The question of how stable the climate in Antarctica has been during the last few million years compared to the rest of the planet is still controversial. This study attempts to add new information to the discussion by reconstructing the timing and spatial extent of glacial advances in northern Victoria Land over tens of thousands to millions of years. In Terra Nova Bay region, surface exposure ages and erosion rates of glacially rounded bedrock and glacial erratics have been determined using the cosmogenic nuclides 3He, 10Be and 21Ne. Three morphological units have been analysed. They yield minimum ages of 11 to 34 ka, 309 ka, and 2.6 Ma, respectively. Erosion rates were as low as 20 cm Ma−1 since middle Pliocene time. Taking erosion into account, the oldest surface is 5.3 Ma old. Pleistocene glacier advances had considerable extent, reaching up to 780 m above modern ice levels, but have been restricted to the valleys since at least mid-Pliocene. The existence of landscapes of mid-Pliocene age in northern Victoria Land implies that the climatic stability of the McMurdo Dry Valleys is not unique within the Transantarctic Mountains, but rather the expression of a constantly cold and hyperarid climate regime in entire Victoria Land.

Field observations involving landform evaluation and the physical characterization of sediments, combined with a detailed analysis of the spatial distribution of bedrock and sediment geochemical patterns, suggests a limit to the glacial transport half-distance of c. 3 km in Vestfold Hills. Four morphologically distinct glacial deposits were sampled (small debris ridges, large debris ridges, debris drapes and valley fills) on the basis of field geometry. These landforms were subsequently distinguished by grain size, mineralogy and geochemistry. Since there are no nunataks south of Vestfold Hills, all debris is derived subglacially and sedimentological differences are attributed to the physical weathering of preglacial surfaces in Vestfold Hills and fluvial winnowing during deposition. Given that thrust geometries may occur in large debris ridges, glacial transport distances were short, and fluvial sorting of sediments was an important mechanism, reconstructions of glacial histories based on the stratigraphy of deposits in Vestfold Hills should be made with caution.

During the 1997–98 Italian Expedition to Antarctica a five-day mesoscale experiment was carried out on the continental shelf-break in the central Ross Sea. This area is oceanographically characterized by shelf/slope interactions, through intense mixing processes, between the Circumpolar Deep Water (CDW) and the Ice Shelf Water (ISW), coming from beneath the Ross Ice Shelf and spilling over the shelf edge. The export of dense shelf waters is of crucial importance not only for the mass balance of the basin, but also for carbon export from the upper layers into the abyssal ones. The study investigated how the ISW interactions with the CDW may influence bacterial metabolism during an ISW downslope event. In particular, what effect does this have on the bacterial activities related to the utilization and transformation of the organic carbon substrate (ectoenzymatic activities, carbon production, growth rate) within the ISW and the CDW cores? Our data show that in the CDW the metabolic response was to increase the biomass and enzymes were less active due to a higher nutritional value for the substrate. In the ISW the bacterial metabolic activity shifted towards degradative processes. These results suggest differences in the quality of the organic carbon pool with a greater concentration of labile organic matter in the CDW and of low-degradable compounds in the ISW. The use of microbial parameters seems to be very promising in the evaluation of the carbon export during mixing processes, when the refractory fraction of the organic carbon pool might play a key role.

A late summer study of marine bacteria activities, and the interrelationships with the microbial loop and the microbial food chain was carried out from 22 January to 10 February 2000 in a coastal area of Terra Nova Bay (Ross Sea). The objective was to investigate the transition from the end of a phytoplanktonic bloom to the start of winter. Intense bacterial activities, comparable to those of temperate marine environments, were observed. The carbon potentially mobilized from proteinaceous matter was quantitatively the most important source of carbon for the bacterioplankton. The leucine aminopeptidase activity was higher in January samples and decreased towards 10 February whereas an opposite trend was observed for alkaline phosphatase and �-glucosidase activities. The bacterial production was supported by c. 0.2% of the amounts of dissolved organic carbon mobilised by hydrolytic activities and by 7% of inorganic phosphate mobilised by alkaline phosphatase activity. A sharp reduction in the bacterial biomass, possibly due to zooplankton grazing or viral lysis, was observed for the first time in Terra Nova Bay.

