| Summary: | Queen Charlotte Sound (QCS) is a broad shelf region off Canada's west coast that is highly biologically productive and hosts several Marine Protected Areas. However, ecosystems in QCS are becoming increasingly susceptible to climate change stressors such as marine heatwaves, ocean acidification, and deoxygenation. In this system, stratification plays an important role in setting the physical and chemical environment, thus impacting how climate change affects the region. Here, one year of near-continuous underwater glider observations are used to investigate how variability in stratification influence the physical and biogeochemical properties in QCS. We document how varying contributions of temperature and salinity to density stratification set up distinct stratification regimes: a salinity-dominated beta regime, a temperature-dominated alpha regime and a transitional regime, whose presence and spatial extent vary seasonally across the shelf. We use this stratification regime characterisation to 1) map where and when these regimes manifest and consider the drivers of variability in regime spatial and temporal extents; 2) quantify the stratification strength as a function of regime; and 3) demonstrate the usefulness of this characterisation to present the differences in biochemical properties and their distribution in the regimes. The relationships between forcing fields (heat fluxes, freshwater inputs, winds, upwelling index) and the active regimes are also investigated to test the sensitivity of each regime to atmospheric and lateral exchange processes. Lastly, we will discuss what these findings inform us about stratification in QCS in the context of climate change with increased riverine inputs, melting glaciers, increased precipitation and warmer waters.
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