Title

Long term chlorophyll observations in the Great Lakes from oceancolor satellite data using multiple retrieval approaches

Document Type

Conference Paper/Presentation

Publication Date

5-2014

Abstract

Ocean color satellites such as CZCS, SeaWiFS, MODIS, MERIS, and VIIRS have been imaging the Great Lakes and providing chlorophyll (chl) concentrations since 1979. Historically, the chl concentrations have been produced using an empirical band ratio technique developed by NASA for the open ocean. An alternative to the ratio technique is the use of semi-analytical Inverse Radiative Transfer Models (IRTM) such as the MTRI CPA-A. The IRTM approach requires knowledge of the optical properties of the Great Lakes and can provide more robust chl estimates in case II coastal waters where the color producing agents (CPAs) in the water include dissolved organic carbon and suspended minerals in addition to chl. Chl estimates from the NASA OC3 band ratio, CPA-A (IRTM), and EPA ship surveys were compared for the period 1998 to 2013. The comparisons which utilized Sea- WiFS and MODIS satellite data show the changing water optical properties of the Great Lakes as a function of nutrient loading and invasive species presence. The comparison also indicated in the present day offshore areas of the Lakes where the dominant CPA is chl, the ratio and CPA-A methods both produce acceptable retrievals. In complex case II water such as Lake Erie and near shore regions throughout the Lakes the CPA-A estimates of chl are significantly more robust.

Publisher's Statement

© 2014 The authors.

Publication Title

IAGLR 57th Annual Conference on Great Lakes Research