ABSTRACT

The ocean covers 71% of Earth's surface and provides highly dynamic ecosystems in which natural and human factors interplay. Understanding oceanic responses to Earth's changing climate, its role in land-ocean-atmosphere carbon cycles, regional ecosystems' responses to hazards, and the health of aquatic fisheries and other critical habits - to name only a few - requires access to substantial volumes of marine biogeochemical data. The advent of satellite oceanography in the late 1970's offered Earth scientists a much-needed wide-angle lens with which to view the vast expanses of life near the ocean's surface. In particular, "ocean color" satellite instruments began providing continuous, synoptic views of ocean ecosystems on spatial and temporal scales that were not only otherwise unobtainable using conventional in situ and airborne platforms, but also useful for retrospective analyses of spatio-temporal trends. This resulted in an explosion of scientific discovery, particularly with regards to distributions of aquatic phytoplankton - the microscopic algae, bacteria, and plants that form the base of the marine food chain by converting inorganic CO2 to organic cellular material while also providing much of the oxygen we breathe. Yes, satellites flying 700 km above us provide invaluable information about the microscopic living (and non-living) ocean. As the contents of the upper ocean shape the distribution of the marine light field, they ultimately give the ocean its color. By measuring the spectral distribution of light leaving the ocean (that is, its "ocean color"), satellite radiometers can be used to infer the contents of the water column, including information useful for climate and carbon cycles studies, fisheries and watershed management, and water quality monitoring. The continuous global data record from polar orbiting ocean color satellites in low earth orbit now spans 25 years. In this talk, I will review the principles of ocean color, its evolution over the past several decades with attention to advances in satellite instrument technologies, bio-optical algorithms, and scientific discoveries, as well as the current state-of-the-art in passive satellite bio-optical oceanography.

About the Speaker:

Dr. Jeremy Werdell is an Oceanographer in the Ocean Ecology Laboratory at NASA Goddard Space Flight Center (GSFC), where he also serves as the Project Scientist for the upcoming NASA Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission. Jeremy resolved to become a marine scientist in 1988 upon his return from an eighth grade science trip to the Bermuda Biological Station for Research. He joined GSFC in 1999, where he has remained ever since in the pursuit of improving our understanding of the ocean's biological responses to Earth's changing climate - namely, how the spatial distributions of phytoplankton communities evolve over time. Given that Jeremy wears a NASA badge, his mandatory secondary interests extend to the more challenging aspects of satellite remote sensing, including the on-orbit calibration of ocean color instruments, the development of remote-sensing algorithms, and the validation of satellite-derived data products. These, in combination with his subject matter living in a three-dimensional fluid on a rotating ellipsoid, create a research environment packed with opportunities to contribute to NASA's pursuit of better understanding our home planet.