Bullister
John L.
Bullister
John L.
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ArticleDetecting anthropogenic CO2 changes in the interior Atlantic Ocean between 1989 and 2005(American Geophysical Union, 2010-11-30) Wanninkhof, Rik ; Doney, Scott C. ; Bullister, John L. ; Levine, Naomi M. ; Warner, Mark J. ; Gruber, NicolasRepeat observations along the meridional Atlantic section A16 from Iceland to 56°S show substantial changes in the total dissolved inorganic carbon (DIC) concentrations in the ocean between occupations from 1989 through 2005. The changes correspond to the expected increase in DIC driven by the uptake of anthropogenic CO2 from the atmosphere, but the ΔDIC is more varied and larger, in some locations, than can be explained solely by this process. Concomitant large changes in oxygen (O2) suggest that processes acting on the natural carbon cycle also contribute to ΔDIC. Precise partial pressure of CO2 measurements suggest small but systematic increases in the bottom waters. To isolate the anthropogenic CO2 component (ΔCanthro) from ΔDIC, an extended multilinear regression approach is applied along isopycnal surfaces. This yields an average depth-integrated ΔCanthro of 0.53 ± 0.05 mol m−2 yr−1 with maximum values in the temperate zones of both hemispheres and a minimum in the tropical Atlantic. A higher decadal increase in the anthropogenic CO2 inventory is found for the South Atlantic compared to the North Atlantic. This anthropogenic CO2 accumulation pattern is opposite to that seen for the entire Anthropocene up to the 1990s. This change could perhaps be a consequence of the reduced downward transport of anthropogenic CO2 in the North Atlantic due to recent climate variability. Extrapolating the results for this section to the entire Atlantic basin (63°N to 56°S) yields an uptake of 5 ± 1 Pg C decade−1, which corresponds to about 25% of the annual global ocean uptake of anthropogenic CO2 during this period.
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ArticleChanges in deep-water CO2 concentrations over the last several decades determined from discrete pCO2 measurements(Elsevier Ltd, 2013-02-09) Wanninkhof, Rik ; Park, Geun-Ha ; Takahashi, Taro ; Feely, Richard A. ; Bullister, John L. ; Doney, Scott C.Detection and attribution of hydrographic and biogeochemical changes in the deep ocean are challenging due to the small magnitude of their signals and to limitations in the accuracy of available data. However, there are indications that anthropogenic and climate change signals are starting to manifest at depth. The deep ocean below 2000 m comprises about 50% of the total ocean volume, and changes in the deep ocean should be followed over time to accurately assess the partitioning of anthropogenic carbon dioxide (CO2) between the ocean, terrestrial biosphere, and atmosphere. Here we determine the changes in the interior deep-water inorganic carbon content by a novel means that uses the partial pressure of CO2 measured at 20 °C, pCO2(20), along three meridional transects in the Atlantic and Pacific oceans. These changes are measured on decadal time scales using observations from the World Ocean Circulation Experiment (WOCE)/World Hydrographic Program (WHP) of the 1980s and 1990s and the CLIVAR/CO2 Repeat Hydrography Program of the past decade. The pCO2(20) values show a consistent increase in deep water over the time period. Changes in total dissolved inorganic carbon (DIC) content in the deep interior are not significant or consistent, as most of the signal is below the level of analytical uncertainty. Using an approximate relationship between pCO2(20) and DIC change, we infer DIC changes that are at the margin of detectability. However, when integrated on the basin scale, the increases range from 8–40% of the total specific water column changes over the past several decades. Patterns in chlorofluorocarbons (CFCs), along with output from an ocean model, suggest that the changes in pCO2(20) and DIC are of anthropogenic origin.
