labs_title

Caldeira Lab Research:Ocean acidification and ocean carbon cycle

Effect of improved subgrid scale transport of tracers on uptake of bomb radiocarbon in the GFDL ocean general circulation model

P.B. Duffy, P. Eltgroth, A.J. Bourgeois, & K. Caldeira

An investigation of how applying the Gent-McWilliams tracer transport parameterization to the GFDL ocean model affects its ability to model uptake of bomb radiocarbon. A model's ability to simulate uptake of bomb radiocarbon because it can be used as a metric of how well it will be able to predict CO2 uptake.


Duffy, P.B., P. Eltgroth, A. J. Bourgeois, and K. Caldeira, Effect of improved subgrid scale transport of tracers on uptake of bomb radiocarbon in the GFDL ocean general circulation model, Geophysical Research Letters 22, 1065–1068, 1995.

Ocean temperatures predicted by the model compared to observed temperatures: Observed ocean temperatures (Levitus) are here graphed against modeled temperatures with (ISO) and without (HOR) added parameterization. Although the original model predicts temperature well in very shallow and very deep water, its estimations are fairly far off in other parts of the ocean. Adding the parameterization greatly improves the quality of temperature predictions.

Bomb radiocarbon concentration graphed by depth: Observed radiocarbon concentration graphed next to modeled radiocarbon with and without the added parameterization. Despite greatly improved temperature predictions, the new parameterization did not improve the model's ability to predict radiocarbon concentration.

Abstract

We show that the Gent-McWilliams tracer transport parameterization greatly improves the ability of the GFDL ocean general circulation model to simulate vertical profile of both temperature and bomb radiocarbon with a single set of model parameter values. This parameterization, which includes new advection terms as well as isopycnal mixing, has previously been shown to greatly improve simulated temperature fields. Here, we show that it does not markedly affect the already good simulation of oceanic absorption of bomb radiocarbon, and discuss the reasons for this result.