John Marshall

Cecil and Ida Green Professor of Oceanography, MIT

Evaluation of ocean model ventilation with CFC-11: comparison of 13 global ocean models

Evaluation of ocean model ventilation with CFC-11: comparison of 13 global ocean models.

(Dutay, J. -C. and Bullister, J. L. and Doney, S. C. and Orr, J. C. and Najjar, R. and Caldeira, K. and Campin, J. -M. and Drange, H. and Follows, M. and Gao, Y. and Gruber, N. and Hecht, M. W. and Ishida, A. and Joos, F. and Lindsay, K. and Madec, G. and Maier-Reimer, E. and Marshall, J. C. and Matear, R. J. and Monfray, P. and Mouchet, A. and Plattner, G. -K. and Sarmiento, J. and Schlitzer, R. and Slater, R. and Totterdell, I. J. and Weirig, M. -F. and Yamanaka, Y. and Yool, A.), OCEAN MODELLING, vol. 4, no. 2, pp. pages, 2002.

Abstract

We compared the 13 models participating in the Ocean Carbon Model Intercomparison Project (OCMIP) with regards to their skill in matching observed distributions of CFC-11. This analysis characterizes the abilities of these models to ventilate the ocean on timescales relevant for anthropogenic CO2) uptake. We found a large range in the modeled global inventory (+/- 30%), mainly due to differences in ventilation from the high latitudes. In the Southern Ocean, models differ particularly in the longitudinal distribution of the CFC uptake in the intermediate water, whereas the latitudinal distribution is mainly controlled by the subgrid-scale parameterization. Models with isopycnal diffusion and eddy-induced velocity parameterization produce more realistic intermediate water ventilation. Deep and bottom water ventilation also varies substantially between the models. Models coupled to a sea-ice model systematically provide more realistic AABW formation source region; however these same models also largely overestimate AABW ventilation if no specific parameterization of brine rejection during sea-ice formation is included. In the North Pacific Ocean, all models exhibit a systematic large underestimation of the CFC uptake in the thermocline of the subtropical gyre, while no systematic difference toward the observations is found in the subpolar gyre. In the North Atlantic Ocean, the CFC uptake is globally underestimated in subsurface. In the deep ocean, all but the adjoint model, failed to produce the two recently ventilated branches observed in the North Atlantic Deep Water (NADW). Furthermore, simulated transport in the Deep Western Boundary Current (DWBC) is too sluggish in all but the isopycnal model, where it is too rapid.

doi = 10.1016/S1463-5003(01)00013-0