Semi-continuous, linear accumulations of poorly-sorted debris are present on the surface of the remnant Larsen-A Ice Shelf, Antarctic Peninsula. These accumulations form a complex of debris bands extending parallel to the front of the ice shelf for several kilometres. Landsat imagery shows that the debris bands originated as lateral moraines along the Nordenskjöld Coast. Almost 80% of clasts sampled from these debris accumulations have shape/roundness characteristics consistent with glacier transport in the zone of basal traction. Angular and very angular clasts account for 15% and 22% of clasts in the pebble- and cobble/boulder-sized fractions, respectively, and originated by rockfall from valley/nunatak sides, with subsequent passive glacier transportation. Lithological analysis indicates that the debris is derived locally from the Nordenskjöld Coast, Cape Fairweather region and interior of the Antarctic Peninsula. Episodic melt-out and resedimentation of this debris from the front of the ice shelf would deliver pulses of coarse-grained sediment to the sea floor. Therefore, coarse-grained debris can also be released along the calving margin of small polar ice shelves fringing mountainous terrain, and could potentially be confused with sediment deposited at the grounding line of Antarctic ice-shelves. Sedimentological criteria to differentiate between these environments are proposed in this paper.

Adélie penguin (Pygoscelis adeliae) stomach contents, krill (Euphausia superba and E. crystallorophias) and silverfish (Pleuragramma antarcticum) from the Ross Sea were analysed to determine several persistent organic pollutants (POPs). In discussing the data, the prey-predator linkage between these species was taken into account. Sampling was carried out during the 1995/96 and 1999/00 Italian Antarctic Expeditions. Fifty four polychlorobiphenyls (PCBs) and p,p’-DDE and hexachlorobenzene (HCB) were quantified in stomach contents of penguins nesting at Edmonson Point (Victoria Land) and in whole specimens of silverfish and krill from the Ross Sea. Xenobiotic concentrations in organisms were low compared to data reported for many marine species of lower latitudes and ranged from 0.22 ng g−1 wet wt p,p’-DDE in krill to 161 ng g−1 wet wt PCBs in silverfish. Fingerprints and class of isomer patterns showed a predominance of low chlorinated PCBs, mainly in pelagic organisms. Average input of these POPs through the diet was also evaluated. Concentrations of the most toxic non-ortho PCBs, IUPAC nos 77 (3,3′,4,4′), 126 (3,3′,4,4′,5) and 169 (3,3′,4,4′,5,5′), were 1.63 pg g−1, 7.31 pg g−1 and 0.23 pg g−1 wet wt, respectively, in stomach content samples. Stomach contents had 0.037 pg g−1 wet wt TEQ (Toxic Equivalents) of which penta-CB126 accounted for most of the toxicity.

Multi-channel seismic data acquired on the South Shetland margin, northern Antarctic Peninsula, show that Bottom Simulating Reflectors (BSRs) are widespread in the area, implying large volumes of gas hydrates. In order to estimate the volume of gas hydrate in the area, interval velocities were determined using a 1-D velocity inversion method and porosities were deduced from their relationship with sub-bottom depth for terrigenous sediments. Because data such as well logs are not available, we made two baseline models for the velocities and porosities of non-gas hydrate-bearing sediments in the area, considering the velocity jump observed at the shallow sub-bottom depth due to joint contributions of gas hydrate and a shallow unconformity. The difference between the results of the two models is not significant. The parameters used to estimate the total volume of gas hydrate in the study area were 145 km of total length of BSRs identified on seismic profiles, 350 m thickness and 15 km width of gas hydrate-bearing sediments, and 6.3% of the average volume gas hydrate concentration (based on the second baseline model). Assuming that gas hydrates exist only where BSRs are observed, the total volume of gas hydrates along the seismic profiles in the area is about 4.8 × 1010 m3 (7.7 × 1012 m3 volume of methane at standard temperature and pressure).

