DeVries
Timothy
DeVries
Timothy
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ArticleDecadal trends in the ocean carbon sink(National Academy of Sciences, 2019-05-28) DeVries, Timothy ; Le Quere, Corinne ; Andrews, Oliver D. ; Berthet, Sarah ; Hauck, Judith ; Ilyina, Tatiana ; Landschützer, Peter ; Lenton, Andrew ; Lima, Ivan D. ; Nowicki, Michael ; Schwinger, Jorg ; Séférian, RolandMeasurements show large decadal variability in the rate of CO2 accumulation in the atmosphere that is not driven by CO2 emissions. The decade of the 1990s experienced enhanced carbon accumulation in the atmosphere relative to emissions, while in the 2000s, the atmospheric growth rate slowed, even though emissions grew rapidly. These variations are driven by natural sources and sinks of CO2 due to the ocean and the terrestrial biosphere. In this study, we compare three independent methods for estimating oceanic CO2 uptake and find that the ocean carbon sink could be responsible for up to 40% of the observed decadal variability in atmospheric CO2 accumulation. Data-based estimates of the ocean carbon sink from pCO2 mapping methods and decadal ocean inverse models generally agree on the magnitude and sign of decadal variability in the ocean CO2 sink at both global and regional scales. Simulations with ocean biogeochemical models confirm that climate variability drove the observed decadal trends in ocean CO2 uptake, but also demonstrate that the sensitivity of ocean CO2 uptake to climate variability may be too weak in models. Furthermore, all estimates point toward coherent decadal variability in the oceanic and terrestrial CO2 sinks, and this variability is not well-matched by current global vegetation models. Reconciling these differences will help to constrain the sensitivity of oceanic and terrestrial CO2 uptake to climate variability and lead to improved climate projections and decadal climate predictions.
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DatasetCompiled dataset consisting of published and unpublished global nitrate d15N measurements from from 1975-2018(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-06-17) Rafter, Patrick ; Bagnell, Aaron ; DeVries, Timothy ; Marconi, DarioNitrate d15N observations were compiled from studies dating from 1975 to 2018. Whenever possible, the data was acquired via the original author, but in other cases the data was estimated from the publication directly. All observations were treated equally, although the failure to remove nitrite when using the "denitrifier method" may bias the nitrate d15N to low values (Rafter et al., 2013). This version of the dataset (1.0) will be updated as new data are published. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/768627
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DatasetEstimated nitrate d15N modeled using an ensemble of artificial neural networks (EANNs)(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-06-17) Rafter, Patrick ; Bagnell, Aaron ; DeVries, Timothy ; Marconi, DarioWe utilize an ensemble of artificial neural networks (EANNs) to interpolate our global ocean nitrate d15N database, producing complete 3D maps of the data. By utilizing an artificial neural network (ANN), a machine learning approach that effectively identifies nonlinear relationships between a target variable (the isotopic dataset) and a set of input features (other available ocean datasets), we can fill holes in our data sampling coverage of nitrate d15N. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/768655
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ArticleGlobal estimate of submarine groundwater discharge based on an observationally constrained radium isotope model(John Wiley & Sons, 2014-12-03) Kwon, Eun Young ; Kim, Guebuem ; Primeau, Francois W. ; Moore, Willard S. ; Cho, Hyung-Mi ; DeVries, Timothy ; Sarmiento, Jorge L. ; Charette, Matthew A. ; Cho, Yang-KiAlong the continental margins, rivers and submarine groundwater supply nutrients, trace elements, and radionuclides to the coastal ocean, supporting coastal ecosystems and, increasingly, causing harmful algal blooms and eutrophication. While the global magnitude of gauged riverine water discharge is well known, the magnitude of submarine groundwater discharge (SGD) is poorly constrained. Using an inverse model combined with a global compilation of 228Ra observations, we show that the SGD integrated over the Atlantic and Indo-Pacific Oceans between 60°S and 70°N is (12 ± 3) × 1013 m3 yr−1, which is 3 to 4 times greater than the freshwater fluxes into the oceans by rivers. Unlike the rivers, where more than half of the total flux is discharged into the Atlantic, about 70% of SGD flows into the Indo-Pacific Oceans. We suggest that SGD is the dominant pathway for dissolved terrestrial materials to the global ocean, and this necessitates revisions for the budgets of chemical elements including carbon.
