Unprecedented Imaging of an Upwelling Event: RCA Slope Base Shallow Profiler Mooring
Co-registered instruments on the Slope Base Shallow Profiler Mooring, located 108 km offshore Newport, Oregon, yield unprecedented high resolution imagery of a possible short-lived upwelling event and resultant bloom, ~July 5-13, 2025. The above plots from live streaming data from sensors on the stationary platform interface assembly (PIA) located at ~ 200 m water depth (150 kHz ADCP, CTD-O2, and pH), and on an instrumented winched science pod (SciP)(CTD-O2, nitrate, pCO2, 3 wavelength fluorometer), which traverses 9 times a day from ~ 200 m to ~ 5 m beneath the ocean’s surface, highlight the arrival of cold, nutrient-rich water to the surface layers, coinciding with elevated chlorophyll-A concentrations and increased echo intensity in the ADCP data, as well as increased pCO2 and decreased dissolved oxygen concentrations at depth. These trends are coincident with a decrease in temperature, conductivity, dissolved oxygen concentrations, and pH on the PIA. In contrast to the SciP chlorophyll profile, which indicate a bloom in the surface waters above 50 meters, the PIA chlorophyll-A concentrations show no active blooms in the deeper waters. Interestingly, this event coincides with an increase of sea water pressure as measured at the 200 platform, indicating possible current forcing from the NE (and eddy?) acting to “blow down” the platform by ~ 6 m. Several other blow down events have occurred at the Slope Base and Oregon Offshore sites, the largest of which in the summer of 2019 blew the Slope Base platform nearly 50 m deeper and ~350 m to the west.
