UCL Discovery
UCL home » Library Services » Electronic resources » UCL Discovery

Calibration and application of B/Ca, Cd/Ca, and δ11B in Neogloboquadrina pachyderma (sinistral) to constrain CO2 uptake in the subpolar North Atlantic during the last deglaciation

Yu, J; Thornalley, DJR; Rae, JWB; McCave, NI; (2013) Calibration and application of B/Ca, Cd/Ca, and δ11B in Neogloboquadrina pachyderma (sinistral) to constrain CO2 uptake in the subpolar North Atlantic during the last deglaciation. Paleoceanography , 28 (2) pp. 237-252. 10.1002/palo.20024. Green open access

[thumbnail of Thornalley_Yu_et_al-2013-Paleoceanography.pdf]
Preview
Text
Thornalley_Yu_et_al-2013-Paleoceanography.pdf

Download (1MB) | Preview

Abstract

The North Atlantic and Norwegian Sea are prominent sinks of atmospheric CO2 today, but their roles in the past remain poorly constrained. In this study, we attempt to use B/Ca and δ11B ratios in the planktonic foraminifera Neogloboquadrina pachyderma (sinistral variety) to reconstruct subsurface water pH and pCO2 changes in the polar North Atlantic during the last deglaciation. Comparison of core-top results with nearby hydrographic data shows that B/Ca in N. pachyderma (s) is mainly controlled by seawater B(OH)4-/HCO3- with a roughly constant partition coefficient KD=B/CaCaCO3BOH4-/ HCO3̄seawater of 1.48 ± 0.15 × 10-3 (2σ), and δ11B in this species is offset below δ11B of the borate in seawater by 3.38 ± 0.71‰ (2σ). These values represent our best estimates with the sparse available hydrographic data close to our core-tops. More culturing and sediment trap work is needed to improve our understanding of boron incorporation into N. pachyderma (s). Application of a constant KD of 1.48 × 10-3 to high resolution N. pachyderma (s) B/Ca records from two adjacent cores off Iceland shows that subsurface pCO2 at the habitat depth of N. pachyderma (s) (∼50 m) generally followed the atmospheric CO2 trend but with negative offsets of ∼10-50 ppmv during 19-10 ka. These B/Ca-based reconstructions are supported by independent estimates from low-resolution δ11B measurements in the same cores. We also calibrate and apply Cd/Ca in N. pachyderma (s) to reconstruct nutrient levels for the same down cores. Like today's North Atlantic, past subsurface pCO2 variability off Iceland was significantly correlated with nutrient changes that might be linked to surface nutrient utilization and mixing within the upper water column. Because surface pCO2 (at 0 m water depth) is always lower than at deeper depths and if the application of a constant KD is valid, our results suggest that the polar North Atlantic has remained a CO2 sink during the calcification seasons of N. pachyderma (s) over the last deglaciation. Key Points Subsurface pCO2 and nutrient from B/Ca, Cd/Ca and d11B in N. pachyderma (s)B/Ca and d11B suggest a CO2 sink off Iceland at 19-10 kaNutrient utilization correlates with millennial-scale pCO2 variations ©2013. American Geophysical Union. All Rights Reserved.

Type: Article
Title: Calibration and application of B/Ca, Cd/Ca, and δ11B in Neogloboquadrina pachyderma (sinistral) to constrain CO2 uptake in the subpolar North Atlantic during the last deglaciation
Open access status: An open access version is available from UCL Discovery
DOI: 10.1002/palo.20024
Publisher version: http://dx.doi.org/10.1002/palo.20024
Language: English
Additional information: © 2013. American Geophysical Union. All Rights Reserved.
Keywords: B/Ca, Cd/Ca, d11B, Neogloboquadrina pachyderma (s), subsurface pH and pCO2 and nutrients
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL SLASH
UCL > Provost and Vice Provost Offices > UCL SLASH > Faculty of S&HS
UCL > Provost and Vice Provost Offices > UCL SLASH > Faculty of S&HS > Dept of Geography
URI: https://discovery.ucl.ac.uk/id/eprint/1396385
Downloads since deposit
31Downloads
Download activity - last month
Download activity - last 12 months
Downloads by country - last 12 months

Archive Staff Only

View Item View Item