12:00 PM - 12:15 PM
[AOS19-06] Ocean acidification in the surface water of the Tsugaru Warm Current
Keywords:Ocean acidification, Coastal region, Carbon cycle
Station SE9 near the Cape Esan occupied Coastal Oyashio Water (COW) from winter to summer. The surface water in the other stations except SE9 is characteristic of the Tsugaru Warm Current (TWC) and agreed with those in the breakwater of the sekinehama port. The surface water in the breakwater are characteristic of TWC.
In 2014 winter, COW reached to the sekinehama port for the first time in 30 years. The COW approaching suddenly dropped Temp, pH and Ωaragonite. This suddenly drops in 2014 affected on anglerfish and scallop in the this strait. We remove these data in the deseasonalization method for calculation of annual mean values.
Deseasonalized annual means of pH and Ωaragonite significantly decreased (pH: −0.0034 ± 0.0009 /yr, p<0.001; Ωaraginite: −0.048 ± 0.006 /yr, p<0.001). These ocean acidification rates were faster than other time-series sites in open ocean (pH: −0.002 /yr, Ωaraginite: −0.01 /yr; MIdorikawa et al., 2010, Dore et al., 2009, Wakita et al., 2017, Ishii et al., 2011). This might be caused by the oceanic uptake of anthropogenic CO2 and DIC increase due to biological production change and the remineralization of organic matter from input form terrestrial, seashore or sea-bottom. The water in the floating pier is more scattered than the breakwater during summer-fall. Diurnal variation on the seashore might result in the faster coastal ocean acidification. We will deploy pH sensor in these port sites this winter to elucidate the impact of the faster coastal ocean acidification on diurnal variation on the seashore.