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Titel |
Investigating late Holocene variations in hydroclimate and the stable isotope composition of precipitation using southern South American peatlands: an hypothesis |
VerfasserIn |
T. J. Daley, D. Mauquoy, F. M. Chambers, F. A. Street-Perrott, P. D. M. Hughes, N. J. Loader, T. P. Roland, S. Bellen, P. Garcia-Meneses, S. Lewin |
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 ; 8, no. 5 ; Nr. 8, no. 5 (2012-09-20), S.1457-1471 |
Datensatznummer |
250005835
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Publikation (Nr.) |
copernicus.org/cp-8-1457-2012.pdf |
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Zusammenfassung |
Ombrotrophic raised peatlands provide an ideal archive for integrating late
Holocene records of variations in hydroclimate and the estimated stable
isotope composition of precipitation with recent instrumental measurements.
Modern measurements of mean monthly surface air temperature, precipitation,
and δD and δ18O-values in precipitation from the late
twentieth and early twenty-first centuries provide a short but invaluable
record with which to investigate modern relationships between these
variables, thereby enabling improved interpretation of the peatland
palaeodata. Stable isotope data from two stations in the Global Network for
Isotopes in Precipitation (GNIP) from southern South America (Punta Arenas,
Chile and Ushuaia, Argentina) were analysed for the period 1982 to 2008 and
compared with longer-term meteorological data from the same locations (1890
to present and 1931 to present, respectively). δD and δ18O-values in precipitation have exhibited quite different trends in
response to local surface air temperature and precipitation amount. At Punta
Arenas, there has been a marked increase in the seasonal difference between
summer and winter δ18O-values. A decline in the deuterium
excess of summer precipitation at this station was associated with a general
increase in relative humidity at 1000 mb over the surface of the Southeast
Pacific Ocean, believed to be the major vapour source for the local
precipitation. At Ushuaia, a fall in δ18O-values was
associated with an increase in the mean annual amount of precipitation. Both records
are consistent with a southward retraction and increase in zonal wind speed
of the austral westerly wind belt. These regional differences, observed in
response to a known driver, should be detectable in peatland sites close to
the GNIP stations. Currently, insufficient data with suitable temporal
resolution are available to test for these regional differences over the
last 3000 yr. Existing peatland palaeoclimate data from two sites near
Ushuaia, however, provide evidence for changes in the late Holocene that are
consistent with the pattern observed in modern observations. |
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