Ocean Acidification in the Gulf of Alaska: A decade of observations from 2008 to 2017

Abstract:

The oceans are currently experiencing ocean acidification (OA) events as a result of anthropogenically increased carbon dioxide levels in the atmosphere and ocean on a global scale. We present a decadal time series of marine carbon dioxide system parameters measured from seawater samples taken during biannual cruises between 2008 and 2017 in the northern Gulf of Alaska (NGA). Seasonal undersaturations with respect to the calcium carbonate mineral aragonite have been observed over the continental shelf areas in the NGA. This region is a dynamic system where multiple biogeochemical influences are at play including naturally cold waters, high productivity, and riverine and glacial freshwater inputs. Cumulative daily Bakun upwelling indices illustrate the overall pattern of annual downwelling in the NGA, with a seasonal period of relaxation in downwelling winds between the May and September cruises. This relaxation of downwelling allows deeper, more corrosive water to shoal in the water column and move shoreward. In addition to this pressure, our observations show sub-surface water masses are more corrosive at the end of this relaxation period, likely due to seasonal respiration processes. The NGA plays an important role in the global climate system with direct links to the Pacific-Arctic and connections to other regions through North Pacific heat waves and El Niño events. This newly public dataset will help lead to understanding of the interactions and feedbacks between the atmosphere, cryosphere, and marine environment, as well as be used to understand seasonal and interannual trends, calculate air-sea carbon dioxide fluxes, and ground truth models.