| SPELEOTHEMS |
Treble et al. 2005 Moondyne Cave Modern Speleothem Stable Isotope Data
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Treble, P.C.,Chappell, J.,Gagan, M.K.,McKeegan, K.D.,Harrison, T.M. 2005 In situ measurement of seasonal d18O variations and
analysis of isotopic trends in a modern speleothem from southwest Australia. Earth and Planetary Science Letters Vol. 233,
pp. 17-32
| Data Coverage |
North: -34.27 * South: -34.27 |
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West: 115.08 * East: 115.08 |
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Altitude: 100 m |
Start Year: 1912 AD
End Year: 1991 AD
Data: Please Cite Data Contributors!
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Summary: We present a record of seasonal and inter-annual oxygen (d18O)
and carbon (d13C) isotope ratios from an 81-year-old stalagmite
from Moondyne Cave, southwest Australia. The growth history of
stalagmite MND-S1 is known since it grew on a cave boardwalk
that was installed in 1911 and removed in 1992. This stalagmite
provides an excellent test of speleothem climate proxies because
the regional climate is strongly seasonal (wet winter/dry summer)
and has experienced a 200 mm (20%) reduction of mean rainfall
since the mid-1960s, and a 0.8 degrees C temperature rise since
~1953. Seasonal variations in calcite d18O were measured in situ
by high spatial resolution ion microprobe, whilst inter-annual
variations of d18O and d13C were measured by conventional gas-source
mass spectrometry. Comparison of the speleothem stable isotopes
and instrumental temperature records reveals that d18O variations
are too large to be driven by temperature alone, and are in the
opposite sense. However, daily rainfall d18O measurements show
that the mean seasonal range in d18O of rainfall in southwest
Australia is large (2 parts per thousand) and inversely correlated
with rainfall amount. A rainfall driver for the speleothem d18O
is confirmed by the detection of seasonal shifts of 0.7-1.5 parts
per thousand in speleothem d18O that track rainfall d18O, smoothed
by storage in the overlying limestone. The seasonal range in
speleothem d18O is larger than any interannual and decadal variation
observed in the record. The prominent annual cycles in speleothem
d18O revealed by ion microprobe analysis indicate that subtle
changes in the frequency of intense winter rainfall events,
or possibly also moisture sources, could produce significant
changes in mean speleothem d18O. The ion microprobe results also
raise the possibility that the masses of speleothem calcite
deposited in winter and summer could vary as a function of the
seasonal drip rate and carbonate saturation state of these waters.
If this is the case, then small changes in the relative masses of
calcite deposited in winter and summer could produce significant
shifts in mean d18O and d13C that have a complex relation to climate.
This finding should be generally applicable to the interpretation
of long-term trends in speleothem geochemical records for shallow
cave sites where seasonal variations in geochemical tracers are
relatively large, including most of the sub-tropical monsoon belts
and mid to high latitudes with distinct rainfall seasons.
More Info on Speleothems |
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Complete XML Record: noaa-cave-6106
(Last Revised: 2009-02-11 )
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| http://www.ncdc.noaa.gov/paleo/ |
| E-mail: bruce.a.bauer@noaa.gov |
| E-mail: paleo@noaa.gov |
Phone: 303-497-6280
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