Productivity and circulation changes during the last deglaciation from biomarkers and Nd isotopes

Online Access: Get full text
Author(s): Calvo, E.; Pena, L. D.; Pelejero, C.; Cacho, I.
Author Affiliation(s): Primary:
CSIC, Institut de Ciències del Mar, Barcelona, Spain
Lamont-Doherty Earth Observatory, United States
CSIC, Institucio Catalana de Recerca i Estudios Avançats (ICREA), Spain
Universitat de Barcelona, Spain
Volume Title: Goldschmidt 2011 abstract volume
Source: Mineralogical Magazine, 75(3), p.614; Goldschmidt2011, Prague, Czech Republic, Aug. 14-19, 2011. Publisher: Mineralogical Society, London, United Kingdom. ISSN: 0026-461X CODEN: MNLMBB
Note: In English. 1 refs.
Summary: The Eastern Equatorial Pacific (EEP) is thought to have exerted a strong control over glacial/interglacial CO2 variations through its link to circulation and nutrient-related changes in the Southern Ocean. Changes in phytoplankton productivity and composition associated with increases in equatorial upwelling intensity and influence of Si-rich waters of Sub-Antarctic origin have been recently detected in ODP Site 1240 (0°01.31'N, 86°27.76'W; 2,921 mbsl). However, these changes do not seem to have been crucial in controlling atmospheric CO2, as they took place during the deglaciation, when atmospheric CO2 concentrations had already started to rise. New results from Nd isotopes in foraminifera shells of Neogloboquadrina dutertrei from the same intervals corroborate this interpretation. N. dutertrei preferentially dwells in the lower thermocline, at the core of the Equatorial Undercurrent (EUC). Therefore, changes in the Nd-isotopic composition of these foraminifera will reflect the composition of the EUC, which, in turn, reflects changes in the advection of Sub-Antarctic Mode Water and Antarctic Intermediate Water and the composition of the Southern Ocean end-member. Our evidence indicates that diatoms outcompeted coccolithophores at times when the influence of Si-rich Southern Ocean intermediate waters was greatest as recorded by low εNd values (-2.8). This shift from calcareous to non-calcareous phytoplankton would cause a lowering in atmospheric CO2 through a reduced carbonate pump, as hypothesized by the Silicic Acid Leakage Hypothesis. However, the concomitant intensification of Antarctic upwelling brought large quantities of deep CO2-rich waters to the ocean surface. This process very likely dominated any biologically mediated CO2 sequestration, and probably accounts for most of the deglacial rise in atmospheric CO2.
Year of Publication: 2011
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 24 Surficial Geology, Quaternary Geology; Biochemistry; Biomarkers; Cenozoic; Climate change; Deglaciation; East Pacific; Equatorial Pacific; Foraminifera; Glacial environment; Globigerinacea; Interglacial environment; Invertebrata; Isotope ratios; Isotopes; Leg 202; Metals; Microfossils; Nd-144/Nd-142; Neodymium; Neogloboquadrina; Neogloboquadrina dutertrei; ODP Site 1240; Ocean Drilling Program; Pacific Ocean; Paleo-oceanography; Paleocirculation; Paleoclimatology; Paleoecology; Paleoenvironment; Panama Basin; Productivity; Protista; Quaternary; Radioactive isotopes; Rare earths; Rotaliina; Southern Ocean; Stable isotopes
Coordinates: N000100 N000100 W0822800 W0822800
Record ID: 2013078503
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland