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Colección de artículos en temáticas antárticas publicados por investigadores de la Universidad de Magallanes en diferentes fuentes, acorde a las políticas del editor.
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Item Mass balance of the antarctic ice sheet at Patriot Hills(International Glaciological Society, 1998) Casassa, Gino; Brecher, Henry H.; Cárdenas, Carlos; Rivera, AndresGlaciological data col lected at Patriot Hills, Antarctica (80°18' S, 81 ~2' W), are used to assess the local mass balance of the ice sheet. The data were collected during two field campaigns conducted by the Instituto Antartico Chileno inJanuary and November 1995. Measurements included surveying of stakes, and ice thickness derived from discrete radar soundings with a ground-based high-frequency impulse system. Ablation occurred on the bare-ice field at the base of Patriot Hills, with a maximum value of 7 gem - 2 a- I. et accumulation was detected away from the mountains, over the firn-covered area of the glacier, with a maximum rate of 10 g cm 2 a '. Ice thickens rapidly away from the mountains, reaching a thickness of 383 m, the maximum range of the radar system, near the center of the blue-ice field. No significant difference in surface elevation of the ice was detected over the 305 d period, which indicates that the ice is in near-equilibrium at Patriot Hills.Item Molluscan assemblages associated with gigartina beds in the strait of magellan and the south shetland islands (Antarctica): a comparison of composition and abundance(Taylor & Francis Group, 2017) Rosenfeld, Sebastián; Aldea, Cristian; Ojeda, Jaime; Marambio, Johanna; Hüne, Mathias; Troncoso, Jesús S.; Mansilla, AndrésIn this paper we evaluated the composition and abundance of molluscs associated with beds of the red algae Gigartina, located in the South Shetland Islands (Antarctic Peninsula) and the Strait of Magellan (southern Chile). During the summer season of 2013, samples were obtained by scuba diving using a 0.25 m2 quadrat, arranged randomly within the bed. We extracted a total of 15 quadrats per sampling site. For Antarctic Peninsula beds the most abundant species were the bivalve Lissarca miliaris (233 individuals) and the gastropod Laevilacunaria antarctica (94 individuals), while for Strait of Magellan beds the most abundant species was the polyplacophoran Callochiton puniceus (36 individuals). Comparative analysis between the two molluscan assemblages showed significant differences in the faunal composition between the Antarctic Peninsula and Strait of Magellan (f = 64.474; p = 0.0001). Therefore, molluscs reported in both areas are characteristic of their respective biogeographic area. Finally, Gigartina species play an important role in the formation of patterns of abundance and diversity of the communities associated with them.Item Evolution of the austral-antarctic flora during the cretaceous: New insights from a paleobiogeographic perspective(Sociedad de Biología de Chile, 2012) Leppe, Marcelo; Mihoc, Maritza; Varela, Natalia; Stinnesbeck, Wolfgang; Mansilla, Héctor; Bierma, Hessel; Cisterna, Katherine; Frey, Eberhard; Jujihara, ThoshiroFores t environments have continuously existed in Antarctica since the late Paleozoic and only disappeared from this continent since the Neogene. Nevertheless, the structure of these forests underwent substantial evolutionary changes. During the late Cretaceous, forests dominated by conifers and pteridophytes were gradually replaced by angiospermdominated forests. Elements common to these Antarctic forests are important constituents of the recent Valdivian Forest. During the Turonian stage of the Late Cretaceous, the Antarctic Peninsula and Patagonia were reconnected by a land bridge after a separation since the end of the Jurassic. Using biogeographic tools applied to the palynological and leaf imprint record, outcrops of Campanian-Maastrichtian age were studied from the Snow Hill, James Ross and Seymour (Marambio) Islands in the James Ross basin, Antarctica; Skua Bay, Half Three Point, Price Point and Zamek Hill on King George Island, Antarctica, and Rocallosa Point, Cerro Guido, Las Chinas, Dorotea Hill, Cazador Hill and La Irene in