scholarly journals Halley Research Station, Antarctica: calving risks and monitoring strategies

2013 ◽  
Vol 1 (6) ◽  
pp. 6227-6256 ◽  
Author(s):  
R. Anderson ◽  
D. H. Jones ◽  
G. H. Gudmundsson
Keyword(s):  
Large Scale ◽  
Weddell Sea ◽  
Research Station ◽  
Future Scenarios ◽  
Historical Records ◽  
Ice Shelf ◽  
Glacier Tongue ◽  
Monitoring Strategies ◽  
The Stability ◽  
Ongoing Monitoring

Abstract. The British Antarctic Survey's Halley Research Station is located on the Brunt Ice Shelf, Antarctica, where it is potentially vulnerable to calving events. Existing historical records show that the Brunt Ice Shelf is currently extended further into the Weddell Sea than it was before its last large calving event, so a new calving event may be overdue. We describe three different possible future scenarios for a large-scale calving event on Brunt Ice Shelf, and conclude that the currently most threatening scenario for the Halley Research Station is a calving event on the neighbouring Stancomb–Wills Glacier Tongue, with subsequent detrimental consequences for the stability of the Brunt Ice Shelf. Based on available data, we suggest an increasing likelihood of this scenario occurring after 2020. We furthermore describe ongoing monitoring efforts aimed at giving advanced warning of an imminent calving event.

scholarly journals Halley Research Station, Antarctica: calving risks and monitoring strategies

2014 ◽  
Vol 14 (4) ◽  
pp. 917-927 ◽  
Author(s):  
R. Anderson ◽  
D. H. Jones ◽  
G. H. Gudmundsson
Keyword(s):  
Large Scale ◽  
Weddell Sea ◽  
Research Station ◽  
Future Scenarios ◽  
Historical Records ◽  
Ice Shelf ◽  
Glacier Tongue ◽  
Monitoring Strategies ◽  
The Stability ◽  
Ongoing Monitoring

Abstract. The British Antarctic Survey's Halley Research Station is located on the Brunt Ice Shelf, Antarctica, where it is potentially vulnerable to calving events. Existing historical records show that the Brunt Ice Shelf is currently extended further into the Weddell Sea than it was before its last large calving event, so a new calving event may be overdue. We describe three different possible future scenarios for a large-scale calving event on Brunt Ice Shelf. We conclude that currently the most threatening scenario for the Halley Research Station is a calving event on the neighbouring Stancomb-Wills Glacier Tongue, with subsequent detrimental consequences for the stability of the Brunt Ice Shelf. Based on available data, we suggest an increasing likelihood of this scenario occurring after 2020. We furthermore describe ongoing monitoring efforts aimed at giving advanced warning of an imminent calving event.

A recent update on the circulation and water masses around the Filchner and Ronne ice shelves in the southern Weddell Sea

2020 ◽  
Author(s):  
Markus Janout ◽  
Hartmut Hellmer ◽  
Tore Hattermann ◽  
Svein Osterhus ◽  
Lucrecia Stulic ◽  
...  
Keyword(s):  
Sea Ice ◽  
Ocean Circulation ◽  
Large Scale ◽  
Austral Summer ◽  
Weddell Sea ◽  
Shelf Water ◽  
Ice Shelf ◽  
Present Context ◽  
The Stability ◽  
Ice Production

<p>The Filchner and Ronne ice sheets (FRIS) compose the second largest contiguous ice sheet on the Antarctic continent. Unlike at several other Antarctic glaciers, basal melt rates at FRIS are comparatively low, as cold and dense waters presently dominate the wide southern Weddell Sea (WS) continental shelf and effectively block out any significant inflow of warmer ocean waters. We revisited the southern WS shelf in austral summer 2018 during Polarstern expedition PS111 with detailed hydrographic and tracer measurements along both the Ronne and Filchner ice fronts. The hydrography along FRIS was characterized by near-freezing high salinity shelf water (HSSW) in front of Ronne, and a striking dominance of ice shelf water (ISW) in Filchner Trough. The cold (-2.2°C) and fresher (34.6) ISW was formed by the interaction of Ronne-sourced HSSW with the ice shelf base. The strong dominance of ISW in Filchner Trough indicates a recently enhanced circulation below FRIS, likely fueled by enhanced sea ice production in the southwestern WS. We view these recent observations in a multidecadal (1973-present) context, contrast the two dominant circulation modes below FRIS, and discuss the importance of sea ice formation and large-scale sea level pressure patterns for the stability of the ocean circulation and basal melt rates underneath FRIS.</p>

scholarly journals Ice calving and deformation from Antarctic Ice margins using RISAT-1 circular polarization SAR data

