Geological evidence shows that the ice sheet and climate in Antarctica has changed considerably since the onset of glaciation around 34 million years ago. By analysing this evidence, important information concerning processes responsible for ice sheet growth and decay can be determined, which is vital for appreciating future changes in Antarctica. Geological records are diverse and their analyses require a variety of techniques. They are, however, essential for the establishment of hypotheses regarding past Antarctic changes. Numerical models of ice and climate are useful for testing such hypotheses, and in recent years there have been several advances in our knowledge relating to ice sheet history gained from these tests. This paper documents five case studies, employing a full range of techniques, to exemplify recent insights into Antarctic climate evolution from modelling ice sheet inception in the earliest Oligocene to quantifying Neogene ice sheet fluctuations and process-led investigations of recent (last glacial) changes.

In the polar regions, dynamical and thermodynamical interactions between atmosphere and ocean are strongly influenced by the presence or absence of the ice cover, which forms an insulating layer over the ocean, hindering sensible heat fluxes and forming an effective barrier to evaporation and thus preventing latent heat loss. In the framework of the CLIMA (Climatic Long-term Interactions for the Mass-balance in Antarctica) project of the Italian PNRA (National Program for Antarctic Research) we focused our attention on the evaluation of the heat fluxes between the ocean and the atmosphere in the Ross Sea, where the ice covers the sea for many months of the year. Wherever the ice cover is absent all year round, such as in leads or polynyas, the air-sea fluxes can be very large, especially in winter when the air-sea temperature differences are strong. In this work heat exchanges between sea and atmosphere, whether ice cover was present or not, were calculated from climatological data obtained from the European Centre for Medium Range Weather Forecasts, while sea ice data were collected from the US National Ice Center and National Climatic Data Center. Each of the terms in the sea surface heat budget were computed for 1994 with a temporal resolution of six hours and a spatial resolution of 0.5° using bulk formulae and obtaining monthly averaged horizontal distributions. The surface heat budget is dominated in November, December, January and February by shortwave radiation, while for the other months the turbulent and conductive heat fluxes dominate the heat exchange between the atmosphere and the sea surface. The annual total heat loss at the surface in 1994 has been estimated at about −90 W m−2 with the highest heat loss occurring close to the coast; the maximum heat loss occurred in May (−217 W m−2) while in January the heat gain by the ocean was 196 W m−2. In addition, weekly averaged values over the whole Ross Sea from 1994 to 1997 were calculated with the same parameterisation in order to study the temporal variability in this basin of each individual component and of the total surface heat budget. For this purpose only the data inside the continental shelf of the Ross Sea were considered in calculating the averaged fluxes. The 1994–97 total heat budget ranges from −87 to −107 W m−2with an average of −96 W m−2; this amount of heat loss was supposed to be compensated for by the heat advected by the Circumpolar Deep Water and its transport was estimated at about 2.9 Sv.

Sterechinus antarcticus inhabits the shelf and the slope of the Weddell Sea and is the predominant echinoid between 450 and 1200 m. Growth lines visible in the half pyramids of the Aristotle's lantern were interpreted as annual growth marks. A Von Bertalanffy growth function was fitted to age-diameter data of 217 specimens (D∞ = 82.4 mm, K = 0.017 y−1, t0 = 1.633 y). Based on 92 trawl samples, a representative size-frequency distriution of S. antarcticus was established. From the growth curve, the size-frequency sample and diameter - weight regressions, mortality and somatic productivity of S. antarcticus were calculated by a size-converted catch curve and the weight specific growth rate method. Gonadal productivity was estimated by an average value for reproductive output of cold water echinoderms. Mortality rate Z as'well as somatic P/B ratio amounted to 0.07 y−1. Annual somatic production was estimated as 0.3 mg m−2y−1, and annual gonadal production as 0.25 mg m−2 y−1 between 100 and 1200 m (0.6 and 0.5 mg m−2 y−1 between 450 and 1200 m).

