Yool
Andrew
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Andrew
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ArticleChallenges of modeling depth-integrated marine primary productivity over multiple decades : a case study at BATS and HOT(American Geophysical Union, 2010-09-15) Saba, Vincent S. ; Friedrichs, Marjorie A. M. ; Carr, Mary-Elena ; Antoine, David ; Armstrong, Robert A. ; Asanuma, Ichio ; Aumont, Olivier ; Bates, Nicholas R. ; Behrenfeld, Michael J. ; Bennington, Val ; Bopp, Laurent ; Bruggeman, Jorn ; Buitenhuis, Erik T. ; Church, Matthew J. ; Ciotti, Aurea M. ; Doney, Scott C. ; Dowell, Mark ; Dunne, John P. ; Dutkiewicz, Stephanie ; Gregg, Watson ; Hoepffner, Nicolas ; Hyde, Kimberly J. W. ; Ishizaka, Joji ; Kameda, Takahiko ; Karl, David M. ; Lima, Ivan D. ; Lomas, Michael W. ; Marra, John F. ; McKinley, Galen A. ; Melin, Frederic ; Moore, J. Keith ; Morel, Andre ; O'Reilly, John ; Salihoglu, Baris ; Scardi, Michele ; Smyth, Tim J. ; Tang, Shilin ; Tjiputra, Jerry ; Uitz, Julia ; Vichi, Marcello ; Waters, Kirk ; Westberry, Toby K. ; Yool, AndrewThe performance of 36 models (22 ocean color models and 14 biogeochemical ocean circulation models (BOGCMs)) that estimate depth-integrated marine net primary productivity (NPP) was assessed by comparing their output to in situ 14C data at the Bermuda Atlantic Time series Study (BATS) and the Hawaii Ocean Time series (HOT) over nearly two decades. Specifically, skill was assessed based on the models' ability to estimate the observed mean, variability, and trends of NPP. At both sites, more than 90% of the models underestimated mean NPP, with the average bias of the BOGCMs being nearly twice that of the ocean color models. However, the difference in overall skill between the best BOGCM and the best ocean color model at each site was not significant. Between 1989 and 2007, in situ NPP at BATS and HOT increased by an average of nearly 2% per year and was positively correlated to the North Pacific Gyre Oscillation index. The majority of ocean color models produced in situ NPP trends that were closer to the observed trends when chlorophyll-a was derived from high-performance liquid chromatography (HPLC), rather than fluorometric or SeaWiFS data. However, this was a function of time such that average trend magnitude was more accurately estimated over longer time periods. Among BOGCMs, only two individual models successfully produced an increasing NPP trend (one model at each site). We caution against the use of models to assess multiannual changes in NPP over short time periods. Ocean color model estimates of NPP trends could improve if more high quality HPLC chlorophyll-a time series were available.
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ArticleEcosystem model intercomparison of under-ice and total primary production in the Arctic Ocean(John Wiley & Sons, 2016-01-27) Jin, Meibing ; Popova, Ekaterina E. ; Zhang, Jinlun ; Ji, Rubao ; Pendleton, Daniel ; Varpe, Øystein ; Yool, Andrew ; Lee, Younjoo J.Previous observational studies have found increasing primary production (PP) in response to declining sea ice cover in the Arctic Ocean. In this study, under-ice PP was assessed based on three coupled ice-ocean-ecosystem models participating in the Forum for Arctic Modeling and Observational Synthesis (FAMOS) project. All models showed good agreement with under-ice measurements of surface chlorophyll-a concentration and vertically integrated PP rates during the main under-ice production period, from mid-May to September. Further, modeled 30-year (1980–2009) mean values and spatial patterns of sea ice concentration compared well with remote sensing data. Under-ice PP was higher in the Arctic shelf seas than in the Arctic Basin, but ratios of under-ice PP over total PP were spatially correlated with annual mean sea ice concentration, with higher ratios in higher ice concentration regions. Decreases in sea ice from 1980 to 2009 were correlated significantly with increases in total PP and decreases in the under-ice PP/total PP ratio for most of the Arctic, but nonsignificantly related to under-ice PP, especially in marginal ice zones. Total PP within the Arctic Circle increased at an annual rate of between 3.2 and 8.0 Tg C/yr from 1980 to 2009. This increase in total PP was due mainly to a PP increase in open water, including increases in both open water area and PP rate per unit area, and therefore much stronger than the changes in under-ice PP. All models suggested that, on a pan-Arctic scale, the fraction of under-ice PP declined with declining sea ice cover over the last three decades.
