Determining the mass balance of the Greenland and Antarctic ice sheets (GIS and AIS) has long been a major challenge for polar science. But until recent advances in measurement technology, the uncertainty in ice sheet mass balance estimates was greater than any net contribution to sea level change. The Fourth Assessment Report of the Intergovernmental Panel on Climate Change (AR4) was able, for the first time, to conclude that, taken together, the GIS and AIS have probably been contributing to sea level rise over the period 1993–2003 at an average rate estimated at 0.4 mm yr-1. Since the cut-off date for work included in AR4, a number of further studies of the mass balance of GIS and AIS have been made using satellite altimetry, satellite gravity measurements and estimates of mass influx and discharge using a variety of techniques. Overall, these studies reinforce the conclusion that the ice sheets are contributing to present sea level rise, and suggest that the rate of loss from GIS has recently increased. The largest unknown in the projections of sea level rise over the next century is the potential for rapid dynamic collapse of ice sheets.

We investigated nutrient composition and the potential for greenhouse gas production in Antarctic penguin guano, ornithogenic soils and seal colony soils through a laboratory incubation experiment. Total organic carbon contents ranged from 0.2–14.7% and total nitrogen contents ranged from 0.05–3.60% across all the samples. Penguin guano and the soils had the δ13Corg values of -28.4‰ to -22.8‰ and highly enriched δ15N values (8.28–35.51‰), indicating a rapid N cycling in local ecosystems. The mean CO2 and CH4 emission rates from penguin guano were significantly higher than those from the soils under aerobic or anaerobic conditions. The CO2-C/TOC rate indicated that the bioavailability of TOC was markedly higher in penguin guano than in the soils. These soils showed higher N2O emission rates under anaerobic conditions, indicating that denitrification may be the major process in N2O emission. The CO2 and CH4 emissions have a significant correlation with TOC in both penguin guano and the soils. Our results show that marine animal excreta are an important factor determining storage and composition of nutrients in coastal Antarctica, and that they may considerably affect current and future net fluxes of greenhouse gases in this region.

Cribroelphidium webbi sp. nov. is the only adequately described sub-Recent elphidiid foraminifer from Antarctica. In Admiralty Bay (King George Island, South Shetland Islands), it is found at several locations within inner fiord setting at water depths between 33 and 165 m, but most commonly shallower than 100 m. In outer basins this foraminifer is absent. In the cores analysed, C. webbi sp. nov. is present in well-constrained sub-Recent horizons that are clearly related to climate warming and deglaciation. These horizons represent a diachronous facies marker rather than a single stratigraphic layer. Cribroelphidium webbi sp. nov. shows clear association with retreating tidewater glaciers, therefore it is an important sensitive glacier-proximal indicator. It appears that it shares similar ecologic affinities with Cribroelphidium excavatum clavatum, which is widely distributed throughout the Arctic.

Antarctic calcified macroorganisms are particularly vulnerable to ocean acidification because many are weakly calcified, the dissolution rates of calcium carbonate are inversely related to temperature, and high latitude seas are predicted to become undersaturated in aragonite by the year 2100. We examined the post-mortem dissolution rates of aragonitic and calcitic shells from four species of Antarctic benthic marine invertebrates (two bivalves, one limpet, one brachiopod) and the thallus of a limpet shell-encrusting coralline alga exposed to acidified pH (7.4) or non-acidified pH (8.2) seawater at a constant temperature of 4°C. Within a period of only 14–35 days, shells of all four species held in pH 7.4 seawater had suffered significant dissolution. Despite calcite being 35% less soluble in seawater than aragonite, there was surprisingly, no consistent pattern of calcitic shells having slower dissolution rates than aragonitic shells. Outer surfaces of shells held in pH 7.4 seawater exhibited deterioration by day 35, and by day 56 there was exposure of aragonitic or calcitic prisms within the shell architecture of three of the macroinvertebrate species. Dissolution of coralline algae was confirmed by differences in weight loss in limpet shells with and without coralline algae. By day 56, thalli of the coralline alga held in pH 7.4 displayed a loss of definition of the conceptacle pores and cracking was evident at the zone of interface with limpet shells. Experimental studies are needed to evaluate whether there are adequate compensatory mechanisms in these and other calcified Antarctic benthic macroorganisms to cope with anticipated ocean acidification. In their absence, these organisms, and the communities they comprise, are likely to be among the first to experience the cascading impacts of ocean acidification.

Two contrasting high nutrient/low chlorophyll regions having different conditions that control phytoplankton production, and separated by an area of blooming, are found during summer in the vicinity of the South Shetland Islands (Antarctica). Low chlorophyll conditions occur either in Fe-rich, deeply mixed and high salinity Weddell Sea shelf waters, or the Fe-poor, shoaled and low salinity Drake Passage Antarctic Circumpolar Current waters, while phytoplankton blooms are located between in mid salinity water. Contrasting phytoplankton communities were found to populate these different biogeochemical provinces. In data from six field seasons (1999–2007), nanoplankton (2–20 μm) were found to be dominant in the phytoplankton populations from light-controlled coastal waters, including blooms, with most chlorophyll found in the 2–5 μm size class. In contrast, the adjacent and presumably Fe-controlled Drake Passage waters were dominated by the microplankton (> 20 μm) size class. The asymmetrical distribution of phytoplankton size classes across the salinity gradient, when analysed independently of total chlorophyll concentration, supports the hypothesis that the different food web grazing dynamics are dependent upon biogeochemical provinces.

