Weddell seals are polar predators that must partition their time between many behaviours, including hunting prey at depth and breathing at the surface. Although they have been well studied, little is known about how foraging behaviour changes when access to breathing holes is restricted, such as in the isolated-hole paradigm. The current study took advantage of previously gathered data for seals diving at an isolated hole to compare with foraging behaviour of free-ranging seals that had access to multiple holes. We examined dive structure, hunting tactics, and allocation of time, locomotor activity and energy based on three-dimensional dive profiles and video imagery of prey encounters for two free-ranging and six isolated-hole seals. Midsummer foraging dives of free-ranging seals were remarkably similar to those of seals diving at an isolated hole, but there were differences in two behavioural states and the frequency of several behavioural transitions. Results indicate that seals employ an energetically more conservative foraging strategy when access to breathing holes is limited and prey are less abundant. These results highlight the importance of understanding the complex interactions between breathing hole access, prey abundance and other factors that may result in different Weddell seal foraging strategies under changing future conditions.

This is the first detailed analysis of a CO2 diffuse degassing time series from Deception volcano, South Shetland Islands, Antarctica, performed during an episode of anomalously high long-period (LP) seismicity. Diffuse CO2 emissions measured by an automatic geochemical station between 7 December 2009 and 13 February 2010 showed an excellent temporal agreement with the LP seismicity in December 2009. The absence of such a temporal correlation with the second burst of seismicity that occurred in late January 2010 suggests a different source for this LP activity. This was confirmed by analysis of seismic array data. The LP seismicity observed during December 2009 was caused by fluid-driven cracks that originated from pressure fluctuations in the volcano-hydrothermal systems beneath Deception volcano that were probably caused by a deep injection of undegassed magma before December 2009. The diffuse CO2 degassing data have provided evidence of the activation of at least two different sources of seismicity during the study period at Deception volcano.

Airborne radar data acquired in 1995 by the Italian Antarctic Programme over Dome C in central East Antarctica were processed to develop maps of internal isochronous ice sheet layering around the EPICA ice core site. Three internal layers were traced continuously across the radar-survey area at ice depths of 1–2 km. The maps reveal that the ice core site is located where internal layers are near horizontal to depths of at least 2 km. The Italian radar data do not resolve internal layers below 2 km. However, radar data collected over this part of East Antarctica in the 1970s show the internal layers to depths of up to 4 km. These internal layers reveal the regional structure of ice to the west of Dome C. Layers from both surveys are dated through an existing chronostratigraphic link between the Vostok ice core site and Dome C. The pattern of internal layering at Dome C reflects relatively steady conditions of ice flow and accumulation for the last 100 000 years. However, for ice older than this we show that there is significant local variation in the thickness between internal layers and the ice-sheet base. Our maps provide an indication of the structure of the ice sheet from which the EPICA deep ice core will be taken.

An examination of 111 fish of eight species, including 92 immature Notothenia rossii Richardson revealed nine acanthocephalan species, including four Echinorhynchida occurring in the alimentary tract and five Polymorphida in the body cavity. Echinorhynchida were much more numerous (87% specimens of 4855 collected), especially Metacanthocephalus johnstoni Zdzitowiecki (the dominant species) and Aspersentis megarhynchus (Linstow). The Polymorphida parasites of seals (three species) were more abundant than species parasitic in birds (two species). Association of most of species, (except Corynosoma bullosum (Linstow) and Echinorhynchus spp.), with the inshore (fjord) environment was confirmed. The species diversity, prevalence and density of infection increased with the size of immature N. rossii. Differences in acanthocephalan occurrence and changes with time are related to differences in host distribution and abundance. For example, the occurrence of C. arctocephali in N. rossii at South Georgia is related to the increase of the fur seal population. A list of acanthocephalans in fish at South Georgia and the South Shetland Islands (14 species in total) is included.