Chilean-Argentinian Patagonia, comparing the current distribution and the paleogeography, as well as the infl uence of potential areas of endemism and vicariants events. The analysis indicates that vegetation evolved under environmental conditions subject to intense volcanic and climatic disturbances, with changes from a period with extreme greenhouse climate (Turonian-Campanian) to strong cooling during the Maastrichtian. We suggest that a continuous forest existed in southern South America and Antarctica, which was shaped during the Latest Cretaceous by the presence of marine basins and and intermittent connection and disconnection of the flora.Item Trophic relationships of a subtidal fish assemblage in the Francisco Coloane coastal marine protected area, southern chilean patagonia(Taylor & Francis Group, 2018-02-27) Hüne, Mathias; Davis, Ernesto; Murcia, Silvia; Gutiérrez, David; Haro, DanielaA combination of stomach content and nitrogen (δ15N) and carbon (δ13C) stable-isotope analysis was used to assess the trophic interactions and feeding habits of three notothenioid coastal fish (Champsocephalus esox, Patagonotothen tessellata and Patagonotothen cornucola) and one exotic salmon species (Oncorhynchus tschawytscha) with diverse life habits (benthic and benthopelagic) in the Francisco Coloane Coastal Marine Protected Area, southern Chile. The stomach contents of C. esox were mainly fish; those of P. cornucola and O. tschawytscha were crustacean decapods, Munida gregaria. A cluster analysis on isotope data and stable-isotope Bayesian ellipses detected two different predator groups, one with benthopelagic habits (C. esox and O. tshawytscha) and one with benthic habits (P. cornucola and P. tessellata). These results were supported with similar isotopic trophic level of each group. We suggest that the exotic salmon O. tschawytscha is a generalist predator with a broad trophic niche that may compete with the native notothenioid C. esox, as both have equivalent trophic levels with substantial overlap. This preliminary study is the first on trophic relationships of a subtidal fish assemblage within a remote ecosystem of fjords and channels in Chile’s southern Patagonia.Item Genetic structure and demographic inference of the regular sea urchin Sterechinus neumayeri (Meissner, 1900) in the southern ocean: The role of the last glaciation(Tzen-Yuh Chiang, National Cheng Kung University, Taiwan, 2018-06-06) Díaz, Angie; Gerard, Karin; González-Wevar, Claudio; Maturana, Claudia; Féral, Jean-Pierre; David, Bruno; Saucède, Thomas; Poulin, ElieOne of the most relevant characteristics of the extant Southern Ocean fauna is its resiliency to survive glacial processes of the Quaternary. These climatic events produced catastrophic habitat reductions and forced some marine benthic species to move, adapt or go extinct. The marine benthic species inhabiting the Antarctic upper continental shelf faced the Quaternary glaciations with different strategies that drastically modified population sizes and thus affected the amount and distribution of intraspecific genetic variation. Here we present new genetic information for the most conspicuous regular sea urchin of the Antarctic continental shelf, Sterechinus neumayeri. We studied the patterns of genetic diversity and structure in this broadcast-spawner across three Antarctic regions: Antarctic Peninsula, the Weddell Sea and Ade lie Land in East Antarctica. Genetic analyses based on mitochondrial and nuclear markers suggested that S. neumayeri is a single genetic unit around the Antarctic continent. The species is characterized by low levels of genetic diversity and exhibits a typical star-like haplotype genealogy that supports the hypothesis of a single in situ refugium. Based on two mutation rates standardized for this genus, the Bayesian Skyline plot analyses detected a rapid demographic expansion after the Last Glacial Maximum. We propose a scenario of rapid postglacial expansion and recolonization of Antarctic shallow areas from a less ice-impacted refugium where the species survived the LGM. Considering the patterns of genetic diversity and structure recorded in the species, this refugium was probably located in East Antarctica.Item The changes in maximal oxygen uptake (V̊O2MAX) induced by physical exertion during an antarctic expedition depend on the initial V̊O2MAX of the individuals: a case study of the Brazilian expedition(Taylor & Francis, 2018-09-25) Moraes, Michele M.; Mendes, Thiago T.; Martins, Ygor A.T.; Espinosa, Cristian N.; Maluf, Chams B.; Soares, Danusa D.; Wanner, Samuel P.; Arantes, Rosa M. E.Antarctic climate is challenging, since the cold, wind and sensory monotony are stressful stimuli to individuals. Moreover, camp activities and heavy clothes may contribute to increase physiological strain. Thus, we aimed to characterise the physiological demand of a 24-day period in the Antarctic field and then to evaluate the effect of this expedition on the aerobic fitness in individuals with heterogeneous initial aerobic fitness (as determined by estimating maximum oxygen consumption – V̊ O2MAX). Before and after the 24-day period in Antarctica, 7 researchers and 2 mountaineers were subjected to incremental tests to estimate their V̊ O2MAX. Field effort was characterised by measuring heart rate (HR). During the field trips, their HR remained 33.4% of the recording time between 50–60% HRMAX, 22.3% between 60–70% HRMAX, and only 1.4% between 80 and 90% HRMAX. The changes in estimated V̊ O2MAX during the expedition depended on the pre-expedition aerobic fitness. The post-expedition V̊ O2MAX increased by 5.9% and decreased by 14.3%in individuals with lower (researchers) and higher (mountaineers) initial V̊ O2MAX, respectively. We concluded that physical effort in the Antarctic field is characterised as predominantly of low- to moderate-intensity. This effort represented an effective training load for individuals with lower initial V̊ O2MAX, but not for those with higher V̊ O2MAX.Item Divergence time estimations and contrasting patterns of genetic diversity between antarctic and southern south america benthic invertebrates(Sociedad de Biología de Chile, 2012) González-Wevar, Claudio Alejandro; Díaz, Angie; Gerard, Karin; Poulin, Elie; Cañete, Juan I.Diversity, abundance and composition of taxonomic groups in the Southern Ocean differ from elsewhere in the planet, since the biogeography in this region refl ects the complex interactions of tectonics, oceanography, climate and biological elements since the Eocene. Several groups of marine benthic organisms exhibit high levels of genetic divergence among provinces in this region, supporting the existence of a vicariance process through plate tectonics, while other groups with high dispersive capacity exhibit recent divergence processes. Moreover, the discovery of non- Antarctic decapod larvae in Antarctic Peninsula suggests that some groups can travel across the Antarctic Circumpolar Current. Here we analyzed levels of genetic divergence in congeneric species of three Southern Ocean’s benthic invertebrate groups with dispersive potential. For this purpose we included in the analyses COI sequences of an echinoid (Sterechinus), a gastropod (Nacella), and a bivalve (Yoldia). Considering the levels of genetic differentiation and assuming the molecular clock hypothesis we estimated the separation of invertebrates from the two continents. We also compared levels of genetic variation between Antarctic and sub-Antarctic species of Nacella and Sterechinus to determine the effect of the Quaternary glacial episodes in the demography of these species. We detected clear genetic differences between Antarctic and sub-Antarctic congeneric species of Sterechinus, Nacella, and Yoldia. According to our results, the installation of an effective barrier between Antarctica and sub-Antarctica occurred almost at the same time (between 3.7 and 5.0 Ma) for these groups of organisms, long after the physical separation of both continents. Genetic comparisons between Antarctic and Sub-Antarctic species of Nacella and Sterechinus detected lower levels of genetic diversity in Antarctic species, suggesting more pronounced effects of the glacial episodes in Antarctica than in South America. These results may refl ect the dramatic effect of the Quaternary glacial cycles on Antarctic population sizes, especially in groups with narrow bathymetric ranges. The present study provides new evidence about the differentiation processes between Antarctic