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Here, we define weather regimes in the East Antarctica—Southern Ocean sector based on daily anomalies of 700 hPa geopotential height derived from ERA5 reanalysis during 1979–2018. Most regimes and their preferred transitions depict synoptic‐scale disturbances propagating eastwards off the Antarctic coastline. While regime sequences are generally short, their interannual variability is strongly driven by the polarity of the Southern Annular Mode (SAM). Regime occurrences are then intersected with atmospheric rivers (ARs) detected over the same region and period. ARs are equiprobable throughout the year, but clearly concentrate during regimes associated with a strong atmospheric ridges/blockings on the eastern part of the domain, which act to channel meridional advection of heat and moisture from the lower latitudes towards Antarctica. Both regimes and ARs significantly shape climate variability in Antarctica. Regimes favorable to AR occurrences are associated with anomalously warm and humid conditions in coastal Antarctica and, to a lesser extent, the hinterland parts of the Antarctic plateau. These anomalies are strongly enhanced during AR events, with warmer anomalies and dramatically amplified snowfall amounts. Large‐scale conditions favoring AR development are finally explored. They show weak dependency to the SAM, but particularly strong atmospheric ridges/blockings over the Southern Ocean appear as the most favorable pattern, in which ARs can be embedded, and to which they contribute. Key Points: Atmospheric rivers (ARs) reaching East Antarctica show strong association with synoptic weather regimesARs enhance the positive temperature and snowfall anomalies associated with the regimesARs occur when the synoptic configuration is anomalously strong over the Southern Ocean [ABSTRACT FROM AUTHOR]

The specified dynamics Whole Atmosphere Community Climate Model with thermosphere and ionosphere extension (SD‐WACCM‐X) was utilized to explore migrating tidal variabilities that occurred during the 2002, 2010, and 2019 Antarctic sudden stratospheric warming (SSW) events. All migrating tides show prominent day‐to‐day variations in the mesosphere and lower thermosphere regions, which can be mainly attributed to each Antarctic SSW event. The westward propagating diurnal tide with zonal wavenumber 1 (DW1) and the westward propagating semidiurnal tide with zonal wavenumber 2 (SW2) show a distinct reduction and an increase during each Antarctic SSW event, respectively. Specifically, the westward propagating terdiurnal tide with zonal wavenumber 3 (TW3) shows an unexpected decrease, which is opposite to the behaviors of TW3 reported during Arctic SSW events. We conclude that the unexpected decrease in TW3 may be mainly caused by the nonlinear interaction between DW1 and SW2, in which DW1 may play a major role. In the ionosphere, the TW3 amplitudes also show a decrease during each Antarctic SSW event, which is in consistency with decreasing tidal amplitudes in the neutral atmosphere. Our study demonstrates that TW3 is also a considerable source for short‐term ionospheric variability during Antarctic SSW events. Key Points: TW3 amplitudes show an unexpected decrease in the neutral atmosphere during Antarctic sudden stratospheric warming (SSW) events as revealed by SD‐WACCM‐XThe decrease in TW3 is likely due to the weakness of DW1 and derived from nonlinear wave‐wave interactionsThe simultaneous decrease in the TW3 amplitudes in the ionosphere indicates neutral‐ion coupling through tides during Antarctic SSW events [ABSTRACT FROM AUTHOR]

A comparative analysis between observational data from McMurdo Station, Antarctica and the Community Atmosphere Model version 6 (CAM6) simulation is performed focusing on cloud characteristics and their thermodynamic conditions. Ka‐band Zenith Radar (KAZR) and High Spectral Resolution Lidar (HSRL) retrievals are used as the basis of cloud fraction and cloud phase identifications. Radiosondes released at 12‐h increments provide atmospheric profiles for evaluating the simulated thermodynamic conditions. Our findings show that the CAM6 simulation consistently overestimates (underestimates) cloud fraction above (below) 3 km in four seasons of a year. Normalized by total in‐cloud samples, ice and mixed phase occurrence frequencies are underestimated and liquid phase frequency is overestimated by the model at cloud fractions above 0.6, while at cloud fractions below 0.6 ice phase frequency is overestimated and liquid‐containing phase frequency is underestimated by the model. The cloud fraction biases are closely associated with concurrent biases in relative humidity (RH), that is, high (low) RH biases above (below) 2 km. Frequencies of correctly simulating ice and liquid‐containing phase increase when the absolute biases of RH decrease. Cloud fraction biases also show a positive correlation with RH biases. Water vapor mixing ratio biases are the primary contributor to RH biases, and hence, likely a key factor controlling the cloud biases. This diagnosis of the evident shortfalls of representations of cloud characteristics in CAM6 simulation at McMurdo Station brings new insight in improving the governing model physics therein. Plain Language Summary: Global climate models (GCMs) historically struggle to accurately estimate the amounts and types of clouds over the polar regions. Cloud cover and thermodynamic phase directly influence Earth's radiation budget and the accuracy of future climate prediction. Particularly, Antarctic ice sheet is vulnerable to a changing climate through interactions with atmosphere and ocean, and the impacts of clouds are still not well understood. In this study, shortcomings of cloud representations in the CAM6 model were diagnosed by comparing with observational data (ground‐based remote sensing and radiosondes), which encompassed a year of measurements at McMurdo Station, Antarctica. Cloud fraction and phase as well as thermodynamic variables were examined to identify model biases. The model overestimates cloud cover above 3 km and underestimates it below that altitude. In cases where cloud cover is greater than 60%, the model also produces excessively large percentages of liquid clouds. These model biases are well correlated with biases in relative humidity, which is further dominated by biases in water vapor concentrations. Thus, these findings indicate that improving representations of water vapor concentrations in the model is a key step toward improving the simulations of cloud characteristics in Antarctica. Key Points: CAM6 shows higher (lower) cloud fraction above (below) 3 km than observations at McMurdo Station, AntarcticaCAM6 underestimates (overestimates) ice phase proportion among all cloud samples at cloud fraction ≥0.6 (<0.6)Model RH biases are dominated by water vapor biases instead of temperature biases, and correlate with cloud fraction and cloud phase biases [ABSTRACT FROM AUTHOR]

Water-stable isotopes in polar ice cores are a widely used temperature proxy in paleoclimate reconstruction, yet calibration remains challenging in East Antarctica. Here, we reconstruct the magnitude and spatial pattern of Last Glacial Maximum surface cooling in Antarctica using borehole thermometry and firn properties in seven ice cores. West Antarctic sites cooled ~10°C relative to the preindustrial period. East Antarctic sites show a range from ~4° to ~7°C cooling, which is consistent with the results of global climate models when the effects of topographic changes indicated with ice core air-content data are included, but less than those indicated with the use of water-stable isotopes calibrated against modern spatial gradients. An altered Antarctic temperature inversion during the glacial reconciles our estimates with water-isotope observations. [ABSTRACT FROM AUTHOR]

