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.

Following a weakening of the semi-annual oscillation (SAO) since the mid-1970s, the half-yearly pressure wave in the Southern Hemisphere has become less significant. As a result, May/June temperatures have decreased in East Antarctica, which has moderated Antarctic warming. Spectral analysis of 87 years of pressure data at Orcadas suggest that the recent weakening of the SAO is part of the natural variability of the Southern Hemisphere circulation on decadal timescales. We interpret the time series of composite Antarctic temperature in terms of the historical strengthening and weakening of the SAO. If the dominant oscillations that occurred in the past prove to be persistent, an accelerated East Antarctic warming trend is expected for the coming decades. There are indications that the strength of the SAO is linked to the Southern Oscillation, in the sense that warm phases of the Southern Oscillation coincide with strong westerlies, a weakly developed SAO and below-average temperatures in East Antarctica. Temperatures on the west coast of the Antarctic Peninsula show strongly deviant patterns, which can not be explained by the same mechanism that applies to East Antarctica.

This review assesses the circumpolar occurrence of emerged marine macrofossils and sediments from Antarctic coastal areas in relation to Late Quaternary climate changes. Radiocarbon ages of the macrofossils, which are interpreted in view of the complexities of the Antarctic marine radiocarbon reservoir and resolution of this dating technique, show a bimodal distribution. The data indicate that marine species inhabited coastal environments from at least 35 000 to 20 000 yr BP, during Marine Isotope Stage 3 when extensive iceberg calving created a ‘meltwater lid’ over the Southern Ocean. The general absence of these marine species from 20 000 to 8500 yr BP coincides with the subsequent advance of the Antarctic ice sheets during the Last Glacial Maximum. Synchronous re-appearance of the Antarctic marine fossils in emerged beaches around the continent, all of which have Holocene marine-limit elevations an order of magnitude lower than those in the Arctic, reflect minimal isostatic rebound as relative sea-level rise decelerated. Antarctic coastal marine habitat changes around the continent also coincided with increasing sea-ice extent and outlet glacial advances during the mid-Holocene. In view of the diverse environmental changes that occurred around the Earth during this period, it is suggested that Antarctic coastal areas were responding to a mid-Holocene climatic shift associated with the hydrological cycle. This synthesis of Late Quaternary emerged marine deposits demonstrates the application of evaluating circum-Antarctic phenomena from the glacial-terrestrial-marine transition zone.

The relationship between colony area and population density of Adélie penguins Pygoscelis adeliae was examined to determine whether colony area, measured from aerial or satellite imagery, could be used to estimate population density, and hence detect changes in populations over time. Using maps drawn from vertical aerial photographs of Adélie penguin colonies in the Mawson region, pair density ranged between 0.1 and 3.1 pairs m−2, with a mean of 0.63 ± 0.3 pairs m−2. Colony area explained 96.4% of the variance in colony populations (range 90.4–99.6%) for 979 colonies at Mawson. Mean densities were not significantly different among the 19 islands in the region, but significant differences in mean pair density were observed among colonies in Mawson, Whitney Point (Casey, East Antarctica) and Cape Crozier (Ross Sea) populations. The relationship between colony area and population may be locality-and/or species-specific, and a robust data set is required to validate the relationship.

The boundary layer thermal structure, observed through Doppler sodar, at Dumont d'Urville, has been analysed. Typical echograms of the spiky layers, wavy layers and thermal plumes, except for the eroding inversion, have been observed. The annual distribution of these thermal structures is presented. The spiky layers are observed to coincide with strong winds (mainly katabatic) flowing from the inner continent sector, 90°–180°. The upper boundary of the spiky layers is correlated to the wind direction; the maximum depths (more than 400 m) are confined to 60° wide span centred at 135°. The predominant waves and the spiky layers, tend to occur alternately in accordance with the relative dominance of the katabatic flow intensity and the stability conditions. The sodar signatures of these structures are examined in relation to the onset and dissipation time, duration and the seasonal distribution. Both waves and spiky layers occur at any hour of the day; their maximum occurrence is in winter months. The persistence of the waves varies from a couple of hours to a couple of days while the spiky layers can occur for periods even longer than 3–4 days. The characteristics of these phenomena are associated with the diurnal radiational cycle and the temperature contrast in proximity to the coast.

The specification, development and deployment of an automated observatory designed to operate unattended for a year in the extreme climatic conditions of the polar regions is presented. Solar- and wind-powered electric generators are used to charge lead/acid batteries to provide a nominal 100 W of electrical power for operating scientific sensors. The equipment is housed in a highly insulated caboose (3m by 2m by 2m). The temperature in the latter is regulated using a unique thermal control system which utilizes the latent heat of 500 l of water stored in 25-l plastic containers. Data are logged to optical disks for collection once per year. The observatory is designed to be air-deployed using a DHC-6 aircraft. The paper discusses the rationale for designing such automated systems, the operational experience gained from several years of operation, and the application of a network of observatories to solar-terrestrial physics research.

