The University of Southampton
University of Southampton Institutional Repository

Deep water formation in the North Pacific and deglacial CO2 rise

Deep water formation in the North Pacific and deglacial CO2 rise
Deep water formation in the North Pacific and deglacial CO2 rise
Deep water formation in the North Atlantic and Southern Ocean is widely thought to influence deglacial CO2 rise and climate change; here we suggest that deep water formation in the North Pacific may also play an important role. We present paired radiocarbon and boron isotope data from foraminifera from sediment core MD02-2489 at 3640?m in the North East Pacific. These show a pronounced excursion during Heinrich Stadial 1, with benthic-planktic radiocarbon offsets dropping to ~350?years, accompanied by a decrease in benthic ?11B. We suggest that this is driven by the onset of deep convection in the North Pacific, which mixes young shallow waters to depth, old deep waters to the surface, and low-pH water from intermediate depths into the deep ocean. This deep water formation event was likely driven by an increase in surface salinity, due to subdued atmospheric/monsoonal freshwater flux during Heinrich Stadial 1. The ability of North Pacific Deep Water (NPDW) formation to explain the excursions seen in our data is demonstrated in a series of experiments with an intermediate complexity Earth system model. These experiments also show that breakdown of stratification in the North Pacific leads to a rapid ~30?ppm increase in atmospheric CO2, along with decreases in atmospheric ?13C and ?14C, consistent with observations of the early deglaciation. Our inference of deep water formation is based mainly on results from a single sediment core, and our boron isotope data are unavoidably sparse in the key HS1 interval, so this hypothesis merits further testing. However, we note that there is independent support for breakdown of stratification in shallower waters during this period, including a minimum in ?15N, younging in intermediate water 14C, and regional warming. We also re-evaluate deglacial changes in North Pacific productivity and carbonate preservation in light of our new data and suggest that the regional pulse of export production observed during the Bølling-Allerød is promoted by relatively stratified conditions, with increased light availability and a shallow, potent nutricline. Overall, our work highlights the potential of NPDW formation to play a significant and hitherto unrealized role in deglacial climate change and CO2 rise.
radiocarbon, boron isotopes, North Pacific, deglacial CO2, deep water formation, atmospheric teleconnections
0883-8305
645-667
Rae, James W.B.
8788a3a1-fec8-46c2-95a4-a59ce25416f5
Sarnthein, Michael
37d635ab-8783-4724-8d6a-799ab56c4821
Foster, Gavin L.
fbaa7255-7267-4443-a55e-e2a791213022
Ridgwell, Andy
769cea5c-e033-456a-8b53-51dfa307dc35
Grootes, Pieter M.
ffd4cbec-8b63-4503-b612-a283554a190f
Elliott, Tim
8e43fe0d-c251-4ee8-80fa-bcffc8c7e153
Rae, James W.B.
8788a3a1-fec8-46c2-95a4-a59ce25416f5
Sarnthein, Michael
37d635ab-8783-4724-8d6a-799ab56c4821
Foster, Gavin L.
fbaa7255-7267-4443-a55e-e2a791213022
Ridgwell, Andy
769cea5c-e033-456a-8b53-51dfa307dc35
Grootes, Pieter M.
ffd4cbec-8b63-4503-b612-a283554a190f
Elliott, Tim
8e43fe0d-c251-4ee8-80fa-bcffc8c7e153

Rae, James W.B., Sarnthein, Michael, Foster, Gavin L., Ridgwell, Andy, Grootes, Pieter M. and Elliott, Tim (2014) Deep water formation in the North Pacific and deglacial CO2 rise. Paleoceanography, 29 (6), 645-667. (doi:10.1002/2013PA002570).

Record type: Article

Abstract

Deep water formation in the North Atlantic and Southern Ocean is widely thought to influence deglacial CO2 rise and climate change; here we suggest that deep water formation in the North Pacific may also play an important role. We present paired radiocarbon and boron isotope data from foraminifera from sediment core MD02-2489 at 3640?m in the North East Pacific. These show a pronounced excursion during Heinrich Stadial 1, with benthic-planktic radiocarbon offsets dropping to ~350?years, accompanied by a decrease in benthic ?11B. We suggest that this is driven by the onset of deep convection in the North Pacific, which mixes young shallow waters to depth, old deep waters to the surface, and low-pH water from intermediate depths into the deep ocean. This deep water formation event was likely driven by an increase in surface salinity, due to subdued atmospheric/monsoonal freshwater flux during Heinrich Stadial 1. The ability of North Pacific Deep Water (NPDW) formation to explain the excursions seen in our data is demonstrated in a series of experiments with an intermediate complexity Earth system model. These experiments also show that breakdown of stratification in the North Pacific leads to a rapid ~30?ppm increase in atmospheric CO2, along with decreases in atmospheric ?13C and ?14C, consistent with observations of the early deglaciation. Our inference of deep water formation is based mainly on results from a single sediment core, and our boron isotope data are unavoidably sparse in the key HS1 interval, so this hypothesis merits further testing. However, we note that there is independent support for breakdown of stratification in shallower waters during this period, including a minimum in ?15N, younging in intermediate water 14C, and regional warming. We also re-evaluate deglacial changes in North Pacific productivity and carbonate preservation in light of our new data and suggest that the regional pulse of export production observed during the Bølling-Allerød is promoted by relatively stratified conditions, with increased light availability and a shallow, potent nutricline. Overall, our work highlights the potential of NPDW formation to play a significant and hitherto unrealized role in deglacial climate change and CO2 rise.

Full text not available from this repository.

More information

Accepted/In Press date: June 2014
Published date: June 2014
Keywords: radiocarbon, boron isotopes, North Pacific, deglacial CO2, deep water formation, atmospheric teleconnections
Organisations: Geochemistry

Identifiers

Local EPrints ID: 366468
URI: https://eprints.soton.ac.uk/id/eprint/366468
ISSN: 0883-8305
PURE UUID: 9cfcdf10-285c-4882-85a6-79b2b47a3bf1

Catalogue record

Date deposited: 30 Jun 2014 10:52
Last modified: 18 Jul 2017 02:12

Export record

Altmetrics

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of https://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×