We present a refined map of geothermal heat flow for Antarctica, Aq1, based on multiple observables. The map is generated using a similarity detection approach by attributing observables from geophysics and geology to a large number of high‐quality heat flow values (N = 5,792) from other continents. Observables from global, continental, and regional datasets for Antarctica are used with a weighting function that allows the degree of similarity to increase with proximity and how similar the observables are. The similarity detection parameters are optimized through cross correlation. For each grid cell in Antarctica, a weighted average heat flow value and uncertainty metrics are calculated. The Aq1 model provides higher spatial resolution in comparison to previous results. High heat flow is shown in the Thwaites Glacier region, with local values over 150 mW m−2. We also map elevated values over 80 mW m−2 in Palmer Land, Marie Byrd Land, Victoria Land and Queen Mary Land. Very low heat flow is shown in the interior of Wilkes Land and Coats Land, with values under 40 mW m−2. We anticipate that the new geothermal heat flow map, Aq1, and its uncertainty bounds will find extended use in providing boundary conditions for ice sheet modeling and understanding the interactions between the cryosphere and solid Earth. The computational framework and open architecture allow for the model to be reproduced, adapted and updated with additional data, or model subsets to be output at higher resolution for regional studies. Plain Language Summary: We present a new map that shows how the heat from the deep Earth varies from place to place in Antarctica. The map shows where raised heat flow values beneath ice sheets need to be included to better predict how ice sheets will respond to the Earth's warming climate. Areas with volcanoes have high geothermal heat flow. Other medium to high heat flow locations are often hard to identify, especially as it is too difficult or expensive to measure the heat directly in the harsh and sensitive Antarctic environment. To overcome this challenge, we use a technique with computer‐aided match between the best data we can compile for Antarctica and corresponding data and heat flow values from other continents. Key Points: A new heat flow map of Antarctica suitable for solid Earth and interdisciplinary studies is presentedMultiple observables are combined in a similarity approach to link global data compilationsA reproducible, adaptable workflow with uncertainty metrics is provided [ABSTRACT FROM AUTHOR]

We present a new approach to account for the influence of subglacial topography on geothermal heat flux beneath the Greenland and Antarctic ice sheets. We first establish a simple empirical proportionality between local geothermal flux and topographic relief within a given radius, based on a synthesis of existing observations of these properties elsewhere on Earth. This analysis essentially yields a high‐pass filter that can be readily applied to existing large‐scale geothermal heat flux fields to render them consistent with known subglacial topography. This empirical approach avoids both the geometric limitations of existing analytic models and the complex boundary conditions required by numerical heat flow models, yet it also produces results that are consistent with both of those methods, for example, increased heat flux within valleys and decreased heat flux along ridges. Comparison with borehole‐derived geothermal heat flux suggests that our topographic correction is also valid for non‐ice‐covered areas of Earth and that a borehole location uncertainty of >100 m can limit the value of its inferred heat flux. Ice‐sheet‐wide application of this approach indicates that the effect of local topography upon geothermal heat flux can be as important as choice of regional geothermal heat flux field across a small portion of Antarctica (2%) and a larger portion of Greenland (13%), where subglacial topography is best resolved. We suggest that spatial variability in geothermal heat flux due to topography is most consequential in slower‐flowing portions of the ice sheets, where there is no frictional heating due to basal sliding. We conclude that studies of interactions between ice sheets and geothermal heat flux must consider the effect of subglacial topography at sub‐kilometer horizontal scales. Plain Language Summary: Earth's thick, polar ice sheets insulate the bedrock beneath them from the colder temperatures at the ice surface. Consequently, the small amount of geothermal heat that Earth's bedrock releases can have a disproportionate role in controlling ice flow. Geothermal heat flux measurements beneath ice sheets are sparse, and models do not presently account for variable bed topography. Here, we present a simple statistical method for correcting geothermal heat flux models to make them consistent with known subglacial bed topography. This method is based on previous geothermal heat flux measurements across valleys and ridges, and it helps us explore the broader significance of geothermal heat flux variability beneath the Greenland and Antarctic ice sheets. Our method can also be used to estimate the influence of topography on geothermal heat flux in non‐ice‐covered areas. Key Points: Deeply incised subglacial valleys can double local geothermal flux beneath the Greenland and Antarctic ice sheetsThe magnitude of topographic correction often exceeds uncertainty in geothermal heat flux where subglacial topography is best resolvedPositional uncertainties for geothermal flux measurements of greater than 100 m can prevent robust topographic corrections thereof [ABSTRACT FROM AUTHOR]

Endophytic bacteria, recognized for their beneficial effects on plant development and adaptation, can facilitate the survival of Antarctic plants in severe environments. Here we studied endophytes of the vascular plant Deschampsia antarctica Ė. Desv. from two distantly located regions in the maritime Antarctic: King George Island (South Shetland Islands) and Galindez Island (Argentine Islands). Bacterial group-specific PCR indicated presence of Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Firmicutes, Cytophaga-Flavobacteria and Actinobacteria in root and leaf endosphere of D. antarctica sampled at four distinct sites of both locations. The diversity of endophytic bacteria was significantly higher in the leaves compared to the roots in plants from Galindez Island. Similarly, the diversity of endophytes was higher in the leaves rather than roots of plants from the King George Island. Twelve bacterial species were isolated from roots of D. antarctica of Galindez Island (the Karpaty Ridge and the Meteo Point) and identified by sequencing the 16S rRNA gene. Isolates were dominated by the Pseudomonas genus, followed by the genera Bacillus and Micrococcus. The vast majority of the isolates exhibited cellulase and pectinase activities, however, Bacillus spp. expressed neither of them, suggesting lack of genetic flow of these traits in endophytic bacilli in the maritime Antarctic. Pseudomonas sp. IMBG305 promoted an increase in the leaf number in most of the treated plant genotypes when compared with noninoculated plants, and a rapid vegetation period of D. antarctica cultured in vitro, albeit the length of leaves in the treated plants was significantly lower, and flavonoid content leveled off in all treated plants. D. antarctica is known to develop diverse ecotypes with regard to ecological conditions, such as organic input, moisture or wind exposition. The D. antarctica phenotype could be extended further through the endophyte colonization, since phenotypic changes were observed in the inoculated D. antarctica plants grown in vitro in our study. Herewith, endophytes can contribute to plant phenotypic plasticity, potentially beneficial for adaptation of D. antarctica. [ABSTRACT FROM AUTHOR]

