Observed oxygen concentrations and a possible implication behind the Muchalat inlet subsurface oxygen maximum

Abstract

[author abstract] It is expected to find the water column in Muchalat inlet to display strong stratification due to the influx of freshwater from sources like the Gold River layering on top of the denser seawater that enters from Nootka Sound and the open ocean. This stratification limits vertical mixing, denying highly oxygenated surface waters to sink below a certain depth. However, after measuring the oxygen concentrations during the 2016 Senior Thesis Cruise (TN334), a layer of relatively higher oxygen was found at a depth that was not expected of that oxygen level. Since vertical mixing through different densities is unlikely to occur, the most likely explanation for this inflow of oxygen is that it originates from a source outside of Muchalat Inlet, more specifically the open ocean. Using nutrient data as a tracer to follow the same circulation pattern as oxygen, it was inferred that the tracers could not have tracked in the hypothesized pattern because the density gradient connecting Muchalat inlet and the open ocean did not contain the same values. Therefore, the open ocean is concluded to be an unlikely source for the influx of oxygen.