This paper provides new observations of volcanic features and hydrological characteristics in and around Southern Thule, the southernmost group of islands in the South Sandwich Islands, including the first high-resolution bathymetric image of the Douglas Strait caldera. The South Sandwich Islands are the summits of several very large subduction-related volcanoes constructed at the eastern boundary of the Scotia Sea. Observations of the islands are scarce owing to their remote location and they are only rarely visited, yet the area is an active volcanic arc that is rapidly changing as a result of eruptions, including one (on Montagu Island) that has been ongoing for six years and is creating new land. The three islands that make up Southern Thule are morphologically different, and they illustrate different stages in the construction and evolution of islands in the South Sandwich group. We present the results of an acoustic and hydrographic survey that resulted in the first high-resolution, multibeam ‘swath’ image of the submarine Douglas Strait caldera. The results confirm the presence of a large sediment mound (c. 1000 m3 in volume) on the floor of the Douglas Strait caldera related to a flank collapse of Thule Island. The image also shows an extensive arcuate fault structure, interpreted as evidence that the caldera is nested, and its geomorphological freshness suggests that it is a very young feature that formed conceivably in the last few decades or centuries. The bathymetric image also reveals at least three cone- or mound-like structures within the caldera that may relate to renewed post-caldera volcanism (as pyroclastic cones and/or pillow mounds). Recently formed cones and faults associated with caldera rims are often associated with hydrothermal activity. However, temperature and salinity data collected within the caldera do not yet show any evidence of hydrothermal venting. The ocean surrounding Southern Thule has a prominent surface layer of low salinity water that is probably caused by a high meltwater flux derived from ice caps on the islands. This flux may have been enhanced by the recent warming trend observed in the Antarctic Peninsula, although volcano-related geothermal melting in the ice-filled Thule Island caldera may also contribute to the meltwater flux.

A sample of 111 fish of eight species caught in two fjords at South Georgia were examined for digenean trematode parasites. The alimentary tracts of all specimens were infected with digeneans. The dominant species was Elytrophalloides oatesi (Leiper & Atkinson) which was found in all fish, with a maximum number of 1961 specimens per fish. Other common species were; Macvicaria pennelli (Leiper & Atkinson), Lepidapedon garrardi (Leiper & Atkinson), Lecithaster macrocotyle Szidat & Graefe, Genolinea bowersi (Leiper & Atkinson) and Postmonorchis variabilis Prudhoe & Bray. Three further species, Neolebouria antarctica (Szidat & Graefe), Discoverytrema markowskii Gibson and Gonocerca phycidis Manter, were rare. Infection of the most commonly caught fish at South Georgia, Notothenia rossii Richardson, is compared with that of N. rossii at Admiralty Bay, South Shetland Islands. The species composition of common parasites was similar in both areas but conspicuous differences in the frequency of individual digenean species were found.

In the open Southern Ocean (SO), both modern and past size changes of the diatom Fragilariopsis kerguelensis appear to be strongly controlled by iron availability. Conversely, sea surface temperatures (SST) and sea ice seasonal dynamics take over in the seasonal sea-ice zone where iron is not limiting. No information exists on F. kerguelensis biometry from the subtropical SO, on the other extreme of the thermal and nutrient gradients. We present here new data on mean valve area of F. kerguelensis (FkergArea) from a sediment core covering the last ~42 cal kyrs from the southern Subtropical Front (SSTF) of the Indian sector of the SO, where iron and silica stocks are thought to have been consistently low over this period. Our results suggest that larger F. kerguelensis valves occurred during the Last Glacial period, and declined during the Holocene period. These findings indicate that more favourable SST, within the F. kerguelensis ecological range, during the Last Glacial period may have enabled F. kerguelensis to make better use of the low silica stocks prevailing in the subtropical zone leading to larger valves. Conversely, declining FkergArea during the deglacial and the Holocene periods may have been a result of higher SST which hampered the utilization of silica.

Magnetic anomaly mapping is used to interpret crustal structure and tectonic evolution of Victoria Land and of the adjacent Ross Sea. Previous interpretation of magnetic anomalies verified seismic and gravimetric findings in the Ross Sea by placing additional constraints both on crustal structure and magmatism of the West Antarctic rift system. An aeromagnetic map of the central-southern part of Victoria Land produced in the framework of the GITARA project, provides new crustal images of part of the Transantarctic Mountains rift shoulder. The map was interpreted to study the transition between the Wilson Terrane and the Precambrian East Antarctic Craton, the extent and distribution of Jurassic tholeiitic magmatism, and the occurrence of post- Jurassic faulting oblique to the rift basins. A compilation with adjacent aeromagnetic data was recently used to study the structures inherited from the Palaeozoic terranes and their reactivation as major fault zones separating different crustal blocks along the TAM rift shoulder. Additional aeromagnetic coverage over a 35 500 km2 sector of northern Victoria Land was acquired during the GITARA 5 (1996/97) survey. The flight altitude was 9000 ft and profile line spacing was 4.4 km for the regional grid and 2.2 km for the detailed one, with a tie line interval of 22 km. Standard processing techniques, optimized with microlevelling procedures were applied to the data to produce a 1:250 000 magnetic anomaly map. The processed GITARA 5 magnetic dataset is a new tool to study the structure of the Rennick Graben, and its relationship to the Palaeozoic Wilson Terrane-Bowers Terrane and Robertson Bay Terrane suture zone. The new map also represents important progress towards a magnetic anomaly compilation over the whole of Victoria Land, since it links previous efforts near the Pacific Coast with those near the Ross Sea.

