Or, the Brooklyn version: What? You kiddin’ me? It’s been >30 years! – Wadd’ya mean we still don’t know for sure if WAIS collapsed during MIS 5e?! John Mercer, Coalsack Bluff, Antarctica,1969 Photo courtesy of Henry Brecher WAIS/FRISP meeting Sept. 29, 2009 Reed Scherer Reflections on Pleistocene marine records of past WAIS collapse

WAIS collapsed during MIS-31 WAIS meeting, October, 2008

In phase with intense insolation (at 1.08 Ma) Reed Scherer Northern Illinois University Analytical Center for Climate & Environmental Change & Department of Geology & Environmental Geosciences WAIS meeting, October, 2008

And it happened ~10 ka before a GIS retreat ! Reed Scherer Northern Illinois University Analytical Center for Climate & Environmental Change & Department of Geology & Environmental Geosciences WAIS meeting, October, 2008

ODP 1094 Cape Roberts Project – 1 McMurdo Sound

Pollard & DeConto MIS-31 WAIS collapse Also, most recently, MIS-7

ANDRILL

Pleistocene record of ANDRILL-1B MIS – 1.06 Ma

Villa et al. in review

But what about the late Pleistocene “superinterglacials”? Years ago I presented diatom evidence from beneath Whillans & Kamb ice stream, but dating was not precise Important questions remain: –How many times? –Specifically when (i.e., which interglacials)? –How quickly? –What was the primary trigger?

“Superinterglacials” MIS 5e, 7, 9, 11, also 15/13

The late Pleistocene record of ANDRILL-1B

What about the late Pleistocene in ANDRILL? Poor recovery Thick diamictites with few, thin mudstone layers No in situ diatoms! Diatomite & volcanics

Proposed correlation of McKay et al., (GSA Bull, in press) Suggested a largely complete record

If all that time is represented, where are the Late Pleistocene “superinterglacials? MIS-31 ?

Alternate Hypotheses for AND-1B Late Pleistocene Option A: No WAIS or RIS collapse events since MIS-31 A fundamental change in ice sheet regime after MIS-31 at the MPT Implies that the current configuration of RIS may be smallest of the last 1 Ma Option B: The AND-1B late Pleistocene record is substantially incomplete. Collapse(s) not represented. Erosion and non-recovery of Late Pleistocene interglacials in the AND-1B core

Where can we find continuous late Pleistocene records proximal enough to the WAIS to have a clear signal? A good core is hard to find! –Major erosion across the continental shelf with each advance. Far-field records provide equivocal results –“How would we know?” –Bamber et al. (2009): WAIS SL effect may be less than had been presumed

Possible collapse events during MIS 7, 9, 15-13, & very brief 5e ****** DeConto & Pollard collapses

Keep looking, keep thinking, keep coring, and keep working with glaciologists, oceanographers & modelers. (and keep thanking NSF! ) Keep looking, keep thinking, keep coring, and keep working with glaciologists, oceanographers & modelers. (and keep thanking NSF! ) IODP Wilkes Land Margin