|
|
Water vapour source impacts on oxygen isotope variability in tropical precipitation during Heinrich events
S. C. Lewis1, A. N. LeGrande2, M. Kelley2, and G. A. Schmidt2
1Research School of Earth Sciences, Australian National University, Canberra, ACT, 0200, Australia
2NASA Goddard Institute for Space Studies and Center for Climate Systems Research, Columbia University, 2880 Broadway, New York, NY, 10025, USA
|  |
Abstract. Water isotope records such as speleothems provide extensive evidence of past tropical
hydrological changes. During Heinrich events, isotopic changes in monsoon regions have been
interpreted as implying a widespread drying through the Northern Hemisphere tropics and an
anti-phased precipitation response in the south. Here, we examine the sources of this
variability using a water isotope-enabled general circulation model, Goddard Institute for
Space Studies ModelE. We incorporate a new suite of vapour source distribution tracers to
help constrain the impact of precipitation source region changes on the isotopic composition
of precipitation and to identify nonlocal amount effects. We simulate a collapse of the
North Atlantic meridional overturning circulation with a large freshwater input to the
region as an idealised analogue to iceberg discharge during Heinrich events. A decrease in
monsoon intensity, defined by vertical wind shear, is modelled over East Asia and an
increase over the South American domain. Simulated isotopic anomalies agree well with proxy
climate records, with lighter isotopic values simulated over South America and enriched
values across East Asia. For this particular abrupt climate event, we identify which
climatic change is most likely linked to water isotope change – changes in local
precipitation amount, monsoon intensity, water vapour source distributions or precipitation
seasonality. We categorise individual sites according to the climate variability that water
isotope changes are most closely associated with, and find that the dominant isotopic
controls are not consistent across the tropics – simple local explanations, in particular,
fall short of explaining water isotope variability at all sites. Instead, the best
interpretations appear to be site specific and often regional in scale.
 Notice on Discussion StatusThe requested discussion paper has a corresponding peer-reviewed
final revised paper in the journal Climate of the Past (CP). You are
encouraged to refer to the final revised version. Final Revised Paper (CP) Discussion Paper (PDF, 4834 KB)
Citation: Lewis, S. C., LeGrande, A. N., Kelley, M., and Schmidt, G. A.: Water vapour source impacts on oxygen isotope variability in tropical precipitation during Heinrich events, Clim. Past Discuss., 6, 87-133, doi:10.5194/cpd-6-87-2010, 2010. Bibtex EndNote Reference Manager XML
|
|
