sources, but as yet the details of the thermosphere’s variation with geomagnetic and solar activity are not clear from observations. The strong vertical winds reported in the literature are certainly indications of powerful heating, but the connection between observations of vertical winds and the production of gravity wave activity has not been established. Halley, Antarctica, is a critical station in the evaluation of model simulations of the winds in the upper thermosphere since it is a high‐latitude station geographically but middle latitude geomagnetically and is subject to an unusual blend of driving forces. The observations are modeled surprisingly well considering the incomplete accounting of asymmetry caused by the large offset of the geomagnetic and geographic poles, and also of the South Atlantic anomaly. It is probable that, globally, there are detailed disagreements between the actual circulation and the simulations which have not yet come to light for the lack of observations. In the absence of new spacecraft experiments, new ground‐based stations are required in the Antarctic region to enable simultaneous measurements to be made over a wide range of the southern polar cap.last_img read more

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Tardigrades, and other cryoconite biota, on the Greenland Ice Sheet

first_imgCryoconite holes, supraglacial ponds and moulins of the Greenland Ice Sheet were surveyed for microbiota and meiofauna. These habitats are colonised by depauperate communities of widespread/cosmopolitan microbes, microalgae, rotifers and tardigrades. All colonists are generalists, pre-adapted to cope with the extreme environmental conditions of, and are effectively stranded in, cryoconite deposits. Cryoconite biota may seed similar local habitats, though it is unlikely that they can escape to colonise new ones, and so they survive in situ until they are ultimately washed into the glacial drainage system.last_img

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An assessment of the surface turbulent heat fluxes from the NCEP-NCAR reanalysis over western boundary currents

first_imgWith the completion of the NCEP-NCAR and ECMWF reanalyses there are now global representations of air-sea surface heat fluxes with sufficient spatial and temporal resolution to be useful in characterizing the air-sea interaction associated with individual weather systems, as well as in developing global-scale oceanic heat and moisture budgets. However, these fluxes are strongly dependent on the numerical models used, and, as a result, there is a clear need to validate them against observations. Accurate air-sea heat flux estimates require a realistic representation of the atmospheric boundary layer, and the implementation of an appropriate surface flux parameterization. Previous work at high latitudes has highlighted the shortcomings of the surface turbulent heat flux parameterization used in the NCEP-NCAR reanalysis during high wind speed conditions, especially when combined with large air-sea temperature differences. Here the authors extend this result through an examination of the air-sea heat fluxes over the western boundary currents of the North Atlantic and North Pacific Oceans. These are also regions where large transfers of heat and moisture from the ocean to the atmosphere take place. A comparison with in situ data shows that the surface layer meteorological fields are reasonably well represented in the NCEP-NCAR reanalysis, but the turbulent heat flux fields contain significant systematic errors. It is argued that these errors are associated with shortcomings in the bulk flux algorithm employed in the reanalysis. Using the NCEP-NCAR reanalysis surface layer meteorological fields and a more appropriate bulk flux algorithm, “adjusted” fields for the sensible and latent heat fluxes are presented that more accurately represent the air-sea exchange of heat and moisture over the western boundary currents.last_img read more

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Damping of tropical instability waves caused by the action of surface currents on stress

first_imgOcean eddies and fronts affect surface stress via two mechanisms: (1) ocean surface currents altering the relative motion between air and sea and, hence, the stress fields and (2) ocean sea surface temperature (SST) gradients forcing changes in stability and near-surface winds. In this paper, we quantify the first effect and how it impacts Tropical Instability Waves (TIW) in the eastern Pacific. High-resolution satellite data and a regional coupled model are used to distinguish between stress changes due to the surface currents and those due to the changes in stability and near-surface winds. It is found that both mechanisms affect the surface stress curl, but they do so at different latitudes, allowing for their effect on Ekman pumping to be distinguished. The Ekman pumping due to the surface current effect alone, leads to significant damping of the TIWs. In terms of the eddy kinetic energy, the inclusion of surface current in the stress leads to decay with an e-folding time comparable with the period of the TIWs. It is, thus, an important damping mechanism to be included in ocean and coupled ocean-atmosphere models.last_img read more

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A ground-based radar for measuring vertical strain rates and time-varying basal melt rates in ice sheets and shelves

first_imgThe ApRES (autonomous phase-sensitive radio-echo sounder) instrument is a robust, lightweight and relatively inexpensive radar that has been designed to allow long-term, unattended monitoring of ice-shelf and ice-sheet thinning. We describe the instrument and demonstrate its capabilities and limitations by presenting results from three trial campaigns conducted in different Antarctic settings. Two campaigns were ice sheet-based – Pine Island Glacier and Dome C – and one was conducted on the Ross Ice Shelf. The ice-shelf site demonstrates the ability of the instrument to collect a time series of basal melt rates; the two grounded ice applications show the potential to recover profiles of vertical strain rate and also demonstrate some of the limitations of the present system.last_img

