Changes in South Pacific anthropogenic carbon

The changes in anthropogenic CO ₂ are evaluated in the South Pacific, along the meridional line P18 (110°W) and the zonal line P06 (32°S), using the extended multiple linear regression (eMLR) method. The structure of the column inventory of anthropogenic CO ₂ on P18 is similar to the southern section of P16 in the central South Pacific (150°W), but the overall increase is greater by approximately 5-10 μmol kg ^-1. The value of the anthropogenic CO ₂ inventory on P18 is in agreement at the crossover point of an earlier evaluation of P06. Subsequent changes in pH due to the increase in anthropogenic CO ₂ are also evaluated. The change in pH is determined from the changes in anthropogenic CO ₂ and do not reflect variability in other decadal signals. For both cruise tracks, the average annual change in pH is-0.0016 mol kg ^-1 yr ^-1. This value is in good agreement with the average decrease in pH in the North Pacific, at the Hawaii Times Series and the subtropical North Atlantic. The uptake rates of anthropogenic CO ₂ are within reasonable agreement with similar studies in the South Pacific. There is evidence for greater uptake of anthropogenic CO ₂ in the western South Pacific and is attributed to the formation of subtropical Mode Water in the region.