Light-absorbing components in the Great Lakes

Features of light absorption are critical in regulating the optical signal available for remote sensing. The magnitudes, spectral characteristics, spatial patterns, and, to a lesser extent, dynamics of light-absorbing components are documented for the Laurentian Great Lakes. This includes the open waters of each of the five lakes, and selected rivers, embayments and near-shore areas. The absorption coefficient, a(m), is partitioned according to the additive components (a.) of colored dissolved organic matter (a(cDom)), non-algal particles (a(NAP)), phytoplankton (a), and water itself (a(w); known). Dependencies of a(x) on various metrics of optically active constituents (OACs), cross-sections, are evaluated. A wide range of magnitudes of a(x) and a, and contributions of a(x) to a are documented. For example, the magnitude of a at a wavelength of 440 nm was nearly 10-fold greater in the western basin of Lake Erie than in the open waters of Lake Huron. Rivers, embayments, and near-shore areas generally had higher levels than the open waters. The largest a(x) throughout the system was acDom, originating mostly from terrestrial sources. Most of amp was associated with clay mineral particles. The distribution of ago was highly correlated to chlorophyll concentration. The collected data set is appropriate to support initiatives to develop and preliminarily test mechanistic retrieval algorithms for OACs in the Great Lakes. (C) 2013 International Association for Great Lakes Research. Published by Elsevier B.V. All rights reserved.