Drange Helge

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Drange
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Helge
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  • 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.
  • Preprint
    Formation and export of deep water in the Labrador and Irminger Seas in a GCM
    ( 2006-12-13) Deshayes, Julie ; Frankignoul, Claude ; Drange, Helge
    The influence of changes in the rate of deep water formation in the North Atlantic subpolar gyre on the variability of the transport in the Deep Western Boundary Current is investigated in a realistic hind cast simulation of the North Atlantic during the 1953–2003 period. In the simulation, deep water formation takes place in the Irminger Sea, in the interior of the Labrador Sea and in the Labrador Current. In the Irminger Sea, deep water is formed close to the boundary currents. It is rapidly exported out of the Irminger Sea via an intensified East Greenland Current, and out of the Labrador Sea via increased southeastward transports. The newly formed deep water, which is advected to Flemish Cap in approximately one year, is preceded by fast propagating topographic waves. Deep water formed in the Labrador Sea interior tends to accumulate and recirculate within the basin, with a residence time of a few years in the Labrador Sea. Hence, it is only slowly exported northeastward to the Irminger Sea and southeastward to the subtropical North Atlantic, reaching Flemish Cap in 1–5 years. As a result, the transport in the Deep Western Boundary Current is mostly correlated with convection in the Irminger Sea. Finally, the deep water produced in the Labrador Current is lighter and is rapidly exported out of the Labrador Basin, reaching Flemish Cap in a few months. As the production of deep-water along the western periphery of the Labrador Sea is maximum when convection in the interior is minimum, there is some compensation between the deep water formed along the boundary and in the interior of the basin, which reduces the variability of its net transport. These mechanisms which have been suggested from hydrographic and tracer observations, help one to understand the variability of the transport in the Deep Western Boundary Current at the exit of the subpolar gyre.