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| Titel |
The summer 2012 Greenland heat wave: monitoring water vapour isotopic composition along an atmospheric river event |
| VerfasserIn |
Jean-Louis Bonne, Hans Christian Steen-Larsen, Valérie Masson-Delmotte, Harald Sodemann, Jean-Lionel Lacour, Camille Risi, Martin Werner, Cathy Clerbaux, Xavier Fettweis |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250091099
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| Publikation (Nr.) |
 EGU/EGU2014-5370.pdf |
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| Zusammenfassung |
| In July 2012, an extreme warm event occurred in Greenland, leading to surface melt over
almost all the ice sheet. This event was recorded in the isotopic composition of water vapour
measured by the IASI satellite along the transport pathway and at two sites where continuous
in situ surface vapour isotopic measurements were conducted, situated at a coastal station of
South Greenland (Ivittuut) and further North on top of the ice sheet (NEEM, NW
Greenland). These observations allowed us to monitor the isotopic composition
of the air mass at different stages of its advection towards Greenland, which can
inform on processes along this trajectory, such as cloud properties and moisture
sources. In addition, two simulations of this event, using the atmospheric general
circulation models LMDZiso and ECHAM5wiso equipped with water stable isotopes and
nudged towards large scale wind fields, are investigated. Furthermore, a regional
high-resolution model was used to study the moisture transport to Greenland during
this event using tagged water tracers of the North Atlantic ocean and coastal land
evaporation.
Using moisture source diagnostic based on the Lagrangian particle dispersion
model Flexpart, we show that this 2012 heat wave event corresponds to moisture
sources located over the subtropical Atlantic Ocean, where intense evaporation was
caused by dry air masses associated with the US intense summer drought. This
moisture was then advected northward along a narrow band, due to a very stationary
surface cyclone southwest of Greenland, reached southern Greenland and Ivittuut
coastal station on July 9th, travelled along the west coast of Greenland, continued
eastwards above the ice sheet and arrived above the NEEM deep drilling camp on July
11th.
Surface isotopic observations during the event show larger variations at NEEM than in
Ivittuut, strongly reducing the isotopic and deuterium excess latitudinal gradient usually
observed between South and North Greenland. This feature clearly deviates from a simple
Rayleigh distillation process. LMDZiso and ECHAM5wiso correctly simulate the
magnitude of humidity and temperature peaks in both surface sites, associated with a
strong isotopic enrichment and a deuterium excess decrease all over Greenland.
Small biases are observed on temperature, humidity as well as isotopes, with an
underestimation of deuterium excess variability, which is typical for these models at those
sites. IASI observations are compared to model outputs along the transport path in
the free troposphere (3-6 km) where the remote sounder is most sensitive to δD
variations.
The fingerprint of this unusual atmospheric event in future Greenland ice cores will likely
be a major melt layer, as already recorded in 1889, where a similar event has probably
also occurred (Neff et al. JGR submitted). Our isotopic observations provide new
insights for understanding Greenland ice core records of extreme warm events. |
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