Middle Jurassic continental flood basalts of Vestfjella, western Dronning Maud Land are cut by gabbroic intrusions that represent rare exposures of Karoo-related mafic plutons in Antarctica. The gabbros and numerous associated dolerites indicate high magmatic activity along the continental margin of Dronning Maud Land during the break-up of Gondwana. The scattered nunataks of Utpostane (∼25 km2) are dominated by olivine gabbronorite and olivine mela-gabbronorite, which can be grouped into four zones. The Utpostane intrusion exhibits inclined sheet-like geometry, is at least ∼3 km thick and shows moderate enrichment of incompatible element contents from its base towards the exposed roof contact (e.g. Zr from ∼15 to ∼60 ppm). High MgO contents (∼8–36 wt%) indicate that the parental magma of Utpostane was more primitive than a typical Karoo tholeiite (MgO ∼6 wt%). At Muren, gabbroic outcrops record a cross section of a ∼1.3 km thick inclined sheet-like intrusion. The intrusion can be divided to two main units, the upper and lower zones, which are dominated by olivine gabbro and gabbronorite, respectively. Parental melts of the geochemically differentiated upper zone and the homogeneous lower zone of Muren were typical low-MgO Karoo tholeiites, but they were chemically distinct and were emplaced as separate magma pulses.

A shark tooth from the Spartan Glacier Formation of the Fossil Bluff Group of Alexander Island, Antarctic Peninsula is described and assigned to Palaeospinacidae, an extinct group of neoselachian sharks. This tooth was previously supposed to have been recovered from Middle Jurassic strata and to belong to Hybodus. However, sedimentation of the Spartan Glacier Formation was from the Valangian to Aptian. Consequently, an Early Cretaceous age is assigned to the specimen although its exact stratigraphical horizon is unknown. A generic assignment, however, is not possible although it may belong to Paraorthacodus. This specimen represents the first record of a neoselachian from the Early Cretaceous of Antarctica.

The analysis of the mixing processes involving water masses on the Ross Sea continental shelf is one of the goals of the CLIMA project (Climatic Long-term Interactions for the Mass balance in Antarctica). This paper uses extended Optimum MultiParameter analysis (OMP), which is applied to four datasets collected during the cruises of 1994/95, 1995/96, 1997/98 and 2000/01 in the Ross Sea (Antarctica). Data include both hydrological, (temperature, salinity, and pressure; T, S, and P, respectively) and chemical parameters (O2, Si(OH)4, PO4, and NO3+NO2). The OMP analysis is based on the assumption that the mixing is a linear process which affects all parameters equally so that each sample shows physical/chemical properties that are the result of the mixing of some properly selected Source Water Types (SWTs). OMP thus evaluates the best set of contributions by all SWTs to each sample, and allows the spatial distribution and structure of the water masses in a basin to be evaluated. Ocean circulation may subsequently be inferred by means of a deeper analysis of the spreading of the water mass. In this study, the “real” Redfield ratios observed in the Ross Sea were used to correct the equations referring to the chemical parameters in accordance with the extended version of OMP. The solutions include some physically realistic constraints. The results allow a detailed description of the water mass distribution, validated through comparison with some “canonical” thermohaline characteristics of the Ross Sea hydrology. In particular our results verify the spreading of the HSSW over the entire continental shelf and emphasize the key role it plays in the ventilation of the deep waters outside the Ross Sea. In addition a description is given of the intrusion of relatively warm waters coming from the open ocean and flowing at some specific locations at the continental shelf break.