Deception Island is a large volcanic centre in Bransfield Strait, a very young marginal basin between the South Shetland Islands and Antarctic Peninsula. It has a historical record of volcanic activity, with the most recent eruption occurring in 1970. The island is a stratovolcano with a large flooded caldera forming a natural harbour known as Port Foster. It has been a focus of human activity since early last century, as a base for whaling and sealing expeditions and the locus of several scientific stations. During that period, many bathymetric surveys were carried out, the earliest in 1829 and the most recent in 1993. This study concentrates on surveys from 1948 onwards. Because Port Foster can be classified as a restless caldera, the bathymetric records were analysed for evidence of volcano-tectonic deformation, particularly caldera resurgence (uplift) which could have significant consequences for hazard and risk assessments of the volcano. The results show that a distinctive pattern of shallowing and uplift is present, correlating well with known and inferred volcanic and volcanotectonic processes on the island. In particular, bathymetric records between 1949 and 1993 show uplift rates as high as 0.3–0.5 m a−1, far exceeding normal sedimentation rates in a caldera this size. Rapid uplift in an arcuate offshore area not affected by the sedimentation of recent eruptions suggests that volcano tectonic resurgence or tectono-magmatic effects of an upward migrating magma chamber present a significant risk to the considerable human activity taking place in the region.

US Joint Ice Center (JIC) Antarctic sea ice extent data, the longest continuous series of its kind for this part of the world, are compared with direct passive microwave-based estimates to assess their overall consistency both spatially and temporally in the period 1979–88. Using ice edge position as a proxy for ice extent, the comparison reveals close agreement in most years, in monthly averaged ice edge positions in all Antarctic regions at the time of maximum ice extent, and also in autumn and spring in the Ross and Weddell Seas. Unexpectedly, JIC relative overestimation prevails during both autumn and spring in some other areas. Previously noted differences in JIC and passive microwave total Antarctic extent in 1979–80 result mainly from problems in the Ross Sea. Reasons for the various discrepancies may lie in differences in the methods used to produce the datasets especially in spring but those in autumn seem to often arise for other reasons. It is found that the prevalent discrepancies in the Ross Sea in 1979–80 as well as those in spring in other regions from 1981 coincide with periods of ice extent change and the evolution/intensification of ice extent anomalies.

The Mesozoic-Cenozoic volcanic arc of the Antarctic Peninsula is represented on Adelaide Island by a sedimentary and volcanic succession intruded by plutons. 40Ar-39 Ar step-heating age spectra have been obtained from volcanic rocks and hornblende separates from sedimentary clasts of plutonic origin. These spectra show evidence for some argon loss, but, in general, have plateau ages which are consistent with the mapped stratigraphy and with other geochronological controls, suggesting that they approximate to original ages. As a result the following events in the evolution of Adelaide Island can be recognized:

1) mostly marine Mesozoic sedimentation, 2) Early Cretaceous (c. 141 Ma) plutonism (recorded in clasts from conglomerates), 3) Cretaceous volcanism, 4) Late Cretaceous (possibly Tertiary) sedimentation, 5) Early Tertiary volcanism, which was acidic in eastern outcrops and intermediate elsewhere, and 6) Eocene intermediate volcanism and deposition of arc-derived conglomerates. Volcanism was possibly coeval with known Palaeocene-Eocene plutonic activity on Adelaide Island (part of the Antarctic Peninsula Batholith) and with volcanism of similar age in northern Alexander Island and the South Shetland Islands. The volcanism on Adelaide Island and the South Shetland Islands, at least, was associated with a westward migration of the Antarctic Peninsula arc.

Minette dykes intersect the Precambrian crystalline basement of Schirmacher Oasis, East Antarctica. The rocks have intermediate to basic compositions, showing shoshonitic to ultrapotassic character. The samples show enhanced concentrations of compatible elements and high mg# combined with extreme enrichments in LILE (especially Ba) and LREE. Mantle-normalized trace element patterns are characterized by coupled relative depletions of Nb and Ti and strong fractionations between LILE and HFSE. The minettes display fractionated chondrite-normalized REE patterns with high and varying LREE concentrations in contrast to relative low and nearly constant HREE contents. High magma-ascent and cooling rates of lamprophyric magmas argue against a fundamental change of the primary geochemical signatures in minette magmas by interactions with the continental crust during ascent. The major and trace element abundances of the studied minettes point to varying degrees of partial melting of a mantle source, which was enriched in LILE and LREE during or before the melting event. Incompatible element signatures argue for the involvement of subducted pelagic sediments.

The first fossil stylasterid from Antarctic is reported from La Meseta Formation (Telm1: Early Eocene) of Seymour Island (Antarctic Peninsula): Conopora mariae sp. nov. This also is the earliest reliable fossil record of the genus Conopora. Conopora mariae differs from congeners by having much larger cyclosystems (diameter 2.5–4.5 mm). Cyclosystems of that size are exceptional among the Stylasteridae.

Observations of satellite passes monitored at Halley and Terra Nova Bay have been combined to produce for the first time measurements of ionospheric electron content spanning the Antarctic continent. Results are presented from a sequence of four successive passes made during a period of some two hours that illustrate the development of the ionosphere over this wide spatial region. The observations are discussed in terms of the convective behaviour of the ionization, using results from the PACE radar and a standard model of the plasma flow.