Two Decades of Ocean Acidification in the Surface Waters of the Beaufort Gyre, Arctic Ocean: Effects of Sea Ice Melt and Retreat From 1997–2016
Y. Zhang, Michiyo Yamamoto‐Kawai, William J. Williams
Abstract
Abstract Anthropogenic CO 2 uptake drives ocean acidification and so decreases the calcium carbonate (CaCO 3 ) saturation state (Ω). Undersaturation of surface water with respect to aragonite‐type CaCO 3 was first reported for 2008 in the Canada Basin, preceding other open ocean basins. This study reveals interannual variation of Ω in the surface Canada Basin before and after 2008. A rapid decrease of Ω occurred during 2003–2007 at a rate of −0.09 year −1 , 10 times faster than other open oceans. This was due to melting and retreat of sea ice, which diluted surface water and enhanced air‐sea CO 2 exchange. After 2007, Ω did not further decrease, despite increasing atmospheric CO 2 and continued sea ice retreat. A weakened dilution effect from sea ice melt and stabilized air‐sea CO 2 disequilibrium state is the main reason for this stabilization of Ω. Aragonite undersaturation has been observed for the last 11 years, and aragonite‐shelled organisms may be threatened.