THE ITALIAN ITASE EXPEDITION FROM TERRA NOVA STATION TO TALOS DOME

Earth SciencesPublished5A. Paleoclima e ricerche polar

Growth processes of an inland Antarctic ice wedge, Mesa Range, northern Victoria Land

During the 16th Italian Antarctic Expedition (2000/01) a geomorphological survey of permafrost-related polygons was carried out in the Mesa Range area, upper Rennick Glacier. The investigated site is located in the uppermost reaches of Pain Mesa, which forms the northern sector of the Mesa Range. An ice wedge was found in a volcanic regolith at about 2200 m a.s.l. This altitude is below a well-defined erosional trimline, located at about 2380 m a.s.l. in this sector of Pain Mesa. The ice was sampled by inserting an ice screw, with an internal diameter of 14 mm, into the ice wedge in vertical sequences. Oriented block samples for thin sections were taken. A co-isotopic study was performed, measuring both oxygen (delta O-18) and hydrogen (delta D) isotope compositions. Tritium activity was measured, and major cations and anions were determined. The delta O-18 and delta D obtained showed a strong divergence from the snowfalls expected to occur at this elevation, with extremely negative d excess values. Sublimation processes were taken into account to define the origin of the ice forming the wedge. The tritium data obtained suggest that the growth process of the ice wedge might still be active today

APPLICATION OF O-H-B-Sr ISOTOPE SYSTEMATICS TO THE EXPLORATION OF SALINIZATION AND FLUSHING IN COASTAL AQUIFERS : PRELIMINARY DATA FROM THE PIALASSA BAIONA ECOSYSTEM (ADRIATIC SEA)

O, H, B and Sr isotopes were identified from surface-waters, ground-waters and waters percolating in soils at the Pialassa Baiona lagoon and nearby inland areas. The preliminary data demonstrate the occurrence of both conservative mixtures between seawater and freshwaters and cation exchange at the salt/fresh water interface during the intrusion. The O and H isotopes indicate that the freshwater component in the binary mixing had the isotopic features of the rainwater from Apennine catchments. Coupled O-H-B isotopes also show that the major contribution of the moving seawater was confined to the deeper aquifers and some of the soil waters. The Sr isotopes highlight the role of cation exchanges when seawater flushes freshwater aquifers, and allow the recognition of the different components of the solute. Deviations from these processes as revealed by B isotopes are interpreted as the evidence of possible anthropogenic inputs

Spatial and temporal variability of snow accumulation in East Antarctica from traverse data

International audienceRecent snow accumulation rate is a key quantity for ice-core and mass-balance studies. Several accumulation measurement methods (stake farm, fin core, snow-radar profiling, surface morphology, remote sensing) were used, compared and integrated at eight sites along a transect from Terra Nova Bay to Dome C, East Antarctica, to provide information about the spatial and temporal variability of snow accumulation. Thirty-nine cores were dated by identifying tritium/b marker levels (1965-66) and non-sea-salt (nss) SO4 2- spikes of the Tambora (Indonesia) volcanic event (1816) in order to provide information on temporal variability. Cores were linked by snow radar and global positioning system surveys to provide detailed information on spatial variability in snow accumulation. Stake-farm and ice-core accumulation rates are observed to differ significantly, but isochrones (snow radar) correlate well with ice-core derived accumulation. The accumulation/ablation pattern from stake measurements suggests that the annual local noise (metre scale) in snow accumulation can approach 2 years of ablation and more than four times the average annual accumulation, with no accumulation or ablation for a 5 year period in up to 40% of cases. The spatial variability of snow accumulation at the kilometre scale is one order of magnitude higher than temporal variability at the multi-decadal/secular scale. Stake measurements and firn cores at Dome C confirm an approximate 30% increase in accumulation over the last two centuries, with respect to the average over the last 5000 years