This paper presents the GRASS GIS-based thematic mapping of Antarctica using scripting approach and associated datasets on topography and geophysics. The state-ofthe art in cartographic development points at two important aspects. The first one comprises shell scripting promoted repeatability of the GIS technique, increased automatization in cartographic workflow, and compatibility of GRASS with Python, PROJ and GDAL libraries which enables advanced geospatial data processing: converting formats, re-projecting and spatial analysis. The second aspect is that data visualization greatly influences geologic research through improving the interpretation between the Antarctic glaciation and surface. This includes the machine learning algorithms of image classification enabling to distinguish between glacier and non-glacier surfaces through automatically partitioning data and analysis of various types of surfaces. Presented detailed maps of Antarctic include visualized datasets from the ETOPO1, GlobSed, EGM96 and Bedmap2 projects. The grids include bed and surface elevation, ETOPO1-based bathymetry and topography, bed, ice and sediment thickness, grounded bed uncertainty, subglacial bed elevation, geoid undulations, ice mask grounded and shelves. Data show the distribution of the present-day glacier, geophysical fields and topographic landforms for analysis of processes and correlations between the geophysical and geological phenomena. Advances in scripting cartography are significant contributions to the geological and glaciological research. Processing high-resolution datasets of Southern Ocean retrieved by remote sensing methods present new steps in automatization of the digital mapping, as presented in this research, and promotes comprehensive monitoring of geological, permafrost and glacial processes in Antarctica. All maps have been plotted using GRASS GIS version 7.8. with technical details of scripts described and interpreted. [ABSTRACT FROM AUTHOR]

Regional fisheries organisations globally are feeling the impacts of non-compliant behaviour by both contracting and non-contracting parties. Non-compliance arising from activities such as illegal, unreported and unregulated fishing, or failures by flag states to appropriately report the activities of their vessels, has resulted in damage to the environment and damage to the performance of regional fisheries management organisations themselves. As a result, many of these organisations are adopting and implementing a relatively new mechanism to tackle non-compliance: the compliance evaluation procedure. This article demonstrates that by adopting a compliance evaluation procedure, regional fisheries organisations are better placed to identify and address non-compliance in an effort to improve compliance with their conservation measures. It analyses in detail the procedure adopted by one particular organisation, the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), to suggest that implementation of their procedure has improved transparency, accountability and enforcement. It is argued that the CCAMLR compliance evaluation procedure represents a model for other polar and high seas areas to promote sustainable, and responsible, fishing practices globally. [ABSTRACT FROM AUTHOR]

While the role of supraglacial environments such as the cryoconite holes and surface snow in cycling of carbon and nutrients has gained momentum in the last decade, little has been done to assess how interactions with sunlight and microbes control the dissolved organic matter cycling in these environments. In this study, the cryoconite holes, which are subjected to different light conditions, were monitored in the coastal Antarctica during the summer in order to determine how the geochemistry of these environments varied through the melt season. Additionally, mesocosm experiments were conducted to understand the impact of photochemical and microbial activities on dissolved organic carbon (DOC) and ionic constituents in the snow and cryoconite holes. In situ measurements of primary and bacterial production carried out in the surface snow and cryoconite holes showed that the primary production rates were higher than the bacterial production rates. Both photochemical and microbial processes resulted in changing the concentration of DOC, carboxylate, and nitrate ions in these environments. Sunlight‐induced production of biologically labile compounds, such as acetate and formate, and photochemical degradation of oxalate were also observed. Microbial activity had the opposite effect, resulting in an increase in oxalate and decrease in acetate and formate concentrations. Consequences of these combined processes would determine the fate of DOC and associated nutrients in the Antarctic supraglacial environments and potentially influence the local productivity within these systems. Key Points: Dissolved organic carbon increased during Antarctic summer in cryoconite holes but decreased in surface snow by the end of melt seasonPrimary production, viral activity, sediment interaction, and photochemical activity contributed to the organic pool in cryoconite holesPhysical and chemical properties of the environment and the initial nature/quantity of organic matter also impacted carbon dynamics [ABSTRACT FROM AUTHOR]

The article discusses the impact of global climate change on Antarctica and the Southern Ocean which are also sites of persistent geopolitical tensions and mentions Antarctic histories and futures. Topics include high temperatures in the Antarctic Peninsula in 2019–2020 summer; prospecting for oil in the Antarctic continental shelf and discussion in Australia about how to react to China's activities in Antarctica; and Antarctic Treaty parties, tourism and Fisheries and Marine Protected Areas.

The article focuses on the unique and hazardous Antarctic environmental and logistical conditions, and the current state of play regarding shipping in the Antarctic, including expected future trends in shipping traffic; and mentions that under the United Nations Convention on the Law of the Sea (UNCLOS),16 coastal States are entitled to certain maritime zones, by virtue of their sovereignty over land with a sea-coastline, within which they may or must exercise jurisdiction.

The ability to identify moisture source regions and sinks and to model the transport pathways that link them in simple yet physical ways is critical for understanding climate today and in the past. Using water tagging and isotopic tracer experiments in the Community Earth System Model, this work shows that poleward moisture transport largely follows surfaces of constant moist entropy. The analysis not only provides insight into why distinct zonal bands supply moisture to high‐ and low‐elevation polar sites but also explains why changes in these source regions are inherently linked to changes in temperature and rainout. Moreover, because the geometry, and specifically length, of the moist isentropic surfaces describes how much integrated rainout occurs, the analysis provides a physical framework for interpreting the isotopic composition of water in poleward‐moving air, thus indicating how variations in moisture transport might influence Antarctic ice cores. Key Points: Model experiments with water tags and isotopic tracers reveal poleward moisture transport largely follows surfaces of constant moist entropyConsequently, high‐elevation Antarctic sites receive moisture from more equatorward sources than lower elevation sitesThe moist isentropic framework suggests shifts in moisture source regions are tightly linked to changes in temperature and rainout [ABSTRACT FROM AUTHOR]