Downward fluxes of particulate matter were investigated in the polynya of Terra Nova Bay (western Ross Sea) from February 1995 to December 1997. Biogenic silica made up the bulk of the sinking matter, reaching a maximum of 85% of the total flux in both the shallow and deep traps. Organic carbon accounted for 2.1 to 23.5% of the sample mass in the shallow trap and 2.8 to 7.2% in the deep trap. Biogenic silica and organic carbon peaks occurred in February–March over the three years and were always coupled in the top trap. Carbonate fluxes showed an uneven temporal trend, were low near the seafloor and contributed up to 69.8% of the material collected by the shallow trap. Vertical fluxes in the polynya showed large seasonal and interannual variability. Differences in primary productivity, ice cover dynamics and current energies accounted for the interannual changes in the flux of materials to the subsurface trap. Advection from sites a few hundred kilometres apart was the most likely reason for the decoupling between shallow and deep fluxes after October 1996. The seasonal pattern of downward fluxes was essentially linked to the seasonal cycle of primary production and spring–summer variations largely resulted from the composition of the phytoplankton assemblage in the overlying water column. The export of phototrophically produced materials to depth was low in late spring–early summer, at the time when Phaeocystis and small flagellates were the predominant autotrophs and the microbial food web prevailed over herbivorous feeding. Enhanced fluxes were linked to the predominance of large diatoms above the trap, in late summer. Temporal dynamics in this polynya were delayed by approximately one month as compared to the southernmost Ross Sea polynya, but showed the same temporal pattern: the time lag between production and accumulation of biogenic materials in the upper water column was a few weeks, while the delay in export from the surface layer relative to the maximum accumulation of biomass was approximately one month.

This paper describes a major calving of the Ninnis Glacier tongue in January 2000. This event, which took 10 years to complete, produced a major change in the George V Land coastline and a large iceberg (∼800 km2). By grounding or becoming “locked in” by fast ice, bergs produced locally and drifting in from afar reside for long periods (10–20 years) in the region ∼146 to 154°E to have a profound impact on sea ice distribution, both locally and 100s of kilometres up- and downstream. They are responsible for the formation of a lens of thick perennial ice to the east (∼14 000 km2 in area), and polynyas. Iceberg movement is sporadic, with intermittent ungroundings of large bergs occurring every 5–13 years. “Escaping” bergs have a temporary impact on the Mertz Glacier polynya to the west. Although public attention focuses on vast bergs, assemblages of small bergs appear to be equally important in terms of their impact on regional fast and pack ice distribution. Possible global change scenarios are discussed. The need for field observations and improved bathymetric and oceanographic data is emphasized.

Fossil diatom-bearing marine sediment cores recovered from Prydz Channel, Prydz Bay, record episodes of glacial advance and retreat in the bay. Diatom frustules are abundant, well preserved, and the species composition is diverse in two biogenic sediment units composed of siliceous diatom ooze (SMO-1 and SMO-2). Between SMO-1 and SMO-2 a terrigenous unit (T) is present, composed of muddy diamicton and sandy silty clay, which contains poorly preserved rare diatoms. The SMO units are interpreted to represent an open marine setting with seasonal sea ice cover; the T unit is interpreted to represent glacial ice expansion from the Amery Ice Shelf over the site. Based on an age model developed previously for other cores from Prydz Channel with analogous stratigraphies, we interpret our record to be late Quaternary through Holocene in age. The T unit records the Last Glacial Maximum (LGM) in Prydz Bay; the SMO-1 and SMO-2 units record interstadial episodes that are post- and pre-LGM respectively. Extinct diatom taxa in the T and SMO-2 units indicate reworked sediment sourced from two different-aged deposits. Our results provide both a new interpretation of late Quaternary deposition in Prydz Channel and support for previous studies in this region.

