Trace elements and isotopes (TEIs) are important to marine life and are essential tools for studying ocean processes 1 . Two different frameworks have arisen regarding marine TEI cycling: reversible scavenging favours water-column control on TEI distributions 2–5 , and seafloor boundary exchange emphasizes sedimentary imprints on water-column biogeochemistry 6,7 . These two views lead to disparate interpretations of TEI behaviours 8–10 . Here we use rare earth elements and neodymium isotopes as exemplar tracers of particle scavenging 11 and boundary exchange 6,7,12 . We integrate these data with models of particle cycling and sediment diagenesis to propose a general framework for marine TEI cycling. We show that, for elements with greater affinity for manganese oxide than biogenic particles, scavenging is a net sink throughout the water column, contrary to a common assumption for reversible scavenging 3,13 . In this case, a benthic flux supports increasing elemental concentrations with water depth. This sedimentary source consists of two components: one recycled from elements scavenged by water-column particles, and another newly introduced to the water column through marine silicate weathering inside sediment 8,14,15 . Abyssal oxic diagenesis drives this benthic source, and exerts a strong influence on water-column biogeochemistry through seafloor geometry and bottom-intensified turbulent mixing 16,17 . Our findings affirm the role of authigenic minerals, often overshadowed by biogenic particles, in water-column cycling 18 , and suggest that the abyssal seafloor, often regarded as inactive, is a focus of biogeochemical transformation 19,20 .

Cerium (Ce) stable isotopes, combined with Ce anomalies, serve as potential proxies for reconstructing Earth's past redox conditions. However, the behavior of Ce isotopes and Ce anomalies across different oceanic redox environments remains underexplored. This study presents a Ce anomaly and Ce isotope dataset of marine sediments from a range of modern oceanographic regimes, including anoxic continental margins and oxic Equatorial Pacific environments. By integrating bulk sediment geochemistry, sequential extraction, and X-ray absorption spectroscopy data, we reveal the decoupling between Ce stable isotope values (delta 142Ce) and Ce anomalies (Ce/ Ce*). Margin sediments exhibit negative Ce anomalies (0.48 to 0.96) that display a negative correlation with delta 142Ce (-0.05 to 0.12 %o), which are close to or higher than the upper continental crust value (-0.03 +/- 0.06 %o). This relationship results from the influence of seawater-derived REEs through authigenic phosphates and organic matter, as well as clastic inputs. In contrast, Equatorial Pacific sediments exhibit positive Ce anomalies (1.05 to 1.23) that are positively correlated to their delta 142Ce values (0.08 to 0.16 %o), which exceed the upper crust baseline. This pattern is attributed to Mn(IV)-oxide-driven oxidative adsorption of Ce. Here, we purpose a first-order estimate for the delta 142Ce value in bottom seawater of the Equatorial Pacific (about 0.3 to 0.4 %o). These findings enhance our understanding of marine Ce geochemistry and underscore the importance of integrating Ce anomalies with Ce isotope signatures for paleoceanographic redox reconstructions.

Rhenium (Re) has been proposed as a tracer of petrogenic organic carbon (OCpetro) oxidation, also known as georespiration, but information regarding the solid phases hosting Re in rocks and Re weathering behavior is limited. Examining grey shale rocks from two small mountainous river basins in the Pacific Northwest, USA, we found that the majority of parent material (bedrock) Re in both basins is associated with OCpetro (average 71 %, range 50 to 93 %), with minimal Re hosted in sulfide minerals. In soil and weathered rock profiles, mass transfer calculations (tau) reveal a clear distinction between the weathering behavior of Re and that of other elements, indicating that Re weathering in these siliclastic rocks and soils does not primarily trace sulfide oxidation or dissolution of primary minerals. We find evidence that Re likely traces OCpetro oxidation, although patterns of Re and OC weathering are influenced by heterogeneity in bedrock composition and inputs of modern OC near the surface. In some cases Re loss exceeds that of OC during weathering, suggesting that the kinetics of Re oxidation are sometimes faster than those of OC oxidation. We observe greater Re loss in systems with slower erosion rate, which implies that systems subject to faster erosion export more unoxidized particulate Re. Our observations of Re phase associations and weathering behavior in soil and rock weathering profiles support the use of the Re proxy for georespiration, but also provide qualifications on its application in future work quantifying georespiration fluxes at regional and global scales.