The eight dominant culturable members of an Antarctic fellfield soil bacterial community were four Arthrobacter species, Sanguibacter suarezii, Aureobacterium testaceum, a Bacillus sp., and a Pseudomonas sp.. All of the isolates grew at 2°C, but two of the Arthrobacter spp. were psychrophilic, while the other six bacterial species were psychrotolerant. However, the fastest growing organisms at low temperatures were not the psychrophiles, and the psychrotolerant Bacillus sp. grew fastest at temperatures up to 25°C. When the growth temperature of cultures was altered, the phospholipid content of the two psychrophilic Arthrobacter spp. decreased, whereas the phospholipid contents of the psychrotolerant spp. either increased or did not change. Only one psychrophilic and one psychrotolerant Arthrobacter sp. modified its polar lipid head-group composition in response to a lowering of growth temperature. The change in Arthrobacter sp. CL2-1 was particularly marked and novel in that at low temperatures phosphatidylethanolamine was replaced completely by a phosphoglycolipid and phosphatidylserine, neither of which was present at higher growth temperatures. All eight isolates altered the fatty acyl compositions of their membrane lipids in a manner that was only partially dependent on taxonomic status. In Bacillus sp. C2-1 the changes were opposite to that predicted on the basis of membrane fluidity considerations. The isolates used different combinations of changes in fatty acid branching, unsaturation and chain length. There was no single strategy of thermal adaptation that was employed and the variety of strategies used did not follow phylogenetic boundaries.

Cephalopod remains from the stomachs of four pilot whales Globicephala melaena (Traill, 1809), two bottlenose whales Hyperoodon planifrons Flower, 1882 and eight Commerson's dolphins Cephalorhynchus commersonii (Lacepede, 1804) stranded in Tierra del Fuego, Argentina were identified and measured. A total of 3365 lower beaks (mandibles) were identified and measured and from the rostral, crest and hood length, total wet and dry mass, mean mass and mean mantle length for each taxon were estimated. Over 68% of the cephalopods eaten by the pilot whales and all cephalopods eaten by the bottlenose whales were oceanic squid species (oegopsids). The Commerson's dolphins had only eaten shelf species of the families Loliginidae (97.5%) and Octopodinae (2.5%). Sixteen cephalopod families comprising 23 species were represented. In samples from Globicephala melaena, Loligo gahi represented 31% by number and 7.1% by estimated dry mass, Histioteuthis eltaninae, 29% by number and 4.9% by dry mass and the onychoteuthid Moroteuthis ingens 17.2% by number and 51.5% by dry mass. In samples from Hyperoodon planifrons, Histioteuthis eltaninae represented 24.0% of cephalopods by number but only 5.2% by dry mass, Taonius pavo 53% by number but only 2.5% by dry mass and the large onychoteuthid Kondakovia longimana only 2.5% by number but 65.8% by dry mass. In samples from Cephalorhynchus commersonii, the neritic Loligo gahi contributed 97.4% by number and 97% by dry mass and a neritic octopodinid contributed the rest of the cephalopod part of the diet. While the cephalopods contributed the major part of the diets of these particular cetaceans, other remains included fish and polychaete worms.

Data from several summer research cruises in the Antarctic Peninsula region were analysed to calculate length (L50) and age at maturity for the Antarctic krill, Euphausia superba. Length at maturity L50 is defined as the length at which 50% of the krill stock attains sexual maturity. L50 values of 34.65–35.91 mm for female krill are the best estimates for the peak spawning season. Males attain sexual maturity later at L50 values of 43.35–43.71 mm. Length at maturity and length at first spawning are identical for krill. Comparisons with mean length-at-age data show that females mature in the third growth season (age class 2+), while males reach maturity in the fourth year (age class 3+). Both sexes show ‘knife-edge maturity’.

The infestation of Weddell seals and several fish species by the anisakid nematodes Contracaecum osculatum and C. radiatum was compared. Nematode numbers in Weddell seal stomachs ranged from 30 560 to 122 640. Third stage larvae from seals and fish were separated into a short and a long type. The short type was related to C. radiatum and the long type to C. osculatum. The short type was more abundant in pelagic fish species, whereas the long type prevailed in benthic fish species. Fish-feeding channichthyids Cryodraco antarcticus and Chionodraco myersi seemed to play an important role as paratenic hosts for the third stage larvae of both Contracaecum species. Different advantageous and detrimental features of a benthic versus a pelagic life cycle under high Antarctic ecological conditions are discussed. Varying abundance of the two nematode species in hosts may be controlled by differences in their life cycles, which follow either a pelagic or a benthic food web. Crucial importance is thus given to the local availability of pelagic versus benthic food resources for Weddell seals.