Although the impacts of biological invasions are widely appreciated, a bias exists in research effort to post dispersal processes because of the difficulties of measuring propagule pressure. Here we quantify the propagule pressure associated with the construction of a research station in Antarctica. Based on quantitative assessment of different classes of cargo, we predict that over 5000 seeds will be entrained during the period of building the station. Seeds from 34 taxa were identified, including known invasive species.

Passive dispersal has traditionally formed a fundamental component of biogeographical theories of the origin of the fauna that occupy the ice-free habitats of mainland Antarctica. But in the context of an emerging picture of endemism for many Antarctic terrestrial invertebrates, is there still a place for such stochastic processes in Antarctic biogeography? The case of the Antarctic fairy shrimp, Branchinecta gaini Daday 1910, may provide an answer - or, at least, an important exception to the rule. Although passive dispersal is certainly a stochastic and contingent phenomenon in Antarctica, the occurrence of B. gaini on the Antarctic Peninsula can only be explained satisfactorily by resort to this explanation. It is, at present, probably the best example of an Antarctic invertebrate with a biogeographic signature of passive - in particular, zoophoretic - dispersal.

Sediment trap arrays were deployed in Brialmont Cove and Andvord Bay, eastern Gerlache Strait, from December 2001–March 2003. The recovered sediments (representing instantaneous deposition from the viewpoint of luminescence dating) encompass all the annual and local glaciomarine depositional processes. Magnetic susceptibility profiles were used to infer seasonality in the trap cores, and thus to select subsamples for luminescence measurements. Multi-aliquot infrared stimulated luminescence (IRSL) apparent ages were used to assess the effectiveness of ‘clock zeroing’ (by daylight) of light sensitive luminescence within fine silt polymineral samples from each trap depth. IRSL apparent ages for 24 samples indicate that the largest age-depth differences occur with the autumn season samples at both trap sites, suggesting a previously unrecognized and regional (within the Gerlache Strait) change in depositional controls in the autumn compared to other seasons. The apparent ages also indicate some differences between the fjords, and a more complex oceanographic regime at Andvord Bay than at Brialmont Cove. Dry-mass sediment fluxes varied from 0.4 to 0.7 g cm-2 yr-1, with the largest flux at Brialmont Cove (∼0.7 g cm-2 yr-1) occurring in the bottom trap, whereas at Andvord Bay, the largest flux (∼0.6 g cm-2 yr-1) occurred in the middle trap (∼45 m above seafloor).

The oldest record of the hexanchiform sharks from the Southern Hemisphere and the second chondrichthyan report known from Carboniferous to Early Cretaceous beds in Antarctica is given. The material was collected in late Aptian rocks of the Kotick Point Formation outcropping in the western part of James Ross Island, near Antarctic Peninsula. It consists of an isolated tooth assignable to a hexanchiform different from the other described genera. The tooth shows putative plesiomorphic cusp (few cusps, no serrations) and apomorphic root characters (relatively deep, quadrangular). It could be related to a species close to the origin of Hexanchus (unknown in beds older than Cenomanian).

Horseshoe Valley (80°18′S, 81°22′W) is a 30 km wide glaciated valley at the south-eastern end of Ellsworth Mountains draining into the Hercules inlet, Ronne Ice Shelf. The ice at Horseshoe Valley has been considered stable; now we use Global Positioning System (GPS) measurements obtained between 1996 and 2006 to investigate ice elevation change and mass balance. Comparison of surface heights on a profile across Horseshoe Valley reveals a slight but significant elevation increase of 0.04 m a-1 ± 0.002 m a-1. The blue ice area of Patriot Hills (∼13 km2) at the mount of Horseshoe Valley shows large interannual variability in area, with a maximum extent in 1997, an exceptionally warm summer, but no clear multi-year trend, and an elevation increase of 0.05 m a-1 in eight years, which agrees with the result from Horseshoe Valley.

We use a combination of satellite techniques (interferometric synthetic aperture radar (InSAR), visible-band imagery, and repeat-track laser altimetry) to develop a benchmark map for the Amery Ice Shelf (AIS) grounding zone (GZ), including its islands and ice rises. The break-in-slope, as an indirect estimate of grounding line location, was mapped for the entire AIS. We have also mapped ∼55% of the landward edge and ∼30% of the seaward edge of the ice shelf flexure boundary for the AIS perimeter. Vertical ice motion from Global Positioning System receivers confirms the location of the satellite-derived GZ in two regions. Our map redefines the extent of floating ice in the south-western AIS and identifies several previously unmapped grounded regions, improving our understanding of the stresses supporting the current dynamical state of the ice shelf. Finally, we identify three along-flow channels in the ice shelf basal topography, approximately 10 km apart, 1.5 km wide and 300–500 m deep, near the southern GZ. These channels, which form at the suture zones between ice streams, may represent zones of potential weakness in the ice shelf and may influence sub-ice-shelf ocean circulation.