Anthropogenic ?13C changes in the North Pacific Ocean reconstructed using a multiparameter mixing approach (MIX)
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A multiparameter mixing approach, ‘MIX’, for determining oceanic anthropogenic CO2 was used to reconstruct the industrial-era change in the C-13/C-12 of dissolved inorganic carbon (delta C-13 of DIC) along the 1992 165 degrees E WOCE P13N section in the North Pacific Ocean. The back-calculation approach was tested against a known anthropogenic tracer, chlorofluorocarbon-11 (CFC-11), and also by reconstructing an ocean general circulation model’s (OGCM) anthropogenic delta C-13 change. MIX proved accurate to +/- 10% against measured CFC-11, but only to +/-similar to 25% reconstructing the OGCM’s delta C-13 change from 1992 model output. The OGCM’s CFC distribution was also poorly reconstructed using MIX, indicating that this test suffers from limitations in the OGCM’s representation of water masses in the ocean. The MIX industrial-era near-surface (200 M) delta C-13 change reconstructed from the WOCE P13N data ranged from -0.8 parts per thousand in the subtropics (15-30 degrees N), to -0.6 parts per thousand in the tropics (10 degrees N), and -0.4 to -0.2 parts per thousand north of 40 degrees N. Depth-integrated changes along 165 degrees E were -400 parts per thousand.m to -500 parts per thousand.m at low latitudes, and were smaller (-200 parts per thousand.m) north of 40 degrees N. The MIX North Pacific delta C-13 change is consistent with the global anthropogenic CO2 inventory of 118 +/- 17 Pg from Delta C*.