Revealing past ocean circulation with neodymium isotopes

doi:10.22498/pages.27.2.54

Cited by 4 publications

(5 citation statements)

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“…The release of heat in the North Atlantic influences the climate of northeastern Europe, leading to relatively mild winter temperatures. (McCarthy et al, 2017) Nd is used as a tracer for ocean circulation (Dausmann et al, 2017;Blaser et al, 2019). Erosion and weathering of continental crust, which displays characteristic, isotopic signatures from the Samarium-Neodymium decay system for different continents, is the source of dissolved Nd in the ocean water.…”

Section: Possible Influence Of the Amoc Strengthmentioning

confidence: 99%

“…Erosion and weathering of continental crust, which displays characteristic, isotopic signatures from the Samarium-Neodymium decay system for different continents, is the source of dissolved Nd in the ocean water. After entry to the sea, convection of the characteristic Nd signature to deep waters allows this tracer to reconstruct large-scale ocean circulations (Blaser et al, 2019).…”

Section: Possible Influence Of the Amoc Strengthmentioning

confidence: 99%

“…Water originating in the Northern Atlantic is known to develop more negative Nd values in comparison to waters of other origin (Dausmann et al, 2017;Blaser et al, 2019). In the study of Dausmann et al (2017) a continuous high-resolution record for Nd at ODP Site 1088 in the Southern Atlantic was (Fig.…”

Section: Possible Influence Of the Amoc Strengthmentioning

confidence: 99%

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Test-Size Evolution of the planktonic Foraminifera <i>Globorotalia menardii</i> in the Eastern Tropical Atlantic since the Late Miocene

Friesenhagen

2021

Preprint

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Abstract. The mean test size of planktonic foraminifera (PF) is known to have increased especially during the last 12 Ma, probably in terms of an adaptive response to an intensification of the surface-water stratification. On geologically short timescales, the test size in PF is related to environmental conditions. In an optimal species-specific environment, individuals exhibit a greater maximum and average test size, while the size decreases the more unfavourable the environment becomes. An interesting case was observed in the late Neogene and Quaternary size evolution of Globorotalia menardii, which seems to be too extreme to be only explained by changes in environmental conditions. In the western tropical Atlantic Ocean (WTAO) and the Caribbean Sea, the test size more than doubles from 2.6 Ma to 1.95 Ma and 1.7 Ma, respectively, following an almost uninterrupted and successive phase of test size decrease from 4 Ma. Two hypotheses have been suggested to explain the sudden occurrence of a giant G. menardii form: it was triggered by either (1) a punctuated, regional evolutionary event or (2) the immigration of specimens from the Indian Ocean via the Agulhas Leakage. Morphometric measurements of tests from sediment samples of the Ocean Drilling Program (ODP) Leg 108 Hole 667A in the eastern tropical Atlantic Ocean (ETAO), show that the giant type already appears 0.1 Ma earlier at this location than in the WTAO, which indicates that the extreme size increase in the early Pleistocene was a tropical-Atlantic-Ocean-wide event. A coinciding change in the predominant coiling direction suggests that probably a new morphotype occurred. If the giant size and the uniform change in the predominant coiling direction are an indicator for this new type, the form already occurred in the eastern tropical Pacific Ocean at the Pliocene/Pleistocene boundary at 2.58 Ma. This finding supports the Agulhas Leakage hypothesis. However, the hypothesis of a regional, punctuated evolutionary event cannot be dismissed due to missing data from the Indian Ocean. This paper presents the AMOC/thermocline hypothesis, which not only suggests an alternative explanation for the sudden test-size increase in the early Pleistocene, but also for the test size evolution within the whole tropical Atlantic Ocean and the Caribbean Sea for the last 8 Ma. The test-size evolution shows a similar trend with indicators for changes in the Atlantic Meridional Overturning Circulation (AMOC) strength. The mechanism behind that might be that changes in the AMOC strength have a major influence on the thermal stratification of the upper water column, which is known to be the habitat of G. menardii.

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Section: Possible Influence Of the Amoc Strengthmentioning

confidence: 99%

Section: Possible Influence Of the Amoc Strengthmentioning

confidence: 99%

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Test-Size Evolution of the planktonic Foraminifera <i>Globorotalia menardii</i> in the Eastern Tropical Atlantic since the Late Miocene

Friesenhagen

2021

Preprint

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“…Unlike other tracers of ocean circulation (e.g. δ 13 C, 14 C), Nd is not fractionated by marine biological cycling, giving rise to its promise as a carbon-cycleindependent ocean circulation tracer (Blaser et al, 2019a). Yet, a fundamental caveat in the application of ε Nd as a reliable oceanographic tracer is that knowledge of the Nd fluxes in and out of the ocean remains incomplete, and while internal cycling must occur, the efficiency of it with different particle types is poorly constrained (Abbott et al, 2015a;Haley et al, 2017;.…”

