The Deuterium Excess record from the Siple Dome ice core

1
The Deuterium Excess record from the Siple Dome
ice core

• Annalisa Schilla, James White, Eric Steig, Ed
  Brook

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Overview

• Regional variation among Antarctic deuterium
  excess records
• Extra-Antarctic/Pacific climate signal in Siple
  Dome deuterium excess
• A Holocene precession signal in the Ross Sea
  region?

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Background

• Deuterium excess is defined as
• ddD-8d18O (indexed to MWL)
• Measure of kinetic fractionation, primarily SST
  (actual T change?)
• Distinct signal from raw isotopes

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Various Antarctic Moisture Sources
Modified from Vimeux et al., 2001
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Pacific as Siple Moisture Source Region

• GCM and simple model results coastal sites have
  gt contribution from proximal ocean basin
• Siple Dome moisture is dominated throughout the
  year by Pacific sources, from 30ºS to the sea
  ice edge

• Siple Dome

• Siple Dome

Delaygue et al., 2000
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Siple d vs. Pacific Records

• Siple d shares variability on several timescales
  with Pacific records

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Other sources of d variability?
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Low-latitude and high-latitude?
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Millennial-scale Spectra
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Climate Change vs. Elevation?
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Siple Dome vs. Taylor Dome
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Precession at Siple Dome?

• Moisture flux during (a) 1980 (normal year) and
  (b) 1982 (El Nino year). From Cullather et al.,
  1996.
• Did ENSO variability really increase in the
  mid-Holocene (e.g., per Clement et al., 2000,
  Rodbell et al. 1999, Moy et al. 2000)?

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Summary

• Deuterium excess varies dramatically across
  Antarctica?various moistures source regions
• Moisture source region for Siple participates in
  global climate changes separately from Antarctica
  at a variety of timescales
• Siple-Taylor isotope divergence through
  Holocene?a precession signal?