The rubidium (Rb) isotope system has the potential for tracing water-silicate interactions and providing information on the global Rb cycling. However, the Rb isotope compositions of modern seawater and its major inputs and outputs remain poorly understood. Here we measured Rb isotope compositions of seawaters, pelagic clay sediments and porewaters from the western and central equatorial Pacific Ocean. Our results show that the delta Rb-87 of modern seawater is homogeneous (0.13 +/- 0.04 parts per thousand; 2SD, n = 13) and higher than both the local sediments (-0.17 parts per thousand to 0.03 parts per thousand) and the bulk lithosphere (Delta Rb-87(seawater-UCC) = 0.27 parts per thousand). The Rb in pelagic clay sediments is primarily associated with silicates (> 90%) and partially with exchangeable fractions (similar to 4%). The exchangeable fractions display relatively lower delta Rb-87 (-0.07 +/- 0.05 parts per thousand; 2SD, n = 6). Meanwhile, the correlation between K/Rb and delta Rb-87 of bulk sediments, along with investigations on the clay sized particles (delta Rb-87 = -0.06 parts per thousand), represents that lithogenic silicates have relatively low K/Rb and delta Rb-87 close to the UCC while formation of authigenic phillipsite or clays can result in higher bulk K/Rb (up to 930) and delta Rb-87 (up to 0.03 parts per thousand). The delta Rb-87 of both authigenic silicates and absorbed fractions in deep-sea sediments are lower than seawater, which can partially contribute to the removal of isotopically light Rb from seawater. The delta Rb-87 of the measured marine porewaters are approximately homogeneous (0.08 parts per thousand to 0.14 parts per thousand) and similar to seawater. The result consistent with previous K isotope investigation in this region with limited impact of authigenic silicates. Using a mass balance estimation in a steady state with isotope data, the flux of sediment removal for Rb in the ocean is about 2.2 - 12.0 x 10(7) kg/year.

To improve our understanding and guide future studies and applications, we review the biogeochemistry of the rare earth elements (REE). The REEs, which form a chemically uniform group due to their nearly identical physicochemical properties, include the lanthanide series elements plus scandium (Sc) and yttrium (Y). These elements, in conjunction with the neodymium isotopes, are powerful tools for understanding key oceanic, terrestrial, biological and even anthropogenic processes. Furthermore, their unique properties render them essential for various technological processes and products. Here, we delve into the characteristics of REE biogeochemistry and discuss normalization procedures and REE anomalies. We also examine the aqueous speciation of REEs, contributing to a better understanding of their behavior in aquatic settings, including the role of neodymium isotopes. We then focus on their environmental distribution, fractionation, and controlling processes in different environmental systems across the land-ocean continuum. In addition, we analyze sinks, sources, and the mobility of REEs, providing insights into their behavior in these environments. We further investigate the sources of anthropogenic REEs and their bioavailability, bioaccumulation, and transfer along food webs. We also explore the potential effects of climate change on the cycling, mobility and bioavailability of REEs, underlining the importance of current research in this evolving field. In summary, we provide a comprehensive review of REE behavior in the environment, from their properties and roles to their distribution and anthropogenic impacts, offering valuable insights and pinpointing key knowledge gaps. Rare earth elements (REE) are powerful tracers of both natural and anthropogenic processes within terrestrial and ocean environments REE are controlled by absorption, adsorption/desorption, co-precipitation, remineralization, and particle dissolution REE are technology-critical metals with broad applications in the future low-carbon global economy