and South American organisms. None of the analyzed genera showed evidence for recurrent gene fl ow across the Antarctic Circumpolar Current since the Mio-Pliocene. Genetic comparisons indicate that Antarctic and Sub-Antarctic species were differentially affected by glacial periods.Item A 17-year record of meteorological observations across the gran campo nevado ice cap in southern patagonia, Chile, related to synoptic weather types and climate modesWeidemann, Stephanie S.; Sauter, Tobías; Kilian, Rolf; Steger, David; Butorovic, Nicolás; Schneider, Christoph; Burkhart, John F.The network of long-term meteorological observations in Southernmost Patagonia is still sparse but crucial to improve our understanding of climatic variability, in particular in the more elevated and partially glaciated Southernmost Andes. Here we present a unique 17-year meteorological record (2000–2016) of four automatic weather stations (AWS) across the Gran Campo Nevado Ice Cap (53◦S) in the Southernmost Andes (Chile) and the conventional weather station Jorge Schythe of the Instituto de la Patagonia in Punta Arenas for comparison. We revisit the relationship between in situ observations and large-scale climate models as well as mesoscale weather patterns. For this purpose, a 37-year record of ERA Interim Reanalysis data has been used to compute a weather type classification based on a hierarchical correlation-based leader algorithm. The orographic perturbation on the predominantly westerly airflow determines the hydroclimatic response across the mountain range, leading to significant west-east gradients of precipitation, air temperature and humidity. Annual precipitation sums heavily drop within only tens of kilometers from ~7,500 mma−1 to less than 800 mma−1. The occurrence of high precipitation events of up to 620 mm in 5 days and wet spells of up to 61 consecutive days underscore the year-around wet conditions in the Southernmost Andes. Given the strong link between large-scale circulation and orographically controlled precipitation, the synoptic-scale weather conditions largely determine the precipitation and temperature variability on all time scales. Major synoptic weather types with distinct low-pressure cells in the Weddell Sea or Bellingshausen Sea, causing a prevailing southwesterly, northwesterly or westerly airflow, determine the weather conditions in Southernmost Patagonia during 68% of the year. At Gran Campo Nevado, more than 80% of extreme precipitation events occur during the persistence of these weather types. The evolution of the El Niño Southern Oscillation and Antarctic Oscillation impose intra- and inter-annual precipitation and temperature variations. Positive Antarctic Oscillation phases on average are linked to an intensified westerly airflow and warmer conditions in Southernmost Patagonia. Circulation patterns with high-pressure influence leading to colder and dryer conditions in Southernmost Patagonia are more frequent during negative Antarctic Oscillation phases.Item UV irradiance and albedo at Union Glacier Camp (Antarctica): a case study(Public Library of Science (PLOS), 2014) Cordero, Raúl R.; Damiani, Alessandro; Ferrer, Jorge; Jorquera, José; Tobar, Mario; Labbe, Fernando; Carrasco, Jorge; Laroze, David; Añel, Juan A.We report on the first spectral measurements of ultraviolet (UV) irradiance and the albedo at a Camp located in the southern Ellsworth Mountains on the broad expanse of Union Glacier (700 m altitude, 79u 469 S; 82u 529W); about 1,000 km from the South Pole. The measurements were carried out by using a double monochromator-based spectroradiometer during a campaign (in December 2012) meant to weight up the effect of the local albedo on the UV irradiance. We found that the albedo measured at noon was about 0.95 in the UV and the visible part of the spectrum. This high surface reflectivity led to enhancements in the UV index under cloudless conditions of about 50% in comparison with snow free surfaces. Spectral measurements carried out elsewhere as well as estimates retrieved from the Ozone Monitoring Instrument (OMI) were used for further comparisons.Item Biogeography in Cellana (Patellogastropoda, Nacellidae) with special emphasis on the relationships of southern hemisphere