• Antarctic and Subantarctic propagules show different photosynthetic responses. • Photosynthesis of propagules could be useful to explain distribution patterns of seaweeds. • UV and temperature affect differentially Antarctic and Subantarctic propagules. Propagules of geographically separated seaweeds distributed in both site of Antarctic Circumpolar Current are expected to show different light and temperature acclimation in order to cope with environmental condition in both Antarctic and Subantarctic regions. The objectives of this study were: (1) to compare the photosynthetic performance (rETR max , E k , and α ETR) of propagules of conspecific (Iridaea cordata and Adenocystis utricularis) and congeneric (Pyropia sp. and Monostroma sp.) seaweeds from Magellan strait (Subantarctic region) and King Gorge Island (Antarctica) using in vivo chlorophyll fluorescence techniques; and (2) to determine the physiological responses (measured by rapid adjustment of photochemistry, F v /F m) of tetraspores of I. cordata from populations of both sites when exposed in laboratory to UV radiation. Differences in photosynthetic characteristics between propagules were observed in I. cordata and Monostroma sp. while I. cordata tetraspores from Subantarctic populations showed high light demands (E k = 150 μmol photon m−2 s−1) when compared to those from Antarctic populations (E k = 50 μmol photon m−2 s−1). Antarctic Monostroma sp. gametes exhibited higher E k (300 μmol photon m−2 s−1) than those of Subantarctic populations (130 μmol photon m−2 s−1). Antarctic tetraspores of I. cordata shown low inhibition in F v /F m (<10%) after a 4-h exposure at 2 °C, while spores from Subantarctic population were more sensitive (>60% inhibition) under similar exposure conditions. Similar as for other cold-temperate species, these differences appear to underlie biogeographical and evolutionary elements: in I. cordata , spores from Antarctica are more tolerant to UV at low temperatures than those from Subantarctic regions, but when exposed to increased temperature the detrimental effects of stress in tetraspores from both Antarctic and Subantarctic populations were ameliorated. This differential photosynthetic response to low temperature and light among algae with Antarctic and Subantarctic disjunction is an important ecophysiological attribute that can be associated with adaptations at a genetic level reported previously for some of these populations. [ABSTRACT FROM AUTHOR]

In the southern high latitudes, dinoflagellate cysts are an important microfossil group for both biostratigraphic and palaeoenvironmental interpretations purposes. In light of this, the peridinioid dinoflagellate cyst Nucicla umbiliphora gen. et sp. nov. from the Antarctic margin is formally described. Nucicla is dorsoventrally compressed, has a rounded pentagonal outline in dorso-ventral view, an epicyst that is only half as high as the hypocyst, an unusual archaeopyle formed by the loss of the three anterior intercalary plates, and a posterior sulcal plate that is positioned at the antapex. The species N. umbiliphora is characterised by a scabrate cyst wall and possesses undulated and/or crenulated folds/ridges. It has been so far exclusively found in Quaternary sediments obtained from the East Antarctic continental shelf and the Ross Sea. Although the dinoflagellate producing this cyst is as yet unknown, its brown color and the lack of autofluorescence suggest that the motile cell is likely a heterotrophic Protoperidinium species. As such, N. umbiliphora might benefit from the phytoplankton blooms occurring close to the Antarctic margin after seasonal sea-ice retreat. [ABSTRACT FROM AUTHOR]

Abstract Large amounts of organic matter deposited by marine birds, especially penguins, accumulate on ice-free areas of maritime Antarctica during the short austral summer. The well-known ornithogenic soils of this region are unique in Antarctica and represent important sites where phosphatization is the main soil-forming process. Most recent studies in ornithogenic soils of maritime Antarctica were conducted on andesitic areas, and no reports are available about ornithogenic soils on basaltic intrusion. The purpose of this study was to report the main chemical, physical, and mineralogical characteristics of ornithogenic soils on basaltic intrusion of Barrientos, and evaluate the effects of different nesting bird species and altitude. The amount of Mehlich-extractable P indicates a close interaction between guano and underlying soils, with different end products depending on altitude, weathering degree and nesting bird species. In the soil collected from the giant petrel's nest, the intensity of organic deposition was much lower. The lower means of Mehlich-extractable P, total organic carbon and total nitrogen in Barrientos Island showed the little influence of marine birds when compared to King George Island. On the other hand, the means of exchangeable Ca and Mg were higher due to the basaltic composition of the regional volcanoes, contrasting with the andesites, which are the commonest rock type in maritime Antarctica. Thus, the soil characteristics of the Barrientos Island are influenced by both parent material and phosphatization. Highlights • Soils from basalts showed higher exchangeable Ca and Mg than soils from andesitos. • Soils showed lower phosphorus than other soils of maritime Antarctica. • The phosphorus content was lower in soils under influence of petrel than penguin. [ABSTRACT FROM AUTHOR]

The article offers information on the declining populations of more than half of the world's 18 species of penguins. It further discusses that threats include habitat loss, drowning in fishing gear and climate change; views of conservation biologist Adrien Chaigne, an expedition organizer who works for the National Nature Reserve of the French Southern and Antarctic Territories, on the issue; and the Antarctic one of the fastest changing places on Earth due to shifting ice and acidifying seas.

Abstract Present study was conducted in water bodies placed at different geographical coordinates viz., Schirmacher Hills and Larsemann Hills in Antarctica. The water bodies situated in Schirmacher Hills revealed the influence of melting glaciers on their hydrological regime during austral summer besides anthropogenic pressure, while, the water bodies situated in Larsemann Hills are under the influence of ingression from sea. Further, the rise in anthropogenic activities has been found to leave a marked impression of degradation in these water bodies. In order to maintain the pristine value of other water bodies attention is invited for reducing the anthropogenic activities in near future. [ABSTRACT FROM AUTHOR]

This paper examines how the EU can best use its powers to establish marine protected areas (MPAs) in Antarctica. It first discusses the EU’s role in Antarctic governance and legal basis for the EU’s actions, with particular focus on the pending Joined Cases C-625/15 and C-659/16 at the Court of Justice of the European Union. Secondly, the paper analyses the negotiation process of the EU’s MPA proposals in the Southern Ocean within the Commission for the Conservation of Antarctic Marine Living Resources. Thirdly, it provides suggestions regarding the EU’s potential actions that might help achieve proposed Antarctic MPAs. [ABSTRACT FROM AUTHOR]

The article presents the author's views on climate change with regard to the melting of icebergs and glaciers in Antarctica which threatens to raise sea levels as of November 2018. Antarctica is reportedly the largest and oldest ice mass on Earth and its long ice cores are used as testing fields by bioprospecting industries. Topics include Antarctica as the center of the world map, efforts to raise awareness about climate change, and the factors that contributed to the melting of ice.