The role of suspended particulate matter in the biogeochemical cycling of neodymium (Nd) in the ocean is not well understood. This study reports the measurement of dissolved Nd concentrations and isotopes (<0.2 um), and particulate Nd concentrations along the Eastern Pacific Zonal Transect (EPZT, GP16) as part of the GEOTRACES program. The western part of the EPZT cruise track is influenced by a hydrothermal plume, observed between 2200 and 2800 m, originating at the southern East Pacific Rise. This setting allows for the investigation of the role of particulate matter in Nd biogeochemical cycling and its contribution in modifying the distribution of dissolved Nd. Results show that the highest removal of dissolved Nd (∼ 21 %) was observed near the hydrothermal ridge crest, decreasing to ∼ 8 % at the westernmost station. Here, we report the partition coefficient (Kd) of each particle constituent (e.g., lithics, CaCO3, POM, Opal, Fe-phase, Mn-phase) to show that particle composition plays an important role in Nd removal alongside particle mass. Along the plume, both particulate Mn and Fe contributed to the removal of Nd, with Mn playing the dominant role in sites closest to the vent. At the western stations, below the plume, the concentration of both dissolved and particulate Nd increased with depth, with particulate Nd one to two orders of magnitude lower than measured in the dissolved phase. The increase in dissolved Nd with depth in the interval below the plume could result either from the continuing remineralization of raining particles or the influx of dissolved Nd from bottom sediments. Close to the ridge crest, where the hydrothermal Nd input is at its highest, there is a hint of local modification of dissolved εNd signature, however not large enough to affect the use of εNd as a water mass tracer.

Concentration-discharge (C-Q) relationships of total suspended solids (TSS), total dissolved solids (TDS), particulate organic carbon (POC), and dissolved organic carbon (DOC) were investigated in the tributaries and main-stems of two mountainous river systems with distinct watershed characteristics (Eel and Umpqua rivers) in Northern California and central Oregon (USA). Power-law (C = a x Q(b)) fits to the data showed strong transport-limited behavior (b > 1) by TSS and POC, moderate transport limitation of DOC (b > 0.3) and chemostatic behavior (b < 0) by TDS in most streams. These contrasts led to significant compositional differences at varying discharge levels, with particle-bound constituents becoming increasingly important (relative abundances of 50% to >90%) at high-flow conditions. Organic carbon contents of TSS displayed marked decreases with discharge whereas they increased in TDS during high-flow conditions. Daily and cumulative material fluxes for different coastal streams were calculated using the C-Q relationships and showed that the delivery of transport-limited constituents, such as TSS and POC (and DOC to a lesser degree), was closely tied to high-discharge events and occurred primarily during the winter season. The coherence between winter fluxes and high wave-southerly wind conditions along the coast highlights how seasonal and inter-annual differences in fluvial discharge patterns affect the fate of land-derived materials delivered to coastal regions.

This study examines dissolved rhenium (Re) concentrations as a function of water runoff using river samples from two contrasting mountainous watersheds, the Eel and Umpqua Rivers in the Pacific Northwest, USA. These watersheds share many key characteristics in terms of size, discharge, climate, and vegetation, but they have a 15-fold difference in sediment yield due to differences in their tectonic setting and uplift and erosion rates. We evaluate concentration-runoff (C-R) relationships and ratios of coeffi-cients of variation (CVC/CVR) for major cations, anions, dissolved inorganic carbon, selected trace ele-ments including Re, and 87Sr/Sr-86 ratios. Recent research outlines the potential of Re to serve as a tracer for the oxidation of ancient/fossil organic matter because of its close association with petrogenic carbon (OCpetro) in rocks. In both the Eel and Umpqua Rivers, our measurements show that Re behaves similarly to major weathering derived-solutes corrected for atmospheric input, such as Ca2+*, Mg2+*, and Na+* with modest dilution across all tributaries with increasing runoff. Rhenium behaves dissimilarly from other trace elements, such as Mo and U, and is also dissimilar to biologically-cycled nutrients, such as NO3 -, PO43-, and K+*, suggesting differences in sources, solute generation mechanisms, and flowpaths. Rhenium behavior is also distinct from that of colloids, which have increasing concentrations with increasing runoff. We find that Re and sulfate corrected for atmospheric input (SO42-*) have distinct C-R relationships, in which SO42-* undergoes greater dilution with increasing runoff. This implies that Re is not dominantly sourced from sulfide weathering, which leaves primary bedrock minerals and OCpetro hosted in bedrock of these watersheds as the likely dominant sources of dissolved Re release. At mean discharge, Re concentration in the Eel river (3.5 pmol L-1) is more than two times greater than Re concentrations in the Umpqua River (1.5 pmol L-1). Furthermore, comparison of two tributary watersheds with similar bedrock but marked differences in erosion rates show higher Re concentrations in Bull Creek (erosion rate of 0.5 mm yr(-1)) relative to Elder Creek (erosion rate of 0.2 mm yr(-1)). The results of this study suggest that dissolved Re in the Eel and Umpqua River basins is likely derived from primary mineral dis-solution or OCpetro oxidation, and Re fluxes are higher in areas with higher erosion rates, suggesting that tectonic setting is one factor that controls Re release and therefore OCpetro oxidation.(C) 2022 Elsevier Ltd. All rights reserved.