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PreprintAnthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms( 2005-07-29) Orr, James C. ; Fabry, Victoria J. ; Aumont, Olivier ; Bopp, Laurent ; Doney, Scott C. ; Feely, Richard A. ; Gnanadesikan, Anand ; Gruber, Nicolas ; Ishida, Akio ; Joos, Fortunat ; Key, Robert M. ; Lindsay, Keith ; Maier-Reimer, Ernst ; Matear, Richard J. ; Monfray, Patrick ; Mouchet, Anne ; Najjar, Raymond G. ; Plattner, Gian-Kasper ; Rodgers, Keith B. ; Sabine, Christopher L. ; Sarmiento, Jorge L. ; Schlitzer, Reiner ; Slater, Richard D. ; Totterdell, Ian J. ; Weirig, Marie-France ; Yamanaka, Yasuhiro ; Yool, AndrewThe surface ocean is everywhere saturated with respect to calcium carbonate (CaCO3). Yet increasing atmospheric CO2 reduces ocean pH and carbonate ion concentrations [CO32−] and thus the level of saturation. Reduced saturation states are expected to affect marine calcifiers even though it has been estimated that all surface waters will remain saturated for centuries. Here we show, however, that some surface waters will become undersaturated within decades. When atmospheric CO2 reaches 550 ppmv, in year 2050 under the IS92a business-as-usual scenario, Southern Ocean surface waters begin to become undersaturated with respect to aragonite, a metastable form of CaCO3. By 2100 as atmospheric CO2 reaches 788 ppmv, undersaturation extends throughout the entire Southern Ocean (< 60°S) and into the subarctic Pacific. These changes will threaten high-latitude aragonite secreting organisms including cold-water corals, which provide essential fish habitat, and shelled pteropods, an abundant food source for marine predators.
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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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ArticleEvaluating global ocean carbon models : the importance of realistic physics(American Geophysical Union, 2004-09-15) Doney, Scott C. ; Lindsay, Keith ; Caldeira, Ken ; Campin, J.-M. ; Drange, Helge ; Dutay, J.-C. ; Follows, Michael J. ; Gao, Y. ; Gnanadesikan, Anand ; Gruber, Nicolas ; Ishida, Akio ; Joos, Fortunat ; Madec, G. ; Maier-Reimer, Ernst ; Marshall, John C. ; Matear, Richard J. ; Monfray, Patrick ; Mouchet, Anne ; Najjar, Raymond G. ; Orr, James C. ; Plattner, Gian-Kasper ; Sarmiento, Jorge L. ; Schlitzer, Reiner ; Slater, Richard D. ; Totterdell, Ian J. ; Weirig, Marie-France ; Yamanaka, Yasuhiro ; Yool, AndrewA suite of standard ocean hydrographic and circulation metrics are applied to the equilibrium physical solutions from 13 global carbon models participating in phase 2 of the Ocean Carbon-cycle Model Intercomparison Project (OCMIP-2). Model-data comparisons are presented for sea surface temperature and salinity, seasonal mixed layer depth, meridional heat and freshwater transport, 3-D hydrographic fields, and meridional overturning. Considerable variation exists among the OCMIP-2 simulations, with some of the solutions falling noticeably outside available observational constraints. For some cases, model-model and model-data differences can be related to variations in surface forcing, subgrid-scale parameterizations, and model architecture. These errors in the physical metrics point to significant problems in the underlying model representations of ocean transport and dynamics, problems that directly affect the OCMIP predicted ocean tracer and carbon cycle variables (e.g., air-sea CO2 flux, chlorofluorocarbon and anthropogenic CO2 uptake, and export production). A substantial fraction of the large model-model ranges in OCMIP-2 biogeochemical fields (±25–40%) represents the propagation of known errors in model physics. Therefore the model-model spread likely overstates the uncertainty in our current understanding of the ocean carbon system, particularly for transport-dominated fields such as the historical uptake of anthropogenic CO2. A full error assessment, however, would need to account for additional sources of uncertainty such as more complex biological-chemical-physical interactions, biases arising from poorly resolved or neglected physical processes, and climate change.
