Ice Shelf Water plume flow beneath Filchner-Ronne Ice Shelf, Antarctica

[1] A two-dimensional plume model is used to study the interaction between Filchner-Ronne Ice Shelf, Antarctica and its underlying ocean cavity. Ice Shelf Water (ISW) plumes are initiated by the freshwater released from a melting ice shelf and, if they rise, may become supercooled and deposit marine ice due to the pressure increase in the in situ freezing temperature. The aim of this modeling study is to determine the origin of the thick accretions of marine ice at the base of Filchner-Ronne Ice Shelf and thus improve our understanding of ISW flow paths. The model domain is defined from measurements of ice shelf draft, and from this ISW the model is able to predict plumes that exit the cavity in the correct locations. The modeled plumes also produce basal freezing rates that account for measured marine ice thicknesses in the western part of Ronne Ice Shelf. We find that the freezing rate and plume properties are significantly influenced by the confluence of plumes from different meltwater sources. We are less successful in matching observations of marine ice under the rest of Filchner-Ronne Ice Shelf, which we attribute primarily to this model’s neglect of circulations in the ocean outside the plume.

The influence of Antarctica on the momentum budget of the southern extratropics

The antarctic plateau acts as a strong heat sink for the global climate, cooling the atmosphere and radiating energy to space. A cold dense atmospheric boundary layer is formed. Strong surface winds are formed as the boundary layer drains off the plateau. These drainage winds and the eddy fluxes necessary to maintain them are analysed in a general circulation model (GCM). The drainage flow is well represented in the GCM. The associated mean meridional circulation is analysed in isentropic coordinates. The momentum budget over Antarctica reveals a balance between the Eliassen-Palm flux convergence and the Coriolis torque exerted by the mean meridional mass flux. Both vertical and horizontal components of the Eliassen-Palm flux contribute, the vertical component being the greater.

Late-Holocene changes in character and behaviour of land-terminating glaciers on James Ross Island, Antarctica

Virtually no information is available on the response of land-terminating Antarctic Peninsula glaciers to climate change on a centennial timescale. This paper analyses the topography, geomorphology and sedimentology of prominent moraines on James Ross Island, Antarctica, to determine geometric changes and to interpret glacier behaviour. The moraines are very likely due to a late-Holocene phase of advance and featured (1) shearing and thrusting within the snout, (2) shearing and deformation of basal sediment, (3) more supraglacial debris than at present and (4) short distances of sediment transport. Retreat of ∼100 m and thinning of 15–20 m has produced a loss of 0.1 km3 of ice. The pattern of surface lowering is asymmetric. These geometrical changes are suggested most simply to be due to a net negative mass balance caused by a drier climate. Comparisons of the moraines with the current glaciological surface structure of the glaciers permits speculation of a transition from a polythermal to a cold-based thermal regime. Small land-terminating glaciers in the northern Antarctic Peninsula region could be cooling despite a warming climate.

Foehn jets over the Larsen C ice shelf, Antarctica

Previously unknown foehn jets have been identified to the east of the Antarctic Peninsula (AP) above the Larsen C Ice Shelf. These jets have major implications for the east coast of the AP, a region of rapid climatic warming and where two large sections of ice shelf have collapsed in recent years. During three foehn events across the AP, leeside warming and drying is seen in new aircraft observations and simulated well by the Met Office Unified Model (MetUM) at ∼1.5 km grid spacing. In case A, weak southwesterly flow and an elevated upwind inversion characterise a highly nonlinear flow regime with upwind flow blocking. In case C strong northwesterly winds characterise a relatively linear case with little upwind flow blocking. Case B resides somewhere between the two in flow regime linearity. The foehn jets – apparent in aircraft observations where available and MetUM simulations of all three cases – are mesoscale features (up to 60 km in width) originating from the mouths of leeside inlets. Through back trajectory analysis they are identified as a type of gap flow. In cases A and B the jets are distinct, being strongly accelerated relative to the background flow, and confined to low levels above the Larsen C Ice Shelf. They resemble the ‘shallow foehn’ of the Alps. Case C resembles a case of ‘deep foehn’, with the jets less distinct. The foehn jets are considerably cooler and moister relative to adjacent regions of calmer foehn air. This is due to a dampened foehn effect in the jet regions: in case A the jets have lower upwind source regions, and in the more linear case C there is less diabatic warming and precipitation along jet trajectories due to the reduced orographic uplift across the mountain passes.

Millennial timescale regeneration in a moss from Antarctica

Mosses, dominant elements in the vegetation of polar and alpine regions, have well-developed stress tolerance features permitting cryptobiosis. However, direct regeneration after longer periods of cryptobiosis has been demonstrated only from herbarium and frozen material preserved for 20 years at most. Recent field observations of new moss growth on the surface of small moss clumps re-exposed from a cold-based glacier after about 400 years of ice cover have been accompanied by regeneration in culture from homogenised material, but there are no reported instances of regrowth occurring directly from older preserved material.

