Investigating late Holocene variations in hydroclimate and the stable isotope composition of precipitation using southern South American peatlands: an hypothesis

T. J. Daley, D. Mauquoy, F. M. Chambers, F. A. Street-Perrott, P. D.M. Hughes, N. J. Loader, T. P. Roland, S. van Bellen, P. Garcia-Meneses, S. Lewin

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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 dD and d18O-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). dD and d18O-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 d18O-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 d18O-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.

Original languageEnglish
Pages (from-to)1457-1471
Number of pages15
JournalClimate of the Past
Early online date20 Sept 2012
Publication statusPublished - 20 Sept 2012

Bibliographical note

Acknowledgements. The authors would like to thank the UK Natural Environment Research Council (NERC grants NE/I022809/1, NE/I022833/1, NE/I022981/1 and NE/I023104/1) for financial support. We are grateful to three reviewers for their very helpful and supportive comments. We would also like to thank the staff of the GeoMapping Unit at Plymouth University for their tireless efforts in the production of figures for this manuscript.


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