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ArticleOn the origin of water masses in the Beaufort Gyre(American Geophysical Union, 2019-06-26) Kelly, Stephen ; Proshutinsky, Andrey ; Popova, Ekaterina E. ; Aksenov, Yevgeny ; Yool, AndrewThe Beaufort Gyre is a key feature of the Arctic Ocean, acting as a reservoir for freshwater in the region. Depending on whether the prevailing atmospheric circulation in the Arctic is anticyclonic or cyclonic, either a net accumulation or release of freshwater occurs. The sources of freshwater to the Arctic Ocean are well established and include contributions from the North American and Eurasian Rivers, the Bering Strait Pacific water inflow, sea ice meltwater, and precipitation, but their contribution to the Beaufort Gyre freshwater accumulation varies with changes in the atmospheric circulation. Here we use a Lagrangian backward tracking technique in conjunction with the 1/12‐degree resolution Nucleus for European Modelling of the Ocean model to investigate how sources of freshwater to the Beaufort Gyre have changed in recent decades, focusing on increase in the Pacific water content in the gyre between the late 1980s and early 2000s. Using empirical orthogonal functions we analyze the change in the Arctic oceanic circulation that occurred between the 1980s and 2000s. We highlight a “waiting room” advective pathway that was present in the 1980s and provide evidence that this pathway was caused by a shift in the center of Ekman transport convergence in the Arctic. We discuss the role of these changes as a contributing factor to changes in the stratification, and hence potentially the biology, of the Beaufort Gyre region.
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ArticleImpact of circulation on export production, dissolved organic matter, and dissolved oxygen in the ocean : results from Phase II of the Ocean Carbon-cycle Model Intercomparison Project (OCMIP-2)(American Geophysical Union, 2007-08-08) Najjar, Raymond G. ; Jin, X. ; Louanchi, F. ; Aumont, Olivier ; Caldeira, Ken ; Doney, Scott C. ; Dutay, J.-C. ; Follows, Michael J. ; Gruber, Nicolas ; Joos, Fortunat ; Lindsay, Keith ; Maier-Reimer, Ernst ; Matear, Richard J. ; Matsumoto, K. ; Monfray, Patrick ; Mouchet, Anne ; Orr, James C. ; Plattner, Gian-Kasper ; Sarmiento, Jorge L. ; Schlitzer, Reiner ; Slater, Richard D. ; Weirig, Marie-France ; Yamanaka, Yasuhiro ; Yool, AndrewResults are presented of export production, dissolved organic matter (DOM) and dissolved oxygen simulated by 12 global ocean models participating in the second phase of the Ocean Carbon-cycle Model Intercomparison Project. A common, simple biogeochemical model is utilized in different coarse-resolution ocean circulation models. The model mean (±1σ) downward flux of organic matter across 75 m depth is 17 ± 6 Pg C yr−1. Model means of globally averaged particle export, the fraction of total export in dissolved form, surface semilabile dissolved organic carbon (DOC), and seasonal net outgassing (SNO) of oxygen are in good agreement with observation-based estimates, but particle export and surface DOC are too high in the tropics. There is a high sensitivity of the results to circulation, as evidenced by (1) the correlation of surface DOC and export with circulation metrics, including chlorofluorocarbon inventory and deep-ocean radiocarbon, (2) very large intermodel differences in Southern Ocean export, and (3) greater export production, fraction of export as DOM, and SNO in models with explicit mixed layer physics. However, deep-ocean oxygen, which varies widely among the models, is poorly correlated with other model indices. Cross-model means of several biogeochemical metrics show better agreement with observation-based estimates when restricted to those models that best simulate deep-ocean radiocarbon. Overall, the results emphasize the importance of physical processes in marine biogeochemical modeling and suggest that the development of circulation models can be accelerated by evaluating them with marine biogeochemical metrics.