Holocene and Pleistocene Sedimentation on the Antarctic Shelf Why study this topic? 1)Holocene: period of dramatic S. Ocean changes w/o large CO 2 change. 2)Pleistocene orbital cycles: 41K, 100K, CO 2 chicken and egg, Ice/Ocean feedback. 3)Estimate volumes/profiles of the ice sheet – studies of grounding lines and how the ice actually retreats….. 4)Pleistocene instabilities of west Antarctic ice at 120 kyr, 400kyr, 1100 kyr 5)Ultra-high resolution records of climate change and Antarctic Margin productivity

The Southwest Pacific during the MPT

Antarctic near shore records of interglacial climate optima What did Antarctic ice sheets do during: MIS-5e (120ka)? MIS-11 (400ka)? MIS-31 (1.07Ma)? Other Pleistocene interglacials? MAJOR SCIENTIFIC GOAL OF THE ANDRILL MIS PROJECT

Ross Ice Shelf behaviour during past warm climate extremes: A geologic analogue for future behaviour? e.g. EPICA ice core MIS-11 analogous to present interglacial MIS 5 & 9 interglacials warmer?

“Determine ice shelf responses to climate forcing, including variability at a range of temporal scales ( years), and possible collapses over the past 5 million years”.

WAIS collapse during MIS-5e? SL slightly higher (~2 – 5m) Global temperatures slightly warmer Short duration Mercer (1978) suggested WAIS collapse during MIS-5e, but few proximal marine records exist (and none convincing) Bahamas Cape Barne, Ross Island Conclusion: Not very likely Conclusion: Not very likely

Marine record indicating long duration Significantly higher sea-level (~20m) But not necessarily much warmer than today Leg 177 shows some very significant changes No well-dated Antarctic proximal records –Late Quaternary diatoms & 10 Be beneath the Ross ice streams (UpB) - assumed to be MIS-11 (Scherer et al, Science, 1998) WAIS collapse during MIS-11? Conclusion: Yes during late Pleistocene Stage 11 most likely Conclusion: Yes during late Pleistocene Stage 11 most likely

The Cape Roberts Project WAIS collapse During MIS-31? WAIS collapse During MIS-31?

CRP-1 Unit 3.2 – recovery of the MIS-31 interglacial Precisely dated: Diatoms, Ar, Sr, Paleomag (1.07Ma)

Holocene and Pleistocene Sedimentation on the Antarctic Shelf Why study this topic? 1)Holocene: period of dramatic S. Ocean changes w/o large CO 2 change. 2)Pleistocene orbital cycles: 41K, 100K, CO 2 chicken and egg, Ice/Ocean feedback. 3)Estimate volumes/profiles of the ice sheet – studies of grounding lines and how the ice actually retreats….. 4)Pleistocene instabilities of west Antarctic ice at 120 kyr, 400kyr, 1100 kyr 5)Ultra-high resolution records of climate change and Antarctic Margin productivity

Marine Biomass

Part 1: ODP Site 1098 Solar Forcing & Holocene Cooling Robert B. Dunbar, Stanford University Ana Christina Ravelo, University of California, Santa Cruz Eugene Domack, Hamilton College Amy Leventer, Colgate University This talk is an update of previous site 1098 work – using a new chronology and a newly-completed biogeochemical time series

Palmer Deep The first high resolution Holocene marine time series from Antarctica Decadal-to-centennial variability in the Southern Ocean

Drilling of Holocene sediments along the Antarctic Peninsula. How has climate varied in the last 10,000 years when CO 2 didn’t change very much?

Site 1098 was triple cored. Samples were collected every 2.5 cm for analysis of tracers of productivity (org C, opal,  13 C,  15 N) Age model is based on AMS dates Using physical properties and sed. rates, we calculate mass accumulation rates. The average sample spacing in time is 7 years.

A New Age Model for Site 1098 Domack et al. (2001) used a constant  R of 1230 years as well as AMS dates from forams, POC, and multiple cores. 1)We use 26 AMS 14 C dates of POC – all from 1098C and one kasten coretop. 2)Dates were calibrated using variable reservoir ages, after Van Beek et al. (2002) who compared barite 226 Ra ages with AMS dates on forams from a core at 53°S, 5°W in the South Atlantic from 0 to 2,000 cal. Yrs B.P. we use a  R = 1200 years from 3,500 to 7,000 cal. Yrs B.P. we use a  R = 900 years from 7,000 to 8,400 cal. Yrs B.P. we use a  R that ramps up from 1200 to 1800 years for samples older than 8,400 cal. Yrs B.P. we use a R = 1800 years 3) 1098A, B, and C holes were correlated and spliced 4) 3 turbidites (all below 25 m) were excised from the composite section 5) A revised composite depth (rmcd) scale was used with the calibrated dates

N=2409

mmol cm -2 kyr -1