杜江辉 Jianghui Du

I am an Assistant Professor in the School of Earth and Space Sciences at Peking University in Beijing, China.

The overarching theme of my research is to understand the evolution of the ocean, climate, and Earth systems and the interactions between them. This inquiry provides insights into climate change and its feedback mechanisms, the maintenance of Earth’s habitability and its role in the origin and evolution of life, and the health of marine ecosystems and economies.

My approach is biogeochemical, through the study of the natural and perturbed cycles of chemical elements in the ocean both today and in the past, to trace the climatic, physical, biological, and geological processes within the ocean and at its boundaries, contributing to the knowledge of how these fundamental processes shape the ocean environment and global climate.

My tools of the trade are trace elements and isotopes (TEIs), which either participate in the biogeochemical cycling of major elements (such as oxygen and carbon), or are remarkably sensitive indicators of ocean and Earth processes. My research combines analytical and modeling methods for quantitative understanding of marine TEI cycles.

news

Feb 19, 2024	I have recented moved to Beijing, China, as an Assistant Professor in the School of Earth and Space Sciences at Peking University, starting from Febrary 2024.
Nov 1, 2023	My paper describing SedTrace, a tool for generating and runing marine sediment diagenetic models, has been published in Geoscientific Model Development. The open-source code can be found on Zenodo.
Jul 29, 2023	I’m changing my website using a new theme!

selected publications

2023

ChemOcean

Model

SedTrace 1.0: a Julia-based framework for generating and running reactive-transport models of marine sediment diagenesis specializing in trace elements and isotopes

Jianghui Du

Geoscientific Model Development, 2023

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2022

ChemOcean

Nd_isotopes

Reactive-transport modeling of neodymium and its radiogenic isotope in deep-sea sediments: The roles of authigenesis, marine silicate weathering and reverse weathering

Jianghui Du, Brian A. Haley, Alan C. Mix, April N. Abbott, James McManus, and Derek Vance

Earth and Planetary Science Letters, 2022

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Dissolved Rare Earth Elements (REE) and radiogenic neodymium (epsilon(Nd)) isotope composition (ENd) of seawater are widely used geochemical tools in studying marine processes, but their modern ocean budgets are poorly understood. Recent discoveries of large benthic fluxes of REE with unique epsilon(Nd) signatures from marine sediments, particularly in the deep-sea, have led to a “bottom-up” hypothesis, which suggests that early diagenesis below the sediment-water interface (SWI) controls the ocean’s REE and epsilon(Nd) budgets. To investigate such sedimentary processes, we created a reactive-transport model for the biogeochemical cycling of Nd and epsilon(Nd) in marine sediments. Here, we attempt to quantify the roles of authigenesis, marine silicate weathering and reverse weathering in the diagenetic cycling of Nd and epsilon(Nd) at a deep-sea (3000 m) site on the Oregon margin. Our model predicts that, at this site, Nd carried by Fe/Mn oxides into sediments eventually transforms to authigenic Nd-phosphate, during which similar to 9% of the incoming solid Nd flux is released as a dissolved benthic flux back to the overlying bottom water. We also find that the classic reversible scavenging formulation applied to Nd co-cycling with Fe/Mn oxides is inconsistent with the data. Rather, a co-precipitation formulation, assuming Nd is structurally incorporated into Fe/Mn oxides, successfully simulates the data. The model also shows that authigenesis alone cannot explain the pore water and authigenic epsilon(Nd), which are both more radiogenic than bottom water at this site. However, the weathering of volcanic silicates sourced from the local subduction zone can successfully explain epsilon(Nd). We suggest that, because reverse weathering by authigenic clay formation maintains the under-saturation of primary silicates in pore water, marine silicate weathering can proceed. The processes we model likely affect the sedimentary cycling of many other trace elements and isotopes, with much broader implications for the understanding of ocean biogeochemistry. (C) 2022 The Author(s). Published by Elsevier B.V.
PaleoOcean

Deoxygenation

Volcanic trigger of ocean deoxygenation during Cordilleran ice sheet retreat

Jianghui Du, Alan C. Mix, Brian A. Haley, Christina L. Belanger, and Sharon

Nature, 2022

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North Pacific deoxygenation events during the last deglaciation were sustained over millennia by high export productivity, but the triggering mechanisms and their links to deglacial warming remain uncertain(1-3). Here we find that initial deoxygenation in the North Pacific immediately after the Cordilleran ice sheet (CIS) retreat(4) was associated with increased volcanic ash in seafloor sediments. Timing of volcanic inputs relative to CIS retreat suggests that regional explosive volcanism was initiated by ice unloading(5,6). We posit that iron fertilization by volcanic ash(7-9) during CIS retreat fuelled ocean productivity in this otherwise iron-limited region, and tipped the marine system towards sustained deoxygenation. We also identify older deoxygenation events linked to CIS retreat over the past approximately 50,000 years (ref. (4)). Our findings suggest that the apparent coupling between the atmosphere, ocean, cryosphere and solid-Earth systems occurs on relatively short timescales and can act as an important driver for ocean biogeochemical change. Deoxygenation in the North Pacific immediately after the Cordilleran ice sheet retreat was shown to be linked with volcanism, suggesting that coupling between atmosphere, ocean, cryosphere and solid-Earth systems can drive biogeochemical change.

