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A low threshold for North Atlantic ice rafting from "low-slung slippery" late Pliocene ice sheets

A low threshold for North Atlantic ice rafting from "low-slung slippery" late Pliocene ice sheets
A low threshold for North Atlantic ice rafting from "low-slung slippery" late Pliocene ice sheets
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” (?18OT) 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 ?18OT 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 ?18OT 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 ?18OT 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.
0883-8305
PA1212-[14pp]
Bailey, Ian
e659068f-e591-4185-afd1-5e19a5794bda
Bolton, Clara T.
d3f550f0-1fe9-4d18-8a9c-a61034ab0280
DeConto, Robert M.
b920aac8-fc77-487c-a85a-95820d007871
Pollard, David
2ecf15f2-499c-4f91-ba64-da03f9f8a789
Schiebel, Ralf
5c48accb-ee14-471a-801f-4267d8e4b2e1
Wilson, Paul A.
f940a9f0-fa5a-4a64-9061-f0794bfbf7c6
National Oceanography Centre, Southampton
Bailey, Ian
e659068f-e591-4185-afd1-5e19a5794bda
Bolton, Clara T.
d3f550f0-1fe9-4d18-8a9c-a61034ab0280
DeConto, Robert M.
b920aac8-fc77-487c-a85a-95820d007871
Pollard, David
2ecf15f2-499c-4f91-ba64-da03f9f8a789
Schiebel, Ralf
5c48accb-ee14-471a-801f-4267d8e4b2e1
Wilson, Paul A.
f940a9f0-fa5a-4a64-9061-f0794bfbf7c6

Bailey, Ian, Bolton, Clara T., DeConto, Robert M., Pollard, David, Schiebel, Ralf and Wilson, Paul A. , National Oceanography Centre, Southampton (2010) A low threshold for North Atlantic ice rafting from "low-slung slippery" late Pliocene ice sheets. Paleoceanography, 25, PA1212-[14pp]. (doi:10.1029/2009PA001736).

Record type: Article

Abstract

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” (?18OT) 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 ?18OT 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 ?18OT 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 ?18OT 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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Published date: 26 March 2010

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Local EPrints ID: 73346
URI: https://eprints.soton.ac.uk/id/eprint/73346
ISSN: 0883-8305
PURE UUID: c9f0ed28-19a6-4bc1-9b96-c9aa5d37d507

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Date deposited: 26 Mar 2010
Last modified: 19 Jul 2019 23:41

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Contributors

Author: Ian Bailey
Author: Clara T. Bolton
Author: Robert M. DeConto
Author: David Pollard
Author: Ralf Schiebel
Author: Paul A. Wilson

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