Low Dissolved Oxygen off Washington and Oregon Coast Impacted by Upwelling in 2017
In the summer of 2020, the Rutgers University Ocean Data Labs project worked with the Rutgers Research Internships in Ocean Science to support ten undergraduate students in a virtual Research Experiences for Undergraduates program. Rutgers led two weeks of research methods training and Python coding instruction. This was followed by six weeks of independent study with one of 13 research mentors.
Dr. Tom Connolly (Moss Landing Marine Labs, San Jose State University) advised Andrea Selkow from Austin College, Texas on her study of dissolved oxygen (DO) off the Washington and Oregon coasts using the OOI Endurance Array.
Selkow evaluated DO data from Endurance Array Surface Moorings during 2017 and 2018. She presented this work as a poster at the conclusion of her summer REU. Selkow focused on the question: Are there similarities in the dissolved oxygen concentrations off the coast of Oregon and Washington during a known low oxygen event? She also considered why there might exist differences based on the spatial variability of wind stress forcing, i.e., do the strong Oregon winds cause dissolved oxygen concentrations to be lower at the Oregon mooring compared to the Washington moorings. Finally, she reviewed the data and tried to answer whether the oxygen data were accurate or affected by biofouling.
She used datasets from the OR and WA Inshore Shelf Mooring time-series and WA Shelf Mooring time-series from Endurance Array. Her focus was on the seafloor data because that is where the lowest oxygen concentrations were expected to be observed.
Selkow focused her attention on low DO observed in the summer of 2017. While Barth et al. (2018) presented a report on these data for one event in July 2017, she expanded the analysis to include the Washington shelf and inshore moorings. She plotted time series data and used cruise data to validate these time series. While overall seasonal trends in DO were similar, she found dissolved oxygen is routinely more quickly depleted off the coast of Oregon than Washington during a low oxygen event (Figure 25). She also looked at the cross-shelf variability in DO time series and found dissolved oxygen is more quickly depleted at the shelf mooring than at the inshore shelf mooring. Upwelling is known to drive the low oxygen events and she inferred that the weaker southward winds over the Washington shelf may be why DO decreases at a slower rate off Washington than Oregon.
References
Barth, J.A., J.P. Fram, E.P. Dever, C.M. Risien, C.E. Wingard, R.W. Collier, and T.D. Kearney. 2018. Warm blobs, low-oxygen events, and an eclipse: The Ocean Observatories Initiative Endurance Array captures them all. Oceanography 31(1):90–97,
Selkow, A. and T. Connelly. Low Dissolved Oxygen off Washington and Oregon Coast Impacted by Upwelling in 2017, Accessed 13 Jan 2021.