Particulate organic matter was collected in the coastal waters of Terra Nova Bay during the Oceanographic Campaign of the Italian Antarctic Research Programme in summer (January–February) 1990. Particulate matter composition was analysed for organic carbon and nitrogen, carbohydrates, proteins, lipids, nucleic acids (DNA and RNA) and ATP. A vertical stratification was evident in the study area, and resulted from prior melting of the pack ice. Suspended organic matter in the mixed layer and below the mixed layer differed in quantitative and qualitative composition. Except for ATP, all the biochemical components showed higher concentrations in the mixed layer than in the deeper waters. The particulate organic matter in Terra Nova Bay was mostly detrital and of algal origin.

Glacial till samples collected from beneath the Bindschadler and Kamb ice streams have a distinct U-Pb detrital zircon signature that allows them to be identified in Ross Sea tills. These two sites contain a population of Cretaceous grains 100–110 Ma that have not been found in East Antarctic tills. Additionally, Bindschadler and Kamb ice streams have an abundance of Ordovician grains (450–475 Ma) and a cluster of ages 330–370 Ma, which are much less common in the remainder of the sample set. These tracers of a West Antarctic provenance are also found east of 180° longitude in eastern Ross Sea tills deposited during the last glacial maximum (LGM). Whillans Ice Stream (WIS), considered part of the West Antarctic Ice Sheet but partially originating in East Antarctica, lacks these distinctive signatures. Its U-Pb zircon age population is dominated by grains 500–550 Ma indicating derivation from Granite Harbour Intrusive rocks common along the Transantarctic Mountains, making it indistinguishable from East Antarctic tills. The U-Pb zircon age distribution found in WIS till is most similar to tills from the west-central Ross Sea. These data provide new specific targets for ice sheet models and can be applied to pre-LGM deposits in the Ross Sea.

Fisher Massif consists of Mesoproterozoic (c. 1300 Ma) lower amphibolite-facies metavolcanic rocks and associated metasediments, intruded by a variety of subvolcanic and plutonic bodies (gabbro to granite). It differs in both composition and metamorphic grade from the rest of the northern Prince Charles Mountains, which were metamorphosed to granulite facies about 1000 m.y. ago. The metavolcanic rocks consist mainly of basalt, but basaltic andesite, andesite, and more felsic rocks (dacite, rhyodacite, and rhyolite) are also common. Most of the basaltic rocks have compositions similar to low-K island arc tholeiites, but some are relatively Nb-rich and more akin to P-MORB. Intermediate to felsic medium to high-K volcanic rocks, which appear to postdate the basaltic succession, have calc-alkaline affinities and probably include a significant crustal component. On the present data, an active continental margin with associated island arc was the most likely tectonic setting for generation of the Fisher Massif volcanic rocks.

We present preliminary results of the first detailied surveys of the former Larsen-A Ice Shelf, Larsen Inlet and southern Prince Gustav Channel, where disintegration of small ice shelves in the past ten years has exposed the seafloor. Glacial troughs in the Larsen-A area, Larsen Inlet and Prince Gustav Channel reach 900–1100 m depth and have hummocky floors. Farther south-east, the continental shelf is shallower (400–500 m) and its surface is fluted to smooth, with the density of iceberg furrowing increasing towards the shelf edge. Acoustic profiles show a drape of transparent sediment 4–8 m thick in Prince Gustav Channel, thinning southwards. In cores, this drape corresponds to diatom-bearing marine and glacial-marine mud. In the Larsen-A area and Larsen Inlet, acoustically opaque sediment includes proximal ice shelf glaciomarine gravelly and sandy muds, and firm to stiff diamicts probably deposited subglacilly. These are overlain by thin (up to 1.3 m) glaciomarine muds, locally with distinctive diatom ooze laminae.

