What do benthic δ13C and δ18O data tell us about Atlantic circulation during Heinrich Stadial 1?. (13th April 2015)

• Record Type: Journal Article
• Authors: Oppo, Delia W.; Curry, William B.; McManus, Jerry F.
• Is Part Of: Paleoceanography. Volume 30:Number 4(2015:Jun.)
• Page Start: 353
• Page End: 368
• Publication Date: 2015-04-13
• Subjects: Paleoceanography -- Periodicals; 551.46
• DOI: 10.1002/2014PA002667
• Languages: English
• ISSNs: 0883-8305

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>Approximately synchronous with the onset of Heinrich Stadial 1 (HS1), δ<sup>13</sup>C decreased throughout most of the upper (~1000–2500 m) Atlantic, and at some deeper North Atlantic sites. This early deglacial δ<sup>13</sup>C decrease has been alternatively attributed to a reduced fraction of high‐δ<sup>13</sup>C North Atlantic Deep Water (NADW) or to a decrease in the NADW δ<sup>13</sup>C source value. Here we present new benthic δ<sup>18</sup>O and δ<sup>13</sup>C 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 δ<sup>13</sup>C and δ<sup>18</sup>O occurred in upper waters containing the highest NADW fraction during the LGM. We show that the δ<sup>13</sup>C decrease can be explained entirely by a lower NADW δ<sup>13</sup>C 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 δ<sup>13</sup>C values in the upper North Atlantic. We suggest that the benthic δ<sup>18</sup>O 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.</p> </abstract>