scholarly journals The Evolution of Deep Ocean Chemistry and Respired Carbon in the Eastern Equatorial Pacific Over the Last Deglaciation

2017 ◽  
Vol 32 (12) ◽  
pp. 1371-1385 ◽  
Author(s):  
Maria de la Fuente ◽  
Eva Calvo ◽  
Luke Skinner ◽  
Carles Pelejero ◽  
David Evans ◽  
...  
Keyword(s):  
Deep Ocean ◽  
Equatorial Pacific ◽  
Last Deglaciation ◽  
Eastern Equatorial Pacific ◽  
The Last Deglaciation ◽  
Ocean Chemistry

scholarly journals Links between eastern equatorial Pacific stratification and atmospheric CO 2 rise during the last deglaciation

2015 ◽  
Vol 30 (11) ◽  
pp. 1407-1424 ◽  
Author(s):  
Samantha C. Bova ◽  
Timothy Herbert ◽  
Yair Rosenthal ◽  
Julie Kalansky ◽  
Mark Altabet ◽  
...  
Keyword(s):  
Equatorial Pacific ◽  
Last Deglaciation ◽  
Eastern Equatorial Pacific ◽  
The Last Deglaciation

scholarly journals Increase in water column denitrification during the deglaciation controlled by oxygen demand in the eastern equatorial Pacific

2009 ◽  
Vol 6 (3) ◽  
pp. 5145-5161 ◽  
Author(s):  
P. Martinez ◽  
R. S. Robinson
Keyword(s):  
Water Column ◽  
Oxygen Demand ◽  
Deep Ocean ◽  
Leading Edge ◽  
Last Deglaciation ◽  
Equatorial Undercurrent ◽  
Export Production ◽  
Eastern Equatorial Pacific ◽  
The Last Deglaciation ◽  
Oxygen Minimum

Abstract. Here we present organic export production and isotopic nitrogen results over the last 30 000 years from one core localized off Costa Rica (ODP Site 1242) on the leading edge of the oxygen minimum zone of the Eastern Tropical North Pacific. Marine export production reveals glacial-interglacial variations with low organic matter (total organic carbon and total nitrogen) contents during warm intervals, twice more during cold episodes and double peaked maximum during the deglaciation, between ~15.5–18.5 and 11–13 ka BP. When this new export production record is compared with four nearby cores localized within the Eastern Pacific along the Equatorial divergence, a good agreement between all the cores is observed, with the major feature being a maximum of export during the early deglaciation. As for export production, water-column denitrification represented by sedimentary δ15N records along the Eastern tropical North and South Pacific between 15° N and 36° S is coherent as well over the last deglaciation period. The whole isotopic nitrogen profiles indicate that denitrification increased abruptly at 19 ka BP to a maximum during the early deglaciation, confirming a typical Antarctic timing. It is proposed that the increase in export production and then in subsurface oxygen demand lead to an intensification of water-column denitrification within the oxygen minimum zones in the easternmost Pacific at the time of the last deglaciation. The triggering mechanism would have been primarily linked to an increase in preformed nutrients contents feeding the Equatorial Undercurrent driven by the resumption of overturning in the Southern Ocean and the return of nutrients from the deep ocean to the sea-surface. An increase in equatorial wind-driven upwelling of sub-surface nutrient-rich waters could have played the role of an amplifier.

scholarly journals The Atmospheric Bridge Communicated the δ<sup>13</sup>C Decline during the Last Deglaciation to the Global Upper Ocean

2020 ◽  
Author(s):  
Jun Shao ◽  
Lowell D Stott ◽  
Laurie Menviel ◽  
Andy Ridgwell ◽  
Malin Ödalen ◽  
...  
Keyword(s):  
Nutrient Transport ◽  
Deep Ocean ◽  
Upper Ocean ◽  
Last Deglaciation ◽  
Planktic Foraminifera ◽  
Proxy Records ◽  
Deep Waters ◽  
Eastern Equatorial Pacific ◽  
The Last Deglaciation ◽  
Atmospheric Pco2

