Monitoring water stable isotopes in surface Arctic water vapor

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Monitoring water stable isotopes in surface Arctic water vapor

Message  Masson-Delmotte Valérie le Mar 30 Avr - 14:43

Due to the role of water vapor and clouds in positive feedback mechanisms, water vapor is a key player in the future of Arctic climate. Ecosystems and human societies are vulnerable to climate change through even minor changes in precipitation patterns, including the occurrence of extreme events. It is therefore essential to monitor, understand and model correctly the mechanisms of transport of moisture, at the regional scale.

Water vapor isotopes – the relative abundance of heavy and light water in the atmosphere – are integrated tracers of the atmospheric water cycle. The physical processes at each phase change leave a fingerprint on the isotopes. Technological progress now allows accurate and precise continuous, in situ and remote sensing monitoring of water vapour isotopic composition. In parallel, a growing number of atmospheric circulation models (AGCMs) are equipped with explicit modeling of water stable isotopes, allowing evaluation of the in-built parameterizations.

Continuous monitoring of Arctic surface water vapour isotopic composition offers new observational constraints on the processes involved in evaporation, moisture transport, cloud- and precipitation formation. This allows for assessing the realism of moisture simulated by AGCMs.

Diurnal, synoptic and seasonal variations have been documented since 2010 in Iceland, south Greenland, northwest Greenland and Siberia through national or bi-national initiatives. Preliminary comparisons between in-situ observations and simulations from several AGCMs allow to identify model-data mismatches related to evaporation from the ocean surface, continental recycling, and moisture formed at the sea ice margin. While nudged simulations correctly capture synoptic variations in 18O or deuterium, large model-data mismatches are reported for the kinetic fractionation driven deuterium excess. The surface data further permit validation of remote sensing deuterium measurements from FTIR and satellite data.

The potential of a coordinated network is illustrated by the case study of July 2012 when a heat wave over the Midwestern USA caused warm dry air to pick up moisture over the western part of the North Atlantic. This warm and moist air moved northwards causing subsequent melting on 97% of the Greenland Ice Sheet. This event was captured by water vapor isotope stations in Bermuda, southern Greenland, and on top of the Greenland Ice Sheet. Ongoing work is investigating the potential of combining these surface measurements together with model outputs and IASI remote sensing data to quantify the processes at play during this extreme event, also associated with liquid water cloud feedbacks above the ice sheet.

The French contribution to this network is at present supported by IPEV (Ivittuut GHG monitoring station), ANR CEPS GREENLAND (extension of Ivittuut station to water vapour isotopes), AXA (postdoctoral fellowship for HC Steen-Larsen), and the WIBISO MEGAGRANT (collaboration with U. of Ural for two Siberian stations). Interest has been manifested by several scientists from LMD and LATMOS.

We aim to maintain one Greenland station and establish measurements in Svalbard, and would like to have national support to establish a coordinated Arctic network.

An international workshop about the monitoring of water stable isotopes will be organised in Oct 15th-18th 2013 in Gif.

STEEN-LARSEN Hans Christian1, MASSON-DELMOTTE Valerie1, JOUZEL Jean1, BONNE Jean-Loise1, SVEINBJORNSDOTTIR Arny2, WERNER Martin3, BUTZIN Martin3, RISI Camille4, YOSHIMURA Kei5, LACOUR Jean-Lionel6, GRIBANOV Konstantin7, ZAKHAROV Vyacheslav7

1 : Laboratoire des Science du Climat et de l’Environnement CEA-CNRS-UVSQ/IPSL, Gif-Sur-Yvette, France, hanschr@gfy.ku.dk
2 : Institute of Earth Science, University of Iceland, Askja, Reykjavik, Iceland
3 : Alfred-Wegener-Institut für Polar- und Meeresforschung, Bremerhaven, Germany
4 : Laboratoire de Météorologie Dynamique, Jussieu, Paris, France
5 : Atmosphere and Ocean Research Institute, University of Tokyo, Japan
6 : Spectroscopie de l’Atmosphére, Université Libre de Bruxelles, Belgium
7 : Climate and Environmental Physics Laboratory, Ural Federal University, Russia

Masson-Delmotte Valérie

Messages : 3
Date d'inscription : 12/04/2013

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