oceanic island species(PLOS, 2017-01-18) González-Wevar, Claudio A.; Nakano, Tomoyuki; Palma, Alvaro; Poulin, ElieOceanic islands lacking connections to other land are extremely isolated from sources of potential colonists and have acquired their biota mainly through dispersal from geographically distant areas. Hence, isolated island biota constitutes interesting models to infer biogeographical mechanisms of dispersal, colonization, differentiation, and speciation. Limpets of the genus Cellana (Nacellidae: Patellogastropoda) show limited dispersal capacity but are broadly distributed across the Indo-Pacific including many endemic species in isolated oceanic islands. Here, we examined main distributional patterns and geographic boundaries among Cellana lineages with special emphasis in the relationships of Southern Hemisphere oceanic islands species. Phylogenetic reconstructions based on mtDNA (COI) recognized three main clades in Cellana including taxa from different provinces of the Indo-Pacific. Clear genetic discontinuities characterize the biogeography of Cellana and several lineages are associated to particular areas of the Indo-Pacific supporting the low dispersal capacity of the genus across recognized biogeographical barriers in the region. However, evolutionary relationships within Cellana suggest that long-distance dispersal processes have been common in the history of the genus and probably associated to the origin of the species in Hawaii and Juan FernaÂndez Archipelago. Therefore, the presence of Cellana species in geographically distant Southern Hemisphere oceanic islands, such as the Juan FernaÂndez Archipelago, suggests that long-distance dispersal mediated by rafting may have played an important role in the biogeography of the genus.Item Human-Associated Extended-Spectrum β - Lactamase in the Antarctic(American Society for Microbiology, 2012-03) Hernández, Jorge; Stedt, Johan; Bonnedahl, Jonas; Molin, Ylva; Drobni, Mirva; Calisto Ulloa, Nancy; Gómez Fuentes, Claudio; Astorga España, María Soledad; González Acuña, Daniel; Waldenström, Jonas; Blomqvist, María; Olsena, BjörnEscherichia coli bacteria with extended-spectrum -lactamase (ESBL) type CTX-M resistance were isolated from water samples collected close to research stations in Antarctica. The isolates had blaCTX-M-1 and blaCTX-M-15 genotypes and sequence types (ST) indicative of a human-associated origin. This is the first record of ESBL-producing enterobacteria from Antarctica.Item Extreme sunbathing: three weeks of small total O3 columns and high UV radiation over the southern tip of South America during the 2009 Antarctic O3 hole season(American Geophysical Union, 2010-07-27) Laat, A.T.J. de; Van der A., R.J.; Alaart, M.A.F.; Van Wheele, M.; Benítez, G.C.; Casiccia, Claudio; Paes Leme, N.M.; Quel, E.; Salvador, J.; Wolfram, E.This paper presents an analysis of satellite and groundbased measurements of total O3 columns and the UV index of a unique event during the 2009 Antarctic O3 hole season. From 11 to 30 November 2009 the Antarctic vortex was located just south of the southern tip of South America rather than at its climatological position over Antarctica. Analysis of 30 years of assimilated total O3 column and UV index measurements shows that this 20‐day event was unique in the history of the ozone hole for these latitudes. During this period, small total O3 columns and large UV index values were observed over the southern tip of South America. Comparison of ground‐based and satellite measurements of total O3 columns and satellite based calculations of the UVI index – never designed nor validated for such extreme Southern Hemisphere conditions – show excellent agreement.Item Synergistic roles of climate warming and human occupation in patagonian megafaunal extinctions during the Last Deglaciation(American Association for the Advancement of Science, 2016-06-17) Metcalf, Jessica L.; Turney, Chris; Barnett, Ross; Martin, Fabiana; Bray, Sara C.; Vilstrup, Julia T.; Orlando, Ludovic; Salas-Gismondi, Rodolfo; Loponte, Daniel; Medina, Matías; De Nigris, Mariana; Civalero, Teresa; Fernández, Pablo Marcelo; Gasco, Alejandra; Durán, Victor; Seymour, Kevin L.; Otaola, Clara; Gil, Adolfo; Paunero, Rafael; Prevosti, Francisco