Section: Introductionmentioning

confidence: 99%

Simulating marine neodymium isotope distributions using Nd v1.0 coupled to the ocean component of the FAMOUS–MOSES1 climate model: sensitivities to reversible scavenging efficiency and benthic source distributions

et al. 2023

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Abstract. The neodymium (Nd) isotopic composition of seawater is a widely used ocean circulation tracer. However, uncertainty in quantifying the global ocean Nd budget, particularly constraining elusive non-conservative processes, remains a major challenge. A substantial increase in modern seawater Nd measurements from the GEOTRACES programme, coupled with recent hypotheses that a seafloor-wide benthic Nd flux to the ocean may govern global Nd isotope distributions (εNd), presents an opportunity to develop a new scheme specifically designed to test these paradigms. Here, we present the implementation of Nd isotopes (143Nd and 144Nd) into the ocean component of the FAMOUS coupled atmosphere–ocean general circulation model (Nd v1.0), a tool which can be widely used for simulating complex feedbacks between different Earth system processes on decadal to multi-millennial timescales. Using an equilibrium pre-industrial simulation tuned to represent the large-scale Atlantic Ocean circulation, we perform a series of sensitivity tests evaluating the new Nd isotope scheme. We investigate how Nd source and sink and cycling parameters govern global marine εNd distributions and provide an updated compilation of 6048 Nd concentrations and 3278 εNd measurements to assess model performance. Our findings support the notions that reversible scavenging is a key process for enhancing the Atlantic–Pacific basinal εNd gradient and is capable of driving the observed increase in Nd concentration along the global circulation pathway. A benthic flux represents a major source of Nd to the deep ocean. However, model–data disparities in the North Pacific highlight that under a uniform benthic flux, the source of εNd from seafloor sediments is too non-radiogenic in our model to be able to accurately represent seawater measurements. Additionally, model–data mismatch in the northern North Atlantic alludes to the possibility of preferential contributions from “reactive” non-radiogenic detrital sediments. The new Nd isotope scheme forms an excellent tool for exploring global marine Nd cycling and the interplay between climatic and oceanographic conditions under both modern and palaeoceanographic contexts.

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“…Owing to somewhat poorly constrained input and output fluxes, the estimated mean ocean residence time of Nd ranges between 360-800 years (Arsouze et al, 2009;Rempfer et al, 2011;Gu et al, 2019;Pöppelmeier et al, 2020a), which is less than the global thermohaline overturning circulation time (i.e., < 1,500 years). The measured Nd isotope composition of seawater is not actively involved in marine biological cycling (Blaser et al, 2019a).…”

Section: Introductionmentioning

confidence: 99%

Optimisation of the marine Nd isotope scheme in the ocean component of the FAMOUS general circulation model

Robinson

Ivanovic²,

Gregoire³

et al. 2022

Preprint

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Abstract. The neodymium (Nd) isotope composition (εNd) of seawater can be used to trace large-scale ocean circulation features. Yet, due to the elusive nature of marine Nd cycling, particularly in discerning non-conservative particle-seawater interactions, there remains considerable uncertainty surrounding a complete description of marine Nd budgets. Here, we present an optimisation of the Nd isotope scheme within the fast coupled atmosphere-ocean general circulation model (FAMOUS), using a statistical emulator to explore the parametric uncertainty and optimal combinations of three key model inputs relating to: (1) the efficiency of reversible scavenging, (2) the magnitude of the seafloor benthic flux, and (3) a riverine source scaling, accounting for release of Nd from river sourced particulate material. Furthermore, a suite of sensitivity tests provide insight on the regional mobilisation and spatial extent (i.e., testing a margin-constrained versus a seafloor-wide benthic flux) of certain reactive sediment components. In the calibrated scheme, the global marine Nd inventory totals 4.27 × 1012 g and has a mean residence time of 727 years. Atlantic Nd isotope distributions are represented well, and the weak sensitivity of North Atlantic Deep Water to highly unradiogenic sedimentary sources implies an abyssal benthic flux is of secondary importance in determining the water mass εNd properties under the modern vigorous circulation condition. On the other hand, Nd isotope distributions in the North Pacific are 3 to 4 εNd-units too unradiogenic compared to water measurements, and our simulations indicate that a spatially uniform flux of bulk sediment εNd does not sufficiently capture the mobile sediment components interacting with seawater. Our results of sensitivity tests suggest that there are distinct regional differences in how modern seawater acquires its εNd signal, in part relating to the complex interplay of Nd addition and water advection.

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Revealing past ocean circulation with neodymium isotopes

Cited by 4 publications

References 10 publications

Test-Size Evolution of the planktonic Foraminifera <i>Globorotalia menardii</i> in the Eastern Tropical Atlantic since the Late Miocene

Test-Size Evolution of the planktonic Foraminifera <i>Globorotalia menardii</i> in the Eastern Tropical Atlantic since the Late Miocene

Simulating marine neodymium isotope distributions using Nd v1.0 coupled to the ocean component of the FAMOUS–MOSES1 climate model: sensitivities to reversible scavenging efficiency and benthic source distributions

Optimisation of the marine Nd isotope scheme in the ocean component of the FAMOUS general circulation model

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Revealing past ocean circulation with neodymium isotopes

Cited by 4 publications

References 10 publications

Test-Size Evolution of the planktonic Foraminifera &lt;i&gt;Globorotalia menardii&lt;/i&gt; in the Eastern Tropical Atlantic since the Late Miocene

Test-Size Evolution of the planktonic Foraminifera &lt;i&gt;Globorotalia menardii&lt;/i&gt; in the Eastern Tropical Atlantic since the Late Miocene

Simulating marine neodymium isotope distributions using Nd v1.0 coupled to the ocean component of the FAMOUS–MOSES1 climate model: sensitivities to reversible scavenging efficiency and benthic source distributions

Optimisation of the marine Nd isotope scheme in the ocean component of the FAMOUS general circulation model

Contact Info

Product

Resources

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Test-Size Evolution of the planktonic Foraminifera <i>Globorotalia menardii</i> in the Eastern Tropical Atlantic since the Late Miocene

Test-Size Evolution of the planktonic Foraminifera <i>Globorotalia menardii</i> in the Eastern Tropical Atlantic since the Late Miocene