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Diversity and Distribution of Deep-Sea Shrimps in the Ross Sea Region of Antarctica  [PDF]
Zeenatul Basher, David A. Bowden, Mark J. Costello
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0103195
Abstract: Although decapod crustaceans are widespread in the oceans, only Natantia (shrimps) are common in the Antarctic. Because remoteness, depth and ice cover restrict sampling in the South Ocean, species distribution modelling is a useful tool for evaluating distributions. We used physical specimen and towed camera data to describe the diversity and distribution of shrimps in the Ross Sea region of Antarctica. Eight shrimp species were recorded: Chorismus antarcticus; Notocrangon antarcticus; Nematocarcinus lanceopes; Dendrobranchiata; Pasiphaea scotiae; Pasiphaea cf. ledoyeri; Petalidium sp., and a new species of Lebbeus. For the two most common species, N. antarcticus and N. lanceopes, we used maximum entropy modelling, based on records of 60 specimens and over 1130 observations across 23 sites in depths from 269 m to 3433 m, to predict distributions in relation to environmental variables. Two independent sets of environmental data layers at 0.05° and 0.5° resolution respectively, showed how spatial resolution affected the model. Chorismus antarcticus and N. antarcticus were found only on the continental shelf and upper slopes, while N. lanceopes, Lebbeus n. sp., Dendrobranchiata, Petalidium sp., Pasiphaea cf. ledoyeri, and Pasiphaea scotiae were found on the slopes, seamounts and abyssal plain. The environmental variables that contributed most to models for N. antarcticus were depth, chlorophyll-a concentration, temperature, and salinity, and for N. lanceopes were depth, ice concentration, seabed slope/rugosity, and temperature. The relative ranking, but not the composition of these variables changed in models using different spatial resolutions, and the predicted extent of suitable habitat was smaller in models using the finer-scale environmental layers. Our modelling indicated that shrimps were widespread throughout the Ross Sea region and were thus likely to play important functional role in the ecosystem, and that the spatial resolution of data needs to be considered both in the use of species distribution models.
Little Ice Age climate and oceanic conditions of the Ross Sea, Antarctica from a coastal ice core record
R. H. Rhodes, N. A. N. Bertler, J. A. Baker, H. C. Steen-Larsen, S. B. Sneed, U. Morgenstern,S. J. Johnsen
Climate of the Past (CP) & Discussions (CPD) , 2012,
Abstract: Increasing paleoclimatic evidence suggests that the Little Ice Age (LIA) was a global climate change event. Understanding the forcings and associated climate system feedbacks of the LIA is made difficult by the scarcity of Southern Hemisphere paleoclimate records. We use a new glaciochemical record of a coastal ice core from Mt. Erebus Saddle, Antarctica, to reconstruct atmospheric and oceanic conditions in the Ross Sea sector of Antarctica over the past five centuries. The LIA is identified in stable isotope (δD) and lithophile element records, which respectively demonstrate that the region experienced 1.6 ± 1.4 °C cooler average temperatures prior to 1850 AD than during the last 150 yr and strong (>57 m s 1) prevailing katabatic winds between 1500 and 1800 AD. Al and Ti concentration increases of an order of magnitude (>120 ppb Al) are linked to enhanced aeolian transport of complex silicate minerals and represent the strongest katabatic wind events of the LIA. These events are associated with three 12–30 yr intervals of cooler temperatures at ca. 1690 AD, 1770 AD and 1840 AD. Furthermore, ice core concentrations of the biogenic sulphur species MS suggest that biological productivity in the Ross Sea polynya was ~80% higher prior to 1875 AD than at any subsequent time. We propose that cooler Antarctic temperatures promoted stronger katabatic winds across the Ross Ice Shelf, resulting in an enlarged Ross Sea polynya during the LIA.
Iron fluxes to Talos Dome, Antarctica, over the past 200 kyr
P. Vallelonga, C. Barbante, G. Cozzi, J. Gabrieli, S. Schüpbach, A. Spolaor,C. Turetta
Climate of the Past (CP) & Discussions (CPD) , 2013,
Abstract: Atmospheric fluxes of iron (Fe) over the past 200 kyr are reported for the coastal Antarctic Talos Dome ice core, based on acid leachable Fe concentrations. Fluxes of Fe to Talos Dome were consistently greater than those at Dome C, with the greatest difference observed during interglacial climates. We observe different Fe flux trends at Dome C and Talos Dome during the deglaciation and early Holocene, attributed to a combination of deglacial activation of dust sources local to Talos Dome and the reorganisation of atmospheric transport pathways with the retreat of the Ross Sea ice shelf. This supports similar findings based on dust particle sizes and fluxes and Rare Earth Element fluxes. We show that Ca and Fe should not be used as quantitative proxies for mineral dust, as they all demonstrate different deglacial trends at Talos Dome and Dome C. Considering that a 20 ppmv decrease in atmospheric CO2 at the coldest part of the last glacial maximum occurs contemporaneously with the period of greatest Fe and dust flux to Antarctica, we confirm that the maximum contribution of aeolian dust deposition to Southern Ocean sequestration of atmospheric CO2 is approximately 20 ppmv.
