HR: 08:20h
AN: C31C-02 INVITED     [Abstracts]
TI: Wind-Driven Sublimation Impact on Surface Mass Balance and Ice Core Interpretation in East Antarctica
AU: * Frezzotti, M
EM: frezzotti@casaccia.enea.it
AB: Temporal and spatial variability of snow accumulation are input parameters in mass balance studies. They are key issues of paleoclimatic reconstructions from ice cores. As part of the International TransAntarctic Scientific Expedition and of the Franco-Italian Concordia Station collaboration, field survey along traverses and spot research at selected sites have been performed over the East and NE Dome C drainage area (East Antarctica). Different methods were adopted, compared and integrated (stake farm, core analysis, snow radar, surface morphology, remote sensing) to develop an understanding of the climatic and surface conditions. The most prominent unexpected results have been discovered through ground survey coupled with satellite observations. Our idea of Antarctica as a flat continent with a homogenous snow accumulation variability has radically altered. Snow precipitation is homogeneous at a large scale (hundreds of km2), but the wind-driven sublimation phenomena controlled by slope along the prevalent wind direction have considerable impact on the spatial distribution of snow at short (tens of m) and medium (km) spatial scales. The maximum value of snow accumulation at one site is very highly correlated with firn temperature and represents the snow precipitation minus ablation not induced by wind. The high variability of surface mass balance is mainly due to ablation processes driven by katabatic winds (wind-driven sublimation); a few strong wind events can greatly decrease the mass through snowdrift sublimation, especially during summer. The spatial variability of snow accumulation at the km scale is one order of magnitude higher than temporal variability at the decadal/secular scale. Ablation processes of snow on short and long spatial scales have a significant impact on snow grain size and post-depositional losses of chemical species by re-emission and therefore on interpretation of ice core palaeoclimatic series. Where snow accumulation rate is relatively high, snow is buried quickly and initial chemistry composition is preserved. On the contrary, in ablation areas, snow is exposed to lengthy vapour exchange with the atmosphere therefore increasing the possibility of re-emission and UV-decomposition processes. The reconstruction of past climates based on firn/ice cores drilled in areas with high snow accumulation spatial variability is more complicated.
DE: 9310 Antarctica
DE: 3344 Paleoclimatology
DE: 3349 Polar meteorology
DE: 1863 Snow and ice (1827)
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting