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Earth and Environmental Sciences pres.

Seminar: Are the North Pacific Chlorophyll Blooms Caused by Breaking Internal Waves?

Dr. Cara Wilson, Research Oceanographer, Environmental Research Division, NOAA/NMFS/SWFSC

Map-Chlorophyll Concentrations Map-Chlorophyll Concentrations
Map-Chlorophyll Concentrations
The analysis of ocean color satellite data has detected summer blooms of chlorophyll that consistently develop in the oligotrophic North Pacific Ocean between Hawaii and 30°N. In this seminar I will describe the features of these blooms and discuss the potential biological and physical forcing mechanisms that cause them. Based on limited field sampling it appears that these blooms often contain diatom—diazotrophic associations (DDAs). Blooms of both Hemiaulus and Rhizosolenia diatoms, both containing the nitrogen-fixing endophyte Richelia intracellularis, have been sampled within the satellite-defined bloom features. The blooms develop in late summer in a very consistent location, ~30°N, and 130-150°W, and they occur almost every year. The general oceanography principals that explain the global chlorophyll distribution cannot account for these blooms, and their existence suggests evidence of enhanced tidal mixing in this area. The region near 30° is a “double” critical latitude, with a transformation of internal waves occurring at both diurnal and semidiurnal frequencies. The breakdown at the critical latitude of internal waves generated at Hawaii could provide the physical mechanism to explain these blooms. Subsurface data will be also be presented from a Biogeochemical-Argo float that collected data synoptic with the development of a chlorophyll bloom in 2014.
Map-Chlorophyll Concentrations Map-Chlorophyll Concentrations
Map-Chlorophyll Concentrations

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