Many of NASA's Earth Science research questions address issues related to the biological and biogeochemical responses to climate forcing. Our research relates to NASA research questions #3: How are global ecosystems changing, and #11: How do ecosystems respond to and affect global environmental change and the carbon cycle? Time-series observations are required tools for answering these questions. Our satellite and in situ time-series measurements of optical, biological and biogeochemical properties in the Sargasso Sea have reached the point where responses to medium-term climate oscillators such as ENSO and NAO can be assessed. We propose to continue our decade-plus series of high-quality in situ optical observations made at the Bermuda Atlantic Time-series site southeast of Bermuda in the North Atlantic subtropical gyre. These observations, which include in-water light fluxes, water leaving radiances, and abundances of chlorophyll, CDOM, and particulate (phytoplankton) absorption spectra, provide information on community structure and biogeochemical cycling in the North Atlantic subtropical gyre, particularly when combined with concurrent measurements made by the BATS program which include primary production, nutrients, phytoplankton pigments, and particulate flux. Our prior results have shown fluctuations in these properties that imply non-local influences (such as the formation of subtropical mode water several hundred miles north of the site), and possible teleconnections to climate oscillators such as the NAO. Thus we propose to combine the in situ observations with remotely sensed observations from EOS platforms, in particular Terra and Aqua MODIS ocean color and aerosol, CERES energy budget products, and other EOS atmospheric products to diagnose decade-scale changes in CDOM abundance, the phytoplankton community, and related ocean properties at the BATS site in the context of regional variability and climate-related forcing including factors controlling mixing and stratification and solar radiation fluxes. Understanding the medium-term responses to climate oscillators will provide us with insight as to the possible changes in the ecosystem driven by longer-term climate change in the future.
