 |
| Titel |
One year observation of water vapour isotopic composition at Ivittuut, Southern Greenland |
| VerfasserIn |
Jean-Louis Bonne, Valérie Masson-Delmotte, Marc Delmotte, Olivier Cattani, Harald Sodemann, Camille Risi |
| Konferenz |
EGU General Assembly 2013
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250079624
|
|
|
|
|
|
| Zusammenfassung |
| In September 2011, an automatic continuous water vapour isotopic composition monitoring
instrument has been installed in the atmospheric station of Ivittuut (61.21Ë N, 48.17Ë W),
southern Greenland. Precipitation has been regularly sampled on site at event to weekly
scales and analysed in our laboratory for isotopic composition. Meteorological parameters
(temperature, pressure, relative humidity, wind speed and direction) and atmospheric
composition (CO2, CH4, Atmospheric Potential Oxygen) are also continuously monitored at
Ivittuut. The meteorological context of our observation period will be assessed by
comparison with the local climatology.
The water vapour analyser is a Picarro Wavelength Scanned Cavity Ring-Down
Spectrometer (WS-CRDS, model L2120i). It is automatically and regularly calibrated on the
VSMOW scale using measurements of the isotopic composition of vaporized reference water
standards using the Picarro Syringe Delivery Module (SDM). As measurements are sensitive
to humidity level, an experimentally estimated calibration response function is used to correct
our isotopic measurements. After data treatment, successive isotopic measurements of
reference waters have a standard deviation of around 0.35 per mil for δ18O and 2.3 per mil for
δD. Our instrumentation protocol and data quality control method will be presented,
together with our one year δ18O, δD and d-excess measurements in water vapour and
precipitation. The relationship between surface water vapour isotopic composition
and precipitation isotopic composition will be investigated based on a distillation
model. Specific difficulties linked to our low maintenance remote station will also be
discussed.
The processes responsible for the synoptic variability of Ivittuut water vapour isotopic
composition will be investigated by comparing our observational dataset with (i) atmospheric
back-trajectories and (ii) results from an isotopically-enabled atmospheric general circulation
model (AGCM).
Simulations of humidity transport based on an adapted version of the Lagrangian
dispersion model Flexpart allows to diagnose Ivittuut moisture sources, to retrieve the
evaporation conditions, and to distinguish the influence of local and remote processes on our
measurements. This site is strongly influenced by large scale humidity transport from distant
sources such as seas surrounding Greenland and western to eastern North Atlantic
ocean. The consistency of Flexpart calculations with isotopic distillation will be
investigated.
Our observations are finally compared to daily outputs of a nudged simulation conducted
with the LMDZiso AGCM nudged to atmospheric analyses. This comparison will be
performed at synoptic to seasonal scales allowing to assess the spatial representativeness of
our station and to identify systematic model biases. The added value of water vapour isotopic
data to constrain moisture sources and assess the realism of their simulation will be
discussed. |
|
|
|
|
|
|