2014 ◽  
Vol XL-8 ◽  
pp. 525-529 ◽  
Author(s):  
P. Jayaprasad ◽  
D. R. Rajak ◽  
R. K. Singh ◽  
S. R. Oza ◽  
R. Sharma ◽  
...  
Keyword(s):  
Large Scale ◽  
Research Station ◽  
Ice Shelf ◽  
Summer Period ◽  
Glacier Tongue ◽  
Amery Ice Shelf ◽  
Antarctic Research ◽  
Sar Data ◽  
Spatio Temporal

In the present study, quantification of spatial and temporal changes has been carried out between Indian Antarctic Research station Bharati and Amery ice shelf by monitoring the ice margins using RISAT-1 Synthetic Aperture Radar (SAR) data. Spatio-temporal change detection was carried out by comparing the feature's geographic locations from geometrically rectified SAR data from RISAT-1 (Dec. 2013), Radarsat-2 (Feb. 2013), and Antarctic Mapping Mission products of Radarsat-1 (1997 & 2000). We report large scale disintegrations at two prominent glacier tongues namely Polar Record Glacier (PRG) and Polar Times Glacier(PTG). The results are verified against in-situ ground observations made during Summer period of 33rd ISEA (Dec. 2013–Feb. 2014) and MODIS images from NSIDC archive. Polar Record Glacier Tongue (PRGT) was drastically deformed by 135.8 km2 and Polar Times Glacier Tongue (PTGT) was partly calved by ~195.6 km2 and moved away by ~23 km especially between February and December 2013.

scholarly journals Summertime productivity and carbon export potential in the Weddell Sea, with a focus on the waters adjacent to Larsen C Ice Shelf

2021 ◽  
Vol 18 (22) ◽  
pp. 6031-6059
Author(s):  
Raquel F. Flynn ◽  
Thomas G. Bornman ◽  
Jessica M. Burger ◽  
Shantelle Smith ◽  
Kurt A. M. Spence ◽  
...  
Keyword(s):  
Large Scale ◽  
Nitrate Uptake ◽  
Net Primary Production ◽  
Biological Activities ◽  
Euphotic Zone ◽  
Early Summer ◽  
Weddell Sea ◽  
Unexpected Result ◽  
Ice Shelf ◽  
Carbon Export

Abstract. The Weddell Sea represents a point of origin in the Southern Ocean where globally important water masses form. Biological activities in Weddell Sea surface waters thus affect large-scale ocean biogeochemistry. During January–February 2019, we measured net primary production (NPP), nitrogen (nitrate, ammonium, urea) uptake, and nitrification in the western Weddell Sea at the Antarctic Peninsula (AP) and Larsen C Ice Shelf (LCIS), in the southwestern Weddell Gyre (WG), and at Fimbul Ice Shelf (FIS) in the south-eastern Weddell Sea. The highest average rates of NPP and greatest nutrient drawdown occurred at LCIS. Here, the phytoplankton community was dominated by colonial Phaeocystis antarctica, with diatoms increasing in abundance later in the season as sea ice melted. At the other stations, NPP was variable, and diatoms known to enhance carbon export (e.g. Thalassiosira spp.) were dominant. Euphotic zone nitrification was always below detection, such that nitrate uptake could be used as a proxy for carbon export potential, which was highest in absolute terms at LCIS and the AP. Surprisingly, the highest f ratios occurred near FIS rather than LCIS (average of 0.73±0.09 versus 0.47±0.08). We attribute this unexpected result to partial ammonium inhibition of nitrate uptake at LCIS (where ammonium concentrations were 0.6±0.4 µM, versus 0.05±0.1 µM at FIS), with elevated ammonium resulting from increased heterotrophy following the accumulation of nitrate-fuelled phytoplankton biomass in early summer. Across the Weddell Sea, carbon export appears to be controlled by a combination of physical, chemical, and biological factors, with the highest potential export flux occurring at the ice shelves and lowest in the central WG.

scholarly journals Circulation beneath the Filchner Ice Shelf, Antarctica, and its sensitivity to changes in the oceanic environment: a case-study

1998 ◽  
Vol 27 ◽  
pp. 99-104 ◽  
Author(s):  
K. Grosfeld ◽  
R. Gerdes
Keyword(s):  
Sea Ice ◽  
Mass Loss ◽  
Ocean Circulation ◽  
Large Scale ◽  
Ocean Model ◽  
Current Situation ◽  
Weddell Sea ◽  
Ice Formation ◽  
Shelf Area ◽  
Ice Shelf

