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| Titel |
What controls the isotopic composition of Greenland surface snow? |
| VerfasserIn |
H. C. Steen-Larsen, V. Masson-Delmotte, M. Hirabayashi, R. Winkler, K. Satow, F. Prié, N. Bayou, E. Brun, K. M. Cuffey, D. Dahl-Jensen, M. Dumont, M. Guillevic, S. Kipfstuhl, A. Landais, T. Popp, C. Risi, K. Steffen, B. Stenni, Á. E. Sveinbjörnsdóttir |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 10, no. 1 ; Nr. 10, no. 1 (2014-02-20), S.377-392 |
| Datensatznummer |
250116916
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| Publikation (Nr.) |
 copernicus.org/cp-10-377-2014.pdf |
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| Zusammenfassung |
| Water stable isotopes in Greenland ice core data provide key
paleoclimatic information, and have been compared with precipitation
isotopic composition simulated by isotopically enabled atmospheric
models. However, post-depositional processes linked with snow
metamorphism remain poorly documented. For this purpose,
monitoring of the isotopic composition (δ18O,
δD) of near-surface water vapor, precipitation and samples of the top
(0.5 cm) snow surface has been conducted during two summers
(2011–2012) at NEEM, NW Greenland. The samples also include
a subset of 17O-excess measurements over 4 days, and the
measurements span the 2012 Greenland heat wave. Our observations are
consistent with calculations assuming isotopic equilibrium between
surface snow and water vapor. We observe a strong correlation
between near-surface vapor δ18O and air temperature
(0.85 ± 0.11‰ °C−1 (R = 0.76) for 2012). The correlation
with air temperature is not observed in precipitation data or
surface snow data. Deuterium excess (d-excess) is strongly
anti-correlated with δ18O with a stronger slope for
vapor than for precipitation and snow surface data. During nine 1–5-day periods between precipitation events, our data demonstrate
parallel changes of δ18O and d-excess in surface snow
and near-surface vapor. The changes in δ18O of the vapor
are similar or larger than those of the snow δ18O. It
is estimated using the CROCUS snow model that 6 to 20% of the surface snow mass is
exchanged with the atmosphere. In our
data, the sign of surface snow isotopic changes is not related to
the sign or magnitude of sublimation or deposition. Comparisons
with atmospheric models show that day-to-day variations in near-surface
vapor isotopic composition are driven by synoptic variations and
changes in air mass trajectories and distillation histories. We
suggest that, in between precipitation events, changes in the
surface snow isotopic composition are driven by these changes in
near-surface vapor isotopic composition. This is consistent with an
estimated 60% mass turnover of surface snow per day driven by
snow recrystallization processes under NEEM summer surface snow
temperature gradients. Our findings have implications for ice core
data interpretation and model–data comparisons, and call for further
process studies. |
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