A 2000-year annual record of snow accumulation rates for Law Dome, East Antarctica

Accurate high-resolution records of snow accumulation rates in Antarctica are crucial for estimating ice sheet mass balance and subsequent sea level change. Snowfall rates at Law Dome, East Antarctica, have been linked with regional atmospheric circulation to the mid-latitudes as well as regional Antarctic snowfall. Here, we extend the length of the Law Dome accumulation record from 750 years to 2035 years, using recent annual layer dating that extends to 22 BCE. Accumulation rates were calculated as the ratio of measured to modelled layer thicknesses, multiplied by the long-term mean accumulation rate. The modelled layer thicknesses were based on a power-law vertical strain rate profile fitted to observed annual layer thickness. The periods 380–442, 727–783 and 1970–2009 CE have above-average snow accumulation rates, while 663–704, 933–975 and 1429–1468 CE were below average, and decadal-scale snow accumulation anomalies were found to be relatively common (74 events in the 2035-year record). The calculated snow accumulation rates show good correlation with atmospheric reanalysis estimates, and significant spatial correlation over a wide expanse of East Antarctica, demonstrating that the Law Dome record captures larger-scale variability across a large region of East Antarctica well beyond the immediate vicinity of the Law Dome summit. Spectral analysis reveals periodicities in the snow accumulation record which may be related to El Niño–Southern Oscillation (ENSO) and Interdecadal Pacific Oscillation (IPO) frequencies.

Fungal community associated with marine macroalgae from Antarctica

Filamentous fungi and yeasts associated with the marine algae Adenocystis utricularis, Desmarestia anceps, and Palmaria decipiens from Antarctica were studied. A total of 75 fungal isolates, represented by 27 filamentous fungi and 48 yeasts, were isolated from the three algal species and identified by morphological, physiological, and sequence analyses of the internal transcribed spacer region and D1/D2 variable domains of the large-subunit rRNA gene. The filamentous fungi and yeasts obtained were identified as belonging to the genera Geomyces, Antarctomyces, Oidiodendron, Penicillium, Phaeosphaeria, Aureobasidium, Cryptococcus, Leucosporidium, Metschnikowia, and Rhodotorula. The prevalent species were the filamentous fungus Geomyces pannorum and the yeast Metschnikowia australis. Two fungal species isolated in our study, Antarctomyces psychrotrophicus and M. australis, are endemic to Antarctica. This work is the first study of fungi associated with Antarctic marine macroalgae, and contributes to the taxonomy and ecology of the marine fungi living in polar environments. These fungal species may have an important role in the ecosystem and in organic matter recycling.

Shape and size of red blood cells from the Pygoscelid penguins of Antarctica using atomic force microscopy

Antarctic biodiversity is evolutionarily complex, reflecting the extreme ambient conditions. Therefore, Antarctic organisms exhibit sophisticated adaptations in all organization levels, including organs, tissues, and cells. Since red blood cells (RBCs) travel through the vertebrates blood delivering O(2) to all tissues and organs and purging the unwanted CO(2), they represent an interesting model to investigate biological adaptations. We have used atomic force microscopy (AFM) to compare the shape and size of RBCs of the Pygoscelid penguins. A total of 18 landmarks were measured in AFM images. When analyzed individually, the parameters were not capable of discriminating the RBCs of each species. However, the simultaneous use of multiple parameters discriminated (74%) among the RBCs. In addition, the use of RBC measurements was sufficient to hierarchically cluster the species in accordance to other common and reliable phylogenetic strategies. In light of these results, the use of RBC characters could effectively benefit taxonomic inferences.

Enantioselective transesterification catalysis by Candida antarctica lipase immobilized on superparamagnetic nanoparticles

Lipase B from Candida antarctica can be directly immobilized onto functionalized superparamagnetic nanoparticles, preserving its enzymatic activity in the enantioselective transesterification of secondary alcohols, with excellent results in terms of enantiomeric discrimination. The immobilized enzyme can be easily recovered with a magnet, allowing its reuse with negligible loss of activity. (C) 2009 Elsevier Ltd. All rights reserved

Catalytic ethanolysis of soybean oil with immobilized lipase from Candida antarctica and (1)H NMR and GC quantification of the ethyl esters (biodiesel) produced