2020

PaleoOcean

Ocean_circulation

Evolution of the Global Overturning Circulation since the Last Glacial Maximum based on marine authigenic neodymium isotopes

Jianghui Du, Brian A. Haley, and Alan C. Mix

Quaternary Science Reviews, 2020

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The Global Overturning Circulation is linked to climate change on glacial-interglacial and multi-millennial timescales. The understanding of past climate-circulation links remains hindered by apparent conflicts among proxy measures of circulation. Here we reconstruct circulation changes since the Last Glacial Maximum (LGM) based on a global synthesis of authigenic neodymium isotope records (epsilon(Nd)). We propose the bottom-up framework of interpreting seawater and authigenic epsilon(Nd) considering not only conservative watermass mixing, but also the preformed properties and the non-conservative behavior of epsilon(Nd), both subject to sedimentary influences. We extract the major spatial-temporal modes of authigenic epsilon(Nd) using Principal Component Analysis, and make a first-order circulation reconstruction with budget-constrained box model simulations. We show that during the LGM, the source region of North Atlantic overturning shifted southward, which led to more radiogenic preformed epsilon(Nd) of glacial Northern Source Water (NSW). Considering this preformed effect, we infer that glacial deep Atlantic had a similar proportion of NSW as today, although the overall strength of glacial circulation appears reduced from both North Atlantic and Southern Ocean sources, which increased the relative importance of nonconservative behavior of epsilon(Nd) and may have facilitated accumulation of respired carbon in the deep ocean. During the deglaciation, we find that Southern Ocean overturning increased, which offset suppressed North Atlantic overturning and resulted in a net stronger global abyssal circulation. Faster global scale deglacial circulation reduced the relative importance of non-conservative effects, resulting in AtlanticPacific convergence of abyssal epsilon(Nd) signatures. Variations of Southern Ocean overturning likely drove a significant fraction of deglacial changes in atmospheric CO2 and oceanic heat budget. (C) 2020 The Author(s). Published by Elsevier Ltd.

2018

PaleoOcean

Ocean_circulation

Flushing of the deep Pacific Ocean and the deglacial rise of atmospheric CO2 concentrations

Jianghui Du, Brian A. Haley, Alan C. Mix, Maureen H. Walczak, and Summer K. Praetorius

Nature Geoscience, 2018

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During the last deglaciation (19,000-9,000 years ago), atmospheric CO2 increased by about 80 ppm. Understanding the mechanisms responsible for this change is a central theme of palaeoclimatology, relevant for predicting future CO2 transfers in a warming world. Deglacial CO2 rise hypothetically tapped an accumulated deep Pacific carbon reservoir, but the processes remain elusive as they are underconstrained by existing tracers. Here we report high-resolution authigenic neodymium isotope data in North Pacific sediment cores and infer abyssal Pacific overturning weaker than today during the Last Glacial Maximum but intermittently stronger during steps of deglacial CO2 rise. Radiocarbon evidence suggestive of relatively ‘old’ deglacial deep Pacific water is reinterpreted here as an increase in preformed C-14 age of subsurface waters sourced near Antarctica, consistent with movement of aged carbon out of the deep ocean and release of CO2 to the atmosphere during the abyssal flushing events. The timing of neodymium isotope changes suggests that deglacial acceleration of Pacific abyssal circulation tracked Southern Hemisphere warming, sea-ice retreat and increase of mean ocean temperature. The inferred magnitude of circulation changes is consistent with deep Pacific flushing as a significant, and perhaps dominant, control of the deglacial rise of atmospheric CO2.

2016

ChemOcean

Nd_isotopes

Neodymium isotopes in authigenic phases, bottom waters and detrital sediments in the Gulf of Alaska and their implications for paleo-circulation reconstruction

Jianghui Du, Brian A. Haley, and Alan C. Mix

Geochimica et Cosmochimica Acta, 2016

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The isotopic composition of neodymium (epsilon(Nd)) extracted from sedimentary Fe-Mn oxyhydroxide offers potential for reconstructing paleo-circulation, but its application depends on extraction methodology and the mechanisms that relate authigenic epsilon(Nd) to bottom water. Here we test methods to extract authigenic epsilon(Nd) from Gulf of Alaska (GOA) sediments and assess sources of leachate Nd, including potential contamination from trace dispersed volcanic ash. We show that one dominant phase is extracted via leaching of core-top sediments. Major and trace element geochemistry demonstrate that this phase is authigenic Fe-Mn oxyhydroxide. Contamination of leachate (authigenic) Nd from detrital sources is insignificant (<1%); our empirical results are consistent with established kinetic mineral dissolution rates and theory. Contamination of extracted epsilon(Nd) from leaching of volcanic ash is below analytical uncertainty. However, the epsilon(Nd) of core-top leachates in the GOA is consistently more radiogenic than bottom water. We infer that authigenic phases record pore water epsilon(Nd), and the relationships of epsilon(Nd) among bottom waters, pore waters, authigenic phases and detrital sediments are primarily governed by the exposure time of bottom water to sea-floor sediments, rate of exchange across the sediment-water interface and the reactivity and composition of detrital sediments. We show that this conceptual model is applicable on the Pacific basin scale and provide a new framework to understand the role of authigenic phases in both modern and paleo-applications, including the use of authigenic epsilon(Nd) as a paleo-circulation tracer.(C) 2016 Elsevier Ltd. All rights reserved.