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.

File structure: Source data Contains source data to main text and extended data figures. Data sources are identified within and listed below. Computer codes Geochemical inversion – “Data for geochemical inversion.xlsx”: contains Gulf of Alaska sediment and volcanic/terrigenous endmember geochemical data used for data inversion. “geochemical inversion.r”: R script used to perform geochemical inversion. “GOA inversion fraction.csv”: Result of the geochemical inversion, including the volcanic and terrigenous fractions in each Gulf of Alaska sediment sample. “GOA inversion residual.csv”: Result of the geochemical inversion, including the residuals of each element. cluster volcanic geochemical data – “Database of volcanic geochemistry.xlsx”: compiled database of the geochemistry of volcanic endmember samples. “cluster.r”: R script used to perform cluster analysis on the volcanic samples. “Clustered volcanic data.csv”: the results of cluster analysis. “Dendroplot.r”: R script used to plot the dendrogram for the cluster analysis. “dendro 15 complete euclidean.pdf”: The dendrogram. “Volcanic endmembers.csv”: final geochemical volcanic endmembers based on the cluster analysis. Global volcanic eruption compilation – “eruption.database.intcal20.xlsx”: This file includes the eruption database compiled by this study, as well as the previous compilation of Huybers and Langmuir 2009 EPSL (referred to as HL09). “eruption.ratio.R” and “volc.freq.R”: These are R scripts that compute the eruption frequency of glaciated and unglaciated volcanoes using the eruption database. “eruption.ratio.R”calls the function inside “volc.freq.R”. “Volcanic eruption summary.xlsx”: This file contains the outputs of the R scripts. PISM sensitivity experiment – “ciscyc.5km.epica.ts.10a.nc” and other netcdf files: The output of PISM sensitivity experiments, from Seguinot. (2020). Cordilleran ice sheet glacial cycle simulations continuous variables [Data set]. Zenodo. https://doi.org/10.5281/zenodo.3606536. Click the link to see the documentation of these files. “temperature timeseries.xlsx”: the temperature forcing used in the sensitivity experiments. “PISM sensitivity.r”: R script used to analyse the PISM sensitivity experiments, including data binning, lag correlation and regression between ice sheeting response and temperature forcing. “PISM sensitivity.xlsx”: Output of the R script. “GOA.calibration.csv”: SST record from the Gulf of Alaska site 85JC/U1419, calibrated using bayspline. “GOA.Ensemble.csv”: 1000 ensemble output of the bayspline calibration. “predict ice volume SST.r”: R script used to predict the response of CIS ice volume to GOA SST forcing. The script will call the results of PISM sensitivity experiments in “PISM sensitivity.xlsx” and the GOA SST forcing in “GOA.calibration.csv” and “GOA.calibration.csv”. “PISM ice vol GOA SST.csv”: predicted PISM ice vol based on GOA SST forcing and taking into account all sensitivity experiments and the uncertainty in SST reconstruction. “PISM ice vol GOA SST model.csv”: predicted PISM ice vol based on GOA SST forcing based on each sensitivity experiment and the uncertainty in SST reconstruction. Please cite the following studies when using the data, in addition to citing the present study: GOA age model, IRD and MAR: Walczak, M. H. et al. Phasing of millennial-scale climate variability in the Pacific and Atlantic Oceans. Science 370, 716–720 (2020). Velle, J. H. et al. High resolution inclination records from the Gulf