Antarctica provides an opportunity to study natural forcing and background values of various constituents in the atmosphere, in particular, aerosols. In a recent effort during the 36th Indian Scientific Expedition to Antarctica (36th ISEA), a Dual Imager System was installed at Indian station Bharati (69.4°S, 76.18°E) to study round-the-clock variations of aerosol optical thickness (AOT). The data reveal a weak diurnal pattern in the AOT variability and the values vary from 0.07 to 0.10 during daytime while they reach ~ 0.12 during nighttime. The daytime (solar zenith angle < 70°) results compare well with collocated sun photometer as well as space based estimates, while the higher solar zenith angle (> 70°) AOT values are reported for the first time over Antarctica. The observed higher AOT values at higher zenith angles, i.e. during nighttime are suggested to be due to variations in wind speed and temperature. [ABSTRACT FROM AUTHOR]

The role of algae for sequestration of atmospheric mercury in the ocean is largely unknown owing to a lack of marine sediment data. We used high-resolution cores from marine Antarctica to estimate Holocene global mercury accumulation in biogenic siliceous sediments (diatom ooze). Diatom ooze exhibits the highest mercury accumulation rates ever reported for the marine environment and provides a large sink of anthropogenic mercury, surpassing existing model estimates by as much as a factor of 7. Anthropogenic pollution of the Southern Ocean began ~150 years ago, and up to 20% of anthropogenic mercury emitted to the atmosphere may have been stored in diatom ooze. These findings reveal the crucial role of diatoms as a fast vector for mercury sequestration and diatom ooze as a large marine mercury sink. [ABSTRACT FROM AUTHOR]

Antarctic mass balance and contribution to sea level rise are dominated by the flow of ice through narrow conduits called ice streams. These regions of relatively fast flow drain over 90% of the ice sheet and generate significant amounts of frictional heat at the ice stream margins where there is a transition to slow flow in the ridge. This heat can generate temperate ice and a sharp transition in flow speed between the stream and the ridge. Within zones of temperate ice, meltwater is produced and drains to the bed. Here we model the downstream development of a temperate zone along an ice stream shear margin and the flow of meltwater through temperate ice into a subglacial hydrologic system. The hydrology sets the basal effective pressure, defined as the difference between ice overburden and water pressure. Using the southern shear margin of Bindschadler Ice Stream as a case study, our model results indicate an abrupt transition from a distributed to channelized hydrologic system within a few ice thicknesses of the point where the temperate zone initiates. This transition leads to a strengthening of the till due to reduced pore pressure because the water pressure in the channel is lower than in the distributed system, a potential mechanism by which hydrology can prevent lateral migration of shear margins. [ABSTRACT FROM AUTHOR]

More than 3 decades after the discovery of the ozone hole, the processes involved in its formation are believed to be understood in great detail. Current state-of-the-art models can reproduce the observed chemical composition in the springtime polar stratosphere, especially regarding the quantification of halogen-catalysed ozone loss. However, we report here on a discrepancy between simulations and observations during the less-well-studied period of the onset of chlorine activation. During this period, which in the Antarctic is between May and July, model simulations significantly overestimate HCl, one of the key chemical species, inside the polar vortex during polar night. This HCl discrepancy is also observed in the Arctic. The discrepancy exists in different models to varying extents; here, we discuss three independent ones, the Chemical Lagrangian Model of the Stratosphere (CLaMS) as well as the Eulerian models SD-WACCM (the specified dynamics version of the Whole Atmosphere Community Climate Model) and TOMCAT/SLIMCAT. The HCl discrepancy points to some unknown process in the formulation of stratospheric chemistry that is currently not represented in the models. We characterise the HCl discrepancy in space and time for the Lagrangian chemistry--transport model CLaMS, in which HCl in the polar vortex core stays about constant from June to August in the Antarctic, while the observations indicate a continuous HCl decrease over this period. The somewhat smaller discrepancies in the Eulerian models SD-WACCM and TOMCAT/SLIMCAT are also presented. Numerical diffusion in the transport scheme of the Eulerian models is identified to be a likely cause for the inter-model differences. Although the missing process has not yet been identified, we investigate different hypotheses on the basis of the characteristics of the discrepancy. An underestimated HCl uptake into the polar stratospheric cloud (PSC) particles that consist mainly of H2O and HNO3 cannot explain it due to the temperature correlation of the discrepancy. Also, a direct photolysis of particulate HNO3 does not resolve the discrepancy since it would also cause changes in chlorine chemistry in late winter which are not observed. The ionisation caused by galactic cosmic rays provides an additional NOx and HOx source that can explain only about 20% of the discrepancy. However, the model simulations show that a hypothetical decomposition of particulate HNO3 by some other process not dependent on the solar elevation, e.g. involving galactic cosmic rays, may be a possible mechanism to resolve the HCl discrepancy. Since the discrepancy reported here occurs during the beginning of the chlorine activation period, where the ozone loss rates are small, there is only a minor impact of about 2% on the overall ozone column loss over the course of Antarctic winter and spring. [ABSTRACT FROM AUTHOR]

Observations of the organic components of the natural aerosol are scarce in Antarctica, which limits our understanding of natural aerosols and their connection to seasonal and spatial patterns of cloud albedo in the region. From November 2015 to December 2016, the ARM West Antarctic Radiation Experiment (AWARE) measured submicron aerosol properties near McMurdo Station at the southern tip of Ross Island. Submicron organic mass (OM), particle number, and cloud condensation nuclei concentrations were higher in summer than other seasons. The measurements included a range of compositions and concentrations that likely reflected both local anthropogenic emissions and natural background sources. We isolated the natural organic components by separating a natural factor and a local combustion factor. The natural OM was 150 times higher in summer than in winter. The local anthropogenic emissions were not hygroscopic and had little contribution to the CCN concentrations. Natural sources that included marine sea spray and seabird emissions contributed 56% OM in summer but only 3% in winter. The natural OM had high hydroxyl group fraction (55%), 6% alkane, and 6% amine group mass, consistent with marine organic composition. In addition, the Fourier transform infrared (FTIR) spectra showed the natural sources of organic aerosol were characterized by amide group absorption, which may be from seabird populations. Carboxylic acid group contributions were high in summer and associated with natural sources, likely forming by secondary reactions. [ABSTRACT FROM AUTHOR]

Recent work suggests that natural variability has played a significant role in the increase of Antarctic sea ice extent during 1979-2013. The ice extent has responded strongly to atmospheric circulation changes, including a deepened Amundsen Sea Low (ASL), which in part has been driven by tropical variability. Nonetheless, this increase has occurred in the context of externally forced climate change, and it has been difficult to reconcile observed and modeled Antarctic sea ice trends. To understand observed-model disparities, this work defines the internally driven and radiatively forced patterns of Antarctic sea ice change and exposes potential model biases using results from two sets of historical experiments of a coupled climate model compared with observations. One ensemble is constrained only by external factors such as greenhouse gases and stratospheric ozone, while the other explicitly accounts for the influence of tropical variability by specifying observed SST anomalies in the eastern tropical Pacific. The latter experiment reproduces the deepening of the ASL, which drives an increase in regional ice extent due to enhanced ice motion and sea surface cooling. However, the overall sea ice trend in every ensemble member of both experiments is characterized by ice loss and is dominated by the forced pattern, as given by the ensemble-mean of the first experiment. This pervasive ice loss is associated with a strong warming of the ocean mixed layer, suggesting that the ocean model does not locally store or export anomalous heat efficiently enough to maintain a surface environment conducive to sea ice expansion. The pervasive upper-ocean warming, not seen in observations, likely reflects ocean mean-state biases. [ABSTRACT FROM AUTHOR]

