Decadal increases of anthropogenic CO 2 along 149°E in the western North Pacific

Using high‐quality data for dissolved inorganic carbon and the related water properties obtained by two cruises over 12 years (1993–2005), we estimated increases in anthropogenic CO 2 (ΔnC T CAL ) along the 149°E meridian (WHP P10) from 4°S to 30°N. Significant ΔnC T CAL was found down to a maximum depth of about 800 m. In the upper thermocline (25.0–26.0 σ θ ), ΔnC T CAL was mostly 10–13 μ mol kg −1 , close to the value expected from recent increases in atmospheric CO 2 . In the lower thermocline (26.1–27.5 σ θ ), ΔnC T CAL was 3.5 ± 0.9 and 4.7 ± 1.7 μ mol kg −1 in North Pacific Intermediate Water and Antarctic Intermediate Water, respectively. Water column inventories of ΔnC T CAL over the 12 years were calculated to be 3.8 ± 1.2 mol m −2 (minimum) and 7.3 ± 2.2 mol m −2 (maximum) at latitudes 0°–10°N and 24°N–30°N, respectively, showing a distribution pattern similar to that of the long‐term anthropogenic CO 2 accumulation reported previously. The uptake rate of anthropogenic CO 2 along the WHP P10 line over the time period was estimated to be 0.5 ± 0.1 mol m −2 a −1 , which is half the rate in the South Pacific (1.0 ± 0.4 mol m −2 a −1 ), but equal to that in the South Atlantic (0.6 ± 0.1 mol m −2 a −1 ). We discuss the relationships between ΔnC T CAL and changes in apparent oxygen utilization from the standpoint of physical‐biological interactions.