of Alaska, IODP Expedition 341 Sites U1418 and U1419. Geophys. J. Int. 229, 345–358 (2022). Heaton, T. J. et al. Marine20—The Marine Radiocarbon Age Calibration Curve (0–55,000 cal BP). Radiocarbon 62, 779–820 (2020). GOA SST: Praetorius, S. K. et al. North Pacific deglacial hypoxic events linked to abrupt ocean warming. Nature 527, 362–366 (2015). Romero, O. E., LeVay, L. J., McClymont, E. L., Müller, J. & Cowan, E. A. Orbital and Suborbital-Scale Variations of Productivity and Sea Surface Conditions in the Gulf of Alaska During the Past 54,000 Years: Impact of Iron Fertilization by Icebergs and Meltwater. Paleoceanogr. Paleoclimatology 37, e2021PA004385 (2022). Tierney, J. E. & Tingley, M. P. BAYSPLINE: A New Calibration for the Alkenone Paleothermometer. Paleoceanogr. Paleoclimatology 33, 281–301 (2018). GOA benthic foraminifera assemblage: Belanger, C. L., Sharon, Du, J., Payne, C. R. & Mix, A. C. North Pacific deep-sea ecosystem responses reflect post-glacial switch to pulsed export productivity, deoxygenation, and destratification. Deep Sea Res. Part Oceanogr. Res. Pap. 164, 103341 (2020). Sharon, Belanger, C., Du, J. & Mix, A. Reconstructing Paleo-oxygenation for the Last 54,000 Years in the Gulf of Alaska Using Cross-validated Benthic Foraminiferal and Geochemical Records. Paleoceanogr. Paleoclimatology 36, e2020PA003986 (2021). GOA productivity: Romero, O. E., LeVay, L. J., McClymont, E. L., Müller, J. & Cowan, E. A. Orbital and Suborbital-Scale Variations of Productivity and Sea Surface Conditions in the Gulf of Alaska During the Past 54,000 Years: Impact of Iron Fertilization by Icebergs and Meltwater. Paleoceanogr. Paleoclimatology 37, e2021PA004385 (2022). Addison, J. A. et al. Productivity and sedimentary δ15N variability for the last 17,000 years along the northern Gulf of Alaska continental slope. Paleoceanography 27, PA1206 (2012). GOA bulk sediment neodymium isotopes: Du, J., Haley, B. A., Mix, A. C., Walczak, M. H. & Praetorius, S. K. Flushing of the deep Pacific Ocean and the deglacial rise of atmospheric CO 2 concentrations. Nat. Geosci. 11, 749–755 (2018). GOA volcanic endmember data compilation: Cameron, C. E., Snedigar, S. F. & Nye, C. J. Alaska Volcano Observatory geochemical database. DDS 8 http://www.dggs.alaska.gov/pubs/id/29120 (2014) doi:10.14509/29120. Sarbas, B., Jochum, K. P., Nohl, U. & Hofmann, A. W. GEOROC, the MPI geochemical rock database: a new tool for geochemists. Eos Trans. AGU 80, F1184 (1999). Global and regional volcanic eruption data compilation: Huybers, P. & Langmuir, C. Feedback between deglaciation, volcanism, and atmospheric CO2. Earth Planet. Sci. Lett. 286, 479–491 (2009). Global Volcanism Program, 2013. Volcanoes of the World, v. 4.8.7. 10.5479/si.GVP.VOTW4-2013. (2013). Bryson, R. U., Bryson, R. A. & Ruter, A. A calibrated radiocarbon database of late Quaternary volcanic eruptions. EEarth Discuss 1, 123–134 (2006). Watt, S. F. L., Pyle, D. M. & Mather, T. A. The volcanic response to deglaciation: Evidence from glaciated arcs and a reassessment of global eruption records. Earth-Sci. Rev. 122, 77–102 (2013). Crosweller, H. S. et al. Global database on large magnitude explosive volcanic eruptions (LaMEVE). J. Appl. Volcanol. 