The Deuterium Excess record from The Deuterium Excess record from the Siple Dome ice corethe Siple Dome ice core

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

OverviewOverview

Regional variation among Antarctic Regional variation among Antarctic deuterium excess recordsdeuterium excess records

Extra-Antarctic/Pacific climate signal in Extra-Antarctic/Pacific climate signal in Siple Dome deuterium excessSiple Dome deuterium excess

A Holocene precession signal in the Ross A Holocene precession signal in the Ross Sea region?Sea region?

BackgroundBackground

Deuterium excess is Deuterium excess is defined as: defined as:

d=d=δδD-8*D-8*δδ1818O (indexed O (indexed to MWL)to MWL)

Measure of kinetic Measure of kinetic fractionation, primarily fractionation, primarily SST (actual T SST (actual T change?)change?)

Distinct signal from Distinct signal from raw isotopesraw isotopes

Various Antarctic Moisture SourcesVarious Antarctic Moisture Sources

Modified from Vimeux et al., 2001

Pacific as Siple Moisture Source Pacific as Siple Moisture Source RegionRegion

GCM and simple model results: coastal sites have > GCM and simple model results: coastal sites have > contribution from proximal ocean basincontribution from proximal ocean basin

Siple Dome moisture is dominated throughout the year Siple Dome moisture is dominated throughout the year by Pacific sources, from ~30by Pacific sources, from ~30ºS to the sea ice edgeºS to the sea ice edge

Delaygue et al., 2000

•Siple Dome •Siple Dome

Siple d vs. Pacific RecordsSiple d vs. Pacific Records

Siple d shares Siple d shares variability on variability on several timescales several timescales with Pacific recordswith Pacific records

Other sources of d variabilityOther sources of d variability??

Low-latitude and high-latitude?Low-latitude and high-latitude?

Millennial-scale SpectraMillennial-scale Spectra

Climate Change vs. Elevation?Climate Change vs. Elevation?

Siple Dome vs. Taylor DomeSiple Dome vs. Taylor Dome

Precession at Siple Dome?Precession at Siple Dome?

Moisture flux during (a) 1980 (normal year) and (b) 1982 (El Nino year). Moisture flux during (a) 1980 (normal year) and (b) 1982 (El Nino year). From Cullather et al., 1996. From Cullather et al., 1996.

Did ENSO variability really increase in the mid-Holocene (e.g., per Clement Did ENSO variability really increase in the mid-Holocene (e.g., per Clement et al., 2000, Rodbell et al. 1999, Moy et al. 2000)? et al., 2000, Rodbell et al. 1999, Moy et al. 2000)?

a) b)

•Siple Dome •Siple Dome•Taylor Dome •Taylor Dome

SummarySummary

Deuterium excess varies dramatically across Deuterium excess varies dramatically across AntarcticaAntarcticavarious moistures source regionsvarious moistures source regions

Moisture source region for Siple participates in Moisture source region for Siple participates in global climate changes separately from global climate changes separately from Antarctica at a variety of timescalesAntarctica at a variety of timescales

Siple-Taylor isotope divergence through Siple-Taylor isotope divergence through HoloceneHolocenea precession signal?a precession signal?