TALDICE (TALos Dome Ice CorE) is a 1620 m deep ice core drilled at Talos Dome, an ice dome located at the edge of the East Antarctic Plateau in the Ross Sea Sector. The Antarctic Ice Core Common Chronology (AICC2012) extended the age scale of the core until ∼150 ka (1438 m depth) (Bazin et al., 2013), while no age scale was available below 1438 m depth. In this work we present the new TALDICE-deep1 chronology using the new measurements of δ18Oatm, δD and 81Kr as well as the inverse model IceChrono1. The TALDICE-deep1 chronology stops at 1548 m, as the portion below this depth is probably affected by mixing processes. The new age scale extends the climate record for the Ross Sea Sector of the East Antarctic Ice Sheet back to MIS 10.1–343 ka (1548 m depth) and identifies both MIS 7 and 9 warm stages, which show specificities in the δD signal. However, it is not possible to recover the isotopic record beyond stage 10.1 as the signal shows a quasi-flat shape. Thereby, the new chronology TADICE-deep1 doubles the extension of the previous age scale as it covers the three past glacial/interglacial cycles.
This data set contains model values from 3 simulations produced with the isotope-enabled atmosphere GCM MIROC5-iso, in which tritium has been implemented. The simulations are for the period 1979-2018 and were performed with different natural tritium production rates. A complete description can be found in Cauquoin, A., Fourré, É., Landais, A., Okazaki, A., and Yoshimura, K.: Modeling natural tritium in precipitation and its dependence on decadal variations of solar activity using the atmospheric general circulation model MIROC5-iso, J. Geophys. Res. Atmos., in review. The data will be made publicly accessible once the paper (hopefully) accepted. The 3 different simulations are: MB2009_3H_cte: with constant long-term average tritium production rate values over time from Masarik and Beer, 2009 (https://doi.org/10.1029/2008JD010557); CRAC_3H_cte: with constant long-term average production rate values over time from CRAC:3H model (https://doi.org/10.1029/2020JD033147); CRAC_3H_solar: with monthly mean tritium production rate variations from CRAC:3H model due to modulation of GCR by heliomagnetic and geomagnetic fields over time. The model data can be downloaded as netcdf files: *.197901-201812.monmean.TU_precip.nc: monthly mean tritium in precipitation over the period 1979-2018; *.200801-201812.timmean.TU_precip.nc: mean tritium in precipitation over the period 2008-2018; *.200801-201812.ymonmean.TU_precip.nc: multi-year monthly mean tritium in precipitation over the period 2008-2018; *.200801-201812.timmean.TU_q.nc: mean tritium in water vapor from 1000 to 10 hPa over the period 2008-2018; MIROC5-iso.197901-201812.monmean.precip.nc: monthly precipitation rate (mm/month) over the period 1979-2018 (same for the three simulations); MIROC5-iso.200801-201812.ymonmean.precip.nc: multi-year monthly precipitation rate (mm/month) over the period 2008-2018 (same for the three simulations); MIROC5-iso.200801-201812.timmean.precip.nc: mean precipitation rate (mm/month) over the period 2008-2018 (same for the three simulations); MIROC5-iso.200801-201812.timmean.q.nc: mean specific humidity (kg/kg) from 1000 to 10 hPa over the period 2008-2018; CRAC_3H_solar.197901-201812.monmean.fldmean.cosmo_HTO_prod.nc: average cosmogenic HTO production monthly variations over the period 1979-2018 according to CRAC_3H_solar simulation.
This paper presents a comprehensive survey of the tritium content of “reference waters” in real working conditions by French laboratories involved in environmental monitoring. Reference waters are virtually tritium-free waters used to determine blanks for the analytical system and to check for any contamination. It is therefore crucial to be sure of the low tritium content of these waters as this can limit the sensitivity and accuracy of the measurements. Water from the commercial brand “Abatilles” is widely used in French laboratories and nine samples were analyzed in this study. Three samples from other deep aquifers were also included. The results all range from 0.004 ± 0.004 Bq/kg to 0.175 ± 0.011 Bq/kg, well below the 0.5 Bq/kg advised by the French Safety Authority. The spread of the results can mainly be attributed to contamination through plastic during bottle storage. As expected, two samples from demineralized tap water showed higher tritium activities (0.3–0.35 Bq/kg). Both waters are suitable as reference water for routine monitoring (DL of about 10 Bq/kg) but should be used with caution for activities in the Bq/kg range.
<p>On December 19-21, 2018, an atmospheric river hit the French-Italian Concordia station, located at Dome C, East Antarctic Plateau, 3 269 m above sea level. It induced an extreme surface warming (+ 15&#176;C in 3 days), combined with high specific humidity (multiplied by 3 in 3 days) and a strong isotopic anomaly in water vapor (+ 15 &#8240; for &#948;18O). The isotopic composition of water vapor monitored during the event may be explained by (1) the isotopic signature of long-range water transport, and by (2) local moisture uptake during the event. In this study we quantify the influence of each of these processes.</p><p>To estimate the isotopic composition of water vapor advected by long-range transport, we perform back-trajectories with the FLEXible PARTicle dispersion model FLEXPART. We retrieve meteorological conditions along different trajectories between the moisture uptake area and Concordia, and use them to compute isotopic fractionation during transport with the mixed cloud isotope model MCIM. While intermediate conditions along the trajectory do not seem to have a major impact on the final isotopic composition (less than 0.1 &#8240;), the latter appears sensitive to surface conditions (temperature, pressure and relative humidity) in the moisture uptake area (&#177;5.1 &#8240;). As the event is characterized by the presence of liquid water clouds above Concordia, we show additional sensitivity tests exploring the impact of mixed phase clouds on the water vapor isotopic composition.</p><p>Finally, we perform a water vapor mass budget in the boundary layer using observations and simulations from the regional atmospheric model MAR, ran with and without drifting snow. The presence of mixed-phase clouds during the event induced a significant increase in downward longwave radiative fluxes, which led to high turbulent mixing in the boundary layer and to heavy drifting snow (white-out conditions). Using MAR simulations, we show that a significant part of the atmospheric water vapor originates from sublimation of drifting snow particles removed from the snowpack. Consequently, the isotopic signal monitored in water vapor during this atmospheric river event reflects both long-range moisture advection and interactions between the boundary layer and the snowpack. Only specific meteorological conditions driven by the atmospheric river, and their associated intense poleward moisture transport, can explain these strong interactions.</p>
We present isotopic analysis of helium in hydrothermal fluids from the Manus back-arc basin, collected during the French-Japanese Manusflux and Manaute cruises in 1995 and 2000, respectively. The helium isotope composition of the fluids is comparable to that measured elsewhere in similar subduction environments, with 3He/4He values (7.4 to 7.9 Ra) slightly lower than typical MORB values, except on the Manus Spreading Center (MSC) where higher values (12 ± 0.1 Ra) are observed. The causal link between the narrow spatial extent of the 3He/4He anomaly at the MSC and a 3He-rich deep mantle component remains elusive, based on available geophysical data. Thus, the Manus Spreading Center results may be an interesting example of small scale upper-mantle heterogeneity.
