Factors affecting the subsurface aragonite undersaturation layer in the Pacific Arctic region

Abstract

This study evaluated interannual variation in the subsurface aragonite undersaturation zone (Ω_Ar<1 layer) in the Pacific Arctic Ocean, using data from the 2016-2019 period. The upper boundary (DEP_Ω<1^UB) of the Ω_Ar<1 layer generally formed at a depth where the contribution of corrosive Pacific water was approximately 98 %. The intensity of the Beaufort Gyre associated with freshwater accumulation mainly determined interannual variation in DEP_Ω<1^UB, but the direction of its effect was opposite west and east of ~166°W. The lower boundary (DEP_Ω<1^LB) of the Ω_Ar<1 layer was generally found at a depth range where equal contributions of Pacific and Atlantic water were expected. An Atlantic-origin cold saline water intrusion event in 2017 caused by an anomalous atmospheric circulation pattern significantly lifted the DEP_Ω<1^LB, thus the thickness of the Ω_Ar<1 layer decreased.

Keywords: Aragonite saturation; Arctic Ocean; Atmospheric circulation; Beaufort gyre; Ocean acidification; Pacific-Arctic regions.