Yellowing coastal seas in the Anthropocene

William M. Balch, Bigelow Laboratory for Ocean Sciences, bbalch@bigelow.org (Presenter)
Thomas Huntington, U.S. Geological Survey
George Aiken, U.S. Geological Survey
David Drapeau, Bigelow Laboratory for Ocean Sciences
Bruce Bowler, Bigelow Laboratory for Ocean Sciences
Laura Lubelczyk, Bigelow Laboratory for Ocean Sciences
Kenna Butler, U.S. Geological Survey

Our presentation will begin with a review of the problem of understanding plant pigments in coastal, river-impacted regions, an issue which has plagued our ability to discriminate between living phytoplankton and chromophoric dissolved organic matter (CDOM) since the very first ocean color mission, the Coastal Zone Color Scanner. This issue has become more problematic recently given the intensifying hydrological cycle which plays a first-order role for mobilizing CDOM and dissolved organic carbon (DOC) from watersheds. This, combined with global warming (and associated increases in bacterial remineralization), means that more CDOM and DOC is being leached from watersheds that drain watersheds into coastal waters. There have been remarkably few opportunities to systematically examine long-term change in ocean color (i.e. that predate ocean color satellites) but thanks to a fortuitous encounter in a New York City antique book store, an observant oceanographer on a schooner in 1912-13 (Henry Bigelow), long-term USGS observations of river discharge in Maine and the NASA-funded Gulf of Maine North Atlantic Time Series (GNATS; 1998-2015), we will show how the Gulf of Maine appears to have yellowed over the last century as more CDOM and DOC have been exported from rivers. Using the Load Estimator (LOADEST) regression software model (with obvious assumptions of stationarity), we also predict that DOC export from landscapes-to-coasts will continue to increase, well into the twenty-first century. The future PACE mission will be well-instrumented to observe this change given its hyperspectral capabilities extending into the UV part of the spectrum.

Presentation Type:  Plenary Talk

Session:  Theme 2: Landscapes to coasts: understanding Earth system connections

Presentation Time:  Mon 3:14 PM  (22 minutes)