Flux data from moored sediment trap experiments and mass accumulation rates in sediments were obtained for three sites in the Ross Sea which are currently studied for the formation and transit of High Salinity Shelf Water and Ice Shelf Water. These two data sets were compared to obtain inferences on the coupling between water column processes and sedimentary records. The depth distribution of physical features and concentrations of organic carbon and biogenic silica in box cores and gravity cores were studied. Mass accumulation rates, established on the basis of two conventional 14C dates for each core, range between 7.64 and 19.46 g m−2 yr−1. Although these are productive areas, downward fluxes measured by sediment traps are low: 7.5–25.6, 2.4–17.9 and 0.5–0.9 g m−2 yr−1 for particles, biogenic silica and organic carbon, respectively. The concentrations of biogenic components in surficial sediments are correspondingly low. Simple mass balances were calculated assuming the conservative behaviour of the lithic fraction of sinking materials and sediment. Lateral advection of suspended particles is needed to balance the fluxes at the three sites. Furthermore, the model suggests that the preservation of biogenic components is lower than at other sites of the Ross Sea, probably due to the low accumulation rates that imply a high residence time of biogenic materials at the sediment-water interface.

Sedimentary sequences spanning early Oligocene and Neogene time intervals were recovered with piston and gravity cores along erosional structures at northern Gunnerus Ridge and Kainan Maru Seamount in the southernmost Indian Ocean. Results of sedimentological investigations help to reconstruct the Cenozoic palaeoenvironment. Main emphasis was placed on grain size and clay mineral data. The clay mineral assemblages are dominated by illite and smectite. Chlorite and kaolinite occur in trace amounts. Whereas illite has a distinct source on the East Antarctic craton, smectite is of somewhat speculative origin, but probably is derived from erosion of Cenozoic or older shelf sediments. The presence of terrigenous sand indicates that ice-rafting was active throughout the time represented by the investigated cores, although with varying intensity. During the early Oligocene interval (30.1–29.0 Ma), siliceous phytoplankton production dominated sedimentation. Environmental conditions were quite different from those on Maud Rise and Kerguelen Plateau. The middle Miocene sedimentary sequence (14.1–12.8 Ma) documents an intensification of East Antarctic glaciation. The sediments deposited during the late Miocene interval (8.7–6.5 Ma) and the Pliocene interval (5.1–2.7 Ma) indicate continued cooling of Antarctica, but a more dynamic Antarctic ice sheet resulting in episodic sedimentation patterns.

The structure and variability of Southern Ocean fronts south of New Zealand are described based on fifteen summer expendable bathythermograph (XBT) sections obtained between 1994 and 2001. The temperature variability north of 60°S is dominated by meanders and meridional shifts of the Sub-Antarctic Front (SAF), which often bifurcates to form northern and southern branches. The northern branch follows the southern edge of the Campbell Plateau, while the southern branch is found over the abyssal plain of the south-west Pacific Basin. The northern and southern branches of the SAF can be separated by as much as 900 km. Intense eddies or meanders of the SAF displace isotherms by as much as 5 degrees of latitude from their positions when such features are absent. The Polar Front (PF) position is more stable in time, although cold-core features associated with eddies or meanders of the front are occasionally observed between the southern SAF and the PF. The position of the southern ACC front is extremely stable, consistently overlying the 3000 m isobath on the northern flank of the Pacific-Antarctic/south-east Indian Ridge.

Data from eight CTD casts and two one-year long current time series collected at 8 and 60 m above the seafloor of a sediment drift, off the Pacific Margin of the Antarctic Peninsula are presented, with special emphasis on bottom boundary layer dynamics and processes relevant to sediment settling and re-suspension. The water masses over the drift are characterized, including also a comparison with other measurements available from that region. The south-westward flow along the continental rise exhibits a strong topographic (bathymetric) control in the near-bottom current regime. A consistent mean flow deflection between an upper and lower current regime suggests that only the lower regime falls within a bottom (turbulent) Ekman layer. The bottom current regime is not energetic enough to maintain the coarse sediment fraction in suspension. The absence of evidence for a nepheloid layer justifies the assumption that most sediment was supplied to the margin during glacial periods. Two events, with peak velocities of up to 20 cm s−1, are associated with barotropic eddies shown as negative (cyclonic) mean sea level anomalies detected by ERS/TOPEX satellite altimeters. These energetic bottom current pulses may give way to episodic sediment re-suspensions of the sortable (non-cohesive) part of the sediment, thus exerting a minor role in redistributing fine sediments through the mean flow regime.