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Estimates of abundance and trend on a Blue Whale feeding ground off Isla de Chiloé, Chile

first_imgSince 1970, blue whales (Balaenoptera musculus) have been seen feeding in the waters off southern Chile during the summer and autumn (December to May). Investigation of the genetic, acoustic and morphological characteristics of these blue whales shows that they are a distinct but unnamed subspecies, called the Chilean blue whales. Photo-identification surveys have been conducted in the waters off northwestern Isla Grande de Chiloé, southern Chile from 2004–2012 and Isla Chañaral, central Chile in 2012. Over this time, 1,070 blue whales were encountered yielding, after photo-quality control, 318 and 267 unique photographs of the left and right side of the flank respectively. Using mark-recapture analysis of left and right side photographs collected from Isla Grande de Chiloé (2004–2012), open population models estimate that ~570–760 whales are feeding seasonally in this region. POPAN superpopulation abundance estimates for the same feeding ground in 2012 are 762 (95% confidence intervals, CI = 638–933) and 570 (95% CI 475–705) for left and right side datasets respectively, very similar to results from closed population models. Estimates of trend revealed strong variation in abundance, peaking in 2009 and [suggesting] fluctuating use in the survey area over time, likely related to the density of their prey. High inter-annual return rates suggest a degree of site-fidelity of individuals to Isla Grande de Chiloé and that the number of whales using this feeding ground is relatively small.last_img read more

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Spatial scales of marine conservation management for breeding seabirds

first_imgKnowing the spatial scales at which effective management can be implemented is fundamental for conservation planning. This is especially important for mobile species, which can be exposed to threats across large areas, but the space use requirements of different species can vary to an extent that might render some management approaches inefficient. Here the space use patterns of seabirds were examined to provide guidance on whether conservation management approaches should be tailored for taxonomic groups with different movement characteristics. Seabird tracking data were synthesised from 5419 adult breeding individuals of 52 species in ten families that were collected in the Atlantic Ocean basin between 1998 and 2017. Two key aspects of spatial distribution were quantified, namely how far seabirds ranged from their colony, and to what extent individuals from the same colony used the same areas at sea. There was evidence for substantial differences in patterns of space-use among the ten studied seabird families, indicating that several alternative conservation management approaches are needed. Several species exhibited large foraging ranges and little aggregation at sea, indicating that area-based conservation solutions would have to be extremely large to adequately protect such species. The results highlight that short-ranging and aggregating species such as cormorants, auks, some penguins, and gulls would benefit from conservation approaches at relatively small spatial scales during their breeding season. However, improved regulation of fisheries, bycatch, pollution and other threats over large spatial scales will be needed for wide-ranging and dispersed species such as albatrosses, petrels, storm petrels and frigatebirds.last_img read more

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Weber State’s Trey Tuttle Named To Fred Mitchell Award List

first_img Brad James FacebookTwitterLinkedInEmailOGDEN, Utah-Weber State kicker Trey Tuttle has been selected as one of 34 placekickers throughout college football to be named to the 2018 Fred Mitchell Award Watch list.Tuttle, a sophomore out of Arlington, Texas, earned All-American honors last season and has been named as a preseason All-American this season.Tuttle tied a school record last season for field goals and helped the Wildcats earn a school-record 11 wins, a co-Big Sky title, a pair of wins in the FCS playoffs and a fifth-place national ranking, the highest in school history.Tuttle is one of 13 players throughout FCS to be named to this list and one of only four sophomores.The Fred Mitchell Award is awarded to the top kicker in FCS, NCAA Division II and III and NAIA, which comprises 750 schools.The top performers will be recognized monthly throughout the season with the award to be bestowed in December. Written by August 28, 2018 /Sports News – Local Weber State’s Trey Tuttle Named To Fred Mitchell Award List Tags: Division II/Division III/FCS/NAIA/Trey Tuttle/Weber State Footballlast_img read more

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SUU Falls To Idaho State In Cross Country Dual Meet

first_img Written by FacebookTwitterLinkedInEmailPOCATELLO, Idaho-Saturday, Idaho State hosted a dual cross country meet with Southern Utah in both men’s and women’s competition at the ISU Bengal Invitational.In the women’s 6-K, Idaho State bested Southern Utah 23-32 as unattached Jenica Dodge took the individual title in a time of 25:08.50.The Thunderbirds were represented in the Top 10 by Samantha Taylor (3rd place), Haley Tanne (6th place), Brighton Glassman (7th place) and Josie Bushar (10th place).For the men, Idaho State edged Southern Utah 28-29 with the Bengals’ Wyatt Diderickson taking the individual title in a time of 21:15:00.Thunderbird men finishing in the Top 10 included Michael Finch (2nd place), Thomas Grant (4th place), Sage Ducote (5th place) and Mark Bennett (6th place). Tags: Brighton Glassman/Cross Country/Haley Tanne/Idaho State/Jenica Dodge/Josie Bushar/Mark Bennett/Michael Finch/Sage Ducote/Samantha Taylor/Southern Utah/Thomas Grant/Wyatt Diedrickson Brad James September 22, 2018 /Sports News – Local SUU Falls To Idaho State In Cross Country Dual Meetlast_img read more

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