The catalytic ethanolysis of soybean oil with commercial immobilized lipase type B from Candida antarctica to yield ethyl esters (biodiesel) has been investigated. Transesterification was monitored with respect to the following parameters: quantity of biocatalyst, reaction time, amount of water added and turnover of lipase. The highest yields of biodiesel (87% by (1)H NMR; 82.9% by GC) were obtained after a reaction time of 24 h at 32 degrees C in the presence of lipase equivalent to 5.0% (w/w) of the amount of soybean oil present. The production of ethyl esters by enzymatic ethanolysis was not influenced by the addition of water up to 4.0% (v/v) of the alcohol indicating that it is possible to use hydrated ethanol in the production of biodiesel catalyzed by lipase. The immobilized enzyme showed high stability under moderate reaction conditions and retained its activity after five production cycles. The (1)H NMR methodology elaborated for the quantification of biodiesel in unpurified reaction mixtures showed good correlations between the signal areas of peaks associated with the alpha-methylene groups of the ethyl esters and those of the triacyl-glycerides in residual soybean oil. Monoacylglycerides, diacylglycerides and triglycerides could also be detected and quantified in the crude biodiesel using (1)H NMR spectroscopic and GC-FID chromatographic methods. The biodiesel production by enzymatic catalysis was promising. In this case, was produced a low concentration of glycerol (0.74%) and easily removed by water extraction. (C) 2010 Elsevier B.V. All rights reserved.

Kinetic resolution of iodophenylethanols by Candida antarctica lipase and their application for the synthesis of chiral biphenyl compounds

The kinetic resolution of (+/-)-iodophenylethanols was carried out using lipase from Candida antarctica and in some cases the enantiomeric excesses were high (up to >98%). Enantiomerically enriched (S)-iodophenylethanols produced by the enzymatic resolution process were used in the synthesis of chiral biphenyl compounds by the Suzuki reaction with good yields (63-65%). (C) 2010 Elsevier Ltd. All rights reserved.

Epiphytic bryophytes of Dicksonia antarctica Labill. from selected pockets of cool temperate rainforest, Central Highlands, Victoria

Epiphytic bryophytes of the Soft Tree-fern Dicksonia antarctica Labill. were examined in four Cool Temperate Rainforest pockets of the Central Highlands of Victoria. Thirty-two species, 17 mosses and 15 liverworts, were noted. There was no distinction in species assemblage between the north and south side of tree-ferns although bryophytes occurred on the south side of more tree-ferns than they did on the north side.

Production of Omega-3 Triacylglycerol concentrates using a new food grade immobilized Candida antarctica Lipase B

Triacylglycerol concentrates of eicosapentaenoic and docosahexaenoic omega-3 fatty acids were synthesized either via transesterification or esterification of glycerol with the corresponding ethyl ester or free fatty acid concentrates, respectively. A newly developed food grade immobilized Candida antarctica lipase Β system using an Amberlite FPX-66 hydrophobic matrix, was compared with a commercially available non-food grade commercial system, for their ability to catalyze these reactions. For either system, the transesterification required higher temperature (90◦C) than esterification (70°C) to achieve maximum triacylglycerol yields. The newly developed immobilized system efficiently catalyzes the esterification of free fatty acids with glycerol and differs from the existing commercial system in that it is food grade and has a more uniform and larger particle distribution. The new system significantly improves flow in a packed bed reactor, enabling multiple reuse of the catalyst for up to 80 repeats.

Environmental impact assessment of the sewage outfall at Davis Station, East Antarctica

During the summer 2009/10, an environmental impact assessment of the sewage outfall was conducted at Davis Station, East Antarctica. An investigation of the nature and extent of impacts to the marine environment associated with current sewage treatment and effluent discharge practices included ecological surveys of macrobiological communities, physico-chemical analysis of sediments and receiving waters, microbiological analysis, and histopathological analysis of fish. Ecotoxicological testing using local invertebrates to determine effluent toxicity was interpreted alongside dispersal modelling data of the discharge plume to determine the potential extent of impacts and inform recommendations on the level of treatment and dilution of sewage required to minimise impacts. No evidence of impacts was detected on soft sediment infaunal or epifaunal communities, and only low levels of contamination and accumulation were found in sediments and waters in the immediate vicinity of the outfall and in the direction of primary current flow. In contrast, sterol biomarkers and faecal coliforms (E. coli) were detected in sediments collected adjacent to the outfall and in most water column samples. Marine invertebrates (Abatus and Laternula) also tested positive for E. coli and antibiotic resistance mechanisms were present in Laternula indicating the introduction and dispersal through the water column of foreign microbes and bacteria associated with human effluent. Fish (Trematomus bernacchii) close to the outfall showed significant histological alterations in all major tissues (liver, gill, gonad, muscle) resulting from exposure to sewage. Effluent was toxic to amphipods (Paramoera walkeri) and microgastropods (Skenella paludionoides), with reduced survival in concentrations as low as 3.125% over a 21d exposure period. Acute effects were also observed in both species following 24h exposure, with 100% mortality at the highest effluent concentrations tested (68%). The application of these results to support and guide decisions regarding the planned installation of new sewage treatment facilities at Davis will be discussed.