J.; Bradshaw, Corey J. A.; Wheeler, Jane C.; Borrero, Luis; Austin, Jeremy J.; Cooper, AlanThe causes of Late Pleistocene megafaunal extinctions (60,000 to 11,650 years ago, hereafter 60 to 11.65 ka) remain contentious, with major phases coinciding with both human arrival and climate change around the world. The Americas provide a unique opportunity to disentangle these factors as human colonization took place over a narrow timeframe (~15 to 14.6 ka) but during contrasting temperature trends across each continent. Unfortunately, limited data sets in South America have so far precluded detailed comparison. We analyze genetic and radiocarbon data from 89 and 71 Patagonian megafaunal bones, respectively, more than doubling the high-quality Pleistocene megafaunal radiocarbon data sets from the region.Weidentify anarrowmegafaunal extinction phase 12,280 ± 110 years ago, some 1 to 3 thousand years after initial human presence in the area. Although humans arrived immediately prior to a cold phase, the Antarctic Cold Reversal stadial, megafaunal extinctions did not occur until the stadial finished and the subsequent warming phase commenced some 1 to 3 thousand years later. The increased resolution provided by the Patagonianmaterial reveals that the sequence of climate andextinctionevents inNorthandSouth America were temporally inverted, but in both cases, megafaunal extinctions did not occur until human presence and climate warming coincided. Overall, metapopulation processes involving subpopulation connectivity on a continental scale appear to have been critical for megafaunal species survival of both climate change and human impacts.Item Glacial reduction and millennial-scale variations in Drake Passage throughflow(National Academy of Sciences, 2015-11-03) Lamy, Frank; Arz, Helge W.; Kilian, Rolf; Lange, Carina B.; Lembke-Jene, Lester; Wengler, Marc; Kaiser, Jerôme; Baeza-Urrea, Oscar; Hall, Ian R.; Harada, Naomi; Tiedemann, Ralf; Thiemens, Mark H.The Drake Passage (DP) is the major geographic constriction for the Antarctic Circumpolar Current (ACC) and exerts a strong control on the exchange of physical, chemical, and biological properties between the Atlantic, Pacific, and Indian Ocean basins. Resolving changes in the flow of circumpolar water masses through this gateway is, therefore, crucial for advancing our understanding of the Southern Ocean’s role in global ocean and climate variability. Here, we reconstruct changes in DP throughflow dynamics over the past 65,000 y based on grain size and geochemical properties of sediment records from the southernmost continental margin of South America. Combined with published sediment records from the Scotia Sea, we argue for a considerable total reduction of DP transport and reveal an up to ∼40% decrease in flow speed along the northernmost ACC pathway entering the DP during glacial times. Superimposed on this long-term decrease are high-amplitude, millennial- scale variations, which parallel Southern Ocean and Antarctic temperature patterns. The glacial intervals of strong weakening of the ACC entering the DP imply an enhanced export of northern ACC surface and intermediate waters into the South Pacific Gyre and reduced Pacific–Atlantic exchange through the DP (“cold water route”). We conclude that changes in DP throughflow play a critical role for the global meridional overturning circulation and interbasin exchange in the Southern Ocean, most likely regulated by variations in the westerly wind field and changes in Antarctic sea ice extent.Item Biogeochemistry of a low-activity cold seep in the Larsen B area, western Weddell Sea, Antarctica(Copernicus Publications on behalf of the European Geosciences Union, 2009-11-02) Niemann, H.; Fisher, D.; Graffe, D.; Knittel, K.; Montiel, Américo; Heilmayer, O.; Knothen, K.; Pape, K.; Kasten, S.; Bohrmann, G.; Boetius, A.; Gutt, J.; Kusel, K.First videographic indication of an Antarctic cold seep ecosystem was recently obtained from the collapsed Larsen B ice shelf, western Weddell Sea (Domack et al., 2005). Within the framework of the R/V Polarstern expedition ANTXXIII-8, we revisited this area for geochemical, microbiological and further videographical examinations. During two dives with ROV Cherokee (MARUM, Bremen), several