Hydrographic controls and seasonal variability on the carbonate system in the northern Gulf of Alaska

Abstract

The Northern Gulf of Alaska (GOA) supports a dynamic and economically viable marine ecosystem. One notable potential stressor to this ecosystem is ocean acidification (OA), a byproduct of the increased uptake of anthropogenic carbon dioxide (CO₂) by the ocean. Measurements of dissolved inorganic carbon (DIC) and total alkalinity (TA) were made along the continental shelf of the northern GOA and in Prince William Sound (PWS) and used to calculate seawater pH and the saturation state of aragonite Warp). Observations showed a high degree of seasonal variability in DIC concentrations in surface and bottom waters. TA was depleted relative to DIC due to the influence of glacial run off. Seasonally high rates of primary production lowered DIC concentrations causing an increase in pH and [omega]arg in the mixed layer. However, DIC concentrations increased in the bottom waters due to the remineralization of exported organic matter and the intrusion of high salinity water from offshore waters, which suppressed pH and caused [omega]arg to become undersaturated. Observations of GOA in 2009 showed a general seasonal cycle of the carbon parameters, while a regional downwelling anomaly observed during transects in 2008 captured the effect physical variability has on the carbonate system in this region.