Isolated fish remains including a tooth of the oldest described frilled shark, Chlamydoselachus thomsoni sp. nov. are described and figured from the Santa Marta Formation (Santonian–Campanian, Late Cretaceous) of James Ross Island, Antarctic Peninsula. Their geological and palaeoecological context is considered in the light of recent geological studies.

The upward evolution of temperatures in the Antarctic Peninsula has weakened and even reversed in the last two decades. Due to the long-term variability in the region it is not easy to assess whether recent cooling trends are consistent with the internal variability or not. For this reason, this paper assesses the robustness of the trends by analysing their sensitivity with respect to the period selected. Every possible temperature trend in the interval 1958–2016 has been calculated and displayed in a two-dimensional parameter diagram. The results suggest that the warming observed in the Antarctic Peninsula since 1958 is quite robust, as all periods longer than 30 years exhibit statistically significant changes, especially in summer (with lower magnitude and higher significance) and autumn and winter (with larger magnitude and lower significance). Periods shorter than 30 years exhibit alternations of warming and cooling periods, and therefore do not represent robust trends even if they are statistically significant. Consequently, the recent 20-year cooling trend cannot be considered at the moment as evidence of a shift in the overall sign of the trend.

A proximal fragment of a gill raker identified as belonging to a shark of the genus Cetorhinus was collected from middle Eocene deposits of the La Meseta Formation in the northern part of Seymour Island, Antarctica. This is the first record of a fossil basking shark from Antarctica and one of the earliest records of the genus. The minimum age of Cetorhinidae is middle Eocene. The only living species of the family Cetorhinidae is a very large plankton feeder, Cetorhinus maximus. Basking sharks are unknown in subantarctic or Antarctic waters but occur on both South American coasts today. The evolution of filter-feeding vertebrates is discussed.

An intensive migration of Arctic terns was observed from 7–9 March 1989 in Marguerite Bay (67°50'S 67°30'W). The movement pattern and speed of tern flocks were analysed from time-lapse films of a marine navigation radar. The terns migrated north at altitudes 30–60 m asl along the inner coast of Marguerite Bay. When approaching Pourquois Pas Island, the majority veered to the NNE flying into Bourgeois Fjord. Mean flock size was 11.6 (s.e. = 1.9). The estimated total during the three observation days was about 7600 migrating terns. Analysing flight speed in relation to wind showed that the terns increased their airspeed when flying into headwinds and decreased it with following winds. The terns' airspeeds, with an estimated mean of 11.3 ms-1 (s.e. = 1.3) with no wind effect, were significantly faster than the predicted maximum range speed. It is suggested that the terns were migrating on a connecting route between the pack ice of the Bellingshausen and Weddell Seas, involving a flight across the Antarctic Peninsula. Topographical conditions are favourable for such a passage close to the observation site in Marguerite Bay, where the distance across the 1500 m high ice cap of the Antarctic Peninsula is only 37 km. It remains to be clarified if the suggested migration route is of importance for regional tern populations only, or if it is part of a circumpolar Antarctic migration pattern.

Bransfield Strait, a narrow active rift with three submarine basins, separates the South Shetland Islands from northern Antarctic Peninsula. Volcanism in Bransfield Strait commenced prior to 0.75 Ma and continues, with recent subaerial eruptions at Deception, Bridgeman and Penguin islands, submarine hydrothermal activity and numerous young basaltic seamounts located along the rift axis. Gravity cores were collected from five locations within the central Bransfield basin. Diatomaceous mud interbedded with terrigenous detritus and discrete ash layers up to 10 cm thick are the commonest sediment types in all the cores. The major element compositions of glass shards within the ash layers are, apart from the uppermost layer, compositionally similar to pyroclastic units preserved on Deception Island, a young (<0.75 Ma) active stratovolcano. The uppermost ash layer cannot be closely matched compositionally to any known source in the Antarctic–Scotia Sea–southern South America region. Its presence indicates that a volcanic centre other than Deception Island contributed ash to the Bransfield basin. Based on the shallow stratigraphical position of the compositionally distinctive ash layer, only a few decimetres beneath the seafloor, its source volcano was probably active in historical times (<few hundred years).

