Precipitation regime and stable isotopes at Dome Fuji, East Antarctica
A unique set of 1-year precipitation and stable water isotope measurements from the Japanese Antarctic station, Dome Fuji, has been used to study the impact of the synoptic situation and the precipitation origin on the isotopic composition of precipitation on the Antarctic Plateau. The Antarctic...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-06-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/16/6883/2016/acp-16-6883-2016.pdf |
| Summary: | A unique set of 1-year precipitation and stable water isotope measurements
from the Japanese Antarctic station, Dome Fuji, has been used
to study the impact of the synoptic situation and the precipitation origin on
the isotopic composition of precipitation on the Antarctic Plateau. The
Antarctic Mesoscale Prediction System (AMPS) archive data are used to analyse
the synoptic situations that cause precipitation. These situations are
investigated and divided into five categories. The most common weather
situation during a precipitation event is an upper-level ridge that extends
onto the Antarctic Plateau and causes strong northerly advection from the
ocean. Most precipitation events are associated with an increase in
temperature and wind speed, and a local maximum of <i>δ</i><sup>18</sup>O. During the
measurement period, 21 synoptically caused precipitation events caused
60 % of the total annual precipitation, whereas the remaining
40 % were predominantly attributed to diamond dust. By combining the
synoptic analyses with 5-day back-trajectories, the moisture source regions
for precipitation events were estimated. An average source region around a
latitude of 55° S was found. The atmospheric conditions in the
source region were used as initial conditions for running a Rayleigh-type
isotopic model in order to reproduce the measured isotopic composition of
fresh snow and to investigate the influence of the precipitation source
region on the isotope ratios. The model represents the measured annual cycle
of <i>δ</i><sup>18</sup>O and the second-order isotopic parameter deuterium excess
reasonably well, but yields on average too little fractionation along the
transport/cooling path. While simulations with an isotopic general
circulation model (GCM) (ECHAM5-wiso) for Dome Fuji are on average closer to
the observations, this model cannot reproduce the annual cycle of deuterium
excess. In the event-based analysis, no evidence of a correlation of the
measured deuterium excess with the latitude of the moisture source region or
the corresponding conditions was identified. Contrary to the assumption used
for decades in ice core studies, a more northerly moisture source does not
necessarily mean a larger temperature difference between source area and
deposition site, thus a more depleted precipitation in heavy isotopes
with a higher deuterium excess. |
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| ISSN: | 1680-7316 1680-7324 |