Polar ice core water isotope records are commonly used to infer past changes in Antarctic temperature, motivating an improved understanding and quantification of the temporal relationship between δ18O and temperature. This can be achieved using simulations performed by atmospheric general circulation models equipped with water stable isotopes. Here, we evaluate the skills of the high-resolution water-isotope-enabled atmospheric general circulation model ECHAM5-wiso (the European Centre Hamburg Model) nudged to European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis using simulations covering the period 1960-2013 over the Antarctic continent. We compare model outputs with field data, first with a focus on regional climate variables and second on water stable isotopes, using our updated dataset of water stable isotope measurements from precipitation, snow, and firn-ice core samples. ECHAM5-wiso simulates a large increase in temperature from 1978 to 1979, possibly caused by a discontinuity in the European Reanalyses (ERA) linked to the assimilation of remote sensing data starting in 1979. Although some model-data mismatches are observed, the (precipitation minus evaporation) outputs are found to be realistic products for surface mass balance. A warm model bias over central East Antarctica and a cold model bias over coastal regions explain first-order δ18O model biases by too-strong isotopic depletion on coastal areas and underestimated depletion inland. At the second order, despite these biases, ECHAM5-wiso correctly captures the observed spatial patterns of deuterium excess. The results of model-data comparisons for the inter-annual δ18O standard deviation differ when using precipitation or ice core data. Further studies should explore the importance of deposition and post-deposition processes affecting ice core signals and not resolved in the model. These results build trust in the use of ECHAM5-wiso outputs to investigate the spatial, seasonal, and inter-annual δ18O-temperature relationships. We thus make the first Antarctica-wide synthesis of prior results. First, we show that local spatial or seasonal slopes are not a correct surrogate for inter-annual temporal slopes, leading to the conclusion that the same isotope-temperature slope cannot be applied for the climatic interpretation of Antarctic ice core for all timescales. Finally, we explore the phasing between the seasonal cycles of deuterium excess and δ18O as a source of information on changes in moisture sources affecting the δ18O-temperature relationship. The few available records and ECHAM5-wiso show different phase relationships in coastal, intermediate, and central regions. This work evaluates the use of the ECHAM5-wiso model as a tool for the investigation of water stable isotopes in Antarctic precipitation and calls for extended studies to improve our understanding of such proxies. [ABSTRACT FROM AUTHOR]

The Eocene-Oligocene transition (EOT), which took place approximately 34 Ma ago, is an interval of great interest in Earth's climate history, due to the inception of the Antarctic ice sheet and major global cooling. Climate simulations of the transition are needed to help interpret proxy data, test mechanistic hypotheses for the transition and determine the climate sensitivity at the time. However, model studies of the EOT thus far typically employ control states designed for a different time period, or ocean resolution on the order of 3◦ . Here we developed a new higher resolution palaeoclimate model configuration based on the GFDL CM2.1 climate model adapted to a late Eocene (38 Ma) palaeogeography reconstruction. The ocean and atmosphere horizontal resolutions are 1◦ × 1.5◦ and 3◦ × 3.75◦ respectively. This represents a significant step forward in resolving the ocean geography, gateways and circulation in a coupled climate model of this period. We run the model under three different levels of atmospheric CO2: 400, 800 and 1600 ppm. The model exhibits relatively high sensitivity to CO2 compared with other recent model studies, and thus can capture the expected Eocene high latitude warmth within observed estimates of atmospheric CO2. However, the model does not capture the low meridional temperature gradient seen in proxies. Equatorial sea surface temperatures are too high in the model (30- 37 ◦C) compared with observations (max 32 ◦C), although observations are lacking in the warmest regions of the western Pacific. The model exhibits bipolar sinking in the North Pacific and Southern Ocean, which persists under all levels of CO2. North Atlantic surface salinities are too fresh to permit sinking (25-30 psu), due to surface transport from the very fresh Arctic (~ 20 psu), where surface salinities approximately agree with Eocene proxy estimates. North Atlantic salinity increases by 1-2 psu when CO2 is halved, and similarly freshens when CO2 is doubled, due to changes in the hydrological cycle. [ABSTRACT FROM AUTHOR]

The long-term evolution of total ozone column inside the Antarctic polar vortex is investigated over the 1980-2017 period. Trend analyses are performed using a multilinear regression (MLR) model based on various proxies for the evaluation of ozone interannual variability (heat flux, quasi-biennial oscillation, solar flux, Antarctic oscillation and aerosols). Annual total ozone column measurements corresponding to the mean monthly values inside the vortex in September and during the period of maximum ozone depletion from 15 September to 15 October are used. Total ozone columns from the Multi-Sensor Reanalysis version 2 (MSR-2) dataset and from a combined record based on TOMS and OMI satellite datasets with gaps filled by MSR-2 (1993-1995) are considered in the study. Ozone trends are computed by a piece-wise trend (PWT) proxy that includes two linear functions before and after the turnaround year in 2001 and a parabolic function to account for the saturation of the polar ozone destruction. In order to evaluate average total ozone within the vortex, two classification methods are used, based on the potential vorticity gradient as a function of equivalent latitude. The first standard one considers this gradient at a single isentropic level (475 or 550 K), while the second one uses a range of isentropic levels between 400 and 600 K. The regression model includes a new proxy (GRAD) linked to the gradient of potential vorticity as a function of equivalent latitude and representing the stability of the vortex during the studied month. The determination coefficient (R²) between observations and modelled values increases by *** 0.05 when this proxy is included in the MLR model. Highest R² (0.92-0.95) and minimum residuals are obtained for the second classification method for both datasets and months. Trends in September over the 2001-2017 period are statistically significant at 2σ level with values ranging between 1.84±1.03 and 2.83±1.48 DU yr-1 depending on the methods and considered proxies. This result confirms the recent studies of Antarctic ozone healing during that month. Trends from 2001 are 2 to 3 times smaller than before the turnaround year, as expected from the response to the slowly ozonedepleting substances decrease in polar regions. For the first time, significant trends are found for the period of maximum ozone depletion. Estimated trends from 2001 for the 15 September-15 October period over 2001± 2017 vary from 1.21±0.83 to 1.96DU±0.99 yr-1 and are significant at 2σ level. MLR analysis is also applied to the ozone mass deficit (OMD) metric for both periods, considering a threshold at 220DU and total ozone columns south of 60° S. Significant trend values are observed for all cases and periods. A decrease of OMD of 0.86±0.36 and 0.65±0.33 Mt yr-1 since 2001 is observed in September and 15 September-15 October, respectively. Ozone recovery is also confirmed by a steady decrease of the relative area of total ozone values lower than 175DU within the vortex in the 15 September-15 October period since 2010 and a delay in the occurrence of ozone levels below 125DU since 2005. [ABSTRACT FROM AUTHOR]

