Rapid changes in meridional advection of Southern Ocean intermediate waters to the tropical Pacific during the last 30 kyr

Type Article
Date 2013-04
Language English
Author(s) Pena L. D.1, Goldstein S. L.1, 2, Hemming S. R.1, 2, Jones K. M.1, 2, Calvo E.3, Pelejero C.3, 4, Cacho I.5
Affiliation(s) 1 : Columbia Univ, Lamont Doherty Earth Observ, Palisades, NY 10964 USA.
2 : Columbia Univ, Dept Earth & Environm Sci, Palisades, NY 10964 USA.
3 : CSIC, Inst Ciencies del Mar, E-08003 Barcelona, Spain.
4 : ICREA, Barcelona 08010, Spain.
5 : Univ Barcelona, Dept Estratig Paleontol & Geociencies Marines, E-08028 Barcelona, Spain.
Source Earth And Planetary Science Letters (0012-821X) (Elsevier Science Bv), 2013-04 , Vol. 368 , P. 20-32
DOI 10.1016/j.epsl.2013.02.028
WOS© Times Cited 51
Keyword(s) neodymium isotopes, planktonic foraminifera, intermediate water masses, Eastern Equatorial Pacific, Equatorial Undercurrent, Southern Ocean
Abstract The Southern Ocean is increasingly recognized as a key player in the general ocean thermohaline circulation and the global climate system during glacial interglacial transitions. In particular, the advection of Southern Ocean intermediate waters (SOIW), like Antarctic Intermediate Water and Sub-Antarctic Mode Water, to the Eastern Equatorial Pacific (EEP), through a so-called "oceanic tunnelling" mechanism, is an important means for rapid transfer of climatic signals (such as heat, fresh water, salt, and chemical species) from high-to-low latitudes. However, information on how intermediate water advection rates changed in the past, and particularly during deglaciations, is fragmentary. We present new results for Nd isotopes (epsilon(Nd)) in cleaned foraminifera shells (Neogloboquadrina dutertrei) for the last 30 kyr at ODP Site 1240 in the EEP. N. dutertrei preferentially dwells in the lower thermocline, at the core of the Equatorial Undercurrent (EUC), and the epsilon(Nd) variability over time provides a record of the changes in the epsilon(Nd) of the EUC. Through mixing models we show that the EUC record is primarily controlled by changes in the volume transport of intermediate waters and not by Southern Ocean epsilon(Nd) changes. Southern Ocean signals in the EUC are stronger during colder intervals (Younger Dryas, last glacial maximum and Heinrich stadials 1 and 2), in agreement with tropical Atlantic intermediate water records. In addition, covariations between N. dutertrei delta C-13, molecular biomarkers, and diatom productivity at Site 1240 confirm the intermediate water route as an important mechanism for the transfer of climate signals from high-to-low latitudes. Changes in the SOIW chemistry during the deglaciation are likely linked to the upwelling of 'old' deep waters in the Southern Ocean and subsequent export as intermediate waters, which are coeval with the atmospheric CO2 rise. Moreover, a comparison of multiple proxy records for the last 30 kyr indicates a latitudinal shift and/or a change in the convection depth of intermediate waters in the Southern Ocean prior to the onset of the deglaciation.
Full Text
File Pages Size Access
Publisher's official version 13 1 MB Open access
Supporting material 12 579 KB Open access
Top of the page