Rafter Patrick A.

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Last Name
Rafter
First Name
Patrick A.
ORCID
0000-0002-6352-7593

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  • Article
    Recent increases in water column denitrification in the seasonally suboxic bottom waters of the Santa Barbara Basin
    (American Geophysical Union, 2019-06-11) White, Margot E. ; Rafter, Patrick ; Stephens, Brandon M. ; Wankel, Scott D. ; Aluwihare, Lihini I.
    Denitrification in the anoxic sediments of the Santa Barbara Basin has been well documented in the historic and modern record, but the regulation of and frequency with which denitrification occurs in the overlying water column are less understood. Since 2004, the magnitude and speciation of redox active nitrogen species in bottom waters have changed markedly. Most notable are periods of decreased nitrate and increased nitrite concentrations. Here we examine these changes in nitrogen cycling as recorded by the stable isotopes of dissolved nitrate from 2010–2016. When compared to previous studies, our data identify an increase in water column denitrification in the bottom waters of the basin. Observations from inside the basin as well as data from the wider California Current Ecosystem implicate a long‐term trend of decreasing oxygen concentrations as the driver for these observed changes, with ramifications for local benthic communities and regional nitrogen loss.
  • Dataset
    Compiled dataset consisting of published and unpublished global nitrate d15N measurements from from 1975-2018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, Dario
    Nitrate 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
  • Dataset
    Estimated 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, Dario
    We 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
  • Working Paper
    EXPORTS Measurements and Protocols for the NE Pacific Campaign
    (NASA STI Program and Woods Hole Oceanographic Institution, 2021-02) Behrenfeld, Michael J. ; Benitez-Nelson, Claudia R. ; Boss, Emmanuel S. ; Brzezinski, Mark A. ; Buck, Kristen N. ; Buesseler, Ken O. ; Burd, Adrian B. ; Carlson, Craig A. ; Cassar, Nicolas ; Cetinić, Ivona ; Close, Hilary G. ; Craig, Susanne E. ; D'Asaro, Eric A. ; Durkin, Colleen A. ; Estapa, Margaret L. ; Fassbender, Andrea ; Fox, James ; Freeman, Scott ; Gifford, Scott M. ; Gong, Weida ; Graff, Jason R. ; Gray, Deric ; Guidi, Lionel ; Halsey, Kim ; Hansell, Dennis A. ; Haëntjens, Nils ; Horner, Tristan J. ; Jenkins, Bethany D. ; Jones, Janice L. ; Karp-Boss, Lee ; Kramer, Sasha J. ; Lam, Phoebe J. ; Lee, Craig M. ; Lee, Jong-Mi ; Liu, Shuting ; Mannino, Antonio ; Maas, Amy E. ; Marchal, Olivier ; Marchetti, Adrian ; McDonnell, Andrew M. P. ; McNair, Heather ; Menden-Deuer, Susanne ; Morison, Francoise ; Nelson, Norman B. ; Nicholson, David P. ; Niebergall, Alexandria K. ; Omand, Melissa M. ; Passow, Uta ; Perry, Mary J. ; Popp, Brian N. ; Proctor, Chris ; Rafter, Patrick ; Roca-Martí, Montserrat ; Roesler, Collin S. ; Rubin, Edwina ; Rynearson, Tatiana A. ; Santoro, Alyson E. ; Siegel, David A. ; Sosik, Heidi M. ; Soto Ramos, Inia ; Stamieszkin, Karen ; Steinberg, Deborah K. ; Stephens, Brandon M. ; Thompson, Andrew F. ; Van Mooy, Benjamin A. S. ; Zhang, Xiaodong
    EXport Processes in the Ocean from Remote Sensing (EXPORTS) is a large-scale NASA-led and NSF co-funded field campaign that will provide critical information for quantifying the export and fate of upper ocean net primary production (NPP) using satellite information and state of the art technology.
  • Dataset
    Nitrate N and O isotopes from the GP12 ("PANDORA") cruise in the South-West Pacific and Solomon Sea from June to August 2012 carried out as part of the international GEOTRACES program
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2021-02-02) Rafter, Patrick ; Jeandel, Catherine ; Sigman, Daniel M.
    Nitrate N and O isotopes from the GP12 ("PANDORA") cruise in the South-West Pacific and Solomon Sea from June to August 2012 carried out as part of the international GEOTRACES program. This dataset was supported by NSF OCE-1060947, NSF OCE-1736652, NSF OCE-0960802, and the Grand Challenges Program of Princeton University. 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/838914
  • Article
    Global 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, Timothy
    Using 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.
  • Article
    Dissolved gases in the deep North Atlantic track ocean ventilation processes
    (National Academy of Sciences, 2023-03-14) Seltzer, Alan M. ; Nicholson, David P. ; Smethie, William M. ; Tyne, Rebecca L. ; Le Roy, Emilie ; Stanley, Rachel H. R. ; Stute, Martin ; Barry, Peter H. ; McPaul, Katelyn ; Davidson, Perrin W. ; Chang, Bonnie X. ; Rafter, Patrick A. ; Lethaby, Paul ; Johnson, Rod J. ; Khatiwala, Samar ; Jenkins, William J.
    Gas exchange between the atmosphere and ocean interior profoundly impacts global climate and biogeochemistry. However, our understanding of the relevant physical processes remains limited by a scarcity of direct observations. Dissolved noble gases in the deep ocean are powerful tracers of physical air-sea interaction due to their chemical and biological inertness, yet their isotope ratios have remained underexplored. Here, we present high-precision noble gas isotope and elemental ratios from the deep North Atlantic (~32°N, 64°W) to evaluate gas exchange parameterizations using an ocean circulation model. The unprecedented precision of these data reveal deep-ocean undersaturation of heavy noble gases and isotopes resulting from cooling-driven air-to-sea gas transport associated with deep convection in the northern high latitudes. Our data also imply an underappreciated and large role for bubble-mediated gas exchange in the global air-sea transfer of sparingly soluble gases, including O, N, and SF. Using noble gases to validate the physical representation of air-sea gas exchange in a model also provides a unique opportunity to distinguish physical from biogeochemical signals. As a case study, we compare dissolved N/Ar measurements in the deep North Atlantic to physics-only model predictions, revealing excess N from benthic denitrification in older deep waters (below 2.9 km). These data indicate that the rate of fixed N removal in the deep Northeastern Atlantic is at least three times higher than the global deep-ocean mean, suggesting tight coupling with organic carbon export and raising potential future implications for the marine N cycle.