Rapid Reduction of pH and CaCO₃ Saturation State in the Tsugaru Strait by the Intensified Tsugaru Warm Current During 2012–2019

Abstract

Ocean absorption of the CO 2 released to the atmosphere by human activities (i.e., anthropogenic CO 2 ) results in acidification of surface waters as the result of the increase in hydrogen ion (H + ) concentration. The oceanic uptake of anthropogenic CO 2 has decreased ocean pH by 0.1 since the beginning of the industrial era (Intergovernmental Panel on Climate Change, 2013). Ocean acidification also lowers the CaCO 3 saturation state (Ω) by decreasing carbonate ion (CO 3 2− ) concentration with concomitant formation of bicarbonate ions. The carbonate chemistry change affects marine calcifying organisms with carbonate shells and skeletons, marine noncalcifying organism, cellular metabolism, organism physiology, biogeochemical cycling of nutrients, and ecosystems (e.g.,

Frontal Waves in the East of the Tsugaru Strait Revealed by the High-Frequency Radar Observation

“…The outflow from the channel encounters low temperature and salinity water described as the coastal Oyashio water by the previous studies (e.g., Kono et al, 2004;Rosa et al, 2007;Saitoh et al, 2008;Kuroda et al 2012;Wakita et al, 2021) in the outlet of the eastern neck of the channel (~141.2°E; Fig. 1b).…”

“…In the Tsugaru Strait, recent studies reported significant disturbance due to the intense flow and tides (e.g., Yamaguchi et al, 2020;Tanaka et al, 2021), and subsequent characteristic change in ocean environment there (Wakita et al, 2021). Yamaguchi et al (2020) suggested generation of internal waves that have large-amplitude in the vertical direction behind a characteristic topography (sill) in the western part of the strait based on observations and numerical experiment.…”

“…The value is far larger than that observed by Kaneko et al (2021) in the subarctic region of the Western North Pacific during summer as ~1 × 10 −2 mmol m −2 day −1 . In addition, Wakita et al (2021) found faster acidification in the strait based on the resent observation (2012)(2013)(2014)(2015)(2016)(2017)(2018)(2019); the decrease rate of pH is 0.0030-0.0051 year −1 ) than that in the open ocean (0.0013-0.0024 year −1 ; Dore et al, 2009;Astor et al, 2013;Wakita et al, 2017;Ono et al, 2019). Moreover, Wagawa et al (2015) suggested that the volume transport of the TWC could affect the temperature in the downstream coastal region, which have a big impact on aquacultures such as a kind of seaweed (Undaria pinnatifida).…”

Continuous Monitoring and Future Projection of Ocean Warming, Acidification, and Deoxygenation on the Subarctic Coast of Hokkaido, Japan

“…Seawater samples were collected when the sensors were calibrated and analyzed using a total alkalinity (TA) titration analyzer (ATT-05; Kimoto Electric) to obtain the TA and a coulometer (MODEL 3000A; Nippon ANS) to determine the dissolved inorganic carbon (DIC) concentration (Wakita et al, 2017(Wakita et al, , 2021Yamaka, 2019). The values were calibrated against certified reference material (CRM) provided by Prof. A. G. Dickson (Scripps Institution of Oceanography, University of California San Diego) and KANSO.…”

“…Therefore, it is likely that we failed to capture the annual minimum value of arag in this study. However, referring to observed seasonal fluctuations in arag (e.g., Ishii et al, 2011;Wakita et al, 2017Wakita et al, , 2021, the annual minimum should appear in winter when the water temperature is low and the value may have already reached close to the critical level of acidification.…”