bivalve shell agglomerations of the seep-associated, chemosynthetic clam Calyptogena sp. were found in the trough of the Crane and Evans glacier. The absence of living clam specimens indicates that the flux of sulphide and hence the seepage activity is diminished at present. This impression was further substantiated by our geochemical observations. Concentrations of thermogenic methane were moderately elevated with 2μM in surface sediments of a clam patch, increasing up to 9μM at a sediment depth of about 1m in the bottom sections of the sediment cores. This correlated with a moderate decrease in sulphate from about 28mM at the surface down to 23.4 mM, an increase in sulphide to up to 1.43mM and elevated rates of the anaerobic oxidation of methane (AOM) of up to 600 pmol cm−3 d−1 at about 1m below the seafloor. Molecular analyses indicate that methanotrophic archaea related to ANME-3 are the most likely candidates mediating AOM in sediments of the Larsen B seep.Item Initial reconnaissance for a South Georgia ice core(Cambridge Universty Press, 2016-03-16) Mayewsky, P.A.; Kuli, A.; Casassa, Gino; Arévalo, M.; Dixon, D.A.; Grigholm, B.; Handley, M.J.; Hoffmann, H.; Introne, D.S.; Kuli, A.G.; Potocki, M.; Sneed, S.B.We present the first snow/ice chemistry and ice radar results ever collected from South Georgia as part of an initial reconnaissance with the ultimate goal of assessing the feasibility of a South Georgia ice core to reconstruct past climate in the South Atlantic. South Georgia is well situated to capture a record of past atmospheric chemical composition over the South Atlantic and of past variability in the position and intensity of the austral westerlies. The question is how well preserved an ice core record can be recovered from a region experiencing accelerated melting? The results presented in this paper offer only a preliminary step in determining the feasibility of future deep ice coring on South Georgia. However, this initial reconnaissance does provide some basic information including: the chemistry of the atmosphere over South Georgia relative to other Southern Hemisphere ice coring sites; the potential for preservation of ‘annual layers’ in old ice on the island; a possible age for deep ice in the region; and an estimate of glacier health in the lower elevation regions of the island.Item Transport of crustal microparticles from Chilean Patagonia to the Antarctic Peninsula by SEM-EDS analysis(Blackwell Munksgaard, 2004) Pereira, Kely Cristine Dalia; Evangelista, Eitor; Pereira, Enio Bueno; Cardia Simoes, Jefferson; Johnson, Erling; Rodrigues Melo, LeticiaThe individual elemental composition of insoluble airborne particulates found in King George Island (KGI), Antarctic Peninsula (atmosphere, snow, firn and ice deposits) and in the atmosphere of Chilean Patagonia by SEM-EDS analysis identify probable sources and transport mechanisms for the atmospheric aerosols observed in these regions. Insoluble airborne particulates found in the snow, firn and ice in a core from Lange Glacier (KGI) call for significant crustal influence, mainly associated with aluminium potassium, aluminium calcium and magnesium iron silicates together with other aluminium silicates of calcium and magnesium, among rare others containing Ti, Ni and Cr. Our study suggests that 95% of the bulk mode insoluble particulates deposited in Lange Glacier can be explained by atmospheric transport from Chilean Patagonia. Cyclonic systems passing between southernmost South America and the Antarctic Peninsula are the most probable atmospheric transport mechanism, tracked by measurements of 222Rn and Si.Item Bioactive monoterpenes from antarctic Plocamium Cartilagineum(Sociedad Chilena de Química, 2013) Rovirosa, Juana; Soler, Agnes; Blanc, Vanessa; León, Rubén; San Martín, AurelioIn a chemical analysis of the red seaweed Plocamium cartilagineum collected in Antarctic Peninsula, four polyhalogenated monoterpenes were isolated. Their structures were established by spectroscopic techniques. Two of them are acyclic monoterpenes and the others are cyclic. We report the antimicrobial, insecticide and acaricide activities of compounds.Item Assessing the impact of retreat mechanisms in a simple antarctic ice sheet model