Abstract. During the early last glacial termination (17.2–15 ka) atmospheric δ13C declined sharply by 0.3–0.4 ‰ as atmospheric pCO2 rose. This was the initial part of the atmospheric δ13C excursion that lasted for multiple thousand years. A similar δ13C decline has been documented in marine proxy records from both surface and thermocline-dwelling planktic foraminifera. The foraminiferal δ13C decline has previously been attributed to a flux of respired carbon from the deep ocean that was subsequently transported within the upper ocean (i.e. bottom up transport) to sites where the signal is recorded. Here, we provide modeling evidence that when respired carbon upwells in the Southern Ocean, negative δ13C anomalies in the global upper ocean were instead transferred from the atmosphere (i.e. top down transport). Due to this efficient atmospheric bridge, the pathway of δ13C transport was likely to be different from nutrient transport during the early deglaciation. This implies that the usage of planktic δ13C records for identifying the carbon source(s) responsible for the atmospheric pCO2 rise during the early deglaciation is limited. The model results also suggest that thermocline waters in upwelling systems like the eastern equatorial Pacific, and even upper deep waters above 2000 m, can be affected by this atmospheric bridge during the early deglaciation. Our results imply that caution must be applied when interpreting early deglacial marine δ13C records from depths that are potentially affected by the atmosphere.

scholarly journals Different ocean states and transient characteristics in Last Glacial Maximum simulations and implications for deglaciation

2013 ◽  
Vol 9 (5) ◽  
pp. 2319-2333 ◽  
Author(s):  
X. Zhang ◽  
G. Lohmann ◽  
G. Knorr ◽  
X. Xu
Keyword(s):  
Last Glacial Maximum ◽  
Model Comparison ◽  
Climate Model ◽  
Deep Ocean ◽  
Glacial Maximum ◽  
Meridional Overturning Circulation ◽  
Last Deglaciation ◽  
New Paradigm ◽  
Last Glacial ◽  
The Last Deglaciation

Abstract. The last deglaciation is one of the best constrained global-scale climate changes documented by climate archives. Nevertheless, understanding of the underlying dynamics is still limited, especially with respect to abrupt climate shifts and associated changes in the Atlantic meridional overturning circulation (AMOC) during glacial and deglacial periods. A fundamental issue is how to obtain an appropriate climate state at the Last Glacial Maximum (LGM, 21 000 yr before present, 21 ka BP) that can be used as an initial condition for deglaciation. With the aid of a comprehensive climate model, we found that initial ocean states play an important role on the equilibrium timescale of the simulated glacial ocean. Independent of the initialization, the climatological surface characteristics are similar and quasi-stationary, even when trends in the deep ocean are still significant, which provides an explanation for the large spread of simulated LGM ocean states among the Paleoclimate Modeling Intercomparison Project phase 2 (PMIP2) models. Accordingly, we emphasize that caution must be taken when alleged quasi-stationary states, inferred on the basis of surface properties, are used as a reference for both model inter-comparison and data model comparison. The simulated ocean state with the most realistic AMOC is characterized by a pronounced vertical stratification, in line with reconstructions. Hosing experiments further suggest that the response of the glacial ocean is dependent on the ocean background state, i.e. only the state with robust stratification shows an overshoot behavior in the North Atlantic. We propose that the salinity stratification represents a key control on the AMOC pattern and its transient response to perturbations. Furthermore, additional experiments suggest that the stratified deep ocean formed prior to the LGM during a time of minimum obliquity (~ 27 ka BP). This indicates that changes in the glacial deep ocean already occur before the last deglaciation. In combination, these findings represent a new paradigm for the LGM and the last deglaciation, which challenges the conventional evaluation of glacial and deglacial AMOC changes based on an ocean state derived from 21 ka BP boundary conditions.

scholarly journals Ventilation of the Deep Ocean Carbon Reservoir During the Last Deglaciation: Results From the Southeast Pacific

