Gao Y.

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Gao
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  • Preprint
    Size-fractionated labile trace elements in the Northwest Pacific and Southern Oceans
    ( 2011-04-11) Baeyens, W. ; Bowie, Andrew R. ; Buesseler, Ken O. ; Gao, Y. ; Lamborg, Carl H. ; Remenyi, Tomas A. ; Zhang, H.
    Photosynthesis by marine phytoplankton requires bioavailable forms of several trace elements that are found in extremely low concentrations in the open ocean. We have compared the concentration, lability and size distribution (< 1 nm and < 10 nm) of a suite of trace elements that are thought to be limiting to primary productivity as well as a toxic element (Pb) in two High Nutrient Low Chlorophyll (HNLC) regions using a new dynamic speciation technique, Diffusive Gradients in Thin-film (DGT). The labile species trapped within the DGT probes have a size that is smaller or similar than the pore size of algal cell walls and thus present a proxy for bioavailable species. Total Dissolvable trace element concentrations (TD concentration) varied between 0.05 nM (Co) and 4.0 nM (Ni) at K2 (Northwest Pacific Ocean) and between 0.026 nM (Co) and 4.7 nM (Ni) in the Southern Ocean. The smallest size fractionated labile concentrations (< 1 nm) observed at Southern Ocean sampling stations ranged between 0.002 nM (Co) and 2.1 nM (Ni). Moreover, large differences in bioavailable fractions (ratio of labile to TD concentration) were observed between the trace elements. In the Northwest Pacific Ocean Fe, Cu and Mn had lower labile fractions (between 10 and 44%) than Co, Cd, Ni and Pb (between 80 and 100%). In the Southern Ocean a similar trend was observed, and in addition: (1) Co, Cd, Ni and Pb have lower labile fractions in the Southern Ocean than in the Northwest Pacific and (2) the ratios of <1nm to dissolvable element concentrations at some Southern Ocean stations were very low and varied between 4 and16 %.
  • Article
    Evaluation 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.
  • Article
    Evaluating 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, Andrew
    A 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.