The McMurdo Dry Valleys of Antarctica are the largest ice-free region on the continent. These valleys contain numerous water bodies that receive seasonal melt from glaciers. For forty years, research emphasis has been placed on the larger water bodies, the permanent ice-covered lakes. We present results from the first study describing the geochemistry of ponds in the higher elevations of Taylor Valley. Unlike the lakes at lower elevations, the landscape on which these ponds lie is among the oldest in Taylor Valley. These upland ponds wax and wane in size depending on the local climatic conditions, and their ionic concentrations and isotopic composition vary annually depending on the amount of meltwater generated and their hydrologic connectivity. This study evaluates the impact of changes in summer climate on the chemistry of these ponds. Although pond chemistry reflects the initial meltwater chemistry, dissolution and chemical weathering within the stream channels, and possibly permafrost fluid input, the primary control is the dilution effect of glacier melt during warmer summers. These processes lead to differences in solute concentrations and ionic ratios between ponds, despite their nearby proximity. The change in size of these ponds over time has important consequences on their geochemical behaviour and potential to provide water and solutes to the subsurface.

Temporal and spatial variations of the hydrogen peroxide accumulation were measured in off-shore waters and in intertidal rockpools near Jubany Station, King George Island, South Shetland Islands. As H2O2 photoformation is mainly driven by the short wavelength radiation in the UV-B and the UV-A range of the solar spectrum, the study was conducted between the beginning of October and the end of December 1995, the period of Antarctic spring ozone depletion. Wet deposition of H2O2 containing snow was identified as a major source of hydrogen peroxide in the surface waters of Potter Cove. As the concentrations of dissolved organic carbon (DOC) in Potter Cove surface waters were low (121 ± 59 μmol Cl−1), when compared to the highly eutrophicated waters on the German Wadden coast (6000–7000 μmol Cl−1), direct UV-induced DOC photo-oxidation was of only limited significance in the Antarctic sampling site. Nonetheless, under experimental conditions, H2O2 photoformation in Potter Cove surface waters amounted to 90 ± 40 nmol H2O2 h−1 l−1 under a UV-transparent quartz plate. When high energy UV-B photons were cut-off by a WG320 filter formation continued at a rate of 66 ± 29 nmol H2O2 h−1 l−1 due to UV-A and visible light photons. Samples from freshly deposited snow contained between 10 000 and 13 600 nmol H2O2 l−1, and a snowfall event in mid November resulted in a maximum concentration of 1450 nmol H2O2 l−1 in the upper 10 cm layer of Potter Cove surface waters. Maximal H2O2 concentrations in intertidal rockpools were even higher and reached up to 2000 nmol H2O2 l−1 after the snowfall event. During a grid survey on December 17 1995, H2O2 concentrations and salinity displayed a north to south gradient, with higher concentrations and PSU at the south coast of the cove. The reasons for this spatial inhomogenety are as yet unknown, but may relate to a minor local input of photo-reactive organic matter from creeks entering the cove in the south-east, as well as to waste water discharge from the station, located on the south beach.

This paper addresses the study of the thermohaline circulation and convective processes induced by the presence of a coastal polynya in Terra Nova Bay (Ross Sea, Antarctica). These processes are analysed by means of oceanographic observations and numerical simulations. Time series of hydrological parameters and currents show the High Salinity Shelf Water (HSSW) formation with the mixing of the water column down to great depths, and a seasonal cycle of kinetic energy. A two-dimensional time dependent model for the numerical simulation of the effects of polynya on the circulation has been implemented. This model allows estimation of the contribution of thermohaline forcing on the circulation pattern, the amount of ice production consistent with the observed salinity distribution and annual cycle of currents and the amount of HSSW exported. The thermohaline forcing due to the polynya is able to induce strong horizontal currents up to 40 cm s−1 near the polynya area, as well as vertical movements of the order of 1 cm s−1. An annual ice production, ranging from 45 m to 90 m, mixes the water column at great depths, up to 750 m, and increases the salinity of the surface incoming waters up to 34.82. The estimated net north-eastward transport of HSSW ranges from 0.34 Sv to 1.23 Sv, depending on ice production.