Abstract
This paper uses the extended multiple linear regression (eMLR) technique to investigate changes over the last decade in dissolved inorganic carbon (DIC) inventories on a meridional line (P16 along 152°W) up the central Pacific and on a zonal line (P02 along 30°N) across the North Pacific. Maximum changes in the total DIC concentrations along P02 are 15–20 μmol kg−1 over 10 years, somewhat higher than the ∼1 μmol kg−1 a−1 increase in DIC expected based on the rate of atmospheric CO2 increase. The maximum changes of 15–20 μmol kg−1 along the P16 line over the 14/15‐year time frame fit with the expected magnitude of the anthropogenic signal, but there is a deeper than expected penetration of the signal in the North Pacific compared to the South Pacific. The effect of varying circulation on the total DIC change, based on decadal alterations of the apparent oxygen utilization rate, is estimated to be greater than 10 μmol kg−1 in the North Pacific, accounting for as much as 80% of the total DIC change in that region. The average anthropogenic CO2 inventory increase along 30°N between 1994 and 2004 was 0.43 mol m−2 a−1, with much higher inventories in the western Pacific. Along P16, the average Northern Hemisphere increase was 0.25 mol m−2 a−1 between 1991/1992 and 2006 compared to an average Southern Hemisphere anthropogenic CO2 inventory increase between 1991 and 2005 of 0.41 mol m−2 a−1.
