| Summary: | Providing specific attribution of observed changes in biogeochemical signals to specific process drivers is notoriously challenging in coastal and estuarine ecosystems, with natural variability often substantially larger than an anthropogenic signal of interest, such as ocean acidification (OA). In 2010, we estimated that anthropogenic OA was responsible for 24–49% of the added corrosiveness observed in the bottom waters of southern Hood Canal, relative to conditions naturally present in CO2-rich upwelling water, with the remaining 51–74% due to respiration processes. For these purposes, “added corrosiveness” referred to the contribution of additional dissolved CO2 from uptake of anthropogenic CO2 (i.e. anthropogenic OA) or respiration within Hood Canal to undersaturation of aragonite beyond that in the upwelled source waters. Here we expand this analysis to encompass five cruise data sets for Hood Canal (2008–2011). We also determine the CO2 variability of marine source waters coming into Puget Sound using moored time-series in combination with empirical relationships developed for coastal waters, as well as the impact of different transport-time scenarios within the basin on our attribution estimates.
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