We investigate the sensitivity of the ocean circulation in the Filchner Trough to changes in the large-scale oceanic environment and its impact on the mass balance of the Filchner Ice Shelf, Antarctica. Three experiments with a three-dimensional ocean model describe (i) the current situation, (ii) a scenario with increased ocean temperatures, and (iii) a scenario with reduced sea-ice formation rates on the adjacent continental shelf. in the final discussion brief results of a combined scenario with increased ocean temperatures and reduced sea-ice formation are presented. The changes from the current situation affect the circulation in the Filchner Trough, and melting and freezing processes beneath the ice shelf. The latter affect the amount and properties of Ice Shelf Water (ISW), a component of Antarctic Bottom Water. Net basal melt rates provide an overall measure for the changes: while the control run yields 0.35 m a−1 net melting averaged over the Filchner Ice Shelf area, the warming scenario results in a more than twofold increase in ice-shelf mass loss. Reduced production of High Salinity ShelfWater due to smaller sea-ice formation rates in the second scenario leads, on the other hand, to a decrease in basal mass loss, because the deep cavity is less well ventilated than in the control run. ISW is cooled and the ice shelf is stabilized under this scenario, which is arguably the more likely development in the southern Weddell Sea.

Meltwater and circulation characteristics adjacent to Larsen C ice shelf: insights from seawater oxygen isotopes

2020 ◽  
Author(s):  
Joshua Mirkin ◽  
Adam West ◽  
Katherine Hutchinson ◽  
Raquel Flynn ◽  
Sarah Fawcett
Keyword(s):  
Large Scale ◽  
Circulation Pattern ◽  
Oxygen Isotopic Composition ◽  
Weddell Sea ◽  
Balance Model ◽  
Ice Shelf ◽  
Study Region ◽  
Isotope Data ◽  
Basal Ice ◽  
Basal Melting

<p>The Larsen C ice shelf (LCIS) in the western Weddell Sea has recently undergone large-scale ice shelf collapse with the detachment of iceberg A68 in 2017. Cold cavity ice shelves, such as LCIS, are critical for the formation of the world’s coldest, densest waters and act to prevent the flow of land-fast ice into the ocean, which would result in sea-level rise. Their disintegration is thus of great scientific interest and growing public concern. It has been hypothesized that ice shelf breakup may result from ice shelf thinning, which can be caused by densification through surface processes, a decrease in grounded ice flow, or increased surface or basal melting. To investigate whether ice shelf melting may be contributing to the collapse of LCIS, we collected full depth profiles of seawater samples at 17 stations in the vicinity of LCIS in January 2019 during the Weddell Sea Expedition. To investigate the formation processes and distribution of water masses, as well as identify regions of ice shelf melt, the samples were measured for seawater oxygen isotopic composition (δ<sup>18</sup>O) using a Picarro Cavity Ring-Down Spectroscope (CRDS). The isotope data provide little evidence of large-scale surface or basal ice shelf melting, with basal ice shelf melt constituting a maximum of 0.5% of the Ice Shelf Water (ISW) observed in the vicinity of LCIS. One implication of this is that surface and basal melting may not be the primary factor driving the collapse of LCIS, although more data and further study are required to confirm this. In addition, the isotope data are consistent with previous work suggesting that the onshore advection of warm offshore waters occurs via the Jason Trough, a remnant depression in the seafloor caused by the flow of a palaeo-ice stream. This, in combination with the observation (based on incorporating seawater δ<sup>18</sup>O into a temperature-salinity-oxygen mass balance model) that the outflow of ISW occurs primarily to the north of the study region, supports a clockwise circulation pattern in the vicinity of LCIS.</p>

scholarly journals Summertime productivity and carbon export potential in the Weddell Sea, with a focus on the waters adjacent to Larsen C Ice Shelf

2021 ◽  
Author(s):  
Raquel Flynn ◽  
Thomas Bornman ◽  
Jessica Burger ◽  
Shantelle Smith ◽  
Kurt Spence ◽  
...  
Keyword(s):  
Large Scale ◽  
Nitrate Uptake ◽  
Net Primary Production ◽  
Biological Activities ◽  
Euphotic Zone ◽  
Early Summer ◽  
Weddell Sea ◽  
Ice Shelf ◽  
Carbon Export ◽  
Ice Melt

