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 Deglacial carbon cycle changes observed in a compilation of 127 benthic <i>δ</i><sup>13</sup>C time series (20–6 ka)

2018 ◽  
Vol 14 (8) ◽  
pp. 1229-1252 ◽  
Author(s):  
Carlye D. Peterson ◽  
Lorraine E. Lisiecki
Keyword(s):  
Time Series ◽  
Carbon Cycle ◽  
Carbon Storage ◽  
Large Scale ◽  
Deep Ocean ◽  
Atmospheric Co2 ◽  
Last Deglaciation ◽  
Terrestrial Biosphere ◽  
Spatial Coverage ◽  
Ocean Carbon

Abstract. We present a compilation of 127 time series δ13C records from Cibicides wuellerstorfi spanning the last deglaciation (20–6 ka) which is well-suited for reconstructing large-scale carbon cycle changes, especially for comparison with isotope-enabled carbon cycle models. The age models for the δ13C records are derived from regional planktic radiocarbon compilations (Stern and Lisiecki, 2014). The δ13C records were stacked in nine different regions and then combined using volume-weighted averages to create intermediate, deep, and global δ13C stacks. These benthic δ13C stacks are used to reconstruct changes in the size of the terrestrial biosphere and deep ocean carbon storage. The timing of change in global mean δ13C is interpreted to indicate terrestrial biosphere expansion from 19–6 ka. The δ13C gradient between the intermediate and deep ocean, which we interpret as a proxy for deep ocean carbon storage, matches the pattern of atmospheric CO2 change observed in ice core records. The presence of signals associated with the terrestrial biosphere and atmospheric CO2 indicates that the compiled δ13C records have sufficient spatial coverage and time resolution to accurately reconstruct large-scale carbon cycle changes during the glacial termination.

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 Glacial – interglacial atmospheric CO<sub>2</sub> change: a simple "hypsometric effect" on deep-ocean carbon sequestration?

2006 ◽  
Vol 2 (5) ◽  
pp. 711-743 ◽  
Author(s):  
L. C. Skinner
Keyword(s):  
Carbon Sequestration ◽  
Carbon Storage ◽  
Ocean Circulation ◽  
Deep Water ◽  
Deep Sea ◽  
Storage Capacity ◽  
Deep Ocean ◽  
Contributing Factors ◽  
Carbon Reservoir ◽  
Ocean Carbon

Abstract. Given the magnitude and dynamism of the deep marine carbon reservoir, it is almost certain that past glacial – interglacial fluctuations in atmospheric CO2 have relied at least in part on changes in the carbon storage capacity of the deep sea. To date, physical ocean circulation mechanisms that have been proposed as viable explanations for glacial – interglacial CO2 change have focussed almost exclusively on dynamical or kinetic processes. Here, a simple mechanism is proposed for increasing the carbon storage capacity of the deep sea that operates via changes in the volume of southern-sourced deep-water filling the ocean basins, as dictated by the hypsometry of the ocean floor. It is proposed that a water-mass that occupies more than the bottom 3 km of the ocean will essentially determine the carbon content of the marine reservoir. Hence by filling this interval with southern-sourced deep-water (enriched in dissolved CO2 due to its particular mode of formation) the amount of carbon sequestered in the deep sea may be greatly increased. A simple box-model is used to test this hypothesis, and to investigate its implications. It is suggested that up to 70% of the observed glacial – interglacial CO2 change might be explained by the replacement of northern-sourced deep-water below 2.5 km water depth by its southern counterpart. Most importantly, it is found that an increase in the volume of southern-sourced deep-water allows glacial CO2 levels to be simulated easily with only modest changes in Southern Ocean biological export or overturning. If incorporated into the list of contributing factors to marine carbon sequestration, this mechanism may help to significantly reduce the "deficit" of explained glacial – interglacial CO2 change.

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 Simulated Last Glacial Maximum Δ14Catm and the Deep Glacial Ocean Carbon Reservoir

Radiocarbon ◽  
2013 ◽  
Vol 55 (3) ◽  
pp. 1595-1602 ◽  
Author(s):  
V Mariotti ◽  
D Paillard ◽  
D M Roche ◽  
N Bouttes ◽  
L Bopp
Keyword(s):  
Southern Ocean ◽  
Last Glacial Maximum ◽  
Saline Water ◽  
Deep Ocean ◽  
Glacial Maximum ◽  
Last Deglaciation ◽  
Production Term ◽  
Last Glacial ◽  
The Difference ◽  
Ocean Carbon

