Seasonal and interannual oxygen variability on the Washington and Oregon continental shelves

TitleSeasonal and interannual oxygen variability on the Washington and Oregon continental shelves
Publication TypeJournal Article
Year of Publication2015
AuthorsSiedlecki S.A, Banas N.S, Davis K.A, Giddings S., Hickey B.M, MacCready P., Connolly T., Geier S.
JournalJournal of Geophysical Research: Oceans
Date Published2015/02
ISBN Number2169-9291
Keywords0466 Modeling; 1615 Biogeochemical cycles, processes, and modeling; 4219 Continental shelf and slope processes; 4279 Upwelling and convergences; 4834 Hypoxic environments; hypoxia; oxygen; respiration; Upwelling

The coastal waters of the northern portion of the California Current System experience a seasonal decline in oxygen concentrations and hypoxia over the summer upwelling season that results in negative impacts on habitat for many organisms. Using a regional model extending from 43°N to 50°N, with an oxygen component developed in this study, drivers of seasonal and regional oxygen variability are identified. The model includes two pools of detritus, which was an essential addition in order to achieve good agreement with the observations. The model was validated using an extensive array of hydrographic and moored observations. The model captures the observed seasonal decline as well as spatial trends in bottom oxygen. Spatially, three regions of high respiration are identified as locations where hypoxia develops each modeled year. Two of the regions are previously identified recirculation regions. The third region is off of the Washington coast. Sediment oxygen demand causes the region on the Washington coast to be susceptible to hypoxia and is correlated to the broad area of shallow shelf (<60 m) in the region. Respiration and circulation-driven divergence contribute similar (60, 40%, respectively) amounts to the integrated oxygen budget on the Washington coast while respiration dominates the Oregon coast. Divergence, or circulation, contributes to the oxygen dynamics on the shelf in two ways: first, through the generation of retention features, and second, by determining variability.

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