Abstract. The Weddell Sea (WS) represents a point of origin in the Southern Ocean where globally-important water masses form. Biological activities in WS surface waters thus affect large-scale ocean biogeochemistry. During summer 2018/2019, we measured net primary production (NPP), nitrogen (nitrate, ammonium, urea) uptake, and nitrification in the western WS at the Antarctic Peninsula (AP) and Larsen C Ice Shelf (LCIS), in the southwestern Weddell Gyre (WG), and at Fimbul Ice Shelf (FIS) in the south-eastern WS. The highest average rates of NPP and greatest nutrient drawdown occurred at LCIS. Here, the phytoplankton community was dominated by colonial Phaeocystis antarctica, with diatoms increasing in abundance later in the season as sea-ice melt increased. At the other stations, NPP was variable, and diatoms known to enhance carbon export (e.g., Thalassiosira spp.) were dominant. Euphotic zone nitrification was always below detection, such that nitrate uptake could be used as a proxy for carbon export potential, which was highest in absolute terms at LCIS and the AP. Surprisingly, the highest f-ratios occurred near FIS rather than LCIS (average of 0.73 ± 0.09 versus 0.47 ± 0.08). We attribute this to ammonium inhibition of nitrate uptake at LCIS (where ammonium concentrations were 0.6 ± 0.4 μM, versus 0.05 ± 0.1 μM at FIS) driven by increased heterotrophy following the accumulation of nitrate-fuelled phytoplankton biomass in early summer. Across the WS, carbon export appears to be driven by a combination of physical, chemical, and biological factors, with the highest export flux occurring at the ice shelves and lowest in the central WG.

scholarly journals Development and Characterization of Two Types of Surface Displayed Levansucrases for Levan Biosynthesis

Catalysts ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 757
Author(s):  
Huiyi Shang ◽  
Danni Yang ◽  
Dairong Qiao ◽  
Hui Xu ◽  
Yi Cao
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Molecular Weight ◽  
Large Scale ◽  
Surface Display ◽  
Yeast Surface Display ◽  
Fusion Partner ◽  
Whole Cell ◽  
Food Industries ◽  
Yeast Surface ◽  
The Stability

Levan has wide applications in chemical, cosmetic, pharmaceutical and food industries. The free levansucrase is usually used in the biosynthesis of levan, but the poor reusability and low stability of free levansucrase have limited its large-scale use. To address this problem, the surface-displayed levansucrase in Saccharomyces cerevisiae were generated and evaluated in this study. The levansucrase from Zymomonas mobilis was displayed on the cell surface of Saccharomyces cerevisiae EBY100 using a various yeast surface display platform. The N-terminal fusion partner is based on a-agglutinin, and the C-terminal one is Flo1p. The yield of levan produced by these two whole-cell biocatalysts reaches 26 g/L and 34 g/L in 24 h, respectively. Meanwhile, the stability of the surface-displayed levansucrases is significantly enhanced. After six reuses, these two biocatalysts retained over 50% and 60% of their initial activities, respectively. Furthermore, the molecular weight and polydispersity test of the products suggested that the whole-cell biocatalyst of levansucrase displayed by Flo1p has more potentials in the production of levan with low molecular weight which is critical in certain applications. In conclusion, our method not only enable the possibility to reuse the enzyme, but also improves the stability of the enzyme.

scholarly journals INTRACISTRONIC MAPPING OF ELECTROPHORETIC SITES IN DROSOPHILA MELANOGASTER: FIDELITY OF INFORMATION TRANSFER BY GENE CONVERSION

Genetics ◽  
1974 ◽  
Vol 76 (2) ◽  
pp. 289-299
Author(s):  
Margaret McCarron ◽  
William Gelbart ◽  
Arthur Chovnick
Keyword(s):  
Drosophila Melanogaster ◽  
Information Transfer ◽  
Large Scale ◽  
Genetic Basis ◽  
Xanthine Dehydrogenase ◽  
Specific Protein ◽  
Wild Type ◽  
Electrophoretic Variation ◽  
The Stability ◽  
Recombination Experiments

ABSTRACT A convenient method is described for the intracistronic mapping of genetic sites responsible for electrophoretic variation of a specific protein in Drosophila melanogaster. A number of wild-type isoalleles of the rosy locus have been isolated which are associated with the production of electrophoretically distinguishable xanthine dehydrogenases. Large-scale recombination experiments were carried out involving null enzyme mutants induced on electrophoretically distinct wild-type isoalleles, the genetic basis for which is followed as a nonselective marker in the cross. Additionally, a large-scale recombination experiment was carried out involving null enzyme rosy mutants induced on the same wild-type isoallele. Examination of the electrophoretic character of crossover and convertant products recovered from the latter experiment revealed that all exhibited the same parental electrophoretic character. In addition to documenting the stability of the xanthine dehydrogenase electrophoretic character, this observation argues against a special mutagenesis hypothesis to explain conversions resulting from allele recombination studies.

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