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,1969Photo 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 SchererNorthern 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 SchererNorthern 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

ANDRILLANDRILL

Pleistocene record of ANDRILL-1B

MIS-31 1.08 – 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 15/13Superinterglacials” MIS 5e, 7, 9, 11, also 15/13

The late Pleistocene record of ANDRILL-1B

What about the late Pleistocene in What about the late Pleistocene in ANDRILL?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