|  |
Program |
 |
| |
 |
General Session 1: Physical oceanic processes: Dynamics and physical-biological-biogeochemical interactions |
| |
|
|
Impact of fine-scale physical processes on marine ecosystem dynamics and carbon cycling in the North Pacific Subtropical Gyre
Monday 9th @ 1045-1100
Conference Hall
Xiao Liu* , University of Southern California
Naomi M. Levine, University of Southern California
Presenter Email: liu284@usc.edu
|
| Subtropical gyres contribute significantly to global ocean productivity. As the climate warms, the strength of these gyres as a biological carbon pump is predicted to diminish due to large-scale stratification and depleted surface nutrients. The impact of fine-scale processes (1-10 km) on the subtropical gyre ecosystems, however, has been poorly understood due to observational and computational constrains. We developed a new statistical tool to quantify fine-scale surface patchiness from high-resolution (1 km) satellite sea surface temperature. Chlorophyll concentrations in the North Pacific Subtropical Gyre were shown to be enhanced by fine-scale frontal dynamics with an average increase of 38% (maximum of 83%) during late winter. The magnitude of this enhancement is comparable to the observed decline in chlorophyll due to a warming of ~1.1°C, suggesting that future trends in the changes of fine-scale physics may either compensate or exacerbate the predicted weakening of biological carbon pump. In order to assess the responsiveness of ecosystem and carbon dynamics to fine-scale physics, we also introduced a new modeling approach, the Spatially Heterogeneous Dynamic Plankton (SHiP) model, which allows for subgridscale heterogeneity in physical and biogeochemical environments through probabilistic representation of fine-scale, episodic disturbances. The model was applied to the Hawaiian Ocean Time-series site in the NPSG. Significant differences were noticed between nutrient concentrations, phytoplankton size composition, and carbon export dynamics when the model was run in a temporally and spatially heterogeneous mode relative to the traditional homogeneous approach. We also suggest that the temporal scale (e.g. duration) of the disturbance events is extremely relevant to the responses of ecosystem and carbon dynamics. These findings indicate that the incorporation of fine-scale bio-physical interactions in global-scale climate models is important for accurately modeling and predicting changes of marine ecosystems under future climate projections. |
|
|
|
|