1, 4 (2012). Cameron, C. E., Snedigar, S. F. & Nye, C. J. Alaska Volcano Observatory geochemical database. DDS 8 http://www.dggs.alaska.gov/pubs/id/29120 (2014) doi:10.14509/29120. Praetorius, S. et al. Interaction between climate, volcanism, and isostatic rebound in Southeast Alaska during the last deglaciation. Earth Planet. Sci. Lett. 452, 79–89 (2016). Wilcox, P. S. et al. A new set of basaltic tephras from Southeast Alaska represent key stratigraphic markers for the late Pleistocene. Quat. Res. 92, 246–256 (2019). Davies, L. J., Jensen, B. J. L., Froese, D. G. & Wallace, K. L. Late Pleistocene and Holocene tephrostratigraphy of interior Alaska and Yukon: Key beds and chronologies over the past 30,000 years. Quat. Sci. Rev. 146, 28–53 (2016). GIA models: Roy, K. & Peltier, W. R. Relative sea level in the Western Mediterranean basin: A regional test of the ICE-7G_NA (VM7) model and a constraint on late Holocene Antarctic deglaciation. Quat. Sci. Rev. 183, 76–87 (2018). Lambeck, K., Purcell, A. & Zhao, S. The North American Late Wisconsin ice sheet and mantle viscosity from glacial rebound analyses. Quat. Sci. Rev. 158, 172–210 (2017). PISM sensitivity experiments and temperature forcing: Seguinot, J., Rogozhina, I., Stroeven, A. P., Margold, M. & Kleman, J. Numerical simulations of the Cordilleran ice sheet through the last glacial cycle. The Cryosphere 10, 639–664 (2016). Seguinot. (2020). Cordilleran ice sheet glacial cycle simulations continuous variables [Data set]. Zenodo. https://doi.org/10.5281/zenodo.3606536 Dansgaard, W. et al. Evidence for general instability of past climate from a 250-kyr ice-core record. Nature 364, 218–220 (1993). Andersen, K. K. et al. High-resolution record of Northern Hemisphere climate extending into the last interglacial period. Nature 431, 147–151 (2004). Jouzel, J. et al. Orbital and Millennial Antarctic Climate Variability over the Past 800,000 Years. Science 317, 793–796 (2007). Petit, J. R. et al. Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica. Nature 399, 429–436 (1999). Herbert, T. D. et al. Collapse of the California Current During Glacial Maxima Linked to Climate Change on Land. Science 293, 71–76 (2001). Be10 data compilation: Lesnek, A. J., Briner, J. P., Baichtal, J. F. & Lyles, A. S. New constraints on the last deglaciation of the Cordilleran Ice Sheet in coastal Southeast Alaska. Quat. Res. 96, 140–160 (2020). Haeussler, P. J. et al. Late Quaternary deglaciation of Prince William Sound, Alaska. Quat. Res. 1–20 (2021) doi:10.1017/qua.2021.33. Walcott, C. K., Briner, J. P., Baichtal, J. F., Lesnek, A. J. & Licciardi, J. M. Cosmogenic ages indicate no MIS 2 refugia in the Alexander Archipelago, Alaska. Geochronology 4, 191–211 (2022). Briner, J. P. et al. The last deglaciation of Alaska. Cuad. Investig. Geográfica 43, 429–448 (2017). Tulenko, J. P., Briner, J. P., Young, N. E. & Schaefer, J. M. Beryllium-10 chronology of early and late Wisconsinan moraines in the Revelation Mountains, Alaska: Insights into the forcing of Wisconsinan glaciation in Beringia. Quat. Sci. Rev. 197, 129–141 (2018). Menounos, B. et al. Cordilleran Ice Sheet mass loss preceded climate reversals near the Pleistocene Termination. Science 358, 781–784 (2017). Dulfer, H. E., Margold, M., Engel, Z., Braucher, R. & Team, A. Using 10Be dating to determine when the Cordilleran Ice Sheet stopped flowing over the Canadian Rocky Mountains. Quat. Res. 102, 222–233 (2021). Lesnek, A. J., Briner, J. P., Lindqvist, C., Baichtal, J. F. & Heaton, T. H. Deglaciation of the Pacific coastal corridor directly preceded the human colonization of the Americas. Sci. Adv. 4, eaar5040 (2018). Tulenko, J. P., Briner, J. P., Young, N. E. & Schaefer, J. M. The last deglaciation of Alaska and a new benchmark 10Be moraine chronology from the western Alaska Range. Quat. Sci. Rev. 287, 107549 (2022).

