Westberry, Toby: Oregon State University (Project Lead)
Project Funding:
2014 - 2016
NRA: 2013 NASA: Terra and Aqua: Algorithms--Existing Data Products
Funded by NASA
Abstract:
The overarching goal of this proposal is to better characterize non-photochemical quenching (NPQ) processes that affect observed satellite fluorescence. Successful removal of the NPQ signal will result in satellite fluorescence products that provide a clearer picture of phytoplankton physiology over the entire surface ocean. This research project is immediately responsive to NASA Solicitation NNH13ZDA001N-TERAQEA (Terra and Aqua - Algorithms - Existing Data Product Refinement) and is a successor proposal to a previously awarded Terra and Aqua proposal selected under the ROSES 2009 A.41 Research Program Element. Success under this prior award has deepened our understanding of phytoplankton physiology at the global scale and provided a foundation for wider use of MODIS fluorescence products by the ocean color community. The work proposed here improves upon these past efforts.
One of the primary advances over predecessor ocean color missions afforded by MODIS on Aqua and Terra is the capability for detecting the fluoresced radiance from chlorophyll in the surface ocean. Chlorophyll fluorescence is the only remotely sensed property uniquely attributable to phytoplankton, and therefore conveys a wealth of information related to standing stocks, rates of photosynthesis, and important physiological processes. Recent progress in interpretation of the satellite fluorescence signal and its sources of variability has provided an intriguing glimpse of previously unresolved photo-physiology with direct links to climate. However, in order to visualize these physiological patterns in the global ocean, we must be able to properly account for known sources of overlying variability, such as light-driven reductions in fluorescence efficiency (e.g., NPQ). Currently, our inability to accurately remove the NPQ signal from satellite fluorescence data hinders its use over large, ecologically, and climactically significant portions of the global ocean.
Two factors which dominate the distribution of observed MODIS fluorescence data are pigment biomass and NPQ. Correction for the former simply requires normalization to estimates of chlorophyll concentration or total photosynthetic pigment absorption, while the latter requires an understanding of the dynamics of NPQ. In our previously funded NASA project on MODIS fluorescence, we assumed a constant global relationship for NPQ that varied inversely with incident light. This relationship appears relatively robust for much of the tropical and mid-latitude oceans, but several inconsistencies are evident in global imagery, particularly at high latitudes. Moreover, recent results from laboratory-based investigations suggest that the NPQ behavior should vary as a function of phytoplankton photoacclimation state. The research project proposed here seeks to merge a mechanistic cellular level understanding of NPQ with MODIS satellite data through 4 complimentary efforts:
- Extrapolation of laboratory findings on NPQ to satellite estimates of photoacclimation

- Establishment of constraints on NPQ dynamics observed in natural phytoplankton populations using an existing database of active fluorescence and passive radiometry
- Evaluation of NPQ behavior over the course of a daily irradiance cycle from a geostationary ocean color satellite (Korean GOCI)
- Use of wintertime MODIS fluorescence data at high latitudes where overlapping swaths provide multiple views on a given day
Publications:
Chen, S., Hu, C., Byrne, R. H., Robbins, L. L., Yang, B. 2016. Remote estimation of surface pCO2 on the West Florida Shelf. Continental Shelf Research. 128, 10-25. DOI: 10.1016/j.csr.2016.09.004
More details may be found in the following project profile(s):