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ArticleA comprehensive estimate for loss of atmospheric carbon tetrachloride (CCl4) to the ocean(Copernicus Publications on behalf of the European Geosciences Union, 2016-09-01) Butler, James H. ; Yvon-Lewis, Shari ; Lobert, Jurgen M. ; King, Daniel B. ; Montzka, Stephen ; Bullister, John L. ; Koropalov, Valentin ; Elkins, James W. ; Hall, Bradley D. ; Hu, Lei ; Liu, YinaExtensive undersaturations of carbon tetrachloride (CCl4) in Pacific, Atlantic, and Southern Ocean surface waters indicate that atmospheric CCl4 is consumed in large amounts by the ocean. Observations made on 16 research cruises between 1987 and 2010, ranging in latitude from 60° N to 77° S, show that negative saturations extend over most of the surface ocean. Corrected for physical effects associated with radiative heat flux, mixing, and air injection, these anomalies were commonly on the order of −5 to −10 %, with no clear relationship to temperature, productivity, or other gross surface water characteristics other than being more negative in association with upwelling. The atmospheric flux required to sustain these undersaturations is 12.4 (9.4–15.4) Gg yr−1, a loss rate implying a partial atmospheric lifetime with respect to the oceanic loss of 183 (147–241) yr and that ∼ 18 (14–22) % of atmospheric CCl4 is lost to the ocean. Although CCl4 hydrolyzes in seawater, published hydrolysis rates for this gas are too slow to support such large undersaturations, given our current understanding of air–sea gas exchange rates. The even larger undersaturations in intermediate depth waters associated with reduced oxygen levels, observed in this study and by other investigators, strongly suggest that CCl4 is ubiquitously consumed at mid-depth, presumably by microbiota. Although this subsurface sink creates a gradient that drives a downward flux of CCl4, the gradient alone is not sufficient to explain the observed surface undersaturations. Since known chemical losses are likewise insufficient to sustain the observed undersaturations, this suggests a possible biological sink for CCl4 in surface or near-surface waters of the ocean. The total atmospheric lifetime for CCl4, based on these results and the most recent studies of soil uptake and loss in the stratosphere is now 32 (26–43) yr.
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ArticleBiogeochemical protocols and diagnostics for the CMIP6 Ocean Model Intercomparison Project (OMIP)(Copernicus Publications on behalf of the European Geosciences Union, 2017-06-09) Orr, James C. ; Najjar, Raymond G. ; Aumont, Olivier ; Bopp, Laurent ; Bullister, John L. ; Danabasoglu, Gokhan ; Doney, Scott C. ; Dunne, John P. ; Dutay, Jean-Claude ; Graven, Heather ; Griffies, Stephen M. ; John, Jasmin G. ; Joos, Fortunat ; Levin, Ingeborg ; Lindsay, Keith ; Matear, Richard J. ; McKinley, Galen A. ; Mouchet, Anne ; Oschlies, Andreas ; Romanou, Anastasia ; Schlitzer, Reiner ; Tagliabue, Alessandro ; Tanhua, Toste ; Yool, AndrewThe Ocean Model Intercomparison Project (OMIP) focuses on the physics and biogeochemistry of the ocean component of Earth system models participating in the sixth phase of the Coupled Model Intercomparison Project (CMIP6). OMIP aims to provide standard protocols and diagnostics for ocean models, while offering a forum to promote their common assessment and improvement. It also offers to compare solutions of the same ocean models when forced with reanalysis data (OMIP simulations) vs. when integrated within fully coupled Earth system models (CMIP6). Here we detail simulation protocols and diagnostics for OMIP's biogeochemical and inert chemical tracers. These passive-tracer simulations will be coupled to ocean circulation models, initialized with observational data or output from a model spin-up, and forced by repeating the 1948–2009 surface fluxes of heat, fresh water, and momentum. These so-called OMIP-BGC simulations include three inert chemical tracers (CFC-11, CFC-12, SF6) and biogeochemical tracers (e.g., dissolved inorganic carbon, carbon isotopes, alkalinity, nutrients, and oxygen). Modelers will use their preferred prognostic BGC model but should follow common guidelines for gas exchange and carbonate chemistry. Simulations include both natural and total carbon tracers. The required forced simulation (omip1) will be initialized with gridded observational climatologies. An optional forced simulation (omip1-spunup) will be initialized instead with BGC fields from a long model spin-up, preferably for 2000 years or more, and forced by repeating the same 62-year meteorological forcing. That optional run will also include abiotic tracers of total dissolved inorganic carbon and radiocarbon, CTabio and 14CTabio, to assess deep-ocean ventilation and distinguish the role of physics vs. biology. These simulations will be forced by observed atmospheric histories of the three inert gases and CO2 as well as carbon isotope ratios of CO2. OMIP-BGC simulation protocols are founded on those from previous phases of the Ocean Carbon-Cycle Model Intercomparison Project. They have been merged and updated to reflect improvements concerning gas exchange, carbonate chemistry, and new data for initial conditions and atmospheric gas histories. Code is provided to facilitate their implementation.