Outputs of the early diagenetic model for neodymium and its radiogenic isotope at deep sea station HH3000 (3060 m, 43°52'N, 125°38'W) from the Oregon margin, Northeast Pacific. Three types of models are included, and the files are named as following: 1. Baseline simulations, "HH3000Nd.baseline.copre_output.xlsx" for the co-precipitation formulation, and "HH3000Nd.baseline.revscan_output.xlsx" for the reversible scavenging formulation. 2. Sensitivity tests of silicate dissolution rate: "HH3000Nd.{mineral}.{dissolution rate}_output.xlsx", where {mineral} can be "Basalt", "Plag" (plagioclase), "Cpx" (clinopyroxene) or "Chl" (chlorite), and {dissolution rate} can be "1e0" to "1e5", referring to the order of magnitude reduction of dissolution rate relative to the laboratory-derived rates. 3. Sensitivity tests of authigenic clay precipitation rate: “HH3000Nd.basalt.{precipitation rate}.illite_output.xlsx", where "{precipitation rate}" can be "no", "slow", "normal", or "fast". Explanations of the modeled variables in the above files can be found in "model variable note.xlsx".

The sedimentary fluxes controlling potassium (K) budget of the oceans and the isotope composition of K (delta K-41) potentially yield valuable information about the global K cycling. However, at present sedimentary diagenesis in the oceans is one of the least well-known components of the seawater K budget. This study presents a dataset of the modern (<50 cm) sediments from a range of hydrographic regimes including continental margin settings (the Peru Margin, California Borderland, and Mexican Margin) and deep-sea environments (the Equatorial Pacific). We determine the K isotope compositions and origins of K in the sediments and compare them with the results of elemental abundances and spectroscopic analyses. The wide variability in sedimentary K/Al and Rb/K ratios, K-phase distributions, and K isotope compositions support the interplay between continental weathering, which provides clastic inputs, and sedimentary diagenesis, which constitutes an important sink of seawater K. The net result of these processes potentially alters the K elemental and isotopic budgets in sediment strata of various marine environments. We demonstrate that K is dominantly hosted by illite, glauconite, and feldspars, and regional K-phase partitioning modulates marine sedimentary K budget. For example, considerable amounts of K hosted in illite (up to 90%) primarily of terrestrial origins increase Rb/K ratios, producing low delta K-41 in California Borderland sediments (-0.57 to -0.40 parts per thousand), the Pescadero Slope from the Mexican Margin (-0.42 to -0.39 parts per thousand), and Equatorial Pacific deep-sea basins (-0.56 to -0.44 parts per thousand). In contrast, glauconite authigenesis causes decreases in the Rb/K ratio and relatively high delta K-41 at a site along the Peru Margin (-0.35 to -0.29 parts per thousand), as well as at two other sites along the Mexican Margin (-0.39 to -0.27 parts per thousand). Despite the presence of feldspar-K (<20%), delta K-41 in the sediments reflects dominant contributions of detrital illite (delta K-41(illite) similar to -0.56 parts per thousand) and authigenic glauconite (delta K-41(glauconite) similar to -0.18 parts per thousand). We conclude that the formation of glauconite in the sediments takes up isotopically light K from seawater and serves as an important sink of seawater K (including K in seawater-derived porewater) (similar to 1 to 16, average similar to 6 Tg K.yr(-1)) during early diagenesis, especially on continental margins. (C) 2022 Elsevier B.V. All rights reserved.