Seabee Hook is a low lying gravel spit adjacent to Cape Hallett, northern Victoria Land, in the Ross Sea region of Antarctica and hosts an Adélie penguin (Pygoscelis adeliae) rookery. Dipwells were inserted to monitor changes in depth to, and volume of, groundwater and tracer tests were conducted to estimate aquifer hydraulic conductivity and groundwater velocity. During summer (November–February), meltwater forms a shallow, unconfined, aquifer perched on impermeable ice cemented soil. Groundwater extent and volume depends on the amount of snowfall as meltwater is primarily sourced from melting snow drifts. Groundwater velocity through the permeable gravel and sand was up to 7.8 m day−1, and hydraulic conductivities of 4.7 × 10−4 m s−1 to 3.7 × 10−5 m s−1 were measured. The presence of the penguin rookery, and the proximity of the sea, affects groundwater chemistry with elevated concentrations of salts (1205 mg L−1 sodium, 332 mg L−1 potassium) and nutrients (193 mg L−1 nitrate, 833 mg L−1 ammonia, 10 mg L−1 total phosphorus) compared with groundwater sourced away from the rookery, and with other terrestrial waters in Antarctica.

The paper discusses ELF-VLF investigations of the low Antarctic ionosphere. Two new methods of lower ionospheric diagnostics are based on an investigation of the VLF electromagnetic field structure in the Earth-ionosphere cavity. One method deals with the analysis of local transverse cavity resonances in the near field of an emitter (a horizontal antenna) with a frequency (~1.5-8 kHz) in the range of the first few resonances. The other method, based on tweek investigations, is applicable under night conditions and enables the characteristics of the low ionosphere to be determined over a signal propagation path. The use of the ELF-VLF transmitter at Siple Station provides a unique opportunity to implement these methods, as does the ELF multipoint recording in the Schumann resonance band of atmospherics excited by powerful lightning discharges.

The aim of the study was to determine if soil salt deliquescence and brine hydration can occur under laboratory conditions using natural McMurdo Dry Valleys soils. The experiment was a laboratory analogue for the formation of isolated patches of hypersaline, damp soil, referred to as ‘wet patches’. Soils were oven dried and then hydrated in one of two humidity chambers: one at 100% relative humidity and the second at 75% relative humidity. Soil hydration is highly variable, and over the course of 20 days of hydration, ranged from increases in water content by mass from 0–16% for 122 soil samples from Taylor Valley. The rate and absolute amount of soil hydration correlates well with the soluble salt content of the soils but not with grain size distribution. This suggests that the formation of bulk pore waters in these soils is a consequence of salt deliquescence and hydration of the brine from atmospheric water vapour.

Surface sediments from six box cores along the north-eastern Antarctic Peninsula document the dinoflagellate cyst (= dinocyst) and other non-pollen palynomorph (NPP) content soon after overlying ice shelves collapsed. Prince Gustav Channel (PGC) and Larsen-A (LA) areas exhibited markedly different dinocyst abundances, concentrations being low in LA (0–20 cysts g-1) and high in PGC (2600–9100 cysts g-1, average: c. 3800 cysts g-1). Since similar water masses impact both areas, differences may be due to low biological productivity, limited sediment accumulation, and/or restricted fine-grain deposition at Larsen-A. Islandinium minutum (Harland & Reid in Harland et al.) Head et al. dominated dinocyst assemblages, occurring as both excysted and encysted forms (lesser abundance). Other taxa (Echinidinium cf. transparantum Zonneveld, Impagidinium pallidum Bujak, Bitectatodinium tepikiense Wilson, Operculodinium centrocarpum Wall & Dale, Brigantedinium spp., Selenopemphix antarctica Marret & de Vernal, Polykrikos? sp. A, and Polykrikos schwartzii Bütschli) were rare. Such assemblage composition is unusual compared to previously published Southern Ocean data, but may be specific to ice shelf and/or recently ice-free environments. Alternatively, it may be attributable to excessive production facilitated by environmental factors and/or abundant food, or similar cyst morphologies produced by different dinoflagellates. Accompanying NPPs included zooplankton remains, acritarchs, and freshwater algae. Tintinnid loricae were most abundant (max. 800 g-1), followed by foraminiferal linings (max. 320 g-1), and the acritarch Palaeostomocystis fritilla (Bujak) Roncaglia (max. 150 g-1). Collectively, NPPs were more abundant in PGC compared to LA samples.

