ABSTRACT. Recent 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) SO 4 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.

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High‐resolution textural signatures of an earthquake‐induced historical ‘homogenite’ layer are presented, as well as its 3D distribution. This homogeneous deposit is correlated with the AD 1822 event (VII–VIII MSK intensity), the main historical earthquake of the French outer Alps, using 210Pb dating and historical chronicles. During this earthquake a violent lake water oscillation was reported (seiche effect). In the present study we discuss the influence of lake water oscillations during earthquake‐induced subaqueous slide, through a pluridisciplinary analysis of subbottom sediments including high‐resolution seismic, sidescan sonar and short gravity coring.

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Dating recent lake sediment records yielding disturbed 210Pb profiles has been a problem of wide interest in palaeoclimatic and palaeoseismic studies over the last few centuries. When applied to an alpine lake sedimentary record, a high‐resolution sedimentological study reveals that the 210Pb profile is disturbed by the occurrence of single‐event deposits triggered by two different mechanisms: flood events deposits and gravity reworking. Removing disturbed layers from the 210Pb profile yields a logarithmic depth–activity relationship. Using a simple 210Pb decay model (CFCS) provides an assessment of mean accumulation rate of `continuous sedimentation', as opposed to `event‐linked sedimentation'. The correlation of the thickest four gravity‐reworked deposits with historically known earthquakes permits both validation and refinement of the age–depth relationship. This refinement highlights variations in accumulation rate consistent with post‐Little Ice Age climatic variations.

A 210Pb database has recently been constructed and is now available. This base includes approximately 800 210Pb measurements of concentration in air at the Earth's surface, together with deposition flux both at the atmosphere‐Earth and water‐sediment interfaces. Here the data are analyzed and summarized. The atmospheric data (concentration and deposition flux) are presented for the different geographical areas when sufficient measurements are available. The trends are discussed in terms of mechanisms (sources, atmospheric circulation, and climate]. Water‐sediment data are classified into four types of water reservoirs which differ in their sedimentation mechanisms or in their in situ 210Pb production. The corresponding histograms are compared with the air‐surface flux histogram. This database points out the complete lack of information in some large areas of the planet.

Snow samples have been taken in the Dome C area in order to study the variations of the accumulation rate and of the stable isotope content over the last century. Stake observations indicate a large spatial variability of the accumulation rate at a 1‐year scale (σs = 2.6 g cm−2 yr−1 for a mean value ā = 3.6 g cm−2 yr−1). The depth of the 1965 and 1955 layers determined from beta radioactivity measurements in 19 sites lets us deduce that the spatial variability becomes small at a 10‐year scale (σs = 0.3 g cm−2 yr−1), showing that the snow collected at one point is well representative of the fallen precipitation over this period. The rate of snow accumulation since 1965 is about 30% higher than during the 1955–1965 period. This conclusion is supported by measurements over a large geographical sector of East Antarctica. Shorter‐term changes of the snow accumulation have been studied by various means and in particular from detailed deuterium content profiles; by comparing with the beta and tritium radioactivity determinations it is shown that the deuterium variations do not allow us to obtain a seasonal record. In such a low‐accumulation area, different mechanisms (such as smoothing of the isotopic signal, roughness of the surface, irregularity of the accumulation) which may disturb the short‐term record are discussed. The interpretation of stratigraphie observations is not straightforward. However, it was possible to obtain a calibration down to the 1955 layer, which allows us to offer a dating of the snow layers over the last century. The mean accumulation so obtained (3.7 g cm−2 yr−1) is in good agreement with the value (3.6±0.5) deduced from lead 210 measurements. Geographical changes of the mean deuterium content are relatively small, showing that at a 10‐year scale the isotopic signal is well representative of the mean deuterium content of the precipitation. This ensures that the smoothed (10‐year running mean values) deuterium profile obtained over the last 160 years provides a good indication of the temperature secular trend in the Dome C area.