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ArticleEvaluation of ocean carbon cycle models with data-based metrics(American Geophysical Union, 2004-04-02) Matsumoto, K. ; Sarmiento, Jorge L. ; Key, Robert M. ; Aumont, Olivier ; Bullister, John L. ; Caldeira, Ken ; Campin, J.-M. ; Doney, Scott C. ; Drange, Helge ; Dutay, J.-C. ; Follows, Michael J. ; Gao, Y. ; Gnanadesikan, Anand ; Gruber, Nicolas ; Ishida, Akio ; Joos, Fortunat ; Lindsay, Keith ; Maier-Reimer, Ernst ; Marshall, John C. ; Matear, Richard J. ; Monfray, Patrick ; Mouchet, Anne ; Najjar, Raymond G. ; Plattner, Gian-Kasper ; Schlitzer, Reiner ; Slater, Richard D. ; Swathi, P. S. ; Totterdell, Ian J. ; Weirig, Marie-France ; Yamanaka, Yasuhiro ; Yool, Andrew ; Orr, James C.New radiocarbon and chlorofluorocarbon-11 data from the World Ocean Circulation Experiment are used to assess a suite of 19 ocean carbon cycle models. We use the distributions and inventories of these tracers as quantitative metrics of model skill and find that only about a quarter of the suite is consistent with the new data-based metrics. This should serve as a warning bell to the larger community that not all is well with current generation of ocean carbon cycle models. At the same time, this highlights the danger in simply using the available models to represent the state-of-the-art modeling without considering the credibility of each model.
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Technical ReportHydrographic data from R/V Endeavor cruise #143(Woods Hole Oceanographic Institution, 1988-03) Stalcup, Marvel C. ; Joyce, Terrence M. ; Bullister, John L. ; Barbour, R. Lorraine ; Dunworth, Jane A.Hydrographic data collected during R/V Endeavor cruise 143 is presented as a preliminary study of subduction in the northeast Atlantic south of the Azores Front. The front is clearly defined at the northern end of CTD section #1 which also shows a layer of 16-18°C water subducted to the south. Section #2, 280 km to the east, is dominated by a large cyclonic ring with characteristics similar to 'eastern' rings reported earlier . An anomalously salty parcel of Mediterranean water in this section is typical of highly saline lenses seen in the Canary Basin.
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PreprintChanges in ocean heat, carbon content, and ventilation : a review of the first decade of GO-SHIP Global Repeat Hydrography( 2015-05-30) Talley, Lynne D. ; Feely, Richard A. ; Sloyan, Bernadette M. ; Wanninkhof, Rik ; Baringer, Molly O. ; Bullister, John L. ; Carlson, Craig A. ; Doney, Scott C. ; Fine, Rana A. ; Firing, Eric ; Gruber, Nicolas ; Hansell, Dennis A. ; Ishii, Masayoshi ; Johnson, Gregory ; Katsumata, K. ; Key, Robert M. ; Kramp, Martin ; Langdon, Chris ; Macdonald, Alison M. ; Mathis, Jeremy T. ; McDonagh, Elaine L. ; Mecking, Sabine ; Millero, Frank J. ; Mordy, Calvin W. ; Nakano, T. ; Sabine, Chris L. ; Smethie, William M. ; Swift, James H. ; Tanhua, Toste ; Thurnherr, Andreas M. ; Warner, Mark J. ; Zhang, Jia-ZhongThe ocean, a central component of Earth’s climate system, is changing. Given the global scope of these changes, highly accurate measurements of physical and biogeochemical properties need to be conducted over the full water column, spanning the ocean basins from coast to coast, and repeated every decade at a minimum, with a ship-based observing system. Since the late 1970s, when the Geochemical Ocean Sections Study (GEOSECS) conducted the first global survey of this kind, the World Ocean Circulation Experiment (WOCE) and Joint Global Ocean Flux Study (JGOFS), and now the Global Ocean Ship-based Hydrographic Investigations Program (GO-SHIP) have collected these “reference standard” data that allow quantification of ocean heat and carbon uptake, and variations in salinity, oxygen, nutrients, and acidity on basin scales. The evolving GO-SHIP measurement suite also provides new global information about dissolved organic carbon, a large bioactive reservoir of carbon.
