Aragonite saturation state dynamics in a coastal upwelling zone

• Published in: Geophysical research letters 2013-06, Vol.40 (11), p.2720-2725
• Main Authors: Harris, Katherine E., DeGrandpre, Michael D., Hales, Burke
• Format: Article
• Language: English
• Subjects: Acidification; Alkalinity; Anthropogenic factors; Aragonite; aragonite saturation states; biogeochemical processes; Carbon dioxide; Coastal; coastal upwelling; Mathematical analysis; Ocean acidification; Oceans; Oregon coast; Phytoplankton; Saturation; Spring; Springs; Time series; Upwelling; Water column
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/grl.50460

Coastal upwelling zones may be at enhanced risk from ocean acidification as upwelling brings low aragonite saturation state (ΩAr) waters to the surface that are further suppressed by anthropogenic CO2. ΩAr was calculated with pH, pCO2, and salinity‐derived alkalinity time series data from autonomous pH and pCO2 instruments moored on the Oregon shelf and shelf break during different seasons from 2007 to 2011. Surface ΩAr values ranged between 0.66 ± 0.04 and 3.9 ± 0.04 compared to an estimated pre‐industrial range of 1.0 ± 0.1 to 4.7 ± 0.1. Upwelling of high‐CO2 water and subsequent removal of CO2 by phytoplankton imparts a dynamic range to ΩAr from ~1.0 to ~4.0 between spring and autumn. Freshwater input also suppresses saturation states during the spring. Winter ΩAr is less variable than during other seasons and is controlled primarily by mixing of the water column. Key Points Aragonite saturation states are calculated from time series pH and pCO2 data Seasonal processes controlling aragonite saturation state are determined Current coastal upwelling zone variability compared to preindustrial range