The 2000-2001 Antarctic Geodesy Summer Program consisted of a number of distinct components including - ARGN reference mark surveys and Orthometric height connections at Mawson and Davis. This report details the work completed in the 2000-2001 summer season, by AUSLIG (now Geoscience Australia) geodetic surveyors between November 2000 and March 2001.

This is an online GIS application of Antarctica

Physical and biological characteristics of benthic communities are analysed from underwater video footage collected across the George V Shelf during the 2007/2008 CEAMARC voyage. Benthic habitats are strongly structured by physical processes operating over a range of temporal and spatial scales. Iceberg scouring recurs over timescales of years to centuries along shallower parts of the shelf, creating communities in various stages of maturity and recolonisation. Upwelling of modified circumpolar deep water (MCDW) onto the outer shelf and cross-shelf flow of high salinity shelf water (HSSW) create spatial contrasts in nutrient and sediment supply, which are largely reflected in the distribution of deposit and filter feeding communities. Long term cycles in the advance and retreat of icesheets (over millennial scales) and subsequent focussing of sediments in troughs such as the Mertz Drift create patches of consolidated and soft sediments, which also provide distinct habitats for colonisation by different biota. These physical processes of iceberg scouring, current regimes and depositional environments, in addition to water depth, are important factors in the structure of benthic communities across the George V Shelf. The modern shelf communities mapped in this study largely represent colonisation over the past 8,000-12,000 years, following retreat of the icesheet and glaciers at the end of the last glaciation. Recolonisation on this shelf may have occurred from two sources: deep-sea environments and possible shelf refugia on the Mertz and Adélie Banks. However, any open shelf area would have been subject to intense iceberg scouring. Understanding the timescales over which shelf communities have evolved and the physical factors which shape them will allow better prediction of the distribution of Antarctic shelf communities and their vulnerability to change. This knowledge can aid better management regimes for the Antarctic margin.

The Cenozoic glacial history of East Antarctica is recorded in part by the stratigraphy of the Prydz Bay-Lambert Graben region. The glacigene strata and associated erosion surfaces record at least 10 intervals of glacial advance (with accompanying erosion and sediment compaction), and more than 17 intervals of glacial retreat (enabling open marine deposition in Prydz Bay and the Lambert Graben). The number of glacial advances and retreats is considerably less than would be expected from Milankovitch frequencies due to the incomplete stratigraphic record. Large advances of the Lambert Glacier caused progradation of the continental shelf edge. At times of extreme glacial retreat, marine conditions reached > 450 km inland from the modern ice shelf edge. This review presents a partial reconstruction of Cenozoic glacial extent within Prydz Bay and the Lambert Graben that can be compared to eustatic sea-level records from the southern Australian continental margin.

Crinoids, and especially comatulids as Anthometra adriani, are well represented among the macrofauna from the continental shelf offshore from Terre Adélie and George V Land, East Antarctica. These animals are suspension feeders that depend on the local current regime to feed. Nearly 500 specimens from this species were sampled during the Collaborative East Antarctic Marine Census (CEAMARC) expedition onboard the RV Aurora Australis (December 2007 to January 2008), from 46 of the 87 stations over a 400 km² area. Abiotic environmental factors (such as depth, temperature, salinity, oxygen) were measured at each site. The ecological niche of Anthometra adriani was described using Ecological Niche Factor Analysis (ENFA) and Mahalanobis Distances Factor Analysis (MADIFA). An Environmental Suitability Map (ESM) was developed for this species on the CEAMARC study area. The results show that A. adriani seems to prefer relatively cold and well-oxygenated waters in moderately deep areas. The ESM shows four optimal regions for this species: the eastern side of the George V Basin, the western part of the Mertz Bank, the southern side of the Adélie Bank, and the coastal area between the Astrolabe and Mertz Glaciers.

CAML is a five year International Program which will be undertaken as a major activity during the International Polar Year. This project will bring together all known data on Antarctic marine biodiversity and ocean change. The Antarctic Ocean is one of the most sensitive ecosystems in the world. Research undertaken via CAML will produce fascinating images of the Southern Ocean Geoscience Australia's Marine and Coastal Group is contributing expertise in sea floor mapping and sediment core collection to CAML. The Australian Government Antarctic Division is collecting oceanographic data, video footage and sediment cores through hot-water drill holes in the Amery Ice Shelf. The sediment cores are collected using a corer designed and built by Geoscience Australia, and are being analysed by scientists at Geoscience Australia to understand the environmental history beneath this ice shelf. This project has now produced four cores. The only other core ever obtained from beneath an extant ice shelf from under the Ross Ice Shelf in the early 1970s showed no signs of life. However, several Amery cores contain diatom-rich sediments, and one contains a succession of benthic faunas that indicate progressive colonisation of the sub-ice sea floor as ice retreated and currents began to seep nutrients and plankton into the sub-ice shelf cavity.