The Antarctic has significant environmental, scientific, historic, and intrinsic values, all of which are worth protecting into the future. Nevertheless, the area is subject to an increasing level and diversity of human activities that may impact these values within marine, terrestrial and cryosphere environments. Threats to the Antarctic environment, and to the aforementioned values, include climate change, pollution, habitat destruction, wildlife disturbance and non-native species introductions. Over time, a suite of legally binding international agreements, which form part of the Antarctic Treaty System (ATS), has been established to help safeguard the Antarctic environment and provide a framework for addressing the challenges arising from these threats. Foremost among these agreements are the Protocol on Environmental Protection to the Antarctic Treaty and the Convention on the Conservation of Antarctic Marine Living Resources. Many scientists working in Antarctica undertake research that is relevant to Antarctic environmental policy development. More effective two-way interaction between scientists and those responsible for policy development would further strengthen the governance framework, including by (a) better communication of policy makers’ priorities and identification of related science requirements and (b) better provision by scientists of ‘policy-ready’ information on existing priorities, emerging issues and scientific/technological advances relevant to environmental protection. The Scientific Committee on Antarctic Research (SCAR) has a long and successful record of summarizing policy-relevant scientific knowledge to policy makers, such as through its Group of Specialists on Environmental Affairs and Conservation (GOSEAC) up to 2002, currently the SCAR Standing Committee on the Antarctic Treaty System (SCATS) and recently through its involvement in the Antarctic Environments Portal. Improvements to science-policy communication mechanisms, combined with purposeful consideration of funding opportunities for policy-relevant science, would greatly enhance international policy development and protection of the Antarctic environment. [ABSTRACT FROM AUTHOR]

Fossil-bearing deposits in the Transantarctic Mountains, Antarctica indicate that, despite the cold nature of the continent’s climate, a tundra ecosystem grew during periods of ice sheet retreat in the mid to late Neogene (17–2.5 Ma), 480 km from the South Pole. To date, palaeotemperature reconstruction has been based only on biological ranges, thereby calling for a geochemical approach to understanding continental climate and environment. There is contradictory evidence in the fossil record as to whether this flora was mixed angiosperm-conifer vegetation, or whether by this point conifers had disappeared from the continent. In order to address these questions, we have analysed, for the first time in sediments of this age, plant and bacterial biomarkers in terrestrial sediments from the Transantarctic Mountains to reconstruct past temperature and vegetation during a period of East Antarctic Ice Sheet retreat. From tetraether lipids (MBT′/CBT palaeothermometer), we conclude that the mean continental summer temperature was ca. 5 °C, in agreement with previous reconstructions. This was warm enough to have allowed woody vegetation to survive and reproduce even during the austral winter. Biomarkers from vascular plants indicate a low diversity and spatially variable flora consisting of higher plants, moss and algal mats growing in microenvironments in a glacial outwash system. Abietane-type compounds were abundant in some samples, indicating that conifers, most likely Podocarpaceae, grew on the Antarctic continent well into the Neogene. This is supported by the palynological record, but not the macrofossil record for the continent, and has implications for the evolution of vegetation on Antarctica. [ABSTRACT FROM AUTHOR]

This work focuses on the near-surface O 3 variability over the eastern Antarctic Plateau. In particular, eight years (2006–2013) of continuous observations at the WMO/GAW contributing station “Concordia” (Dome C–DMC: 75°06′S, 123°20′E, 3280 m) are presented, in the framework of the Italian Antarctic Research Programme (PNRA). First, the characterization of seasonal and diurnal O 3 variability at DMC is provided. Then, for the period of highest data coverage (2008–2013), we investigated the role of specific atmospheric processes in affecting near-surface summer O 3 variability, when O 3 enhancement events (OEEs) are systematically observed at DMC (average monthly frequency peaking up to 60% in December). As deduced by a statistical selection methodology, these OEEs are affected by a significant interannual variability, both in their average O 3 values and in their frequency. To explain part of this variability, we analyzed OEEs as a function of specific atmospheric variables and processes: (i) total column of O 3 (TCO) and UV-A irradiance, (ii) long-range transport of air masses over the Antarctic Plateau (by Lagrangian back-trajectory analysis – LAGRANTO), (iii) occurrence of “deep” stratospheric intrusion events (by using the Lagrangian tool STLEFLUX). The overall near-surface O 3 variability at DMC is controlled by a day-to-day pattern, which strongly points towards a dominating influence of processes occurring at “synoptic” scales rather than “local” processes. Even if previous studies suggested an inverse relationship between OEEs and TCO, we found a slight tendency for the annual frequency of OEEs to be higher when TCO values are higher over DMC. The annual occurrence of OEEs at DMC seems related to the total time spent by air masses over the Antarctic plateau before their arrival to DMC, suggesting the accumulation of photochemically-produced O 3 during the transport, rather than a more efficient local production. Moreover, the identification of recent (i.e., 4-day old) stratospheric intrusion events by STEFLUX suggested only a minor influence (up to 3% of the period, in November) of “deep” events on the variability of near-surface summer O 3 at DMC. [ABSTRACT FROM AUTHOR]

Tropical sea surface temperatures (SSTs) warmed and cooled in step with the Pleistocene ice age cycles, but the mechanisms are not known. It is assumed that the answer must involve radiative forcing by CO 2 but SST reconstructions have been too sparse for a conclusive test. Here I present a 230,000-yr tropical SST stack from the eastern equatorial Pacific (EEP) using two new Mg/Ca reconstructions combined with three earlier ones. The EEP stack shows persistent covariation with Antarctic temperature on orbital and millennial timescales indicating tight coupling between the two regions. This coupling however cannot be explained solely by CO 2 forcing because in at least one important case, the Marine Isotope Stage (MIS) 5e–5d glacial inception, both regions cooled ∼5–6.5 thousand years before CO 2 decreased. More likely, their covariation was due to advection of Antarctic climate signals to the EEP by the ocean. To explain the MIS 5e–5d event and glacial inception in general the hypothesis is advanced that the cooling signal spreads globally from the Northern Hemisphere with an active ocean circulation – first from the North Atlantic to the Southern Ocean with a colder North Atlantic Deep Water, and then to the Indian and Pacific Oceans with cooler Antarctic deep and intermediate waters. [ABSTRACT FROM AUTHOR]

Abstract: Long‐term observations of ecological communities are necessary for generating and testing predictions of ecosystem responses to climate change. We investigated temporal trends and spatial patterns of soil fauna along similar environmental gradients in three sites of the McMurdo Dry Valleys, Antarctica, spanning two distinct climatic phases: a decadal cooling trend from the early 1990s through the austral summer of February 2001, followed by a shift to the current trend of warming summers and more frequent discrete warming events. After February 2001, we observed a decline in the dominant species (the nematode Scottnema lindsayae) and increased abundance and expanded distribution of less common taxa (rotifers, tardigrades, and other nematode species). Such diverging responses have resulted in slightly greater evenness and spatial homogeneity of taxa. However, total abundance of soil fauna appears to be declining, as positive trends of the less common species so far have not compensated for the declining numbers of the dominant species. Interannual variation in the proportion of juveniles in the dominant species was consistent across sites, whereas trends in abundance varied more. Structural equation modeling supports the hypothesis that the observed biological trends arose from dissimilar responses by dominant and less common species to pulses of water availability resulting from enhanced ice melt. No direct effects of mean summer temperature were found, but there is evidence of indirect effects via its weak but significant positive relationship with soil moisture. Our findings show that combining an understanding of species responses to environmental change with long‐term observations in the field can provide a context for validating and refining predictions of ecological trends in the abundance and diversity of soil fauna. [ABSTRACT FROM AUTHOR]

In recent years, much attention has been paid to the behavior of passive microwave sea ice concentration (SIC) products for marginal ice zones. Based on the definition of ice edges from ship observations, we identified pseudo-ship observations (PSO) and generated PSO ice edges from twelve cloud-free moderate-resolution imaging spectroradiometer (MODIS) images. Two SIC products of the advanced microwave scanning radiometer 2 (AMSR2) were compared at the PSO ice edges: ARTIST (arctic radiation and turbulence interaction study) sea ice (ASI-SIC) and bootstrap (BST-SIC). The mean values of ASI-SIC pixels located at ice edges were 10.5% and 10.3% for the Arctic and the Antarctic, respectively, and are below the commonly applied 15% threshold, whereas the mean values of corresponding BST-SIC pixels were 23.6% and 27.3%, respectively. The mean values of both ASI-SIC and BST-SIC were lower in summer than in winter. The spatial gaps among the 15% ASI-SIC ice edge, the 15% BST-SIC ice edge and the PSO ice edge were mostly within 35 km, whereas the 15% ASI-SIC ice edge matched better with the PSO ice edge. Results also show that the ice edges were located in the thin ice region, with a mean ice thickness of around 5-8 cm. We conclude that the 15% threshold well determines the ice edge from passive microwave SIC in both the Arctic and the Antarctic. [ABSTRACT FROM AUTHOR]

The Dobson spectrophotometer, which was developed in the late 1920s, measures atmospheric total column ozone. This paper presents the history of Dobson spectrophotometer #17 (D#17), which arrived in New Zealand in 1950. D#17 has been in operation at Kelburn in Wellington (1951 - 1970), Invercargill (1970 - 1987), and Arrival Heights in Antarctica (1988 - present). D#17's history includes a flooding, several overhauls, a semi-automation, and finally a complete automation. In the early days the main reasons for measuring total ozone were to develop an ozone climatology, and to investigate the relationship between ozone and the weather. From the mid-1970s the focus of ozone measurement largely changed to studying ozone trends (which includes Antarctic ozone depletion). This requires a traceable calibration history, which is discussed in detail. Plots of the D#17 total ozone record are provided. [ABSTRACT FROM AUTHOR]

Sea levels at the end of this century are projected to be 0.26–0.98 m higher than today. The upper end of this range, and even higher estimates, cannot be ruled out because of major uncertainties in the dynamic response of polar ice sheets to a warming climate. Here, we propose an ecological genetics approach that can provide insight into the past stability and configuration of the West Antarctic Ice Sheet (WAIS). We propose independent testing of the hypothesis that a trans-Antarctic seaway occurred at the last interglacial. Examination of the genomic signatures of bottom-dwelling marine species using the latest methods can provide an independent window into the integrity of the WAIS more than 100,000 years ago. Periods of connectivity facilitated by trans-Antarctic seaways could be revealed by dating coalescent events recorded in DNA. These methods allow alternative scenarios to be tested against a fit to genomic data. Ideal candidate taxa for this work would need to possess a circumpolar distribution, a benthic habitat, and some level of genetic structure indicated by phylogeographical investigation. The purpose of this perspective piece is to set out an ecological genetics method to help resolve when the West Antarctic Ice Shelf last collapsed. [ABSTRACT FROM AUTHOR]

The response of the Antarctic ice sheet (AIS) to changing global temperatures is a key component of sea-level projections. Current projections of the AIS contribution to sea-level changes are deeply uncertain. This deep uncertainty stems, in part, from (i) the inability of current models to fully resolve key processes and scales, (ii) the relatively sparse available data, and (iii) divergent expert assessments. One promising approach to characterizing the deep uncertainty stemming from divergent expert assessments is to combine expert assessments, observations, and simple models by coupling probabilistic inversion and Bayesian inversion. Here, we present a proof-of-concept study that uses probabilistic inversion to fuse a simple AIS model and diverse expert assessments. We demonstrate the ability of probabilistic inversion to infer joint prior probability distributions of model parameters that are consistent with expert assessments. We then confront these inferred expert priors with instrumental and paleoclimatic observational data in a Bayesian inversion. These additional constraints yield tighter hindcasts and projections. We use this approach to quantify how the deep uncertainty surrounding expert assessments affects the joint probability distributions of model parameters and future projections. [ABSTRACT FROM AUTHOR]

Colobanthus quitensis (Antarctic pearlwort) is one of the only two native vascular plants to inhabit the extreme environmental conditions of Antarctica . Colobanthus quitensis has a wide geographic distribution, both in latitude and altitude, and always inhabits extreme environments. This makes it crucial for understanding environmental tolerance mechanisms, and a useful model for studies regarding genetic diversity and intraspecific morphology. Several morphological and molecular descriptors were applied to C. quitensis populations, constituting the first study of its kind in these species. We postulated that morphological variability is strongly linked to geographic distribution, and that this is manifested in external morphological characteristics and genetic structure. A large intra- and interpopulational morphological variability was verified. Both morphological variability and genetics made it possible to form two separate groups between continental and Antarctic island populations. The genetic diversity was high to moderate with the least amount of diversity towards the north. The genetic structure was high, and the gene flow between populations was low. The correlation between morphological, genetic, geographic and altitudinal distances permits the proposal of an isolation by distance model that can be used between populations with high Bio-geographical influence. Understanding what factors lead to local or colonization adaptation, and determining the morphological variations and genetic differentiation in populations of C. quitensis, is vital for the understanding of the evolutionary history that has contributed to the success of the establishment of this species in an environment as extreme as Antarctica. Additionally, this study demonstrates the usefulness of the combined use of morpho-physiological and molecular markers for variability and diversity studies. [ABSTRACT FROM AUTHOR]