Reduced deep ocean ventilation in the Southern Pacific Ocean during the last glaciation persisted into the deglaciation

Reduced deep ocean ventilation in the Southern Pacific Ocean during the last glaciation persisted... Marine radiocarbon (14C) is widely used to trace ocean circulation and the 14C levels of interior ocean water masses can provide insight into atmosphere–ocean exchange of CO2 the since the last glaciation. Using tephras as stratigraphic tie points with which to estimate past atmospheric Δ14C, we reconstructed a series of deep radiocarbon ages for several time slices from the last glaciation through the deglaciation and Holocene in the Southwestern Pacific. Glacial ventilation ages were much greater in magnitude than modern and had a strong mid-depth Δ14C minimum centered on ∼2500 m. Glacial radiocarbon ages of intermediate depth waters (600–1200 m) were ∼800 to 1600 14C years, about twice modern and persisted through the early deglaciation. Notably, in the glaciation shallower depths were significantly more enriched in 14C than waters between 1600 and 3800 m, which were ∼4000 to 6200 14C years, or about 3–5 times older than modern. Abyssal waters deeper than 4000 m were also more 14C rich than the overlying deep water. With radiocarbon ages of 1800–2300 14C years, this was similar to modern values. In the early deglaciation, Δ14C depleted waters were flushed from shallower depths first and replaced with progressively younger waters such that by ∼18 ka, the deep to intermediate age difference was reduced by half, and by ∼14 ka a modern-type Δ14C profile for deep ocean water masses was in place. Our results 1) confirm a deep 14C depleted water mass during the LGM and early deglaciation, and 2) constrain the extent of this “old” water in the Southern Pacific as between 1600 m and 3800 m. The availability of atmospheric ages from tephras reveals that the presence of older surface reservoir ages in the glaciation caused the estimation of ventilation ages from simple benthic–planktonic offsets to significantly underestimate the depletion of Δ14C in deep waters. This may have had a role in masking the large change in reservoir ages since the glaciation when using benthic–planktonic reservoir age estimates. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Earth and Planetary Science Letters Elsevier

Reduced deep ocean ventilation in the Southern Pacific Ocean during the last glaciation persisted into the deglaciation

Loading next page...
 
/lp/elsevier/reduced-deep-ocean-ventilation-in-the-southern-pacific-ocean-during-x54Kt6WDEu
Publisher
Elsevier
Copyright
Copyright © 2016 Elsevier B.V.
ISSN
0012-821X
eISSN
1385-013X
D.O.I.
10.1016/j.epsl.2015.12.039
Publisher site
See Article on Publisher Site

Abstract

Marine radiocarbon (14C) is widely used to trace ocean circulation and the 14C levels of interior ocean water masses can provide insight into atmosphere–ocean exchange of CO2 the since the last glaciation. Using tephras as stratigraphic tie points with which to estimate past atmospheric Δ14C, we reconstructed a series of deep radiocarbon ages for several time slices from the last glaciation through the deglaciation and Holocene in the Southwestern Pacific. Glacial ventilation ages were much greater in magnitude than modern and had a strong mid-depth Δ14C minimum centered on ∼2500 m. Glacial radiocarbon ages of intermediate depth waters (600–1200 m) were ∼800 to 1600 14C years, about twice modern and persisted through the early deglaciation. Notably, in the glaciation shallower depths were significantly more enriched in 14C than waters between 1600 and 3800 m, which were ∼4000 to 6200 14C years, or about 3–5 times older than modern. Abyssal waters deeper than 4000 m were also more 14C rich than the overlying deep water. With radiocarbon ages of 1800–2300 14C years, this was similar to modern values. In the early deglaciation, Δ14C depleted waters were flushed from shallower depths first and replaced with progressively younger waters such that by ∼18 ka, the deep to intermediate age difference was reduced by half, and by ∼14 ka a modern-type Δ14C profile for deep ocean water masses was in place. Our results 1) confirm a deep 14C depleted water mass during the LGM and early deglaciation, and 2) constrain the extent of this “old” water in the Southern Pacific as between 1600 m and 3800 m. The availability of atmospheric ages from tephras reveals that the presence of older surface reservoir ages in the glaciation caused the estimation of ventilation ages from simple benthic–planktonic offsets to significantly underestimate the depletion of Δ14C in deep waters. This may have had a role in masking the large change in reservoir ages since the glaciation when using benthic–planktonic reservoir age estimates.

Journal

Earth and Planetary Science LettersElsevier

Published: Mar 15, 2016

References

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 12 million articles from more than
10,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Unlimited reading

Read as many articles as you need. Full articles with original layout, charts and figures. Read online, from anywhere.

Stay up to date

Keep up with your field with Personalized Recommendations and Follow Journals to get automatic updates.

Organize your research

It’s easy to organize your research with our built-in tools.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve Freelancer

DeepDyve Pro

Price
FREE
$49/month

$360/year
Save searches from Google Scholar, PubMed
Create lists to organize your research
Export lists, citations
Access to DeepDyve database
Abstract access only
Unlimited access to over
18 million full-text articles
Print
20 pages/month
PDF Discount
20% off