Variations in the particulate flux of Th-230 and Pa-231 and paleoceanograhpic applications of the Pa-231/Th-231 ratio

Yu, Ein-Fen

doi:10.1575/1912/5564

Cited by 19 publications

(18 citation statements)

References 80 publications

(179 reference statements)

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“…5. The linear regression coefficient between model results and observations (references of observations are listed in Table 3), an indication of model ability to simulate 231 Pa and 230 Th activity Guo et al, 1995Yu, 1994Cochran et al, 1987DeMaster, 1979Bacon and Rosholt, 1982Bacon and Anderson, 1982Mangini and Diester-Hass, 1983Bacon et al, 1989Kumar, 1994Huh and Beasley, 1987Yang et al, 1986Rutgers van der Loeff and Berger, 1993Anderson et al, 1983Nozaki et al, 1981Anderson et al, 1994Nozaki and Nakanishi, 1985Ku, 1966Mangini and Key, 1983Ku et al, 1972Nozaki and Horibe, 1983Frank et al, 1994Moore, 1981Shimmield et al, 1986Frank, 1996Roy-Barman et al, 1996Yong Lao et al, 1992Francois et al, 1993Moran et al, 1995Anderson et al, 1990Luo et al, 1995Mangini and Sonntag, 1977Colley et al, 1995Schmitz et al, 1986Scholten et al, 1995Shimmield and Price, 1988Cochran et al, 1995Yong-Liang Yang et al, 1995Vogler et al, 1998Müller and Mangini, 1980Moran et al, 1997Mangini and Kühnel, 1987…”

Section: Methodsmentioning

confidence: 99%

231Pa and 230Th in the ocean model of the Community Earth System Model (CESM1.3)

Liu

2017

Geosci. Model Dev.

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Abstract. The sediment 231 Pa / 230 Th activity ratio is emerging as an important proxy for deep ocean circulation in the past. In order to allow for a direct model-data comparison and to improve our understanding of the sediment 231 Pa / 230 Th activity ratio, we implement 231 Pa and 230 Th in the ocean component of the Community Earth System Model (CESM). In addition to the fully coupled implementation of the scavenging behavior of 231 Pa and 230 Th with the active marine ecosystem module (particle-coupled: hereafter p-coupled), another form of 231 Pa and 230 Th have also been implemented with prescribed particle flux fields of the present climate (particle-fixed: hereafter p-fixed). The comparison of the two forms of 231 Pa and 230 Th helps to isolate the influence of the particle fluxes from that of ocean circulation. Under present-day climate forcing, our model is able to simulate water column 231 Pa and 230 Th activity and the sediment 231 Pa / 230 Th activity ratio in good agreement with available observations. In addition, in response to freshwater forcing, the p-coupled and p-fixed sediment 231 Pa / 230 Th activity ratios behave similarly over large areas of low productivity on long timescales, but can differ substantially in some regions of high productivity and on short timescales, indicating the importance of biological productivity in addition to ocean transport. Therefore, our model provides a potentially powerful tool to help the interpretation of sediment 231 Pa / 230 Th reconstructions and to improve our understanding of past ocean circulation and climate changes.

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Section: Methodsmentioning

confidence: 99%

231Pa and 230Th in the ocean model of the Community Earth System Model (CESM1.3)

Liu

2017

Geosci. Model Dev.

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“…We assembled from the literature 185 Th‐normalized opal burial measurements from surface sediments of the Southern Ocean (defined as south of 40°S) (Figure and Table ). The majority of the measurements (111) are from Geibert et al [], with the remainder from eight other publications [ Bradtmiller et al , ; Chase et al , ; Dezileau et al , ; Frank et al , , ; Kumar , ; Pondaven et al , ; Yu , ] that extend the geographic coverage into the SW Pacific and Indian oceans. We also compiled a total of 493 opal concentration measurements (Figure ), largely composed of measurements made at LDEO (L. Burkle, pers.…”

Section: Methodsmentioning

confidence: 99%

Controls on biogenic silica burial in the Southern Ocean

Chase

Kohfeld

Matsumoto

2015

Global Biogeochemical Cycles

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Understanding the controls on opal export in the Southern Ocean can inform both the prediction of how the leakage of silicic acid from the Southern Ocean responds to climate and the interpretation of paleo-proxies. We have compiled a database of 185 230 Thorium-normalized opal burial rates and 493 opal concentration measurements in Southern Ocean sediments and matched these with environmental climatologies. By subdividing the Southern Ocean on the basis of oceanographic regions and interpolating the opal burial rates, we estimate a total biogenic Si burial south of 40°S of 2.3 ± 1.0 Tmol Si yr À1. In both the seasonally ice-covered and permanently ice-free regions we can explain 73% of opal burial variability from surface ocean properties. Where sea ice is present for at least part of the year, the length of the ice-free season determines the upper limit of opal burial in the underlying sediments. In the ice-free regions of the Southern Ocean, the supply of silicic acid through winter mixing is the most important factor. Our results do not support a strong role of iron in controlling opal burial. We do however find that satellite-derived net primary production increases with increasing (modeled) dust delivery. These findings support the decoupling between carbon and opal fluxes in the Southern Ocean. When corrected for opal dissolution, the observed opal fluxes are in reasonable agreement with fluxes simulated using an ocean biogeochemical model. However, the results suggest current preservation algorithms for opal could be improved by incorporating the composition of particle flux, not only its magnitude.

