Abstract
Past temperature reconstructions from Antarctic ice cores require a good
quantification and understanding of the relationship between snow isotopic
composition and 2 m air or inversion (condensation) temperature. Here, we
focus on the French–Italian Concordia Station, central East Antarctic
plateau, where the European Project for Ice Coring in Antarctica (EPICA) Dome
C ice cores were drilled. We provide a multi-year record of daily
precipitation types identified from crystal morphologies, daily precipitation
amounts and isotopic composition. Our sampling period (2008–2010)
encompasses a warmer year (2009, +1.2 °C with respect to 2 m air
temperature long-term average 1996–2010), with larger total precipitation
and snowfall amounts (14 and 76 % above sampling
period average, respectively), and a colder and drier year (2010,
−1.8 °C, 4 % below long-term and sampling period averages,
respectively) with larger diamond dust amounts (49 % above sampling
period average). Relationships between local meteorological data and
precipitation isotopic composition are investigated at daily, monthly and
inter-annual scale, and for the different types of precipitation. Water
stable isotopes are more closely related to 2 m air temperature than to
inversion temperature at all timescales (e.g. R2 = 0.63 and 0.44,
respectively for daily values). The slope of the temporal relationship
between daily δ18O and 2 m air temperature is approximately 2
times smaller (0.49 ‰ °C−1) than the average Antarctic spatial
(0.8 ‰ °C−1) relationship initially used for the
interpretation of EPICA Dome C records. In accordance with results from
precipitation monitoring at Vostok and Dome F, deuterium excess is
anti-correlated with δ18O at daily and monthly scales, reaching maximum values in winter. Hoar frost precipitation samples have a specific
fingerprint with more depleted δ18O (about 5 ‰ below
average) and higher deuterium excess (about 8 ‰ above average)
values than other precipitation types. These datasets provide a basis for
comparison with shallow ice core records, to investigate post-deposition
effects. A preliminary comparison between observations and precipitation from
the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis and
the simulated water stable isotopes from the Laboratoire de
Météorologie Dynamique Zoom atmospheric general circulation model
(LMDZiso) shows that models do correctly capture the amount of precipitation
as well as more than 50 % of the variance of the observed δ18O,
driven by large-scale weather patterns. Despite a warm bias and an
underestimation of the variance in water stable isotopes, LMDZiso correctly
captures these relationships between δ18O, 2 m air temperature
and deuterium excess. Our dataset is therefore available for further in-depth
model evaluation at the synoptic scale.
Citation
ID:
157849
Ref Key:
stenni2016thethree-year