Iron fluxes to Talos Dome, Antarctica, over the past 200 kyr  [PDF]
P. Vallelonga,C. Barbante,G. Cozzi,J. Gabrieli
Climate of the Past Discussions , 2012, DOI: 10.5194/cpd-8-6093-2012
Abstract: Atmospheric fluxes of iron (Fe) over the past 200 kyr are reported for the coastal Antarctic Talos Dome ice core, based on acid leachable Fe concentrations. Fluxes of Fe to Talos Dome were consistently greater than those at Dome C, with the greatest difference observed during interglacial climates. We observe different Fe flux trends at Dome C and Talos Dome during the deglaciation and early Holocene, attributed to a combination of deglacial activation of dust sources local to Talos Dome and reorganization of atmospheric transport pathways with the retreat of the Ross Sea ice shelf. This supports similar findings based on dust particle sizes and fluxes and Rare Earth Element fluxes. We show that Ca and Fe should not be used as quantitative proxies for mineral dust, as they all demonstrate different deglacial trends at Talos Dome and Dome C. Considering that a 20 ppmv decrease in atmospheric CO2 at the coldest part of the last glacial maximum occurs contemporaneously with the period of greatest Fe and dust flux to Antarctica, we conclude that the maximum contribution of aeolian dust deposition to Southern Ocean sequestration of atmospheric CO2 is approximately 20 ppmv.
BIOGENIC AMINES CONTENT IN SELECTED WINES DURING WINEMAKING  [PDF]
Franti?ek Buňka,Barbora Ivi?i?ová,Leona Buňková,Radka Flasarová
Journal of Microbiology, Biotechnology and Food Sciences , 2012, DOI: 13385178
Abstract: The aim of this study was to describe the development of selected biogenic amines (histamine; tyramine; phenylethylamine; putrescine; agmatine; and cadaverine) during the winemaking in 10 selected species grown in Central Europe in 2008. The analysis was performed using ion-exchange chromatography by the sodium-citrate buffers with the post-column ninhydrin derivatization and photometric detection. A comparison of the content of biogenic amines in red and wine varieties showed that red wines have higher concentrations of biogenic amines.
Glacial Intensification During the Neogene: A Review of Seismic Stratigraphic Evidence from the Ross Sea, Antarctica, Continental Shelf  [PDF]
Philip J. Bart,Laura De Santis
Oceanography , 2012,
Abstract: Seismic stratigraphic and drill data from Antarctic continental margins have provided much direct evidence concerning ice sheet evolution as Earth's climate cooled from the warmth of the Eocene. Seismic facies analyses and correlations to sediment cores from Deep Sea Drilling Project Leg 28 drill sites show that the Ross Sea, the southwestern Pacific gateway of West Antarctica, was still mostly free of grounded ice for ~ 6 million years after Oi-1, the large-amplitude oxygen-isotope shift that signaled the abrupt onset of the current Antarctic glaciation. In the Ross Sea, our analysis shows that West Antarctic glaciation had begun by the late Oligocene, much earlier than usually interpreted from the paleoceanographic proxy data. Continental ice probably existed on Marie Bird Land and other highland areas of the West Antarctica. In the central Ross Sea, ice caps nucleated on the subaerially elevated basement horst blocks of the Central and Coulman Highs. Ice caps waxed and waned across the shallow-marine platforms rimming these broad basement uplifts. These temperate glacial systems delivered much sediment to the surrounding deepwater shelf basins. Ice cap oscillations during the early and middle Miocene also included significant intervals of grounded ice retreat and resumption of widespread marine sedimentation. By the end of the middle Miocene, glaciation intensified, local ice caps coalesced, and grounded ice with cross-shelf ice streams eventually extended across the entire Ross Sea continental shelf. Antarctic climate shifted from polar to temperate conditions during this time and ice streams advanced to the shelf edge. Full-bodied West Antarctic Ice Sheet advances continued and even occurred during the warmer-than-present early Pliocene. As a consequence of widespread and progressive glacial erosion, the shelf overdeepened in the latest Miocene. The surprisingly few advances of grounded ice preserved in Plio-Pleistocene strata suggest that the record is amalgamated and/or otherwise below the resolution of seismic data.
Little Ice Age climate and oceanic conditions of the Ross Sea, Antarctica from a coastal ice core record  [PDF]
R. H. Rhodes,N. A. N. Bertler,J. A. Baker,H. C. Steen-Larsen
Climate of the Past Discussions , 2012, DOI: 10.5194/cpd-8-215-2012
Abstract: The Little Ice Age (LIA) is the most recent abrupt climate change event. Understanding its forcings and associated climate system feedbacks is made difficult by a scarcity of Southern Hemisphere paleoclimate records. In this paper we utilise ice core glaciochemical records to reconstruct atmospheric and oceanic conditions in the Ross Sea sector of Antarctic, a region influenced by two contrasting meteorological regimes: katabatic winds and cyclones. Stable isotope (δD) and lithophile element concentration (e.g., Al) records indicate that the region experienced ~1.75 °C cooler temperatures and strong (>57 m s 1) prevailing katabatic winds during the LIA. We observe that the 1590–1875 record is characterised by high d-excess values and marine element (e.g., Na) concentrations, which are linked to the intrusion of cyclonic systems. The strongest katabatic wind events of the LIA, marked by Al, Ti and Pb concentration increases of an order of magnitude (>120 ppb Al), also occur during this interval. Furthermore, concentrations of the biogenic sulphur species MS suggest that biological productivity in the Ross Sea Polynya was ~80% higher prior to 1875 than in the subsequent time. We propose that colder temperatures and intensified cyclonic activity in the Ross Sea promoted stronger katabatic winds across the Ross Ice Shelf, resulting in an enlarged polynya with increased sea ice and bottom water production. It is therefore hypothesised that increased bottom water formation during the LIA occurred in response to atmospheric circulation change.
A Study of an Inversion Model for Sea Ice Thickness Retrieval in Ross Island, Antarctica
Yu Jen Lee;Wee Keong Lim;Hong-Tat Ewe
PIER , 2011, DOI: 10.2528/PIER10100411
Abstract: In this study, an inverse microwave scattering model for sea ice has been developed for the purpose of sea ice thickness retrieval using radar backscatter data. The model is loosely based on the Radiative-Transfer-Thermodynamic Inverse Model for Sea Ice Thickness Retrieval from Time-Series Scattering Data. The developed inverse model is a combination of the Radiative Transfer Theory with Dense Medium Phase and Amplitude Correction Theory (RT-DMPACT) forward model and the Levenberg-Marquardt Optimization algorithm. Using input data from ground truth measurements carried out in Ross Island, Antarctica, together with radar backscatter data extracted from purchased satellite images, the sea ice thickness of an area is estimated using the inverse model developed. The estimated sea ice thickness is then compared with the ground truth measurement data to verify its accuracy. The results have shown good promise, with successful estimation of the sea ice thickness within ±0.15 m of the actual measurement. A theoretical analysis has also revealed that the model faces difficulty once the sea ice thickness exceeds 1.7m. This can be considered in the future development and improvement of the model.
Snow accumulation and compaction derived from GPR data near Ross Island, Antarctica  [PDF]
N. C. Kruetzmann,W. Rack,A. J. McDonald,S. E. George
The Cryosphere Discussions , 2011, DOI: 10.5194/tcd-5-1-2011
Abstract: We present a new method of using ground penetrating radar (GPR) for estimating snow accumulation and compaction rates in Antarctica. We process 500 MHz data to produce radargrams with unambiguous reflection horizons that can be observed and tracked in repeat GPR measurements made one year apart. Our processing methodology is a deterministic deconvolution via the Fourier domain using an estimate of the emitted waveform from direct measurement. At two measurement sites near Scott Base, Antarctica, point measurements of average accumulation from snow pits and firn cores are extrapolated to a larger area by identifying a dateable dust layer in the radargrams. Over an 800 m×800 m area on the McMurdo Ice Shelf (77°45′ S, 167°17′ E) the average accumulation is found to be 269 ± 9 kg m 2 a 1. The accumulation over an area of 400 m×400 m in the dry snow zone on Ross Island (77°40′ S, 167°11′ E, 350 m a.s.l.) is found to be higher (404 ± 22 kg m 2 a 1) and shows increased variability related to undulating terrain. Compaction of snow between 2 m and 13 m depth is estimated at both sites by tracking several internal reflection horizons along the radar profiles and calculating the average change in separation of horizon pairs from one year to the next. The derived compaction rates range from 7 cm m 1 at a depth of two metres, down to no measurable compaction at 13 m depth, and are similar to published values from point measurements.
Snow accumulation and compaction derived from GPR data near Ross Island, Antarctica  [PDF]
N. C. Kruetzmann,W. Rack,A. J. McDonald,S. E. George
The Cryosphere , 2011, DOI: 10.5194/tc-5-391-2011
Abstract: We present an improved method for estimating accumulation and compaction rates of dry snow in Antarctica with ground penetrating radar (GPR). Using an estimate of the emitted waveform from direct measurements, we apply deterministic deconvolution via the Fourier domain to GPR data with a nominal frequency of 500 MHz. This reveals unambiguous reflection horizons which can be observed in repeat measurements made one year apart. At two measurement sites near Scott Base, Antarctica, we extrapolate point measurements of average accumulation from snow pits and firn cores to a larger area by identifying a dateable dust layer horizon in the radargrams. Over an 800 m × 800 m area on the McMurdo Ice Shelf (77°45′ S, 167°17′ E) the average accumulation is found to be 269 ± 9 kg m 2 a 1. The accumulation over an area of 400 m × 400 m on Ross Island (77°40′ S, 167°11′ E, 350 m a.s.l.) is found to be higher (404 ± 22 kg m 2 a 1) and shows increased variability related to undulating terrain. Compaction of snow between 2 m and 13 m depth is estimated at both sites by tracking several internal reflection horizons along the radar profiles and calculating the average change in separation of horizon pairs from one year to the next. The derived compaction rates range from 7 cm m 1 at a depth of 2 m, down to no measurable compaction at 13 m depth, and are similar to published values from point measurements.
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