2019 ◽  
Vol 34 (12) ◽  
pp. 2080-2097 ◽  
Author(s):  
Consuelo Martínez Fontaine ◽  
Ricardo De Pol‐Holz ◽  
Elisabeth Michel ◽  
Giuseppe Siani ◽  
Dharma Reyes‐Macaya ◽  
...  
Keyword(s):  
Deep Ocean ◽  
Last Deglaciation ◽  
Southeast Pacific ◽  
Carbon Reservoir ◽  
The Last Deglaciation ◽  
Ocean Carbon

scholarly journals Rapid shifts in circulation and biogeochemistry of the Southern Ocean during deglacial carbon cycle events

2020 ◽  
Vol 6 (42) ◽  
pp. eabb3807
Author(s):  
Tao Li ◽  
Laura F. Robinson ◽  
Tianyu Chen ◽  
Xingchen T. Wang ◽  
Andrea Burke ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Ocean Circulation ◽  
Deep Sea ◽  
Deep Ocean ◽  
Biological Pump ◽  
Last Deglaciation ◽  
Proxy Data ◽  
Ocean Ventilation ◽  
Carbon Release ◽  
The Last Deglaciation

The Southern Ocean plays a crucial role in regulating atmospheric CO2 on centennial to millennial time scales. However, observations of sufficient resolution to explore this have been lacking. Here, we report high-resolution, multiproxy records based on precisely dated deep-sea corals from the Southern Ocean. Paired deep (∆14C and δ11B) and surface (δ15N) proxy data point to enhanced upwelling coupled with reduced efficiency of the biological pump at 14.6 and 11.7 thousand years (ka) ago, which would have facilitated rapid carbon release to the atmosphere. Transient periods of unusually well-ventilated waters in the deep Southern Ocean occurred at 16.3 and 12.8 ka ago. Contemporaneous atmospheric carbon records indicate that these Southern Ocean ventilation events are also important in releasing respired carbon from the deep ocean to the atmosphere. Our results thus highlight two distinct modes of Southern Ocean circulation and biogeochemistry associated with centennial-scale atmospheric CO2 jumps during the last deglaciation.

scholarly journals The atmospheric bridge communicated the <i>δ</i><sup>13</sup>C decline during the last deglaciation to the global upper ocean

2021 ◽  
Vol 17 (4) ◽  
pp. 1507-1521
Author(s):  
Jun Shao ◽  
Lowell D. Stott ◽  
Laurie Menviel ◽  
Andy Ridgwell ◽  
Malin Ödalen ◽  
...  
Keyword(s):  
Fossil Fuel ◽  
Deep Ocean ◽  
Upper Ocean ◽  
Last Deglaciation ◽  
Planktic Foraminifera ◽  
Proxy Records ◽  
The Last Deglaciation ◽  
The Tropical Pacific ◽  
The Last Glacial

Abstract. During the early part of the last glacial termination (17.2–15 ka) and coincident with a ∼35 ppm rise in atmospheric CO2, a sharp 0.3‰–0.4‰ decline in atmospheric δ13CO2 occurred, potentially constraining the key processes that account for the early deglacial CO2 rise. A comparable δ13C decline has also been documented in numerous marine proxy records from surface and thermocline-dwelling planktic foraminifera. The δ13C decline recorded in planktic foraminifera has previously been attributed to the release of respired carbon from the deep ocean that was subsequently transported within the upper ocean to sites where the signal was recorded (and then ultimately transferred to the atmosphere). Benthic δ13C records from the global upper ocean, including a new record presented here from the tropical Pacific, also document this distinct early deglacial δ13C decline. Here we present modeling evidence to show that rather than respired carbon from the deep ocean propagating directly to the upper ocean prior to reaching the atmosphere, the carbon would have first upwelled to the surface in the Southern Ocean where it would have entered the atmosphere. In this way the transmission of isotopically light carbon to the global upper ocean was analogous to the ongoing ocean invasion of fossil fuel CO2. The model results suggest that thermocline waters throughout the ocean and 500–2000 m water depths were affected by this atmospheric bridge during the early deglaciation.

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