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ArticleAn intercomparison of oceanic methane and nitrous oxide measurements(Copernicus Publications on behalf of the European Geosciences Union, 2018-10-05) Wilson, Samuel T. ; Bange, Hermann W. ; Arévalo-Martínez, Damian L. ; Barnes, Jonathan ; Borges, Alberto V. ; Brown, Ian ; Bullister, John L. ; Burgos, Macarena ; Capelle, David W. ; Casso, Michael A. ; de la Paz, Mercedes ; Farías, Laura ; Fenwick, Lindsay ; Ferrón, Sara ; Garcia, Gerardo ; Glockzin, Michael ; Karl, David M. ; Kock, Annette ; Laperriere, Sarah ; Law, Cliff S. ; Manning, Cara C. ; Marriner, Andrew ; Myllykangas, Jukka-Pekka ; Pohlman, John W. ; Rees, Andrew P. ; Santoro, Alyson E. ; Tortell, Philippe D. ; Upstill-Goddard, Robert C. ; Wisegarver, David P. ; Zhang, Gui-Ling ; Rehder, GregorLarge-scale climatic forcing is impacting oceanic biogeochemical cycles and is expected to influence the water-column distribution of trace gases, including methane and nitrous oxide. Our ability as a scientific community to evaluate changes in the water-column inventories of methane and nitrous oxide depends largely on our capacity to obtain robust and accurate concentration measurements that can be validated across different laboratory groups. This study represents the first formal international intercomparison of oceanic methane and nitrous oxide measurements whereby participating laboratories received batches of seawater samples from the subtropical Pacific Ocean and the Baltic Sea. Additionally, compressed gas standards from the same calibration scale were distributed to the majority of participating laboratories to improve the analytical accuracy of the gas measurements. The computations used by each laboratory to derive the dissolved gas concentrations were also evaluated for inconsistencies (e.g., pressure and temperature corrections, solubility constants). The results from the intercomparison and intercalibration provided invaluable insights into methane and nitrous oxide measurements. It was observed that analyses of seawater samples with the lowest concentrations of methane and nitrous oxide had the lowest precisions. In comparison, while the analytical precision for samples with the highest concentrations of trace gases was better, the variability between the different laboratories was higher: 36% for methane and 27% for nitrous oxide. In addition, the comparison of different batches of seawater samples with methane and nitrous oxide concentrations that ranged over an order of magnitude revealed the ramifications of different calibration procedures for each trace gas. Finally, this study builds upon the intercomparison results to develop recommendations for improving oceanic methane and nitrous oxide measurements, with the aim of precluding future analytical discrepancies between laboratories.
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ArticlePacific anthropogenic carbon between 1991 and 2017(American Geophysical Union, 2019-04-29) Carter, Brendan ; Feely, Richard A. ; Wanninkhof, Rik ; Kouketsu, Shinya ; Sonnerup, Rolf E. ; Pardo, Paula Conde ; Sabine, Christopher L. ; Johnson, Gregory C. ; Sloyan, Bernadette M. ; Murata, Akihiko ; Mecking, Sabine ; Tilbrook, Bronte ; Speer, Kevin G. ; Talley, Lynne D. ; Millero, Frank J. ; Wijffels, Susan E. ; Macdonald, Alison M. ; Gruber, Nicolas ; Bullister, John L.We estimate anthropogenic carbon (Canth) accumulation rates in the Pacific Ocean between 1991 and 2017 from 14 hydrographic sections that have been occupied two to four times over the past few decades, with most sections having been recently measured as part of the Global Ocean Ship‐based Hydrographic Investigations Program. The rate of change of Canth is estimated using a new method that combines the extended multiple linear regression method with improvements to address the challenges of analyzing multiple occupations of sections spaced irregularly in time. The Canth accumulation rate over the top 1,500 m of the Pacific increased from 8.8 (±1.1, 1σ) Pg of carbon per decade between 1995 and 2005 to 11.7 (±1.1) PgC per decade between 2005 and 2015. For the entire Pacific, about half of this decadal increase in the accumulation rate is attributable to the increase in atmospheric CO2, while in the South Pacific subtropical gyre this fraction is closer to one fifth. This suggests a substantial enhancement of the accumulation of Canth in the South Pacific by circulation variability and implies that a meaningful portion of the reinvigoration of the global CO2 sink that occurred between ~2000 and ~2010 could be driven by enhanced ocean Canth uptake and advection into this gyre. Our assessment suggests that the accuracy of Canth accumulation rate reconstructions along survey lines is limited by the accuracy of the full suite of hydrographic data and that a continuation of repeated surveys is a critical component of future carbon cycle monitoring.