using bayesian calibration(Public Library of Science, 2017-01-12) Ruckert, Kelsey L.; Shaffer, Gary; Pollard, David; Guan, Yaguen; Wong, Tony E.; Forest, Chris E.; Keller, Klaus; Añel, Juan A.The response of the Antarctic ice sheet (AIS) to changing climate forcings is an important driver of sea-level changes. Anthropogenic climate change may drive a sizeable AIS tipping point response with subsequent increases in coastal flooding risks. Many studies analyzing flood risks use simple models to project the future responses of AIS and its sea-level contributions. These analyses have provided important new insights, but they are often silent on the effects of potentially important processes such as Marine Ice Sheet Instability (MISI) or Marine Ice Cliff Instability (MICI). These approximations can be well justified and result in more parsimonious and transparent model structures. This raises the question of how this approximation impacts hindcasts and projections. Here, we calibrate a previously published and relatively simple AIS model, which neglects the effects of MICI and regional characteristics, using a combination of observational constraints and a Bayesian inversion method. Specifically, we approximate the effects of missing MICI by comparing our results to those from expert assessments with more realistic models and quantify the bias during the last interglacial when MICI may have been triggered. Our results suggest that the model can approximate the process of MISI and reproduce the projected median melt from some previous expert assessments in the year 2100. Yet, our mean hindcast is roughly 3/4 of the observed data during the last interglacial period and our mean projection is roughly 1/6 and 1/10 of the mean from a model accounting for MICI in the year 2100. These results suggest that missing MICI and/or regional characteristics can lead to a low-bias during warming period AIS melting and hence a potential low-bias in projected sea levels and flood risks.Item Historically unprecedented global glacier decline in the early 21st century(International Glaciological Society, 2015) Zemp, Michael; Frey, Holger; Garnert-Roer, Isabelle; Nussbaumer, Samuel U.; Hoelzle, Martin; Paul, Frank; Haeberli, Wilfried; Denzinger, Florian; Anderson, Brian; Bajracharya, Samjwal; Baroni, Carlo; Braun, Ludwing N.; Cáceres, Bolívar E.; Casassa, Gino; Dávila, Luzmila R.; Delgado Granados, Hugo; Demuth, Michael N.; Espizua, Lydia; Fisher, Andrea; Fujita, Koji; Gadek, Bogdan; Ghazanfar, Ali; Hagen, Jon Ovi; Holmlund, Per; Karimi, Neamat; Li, Zhonqin; Pelto, Mauri; Pitte, Pierre; Popovnin, Victor V.; Portocarrero, Cesar A.; Prinz, Rainer; Sangewar, Chandrashekhar; Severskiy, Igor; Sigurdsson, Oddur; Soruco, Alvaro; Usubaliev, Ryskul; Vincent, Christian; Ahlstrom, Andreas P.; Cobos, GuillermoObservations show that glaciers around the world are in retreat and losing mass. Internationally coordinated for over a century, glacier monitoring activities provide an unprecedented dataset of glacier observations from ground, air and space. Glacier studies generally select specific parts of these datasets to obtain optimal assessments of the mass-balance data relating to the impact that glaciers exercise on global sea-level fluctuations or on regional runoff. In this study we provide an overview and analysis of the main observational datasets compiled by the World Glacier Monitoring Service (WGMS). The dataset on glacier front variations (~42 000 since 1600) delivers clear evidence that centennial glacier retreat is a global phenomenon. Intermittent readvance periods at regional and decadal scale are normally restricted to a subsample of glaciers and have not come close to achieving the maximum positions of the Little Ice Age (or Holocene). Glaciological and geodetic observations (~5200 since 1850) show that the rates of early 21st-century mass loss are without precedent on a global scale, at least for the time period observed and probably also for recorded history, as indicated also in reconstructions from written and illustrated documents. This strong imbalance implies that glaciers in many regions will very likely suffer further ice loss, even if climate remains stable.
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