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ArticleReviews and syntheses: the biogeochemical cycle of silicon in the modern ocean(European Geosciences Union, 2021-02-18) Tréguer, Paul J. ; Sutton, Jill N. ; Brzezinski, Mark A. ; Charette, Matthew A. ; DeVries, Timothy ; Dutkiewicz, Stephanie ; Ehlert, Claudia ; Hawkings, Jon ; Leynaert, Aude ; Liu, Su Mei ; Llopis Monferrer, Natalia ; López-Acosta, María ; Maldonado, Manuel ; Rahman, Shaily ; Ran, Lihua ; Rouxel, OlivierThe element silicon (Si) is required for the growth of silicified organisms in marine environments, such as diatoms. These organisms consume vast amounts of Si together with N, P, and C, connecting the biogeochemical cycles of these elements. Thus, understanding the Si cycle in the ocean is critical for understanding wider issues such as carbon sequestration by the ocean's biological pump. In this review, we show that recent advances in process studies indicate that total Si inputs and outputs, to and from the world ocean, are 57 % and 37 % higher, respectively, than previous estimates. We also update the total ocean silicic acid inventory value, which is about 24 % higher than previously estimated. These changes are significant, modifying factors such as the geochemical residence time of Si, which is now about 8000 years, 2 times faster than previously assumed. In addition, we present an updated value of the global annual pelagic biogenic silica production (255 Tmol Si yr−1) based on new data from 49 field studies and 18 model outputs, and we provide a first estimate of the global annual benthic biogenic silica production due to sponges (6 Tmol Si yr−1). Given these important modifications, we hypothesize that the modern ocean Si cycle is at approximately steady state with inputs =14.8(±2.6) Tmol Si yr−1 and outputs =15.6(±2.4) Tmol Si yr−1. Potential impacts of global change on the marine Si cycle are discussed.
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ArticleHow data set characteristics influence ocean carbon export models(John Wiley & Sons, 2018-09-13) Bisson, Kelsey ; Siegel, David A. ; DeVries, Timothy ; Cael, B. Barry ; Buesseler, Ken O.Ocean biological processes mediate the transport of roughly 10 petagrams of carbon from the surface to the deep ocean each year and thus play an important role in the global carbon cycle. Even so, the globally integrated rate of carbon export out of the surface ocean remains highly uncertain. Quantifying the processes underlying this biological carbon export requires a synthesis between model predictions and available observations of particulate organic carbon (POC) flux; yet the scale dissimilarities between models and observations make this synthesis difficult. Here we compare carbon export predictions from a mechanistic model with observations of POC fluxes from several data sets compiled from the literature spanning different space, time, and depth scales as well as using different observational methodologies. We optimize model parameters to provide the best match between model‐predicted and observed POC fluxes, explicitly accounting for sources of error associated with each data set. Model‐predicted globally integrated values of POC flux at the base of the euphotic layer range from 3.8 to 5.5 Pg C/year, depending on the data set used to optimize the model. Modeled carbon export pathways also vary depending on the data set used to optimize the model, as well as the satellite net primary production data product used to drive the model. These findings highlight the importance of collecting field data that average over the substantial natural temporal and spatial variability in carbon export fluxes, and advancing satellite algorithms for ocean net primary production, in order to improve predictions of biological carbon export.
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ArticleGlobal reorganization of deep-sea circulation and carbon storage after the last ice age(American Association for the Advancement of Science, 2022-11-16) Rafter, Patrick A. ; Gray, William R. ; Hines, Sophia K. V. ; Burke, Andrea ; Costa, Kassandra M. ; Gottschalk, Julia ; Hain, Mathis P. ; Rae, James W. B. ; Southon, John R. ; Walczak, Maureen H. ; Yu, Jimin ; Adkins, Jess F. ; DeVries, TimothyUsing new and published marine fossil radiocarbon (C/C) measurements, a tracer uniquely sensitive to circulation and air-sea gas exchange, we establish several benchmarks for Atlantic, Southern, and Pacific deep-sea circulation and ventilation since the last ice age. We find the most C-depleted water in glacial Pacific bottom depths, rather than the mid-depths as they are today, which is best explained by a slowdown in glacial deep-sea overturning in addition to a "flipped" glacial Pacific overturning configuration. These observations cannot be produced by changes in air-sea gas exchange alone, and they underscore the major role for changes in the overturning circulation for glacial deep-sea carbon storage in the vast Pacific abyss and the concomitant drawdown of atmospheric CO.
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PresentationTemporal and spatial perspectives on the fate of anthropogenic carbon : a carbon cycle slide deck for broad audiences(Ocean Carbon & Biogeochemistry Program, 2015-12-08) Khatiwala, Samar ; DeVries, Timothy ; Cook, Jack ; McKinley, Galen A. ; Carlson, Craig A. ; Benway, Heather M.This slide deck was developed to inform broader scientific, as well as general audiences about the role of the ocean in the global carbon cycle, including key sinks and sources of anthropogenic carbon and how they have evolved through time and space.