Several grounding zone wedges were left on the floor and flanks of Prydz Channel in western Prydz Bay by the Lambert Glacier during the last glacial cycle. Seismic profiles indicate that vertical accretion at the glacier bed was the most important depositional process in forming the wedges, rather than progradation by sediment gravity flows. Sidescan sonographs reveal extensive development of flutes on the sea floor inshore from the wedges, indicating deformable bed conditions beneath the ice. The region inshore of the east Prydz Channel wedge features extensive dune fields formed by currents flowing towards the grounding zone. This orientation is consistent with models of circulation beneath ice shelves in which melting at the grounding line generates plumes of fresher water that rise along the base of the ice shelf, entraining sea water into a circulation cell. The Lambert Deep is surrounded by a large composite ridge of glacial sediments. Internal reflectors suggest formation mostly by subglacial accretion. The sea floor in the Lambert Deep lacks dune fields and shows evidence of interspersed subglacial cavities and grounded ice beneath the glacier. The absence of bedforms reflects sea floor topography that would have inhibited the formation of energetic melt water-driven circulation.

Lithostratigraphy, grain sizes and down-hole logs of Site 1166 on the continental shelf, and Site 1167 on the upper slope, are analyzed to reconstruct glacial processes in eastern Prydz Bay and the development of the Prydz trough-mouth fan. In eastern Prydz Bay upper Pliocene-lower Pleistocene glaciomarine sediments occur interbedded with open-marine muds and grade upward into waterlaid tills and subglacial tills. Lower Pleistocene sediments of the trough-mouth fan consist of coarse-grained debrites interbedded with bottom-current deposits and hemipelagic muds, indicating repeated advances and retreats of the Lambert Glacier-Amery Ice Shelf system with respect to the shelf break. Systematic fluctuations in lithofacies and down-hole logs characterize the upper Pliocene-lower Pleistocene transition at Sites 1166 and 1167 and indicate that an ice stream advanced and retreated within the Prydz Channel until the mid Pleistocene. The record from Site 1167 shows that the grounding line of the Lambert Glacier did not extend to the shelf break after 0.78 Ma. Published ice-rafted debris records in the Southern Ocean show peak abundances in the Pliocene and the early Pleistocene, suggesting a link between the nature of the glacial drainage system as recorded by the trough-mouth fans and increased delivery of ice-rafted debris to the Southern Ocean.

This study presents compelling evidence for a diverse and abundant seabed community which has developed over the course of the Holocene beneath the Amery Ice Shelf in East Antarctica. Fossil analysis of a 47 cm long sediment core reveals a rich modern fauna, dominated by filter feeders (sponges and bryozoans), with an abundant infauna predominantly of polychaetes. The down-core assemblage reveals a succession in the colonisation of this site. The lower portion of the core (prior to ~9600 yr BP) is completely devoid of preserved fauna. The first colonisers of the site after this time were the mobile benthic organisms. Their occurrence in the core is matched by the first appearance of planktonic taxa, indicating a retreat of the ice shelf following the last glaciation to within sufficient distance to advect planktonic particles via bottom currents. The benthic infauna and filter feeders emerged during the peak abundance of the planktonic organisms, indicating their dependence on this advected food supply which is brought via bottom currents flowing from the open shelf waters of Prydz Bay. Understanding patterns of species succession in this environment has important implications for determining the potential significance of future global change. The collapse of Antarctic ice shelves, as has happened in recent times, would significantly change the organic supply regime, and therefore the nature of these sub-ice shelf benthic communities.

Data from surveys along the East Antarctic margin will be presented to provide insights into the diversity and distribution of benthic communities on the continental shelf and slope, and their relationship to physical processes. Seabed video and still imagery collected from the George V shelf and slope and the sub-ice shelf environment of the Amery Ice Shelf indicate that the benthic communities in these regions are highly diverse, and are strongly associated with the physical environment. Variations in seafloor morphology, depth, sediment type and bottom circulation create distinct seabed habitats, such as muddy basins, rugged slope canyons and scoured sandy shelf banks, which are, in turn, inhabited by discrete seabed communities. The infauna dominated muddy basins contrast sharply with the diverse range of filter-feeding communities that occur in productive canyons and rugged inner shelf banks and channels. In the sub-ice shelf environment, differences in organic supply, linked to the circulation patterns, cause distinct differences in the seabed communities. The strong association between benthic communities and seafloor characteristics allows physical parameters to be used to extend our knowledge of the nature of benthic habitats into areas with little or no biological data. Comprehensive biological surveys of benthic communities in the East Antarctic region are sparse, while physical datasets for bathymetry, morphology and sediment composition are considerably more extensive. Physical data compiled within the proposed network of East Antarctic Marine Protected Areas (MPAs) is used to aid our understanding of the nature of the benthic communities. The diversity of physical environments within the proposed MPAs suggests that they likely support a diverse range of benthic communities.