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| Titel |
Isotopes in the Arctic atmospheric water cycle |
| VerfasserIn |
Jean-Louis Bonne, Martin Werner, Hanno Meyer, Sepp Kipfstuhl, Benjamin Rabe, Melanie Behrens, Lutz Schönicke, Hans Christian Steen Larsen, Valérie Masson-Delmotte |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250136033
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| Publikation (Nr.) |
 EGU/EGU2016-16983.pdf |
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| Zusammenfassung |
| The ISO-ARC project aims at documenting the Arctic atmospheric hydrological
cycle, by assessing the imprint of the marine boundary conditions (e.g. temperature
variations, circulation changes, or meltwater input) to the isotopic composition of the
atmospheric water cycle (H218O and HDO) with a focus on North Atlantic and Arctic
oceans.
For this purpose, two continuous monitoring water vapour stable isotopes cavity
ring-down spectrometers have been installed in July 2015: on-board the Polarstern research
vessel and in the Siberian Lena delta Samoylov research station (N 72˚ 22’, E 126˚ 29’). The
Polarstern measurements cover the summer 2015 Arctic campaign from July to mid-October,
including six weeks in the Fram Strait region in July- August, followed by a campaign
reaching the North Pole and a transect from the Norwegian Sea to the North Sea. These
vapour observations are completed by water isotopic measurements in samples from the
surface ocean water for Polarstern and from precipitation in Samoylov and Tiksi (120 km
south-east of the station).
A custom-made designed automatic calibration system has been implemented in a
comparable manner for both vapour instruments, based on the injection of different liquid
water standards, which are completely vaporised in dry air at high temperature. Subsequent
humidity level can be adjusted from 2000 to at least 30000 ppm. For a better resilience, an
independent calibration system has been added on the Samoylov instrument, allowing
measurements of one standard at humidity levels ranging from 2000 to 15000 ppm: dry air is
introduced in a tank containing a large amount of liquid water standard, undergoing
evaporation under a controlled environment. The measurement protocol includes an
automatic calibration every 25 hours. First instrument characterisation experiments depict a
significant isotope-humidity effect at low humidity, dependant on the isotopic composition of
the standard.
For ambient air, our first isotope measurements highlighted significant synoptic variations
in summer in both sites. In Samoylov, the premises of a seasonal cycle have been
observed during the summer-fall transition, with a fast humidity level and isotopic
decrease. The latitudinal gradient is also highly visible on the Polarstern record.
Complementing simulations of the water vapour isotopic composition by the ECHAM5-wiso
model reproduce the Polarstern synoptic variability and spatial patterns with a good
accuracy.
In the near future, our records will be combined with simultaneous water isotope
measurements in Iceland (by Hans Christian Steen-Larsen, CIC), Svalbard (by
Valérie-Masson Delmotte, LSCE) and paired with complementing climate simulations
enhanced by water isotope diagnostics. These data sets, covering an approx. 6,000 km
transect of Northern Eurasia will allow for a quantitative assessment of the isotopic variations
of the Arctic water cycle. The results of these analyses will also be of relevance for the
interpretation of isotope signals found in ice cores and on terrestrial Arctic sites in terms of
past climate change. |
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