Seven independent clone libraries were constructed to study the biodiversity of the bacterioplankton in the surface waters around Southern Thule, South Sandwich Islands, in order to identify the species present, to determine the sample effort required to estimate the total diversity, and to determine whether the surface waters around Southern Thule represented a highly specialized local anomaly or a subset of the marine meta-community. In total, 672 clones generated 629 useable sequences. These 629 clones matched 278 different sequences deposited in the 16S rDNA sequence databases. The majority of the clones were related to marine microorganisms, many of which had been previously detected in permanently cold Arctic and Antarctic marine environments. Each clone library generated an average of 35.8 new sequence matches. 346 clones covered two-thirds of the total estimated diversity, while 438 clones covered three-quarters of the total estimated diversity. Above this number, the coverage tended to stabilize and a relatively large number of additional clones were required to improve coverage significantly, increasing at the rate of about one new sequence match per 100 new clones. Comparing the different clone libraries, eight matches occurred in each of the seven libraries, whilst fifty-five occurred in only one, suggesting that there might be a relatively small number of common dominant ubiquitous species, with a much larger underlying diversity or ‘seed bank’ from which this dominant diversity is drawn. This study suggests that the dominant bacterioplankton in the surface waters around Southern Thule represent a subset of the marine meta-community, whilst sub-dominant diversity appears to be a highly specialized local anomaly.

As Antarctic subglacial lake research progresses to in situ exploration an important topic is the lake's probable gas concentration. Depending on hydrological setting, subglacial lakes may contain large amounts of dissolved gas or gas trapped within clathrates. Consequently, access can be potentially dangerous due to the risk of blowout where depressurization could lead to high-speed ejection of water and gas from a borehole. We present a structured approach to assess the blowout risk in subglacial lake exploration. The approach integrates a generic event tree, applicable to open and closed hydrological systems, with site-specific expert judgment incorporating rigorous probabilistic formulations. The methodology is applied to a motivating example: Ellsworth Subglacial Lake. Judgments elicited through a formal process were provided by five experts with 88 years combined experience that, after aggregation, gave a median risk of blowout of 1 in 2186 with a lower quartile of 1 in 3433 and an upper quartile of 1 in 1341. This approach can be applied to any subglacial lake given a modicum of knowledge on its hydrological setting, as uncertainty can be captured through the elicited judgments. Additionally, the event tree analysis informs blowout mitigation strategies to reduce risk of injury or death.

Over the last decade, the Antarctic continent has been the object of intensive scientific programmes. However, the emphasis of these studies rarely focuses on the Antarctic as a source of potential elements such as mercury. The release of mercury to the environment is known to occur at Deception Island, associated with volcanic activity. In this study, a 3D hydrodynamic model was used to assess the role of water circulation on the dispersion of released mercury. Sea level variation and tidal circulation data were obtained. Residence time was calculated using two different approaches. Internal tide generation in summer and winter were recognized and the barotropic tidal components obtained. Lagrangian tracers were used to depict particle circulation (simulating particulate mercury) in a three month summer simulation for barotropic and baroclinic conditions. The results show that particles accumulate in the northern and western parts of the bay. It is acknowledged that the results of the 3D model are associated with a non-negligible uncertainty, which can only be reduced with an ongoing commitment to monitoring. The findings of this study indicate that mercury accumulation is occurring in Port Foster (Deception Island), which is a potential threat to the local ecosystem.

Palynomorph assemblages dominated by dinoflagellate cysts are described from seventeen samples from the Rabot Member of the Santa Marta Formation at Ekelöf Point, eastern James Ross Island, Antarctic Peninsula. Although the assemblages are of relatively low diversity, the dinoflagellate cyst taxa recorded indicate a mid to late Campanian (Late Cretaceous) age. Changes in species diversity, dominance and gonyaulacacean ratio suggest a gradually reducing distance from shore during deposition, with a return to more offshore conditions towards the section top. A new species of dinoflagellate cyst, Isabelidinium papillum, is described.

The goal of this study was to demonstrate the role of isolation on the social behaviour of individuals and to characterize its adaptation as a function of time. The ethological method used was a quantitative description of the spatial positioning of a sub-group of 13 wintering members during the morning, midday and evening meals at Dumont d'Urville station. The observation protocol required the completion of first daily and then weekly (every Thursday) observation maps at different stages of the 13 month long polar mission, from the information seminar in France, the trips outward and return aboard the Astrolabe, the two summer campaigns at the beginning and at the end of the mission and the overwintering period. Results, mainly expressed as human concentration and spatial dispersion indexes, have successively shown organization, disorganization and reorganization periods of the small group without any significant cycling. Socialisation rules promoting the group building in the early period, conflict factors and relay steps (external perturbations breaking the isolation, transitions during group displacement from one stage to another) promoting the maintenance of the social cohesion, are outlined in the discussion.