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UBC Theses and Dissertations

A submesoscale modelling approach to understanding the past, present, and future carbonate chemistry balance of the Salish Sea Jarníková, Tereza


Over the past 250 years, atmospheric levels of carbon dioxide (CO₂) have increased at an unprecedented rate. The ocean has absorbed a significant proportion of this anthro- pogenic carbon, resulting in changes to marine chemistry that negatively impact a wide variety of ocean organisms. Disproportionately productive coastal systems may be par- ticularly vulnerable to these changes; however, the detection and impact of secular carbon trends in these systems is complicated by heightened natural variability as compared to open-ocean regimes and is comparatively poorly understood. This dissertation inves- tigates the changing carbonate chemistry of the Salish Sea, a representative Northeast Pacific coastal system. Both physical-oceanographic factors and primary productivity exert a control on the inorganic carbon balance. I first investigate their interaction in the Salish Sea by apply- ing a clustering method to four factors relating to stratification and to depth-integrated phytoplankton biomass extracted from an existing biophysical model, finding coherent biophysical provinces. I then develop and evaluate a carbonate chemistry model for the Salish Sea and use it to evaluate biogeochemical changes between the pre-industrial and modern periods. I find that to date, the increase in inorganic carbon in the Salish Sea has been 29-39 mmol m−3, a modest amount relative to other parts of the global ocean. However, because of the naturally high inorganic carbon content of Pacific waters, this increased carbon drives the estuary towards domain-wide undersaturation of aragonite year-round, negatively impacting shell-forming organisms. I then use a global database of coastal carbonate chemistry observations to show that estuaries throughout the Pacific Rim have likely already undergone a similar saturation state regime shift. I then quan- tify the relative components of the Salish Sea carbonate chemistry budget in the context of the identified biophysical provinces. I note the dominant role and large variability of lateral boundary fluxes in setting the inorganic carbonate chemistry of the system. Fi- nally, I estimate that future anthropogenic carbon increase in the system by year 2050, under a conservative emissions scenario, will be approximately 80% of the increase from pre-industrial to present, and that this increase will have further significant effects on aragonite saturation states.

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