What do benthic δ13C and δ18O data tell us about Atlantic circulation during Heinrich Stadial 1?

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doi: 10.1002/2014PA002667
Author(s): Oppo, Delia W.; Curry, William B.; McManus, Jerry F.
Author Affiliation(s): Primary:
Woods Hole Oceanographic Institution, Department of Geology and Geophysics, Woods Hole, MA, United States
Other:
Bermuda Institute of Ocean Sciences, Bermuda
Lamont-Doherty Earth Observatory, United States
Volume Title: Paleoceanography
Source: Paleoceanography, 30(4), p.353-368. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0883-8305 CODEN: POCGEP
Note: In English. NSF grants OCE13-35191, OCE07-50880, and OCE05-84911. 87 refs.; illus., incl. 2 tables
Summary: Approximately synchronous with the onset of Heinrich Stadial 1 (HS1), δ13C decreased throughout most of the upper (∼1000-2500 m) Atlantic, and at some deeper North Atlantic sites. This early deglacial δ13C decrease has been alternatively attributed to a reduced fraction of high-δ13C North Atlantic Deep Water (NADW) or to a decrease in the NADW δ13C source value. Here we present new benthic δ18O and δ13C records from three relatively shallow (∼1450-1650 m) subpolar Northeast Atlantic cores. With published data from other cores, these data form a depth transect (∼1200-3900 m) in the subpolar Northeast Atlantic. We compare Last Glacial Maximum (LGM) and HS1 data from this transect with data from a depth transect of cores from the Brazil Margin. The largest LGM-to-HS1 decreases in both benthic δ13C and δ18O occurred in upper waters containing the highest NADW fraction during the LGM. We show that the δ13C decrease can be explained entirely by a lower NADW δ13C source value, entirely by a decrease in the proportion of NADW relative to Southern Ocean Water, or by a combination of these mechanisms. However, building on insights from model simulations, we hypothesize that reduced ventilation due to a weakened but still active Atlantic Meridional Overturning Circulation also contributed to the low δ13C values in the upper North Atlantic. We suggest that the benthic δ18O gradients above ∼2300 m at both core transects indicate the depth to which heat and North Atlantic deglacial freshwater had mixed into the subsurface ocean by early HS1. Abstract Copyright (2015), . The Authors.
Year of Publication: 2015
Research Program: IODP Integrated Ocean Drilling Program
ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 24 Surficial Geology, Quaternary Geology; Anomalinidae; Atlantic Ocean; Benthic taxa; C-13/C-12; Carbon; Cassidulinacea; Cenozoic; Cibicidoides; Cibicidoides wuellerstorfi; Cores; Expedition 303; Expeditions 303/306; Foraminifera; Heinrich events; IODP Site U1308; Integrated Ocean Drilling Program; Invertebrata; Isotope ratios; Isotopes; Last glacial maximum; Leg 162; Marine environment; Marine sediments; Mid-Atlantic Ridge; North Atlantic; North Atlantic Deep Water; Northeast Atlantic; O-18/O-16; ODP Site 984; Ocean Drilling Program; Ocean circulation; Oxygen; Paleo-oceanography; Paleoenvironment; Pleistocene; Protista; Quaternary; Reykjanes Ridge; Rotaliina; Sediments; Stable isotopes; Upper Pleistocene
Coordinates: N612532 N612532 W0240457 W0240457
N495300 N495300 W0241400 W0241400
N614500 N622000 W0212700 W0214000
Record ID: 2015102241
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from John Wiley & Sons, Chichester, United Kingdom