Dataset: Biological influences on mixed-layer dynamics and global ocean circulation, OGCM/OCMIP-Caldeira, 2001 (U.S. JGOFS Synthesis & Modeling Phase project results)

It is well known that (1) plankton dynamics are affected by solar radiation and mixed-layer dynamics, (2) plankton dynamics affect water transparency and solar extinction, and (3) solar extinction affects mixed-layer dynamics. We propose to test the hypotheses that:

1. Solar extinction in the water column is an important factor affecting absorption of excess CO2 in the global ocean.
2. Feedbacks involving marine biology, turbidity, solar-extinction, and mixed-layer dynamics, significantly affect oceanic carbon fluxes and air-sea gas exchange, both in the steady state and in response to climate change.

We will investigate the effect of these factors on CO2 fluxes in the global ocean by performing a suite of ocean general circulation (and one-dimensional) model simulations (some driven with satellite color data, others using a simple trophic-level model), and evaluating these GCM simulations by comparing model results with observations collected at the JGOFS times series sites and process study areas (and other available observations). Our general circulation and carbon-cycle models already exist and run on massively parallel machines; the proposed study involves a modest amount of new model development. This development will focus on estimating export production using satellite-based methods of estimating primary production (e.g., Behrenfeld and Falkowski, 1997; Longhurst et al., 1995).

The proposed study supports NASA and JGOFS objectives by using remote sensing, and in situ data from JGOFS, to study the impact on carbon dioxide fluxes of feedbacks involving primary production, transparency, and upper ocean dynamics. This study will emphasize satellite ocean color scanner imagery as a principal data source, although satellite derived fields such as wind speeds and irradiances will also be used in this study to drive the ocean model. In situ data collected as part of JGOFS and other programs will be essential to determining appropriate model parameter values and in evaluating model results. Conversely, the model results should help in understanding the dynamics observed at the U.S. JGOFS process study and time-series stations.

By the end of our study, it will be clear if, how, and why subsurface penetration of solar radiation is an important factor affecting global and regional scale air-sea CO2 fluxes and ocean carbon transport.