Enduring questions remain regarding the transition from relatively warm and stable pre‐ and early‐Pleistocene climate to that of the high amplitude glacial‐interglacial cycles later in the Quaternary. The main shift in glacial intensity and periodicity around 1 Ma is known as the Mid‐Pleistocene Transition (MPT). Here we analyze detrital strontium (Sr) and neodymium (Nd) isotopes in a western Arctic sediment core P23 previously investigated using several litho/biostratigraphic proxies. Based on an improved age framework combining lithostratigraphic cyclicity and Sr isotope stratigraphy, the P23 record extends to ∼3.3 Ma, thus providing a rare insight into the Quaternary Arctic climate change. The distinct pre‐MPT P23 record is dominated by Pacific‐sourced sediment inputs, with little to no intra‐Arctic glacial inputs, except for a sandy interval around ∼2.5 Ma. A consistent decrease of Nd isotopic values toward North American continental signatures started in both the Arctic and Bering Sea at ∼1.5 Ma and led to a major threshold shift in P23 proxies at ∼0.9 Ma. We argue that this threshold was associated with the first prolonged closure of the Bering Strait for an entire obliquity cycle. This shift marked the expansion of the North American ice sheets to the Arctic margin, with dramatic impacts on depositional and hydrographic environments in the Arctic Ocean. These impacts intensified in the subsequent glacial intervals indicating further ice‐sheet growth, probably fed back by continuing prolonged Bering Strait closures.

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 uncertain1–3. Here we find that initial deoxygenation in the North Pacific immediately after the Cordilleran ice sheet (CIS) retreat4 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 unloading5,6. We posit that iron fertilization by volcanic ash7–9 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.

Dissolved rare earth element ([REE]) and neodymium isotopic (epsilon(Nd)) data from the US GEOTRACES Eastern Equatorial Pacific Transect (EPZT) are presented. These data are compared to watermass distributions (Peters etal., 2018), particulate data (Lam etal., 2018) and carbonate species data (Bates, 2018) to evaluate present theories of REE and epsilon(Nd) geochemistry, given that the Pacific has been notably intractable in relation to these ideas (Jones etal., 2008). The [REEs] have typical depth profile distributions (e.g., [La] ranges from similar to 5 to 15 pmol/kg in the surface, increasing with depth to values of similar to 40 pmol/kg), as does epsilon(Nd) (ranging from similar to-1 to -6 epsilon(Nd); similar to previous Pacific data). However, despite the unsurprising nature of these data, several apparent inconsistencies with respect to current models for REE/ epsilon(Nd) geochemistry arise. These are: (1) While eNdremarkably maintains watermass distribution information, there is a significant (+1.4 epsilon(Nd)) offset in the data compared to published end-member compositions, indicating a strong but largely consistent non-conservative component; (2) Reversiblescavenging seems an unlikely mechanism for redistribution of [REE] and epsilon(Nd) in the water column; (3) There does not appear to be any correlation of [REE] to carbonate ion concentration, and; (4) There are indications of influence from a benthic flux, but the evidence is ambiguous. (C) 2021 Elsevier B.V. All rights reserved.

Our understanding of the marine budget of the rare earth elements (REEs) is plagued by concerns of both the input and internal cycling of these trace elements (and their isotopes). Contrary to established views, we argue that marine REE cycles are driven from the bottom up, rather than top down. That is, surface inputs (e.g., rivers, dust) and possibly some of the internal cycling processes (e.g., reversible scavenging) are of only limited importance compared to benthic sources and processes that dominate these cycles. However, existing observational data is limited and largely only from marginal sites; it is unclear if these observations are applicable to the broader ocean basins. We