TY - JOUR
T1 - A low threshold for North Atlantic ice rafting from "low-slung slippery" late Pliocene ice sheets
AU - Bailey, Ian
AU - Bolton, Clara T.
AU - Deconto, Robert M.
AU - Pollard, David
AU - Schiebel, Ralf
AU - Wilson, Paul A.
N1 - Funding Information:
This research used samples provided by the Integrated Ocean Drilling Program (IODP). The IODP is sponsored by the U.S. National Science Foundation and participating countries under management of the Joint Oceanographic Institutions (JOI), Inc. We thank the shipboard party of IODP Expeditions 303 and 306 and A. Wuelbers and W. Hale for their help at the Bremen Core Repository. We are also grateful to N. Andersen for his help with laboratory work and R. Zhan, E. Rohling, J. Stanford, D. Hodell, M. Maslin, and L. Skinner for useful discussions regarding the Last Glacial Cycle and Plio]Pleistocene suborbital ice rafting. We are grateful to J. Becker and an anonymous individual for their manuscript reviews. We are also especially grateful to R. van de Wal for his constructive comprehensive review and subsequent conversations that helped to improve this manuscript. Financial support was provided by the Natural Environmental Research Council, NERC, in the form of a UK IODP grant to P.A.W., R.S., and I.B. and a Ph.D. studentship to C.T.B. R.S. is grateful to the Swiss IODP and J. McKenzie (ETH Zurich) for financial support for shipboard and postcruise participation in IODP Exp. 303.
Publisher Copyright:
© Copyright 2010 by the American Geophysical Union.
PY - 2010/3/1
Y1 - 2010/3/1
N2 - Suborbital variability in late Pleistocene records of ice-rafted debris and sea surface temperature in the North Atlantic Ocean appears most extreme during times of enlarged ice sheets with a well-constrained benthic oxygen isotope-defined "ice volume threshold" (δ18OT) for the "100 ka (inter)glacial" world. Information on climate instability for the earlier Pleistocene and late Pliocene is more fragmentary and/or of much lower temporal resolution, but the data available suggest similar behavior with δ18OT remaining more or less constant over the past 3000 ka. This finding is puzzling because it implies that ice rafting is highly sensitive to ice volume on short (suborbital/glacial-interglacial) time scales but not to the long-term changes in ice sheet composition associated with intensification of Northern Hemisphere glaciation (NHG). Here we report new high-resolution records of stable isotope change and ice rafting in the North Atlantic at Integrated Ocean Drilling Program Site U1308 (reoccupation of Deep Sea Drilling Project Site 609) during two glacials key to intensification of NHG (marine isotope stages G4, ∼2640 ka, and 100, ∼2520 ka). We find a pattern of suborbital ice rafting events showing clear evidence of threshold behavior. However, contrary to previous reports, we find that δ18OT for the late Pliocene is up to 0.45‰ Vienna Peedee belemnite (VPDB) lower than for the late Pleistocene. Using published Plio-Pleistocene global sea level records, we evaluate different potential explanations for this finding. We conclude that the observed Pliocene-Pleistocene offset in δ18OT is attributable to the existence of low-slung Pliocene ice sheets that flowed more readily than their late Pleistocene counterparts, associated with a smaller contemporaneous continental ice volume and less isotopically depleted ice.
AB - Suborbital variability in late Pleistocene records of ice-rafted debris and sea surface temperature in the North Atlantic Ocean appears most extreme during times of enlarged ice sheets with a well-constrained benthic oxygen isotope-defined "ice volume threshold" (δ18OT) for the "100 ka (inter)glacial" world. Information on climate instability for the earlier Pleistocene and late Pliocene is more fragmentary and/or of much lower temporal resolution, but the data available suggest similar behavior with δ18OT remaining more or less constant over the past 3000 ka. This finding is puzzling because it implies that ice rafting is highly sensitive to ice volume on short (suborbital/glacial-interglacial) time scales but not to the long-term changes in ice sheet composition associated with intensification of Northern Hemisphere glaciation (NHG). Here we report new high-resolution records of stable isotope change and ice rafting in the North Atlantic at Integrated Ocean Drilling Program Site U1308 (reoccupation of Deep Sea Drilling Project Site 609) during two glacials key to intensification of NHG (marine isotope stages G4, ∼2640 ka, and 100, ∼2520 ka). We find a pattern of suborbital ice rafting events showing clear evidence of threshold behavior. However, contrary to previous reports, we find that δ18OT for the late Pliocene is up to 0.45‰ Vienna Peedee belemnite (VPDB) lower than for the late Pleistocene. Using published Plio-Pleistocene global sea level records, we evaluate different potential explanations for this finding. We conclude that the observed Pliocene-Pleistocene offset in δ18OT is attributable to the existence of low-slung Pliocene ice sheets that flowed more readily than their late Pleistocene counterparts, associated with a smaller contemporaneous continental ice volume and less isotopically depleted ice.
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U2 - 10.1029/2009PA001736
DO - 10.1029/2009PA001736
M3 - Article
AN - SCOPUS:77956013038
VL - 25
JO - Paleoceanography and Paleoclimatology
JF - Paleoceanography and Paleoclimatology
SN - 0883-8305
IS - 1
M1 - PA1212
ER -