Δ14Catm has been estimated as 420 ± 80% (IntCal09) during the Last Glacial Maximum (LGM) compared to preindustrial times (0%), but mechanisms explaining this difference are not yet resolved. Δ14Catm is a function of both cosmogenic production in the high atmosphere and of carbon cycling and partitioning in the Earth system. 10Be-based reconstructions show a contribution of the cosmogenic production term of only 200 ± 200% in the LGM. The remaining 220% have thus to be explained by changes in the carbon cycle. Recently, Bouttes et al. (2010, 2011) proposed to explain most of the difference in pCO2atm and Δ13C between glacial and interglacial times as a result of brine-induced ocean stratification in the Southern Ocean. This mechanism involves the formation of very saline water masses that contribute to high carbon storage in the deep ocean. During glacial times, the sinking of brines is enhanced and more carbon is stored in the deep ocean, lowering pCO2atm. Moreover, the sinking of brines induces increased stratification in the Southern Ocean, which keeps the deep ocean well isolated from the surface. Such an isolated ocean reservoir would be characterized by a low Δ14C signature. Evidence of such 14C-depleted deep waters during the LGM has recently been found in the Southern Ocean (Skinner et al. 2010). The degassing of this carbon with low Δ14C would then reduce Δ14Catm throughout the deglaciation. We have further developed the CLIMBER-2 model to include a cosmogenic production of 14C as well as an interactive atmospheric 14C reservoir. We investigate the role of both the sinking of brine and cosmogenic production, alongside iron fertilization mechanisms, to explain changes in Δ14Catm during the last deglaciation. In our simulations, not only is the sinking of brine mechanism consistent with past Δ14C data, but it also explains most of the differences in pCO2atm and Δ14Catm between the LGM and preindustrial times. Finally, this study represents the first time to our knowledge that a model experiment explains glacial-interglacial differences in pCO2atm, Δ13C, and Δ14C together with a coherent LGM climate.

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 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.

On new developments in accelerator mass spectrometry and how they promote our understanding of global carbon cycle dynamics during the last deglaciation

2020 ◽  
Author(s):  
Julia Gottschalk ◽  
Robert F. Anderson ◽  
David A. Hodell ◽  
Alfredo Martinez-Garcia ◽  
Alain Mazaud ◽  
...  
Keyword(s):  
High Resolution ◽  
Southern Ocean ◽  
Bottom Water ◽  
Deep Ocean ◽  
Global Ocean ◽  
Last Deglaciation ◽  
Surface Ocean ◽  
Ocean Atmosphere ◽  
The Last Deglaciation ◽  
Reservoir Age

&lt;p&gt;Ocean-atmosphere &lt;sup&gt;14&lt;/sup&gt;C disequilibria of the surface and deep ocean reflect past changes in the efficiency of ocean-atmosphere CO&lt;sub&gt;2&lt;/sub&gt; exchange and ocean mixing, while it may also be related to variations in global-ocean respired carbon content. A full assessment of the oceanic mechanisms controlling deglacial changes in atmospheric CO&lt;sub&gt;2&lt;/sub&gt; is complicated by a lack of high-resolution &lt;sup&gt;14&lt;/sup&gt;C ventilation age estimates from the Southern Ocean and other key regions due to low foraminiferal abundances in marine sediments in those areas. Here we present high-resolution deglacial &lt;sup&gt;14&lt;/sup&gt;C ventilation age records from key sites in the Atlantic and Indian Sector of the Southern Ocean obtained by radiocarbon analyses of small benthic and planktic foraminiferal samples (&lt;1 mg CaCO&lt;sub&gt;3&lt;/sub&gt;) with the UniBe Mini-Carbon Dating System (MICADAS). Our analyses specifically circumvent foraminiferal sample size requirements related to &amp;#8220;conventional&amp;#8221; accelerator mass spectrometer analyses involving sample graphitization (&gt;1 mg CaCO&lt;sub&gt;3&lt;/sub&gt; in most laboratories). Complementing multi-proxy analyses of sea surface temperature (SST) changes at these sites allow the construction of a radiocarbon-independent age model through a stratigraphic alignment of SST changes to Antarctic (ice core) temperature variations. We demonstrate the value of refining the age models of our study cores on the basis of high-resolution sedimentary U- and Th flux estimates, which allows an improved quantification of surface ocean reservoir age variations in the past. The resulting deep-ocean ventilation age changes are compared against qualitative and quantitative indicators of bottom water [O&lt;sub&gt;2&lt;/sub&gt;] variations, in order to assess the role of Southern Ocean overturning dynamics in respired carbon changes at our study sites. We discuss the implications of our new radiocarbon- and bottom water [O&lt;sub&gt;2&lt;/sub&gt;] data for the ocean&amp;#8217;s role in atmospheric CO&lt;sub&gt;2&lt;/sub&gt; changes throughout the last deglaciation, and evaluate down-stream effects of southern high-latitude surface ocean reservoir age anomalies.&lt;/p&gt;

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