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“…231 Pa o / ex. 230 Th o and particle flux is complex 25 , however, and depends on the particle flux not only at the site of study, but also at neighbouring sites, on the rate of lateral transport of 231 Pa between sites, and on opal concentration in settling particles 26 . In particular, when applying this approach to the Southern Ocean, advection of 231 Pa from the Atlantic Ocean with North Atlantic Deep Water must be taken into consideration, as ϳ50% of the 231 Pa produced in the Atlantic is exported into the Southern Ocean 27 Subantarctic Front (Fig.…”

Section: Opal Fluxesmentioning

confidence: 99%

Contribution of Southern Ocean surface-water stratification to low atmospheric CO2 concentrations during the last glacial period

Franois¹,

Altabet

et al. 1997

Nature

Self Cite

548

424

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The nitrogen-isotope record preserved in Southern Ocean sediments, along with several geochemical tracers for the settling fluxes of biogenic matter, reveals patterns of past nutrient supply to phytoplankton and surface-water stratification in this oceanic region. Areal averaging of these spatial patterns indicates that reduction of the CO 2 'leak' from ocean to atmosphere by increased surface-water stratification south of the Polar Front made a greater contribution to the lowering of atmospheric CO 2 concentration during the Last Glacial Maximum than did the increased export of organic carbon from surface to deep waters occurring further north.The unstratified, nutrient-rich surface waters in the modern highlatitude ocean provide the main conduit for transferring deep-water CO 2 back into the atmosphere. This CO 2 'leak' to the atmosphere is particularly effective in the modern Southern Ocean, because of intensive vertical mixing and low nutrient utilization. Building on this observation, a series of papers 1-6 attributed the glacial lowering of atmospheric CO 2 either to enhanced biological removal of the nutrients and CO 2 in high-latitude surface waters resulting in higher sinking fluxes of organic matter (that is, higher export production), or to a lower supply rate of nutrients and CO 2 from intermediate waters produced by lower vertical mixing. But the extensive deepor intermediate-water anoxia predicted by these models, and the lack of palaeo-oceanographic evidence for increased export production in the glacial Southern Ocean, has led to the questioning of the validity of these models. Here we present new evidence which supports increased stratification south of the position of the modern Polar Front (MPF) during the Last Glacial Maximum as a mechanism that contributed to lower glacial atmospheric CO 2 and deep-water oxygen concentration.The sedimentary record of several palaeoproductivity proxies was recently presented as support for a large increase in the export flux of organic carbon in the Atlantic sector of the Southern Ocean, north of the position of the MPF, which could have contributed to lowering glacial atmospheric CO 2 as a result of Fe fertilization 7 . Here we combine a similar suite of geochemical proxies for palaeoproductivity and its fate with bulk-sediment d 15 N values to better constrain past changes in the nutrient balance of surface waters and its influence on atmospheric CO 2 . Bulk-sediment d 15 N provides a means of evaluating the fraction of surface nitrate utilized by phytoplankton [8][9][10][11] . By combining this information with export flux of nitrogen estimated from palaeoproductivity proxies, we constrain the supply rate of nitrate to surface waters. Our results indicate that, despite higher export flux of organic carbon in the Atlantic sector of the Southern Ocean north of the MPF during the last glacial period, the fraction of nitrate utilized by phytoplankton in this region did not increase, implying a sustained supply of nutrients (and thus CO 2 ) to surface waters. In...

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Variations in the particulate flux of Th-230 and Pa-231 and paleoceanograhpic applications of the Pa-231/Th-231 ratio

Cited by 19 publications

References 80 publications

<sup>231</sup>Pa and <sup>230</sup>Th in the ocean model of the Community Earth System Model (CESM1.3)

<sup>231</sup>Pa and <sup>230</sup>Th in the ocean model of the Community Earth System Model (CESM1.3)

Controls on biogenic silica burial in the Southern Ocean

Contribution of Southern Ocean surface-water stratification to low atmospheric CO2 concentrations during the last glacial period

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Variations in the particulate flux of Th-230 and Pa-231 and paleoceanograhpic applications of the Pa-231/Th-231 ratio

Cited by 19 publications

References 80 publications

&lt;sup&gt;231&lt;/sup&gt;Pa and &lt;sup&gt;230&lt;/sup&gt;Th in the ocean model of the Community Earth System Model (CESM1.3)

&lt;sup&gt;231&lt;/sup&gt;Pa and &lt;sup&gt;230&lt;/sup&gt;Th in the ocean model of the Community Earth System Model (CESM1.3)

Controls on biogenic silica burial in the Southern Ocean

Contribution of Southern Ocean surface-water stratification to low atmospheric CO2 concentrations during the last glacial period

Contact Info

Product

Resources

About

<sup>231</sup>Pa and <sup>230</sup>Th in the ocean model of the Community Earth System Model (CESM1.3)

<sup>231</sup>Pa and <sup>230</sup>Th in the ocean model of the Community Earth System Model (CESM1.3)