Ice Cores and the WAISWhat we’ve learned

What we still need to accomplish

Eric Steig

University of Washington

Conclusions

It is important that we drill deep ice.

It is important that we drill more than one new intermediate to deep ice core (but fewer than 23) in the WAIS.

It is important where we drill.

Why?Low frequency climate variability is not understood.

Why?

Low frequency climate variability is not understood but is the fundamental to the climate change debate (“does recent warming exceed the range of “natural variability”?).

-->Ice cores provide the best low frequency information we have (need ice cores).

-->To assess climate change (at any frequency) we need to get the spatial patterns right (>>1 core).

-->To get the spatial patterns right we need to get the cross-dating right (it matters where we drill).

Modeled pattern of millennial-scale climate change

Vellinga and Wood, 2002

“Patterns of variability” hypothesis

Deep ice cores

Vellinga and Wood, 2002

Well dated deep ice cores

Byrd

Siple Dome

Byrd and Siple Coherence, Holocene

Steig and Alley, 2002, Annals

Papers since 2002 on the GISP2/WAIS relationship

• Ganopolski and Ramstorff, 2002 - Science• Wunsch, 2003 - Quaternary Science Reviews• Schmittner et al., 2003 - QSR• Huybers, 2003 - QSR• Stocker and Johnson, 2003 - QSR• Chaing, Battisti et al., 2004 - Paleoceanography • Roe and Steig, 2004 - Journal of Climate• Brook et al., in review - QSR

Huybers, 2003, QSR

Coherenceof temperature

Phase oftemperature

Coherence Of CH4

Siple, GISP2 Coherence, Glacial

Byrd vs SDM

White & Brook

Z500 PCs vs. T

US ITASE Cores in West Antarctica

3433

47 22

Accumulation(water equiv cm/year)

RAW xsSO4 (RED) AND ssSO4 (GREEN)CONCENTRATIONS FROM 1800-2002 AD

ConclusionsIt is important that we drill deep ice -- because the dating

quality is not yet good enough. The new WAIS core will offer significantly improved dating precision.

It is important that we drill more than one new intermediate to deep ice core (but fewer than 23) in the WAIS -- because there are clearly spatial differences within WAIS.

It is important where we drill.We will still need deep core east of the divide, in the Amundsen

and/or Weddell drainages to capture the full spatial characteristics of low frequency climate variability.