Rapid Anthropogenic Changes in CO2 and pH in the Atlantic Ocean: 2003-2014

Abstract:

The extended multi-linear regression (eMLR) method is used to determine the uptake of anthropogenic carbon in the Atlantic Ocean based on repeat occupations of 4 cruises from 1989 – 2014 (A16, A20, A22, and A10), with an emphasis on the 2003–2014 period. The results show a significant increase in basin wide anthropogenic carbon storage in the North Atlantic, which absorbed 4.4± 1.2 Pg C/decade from 2003 – 2014 compared to 1.9 ± 1 Pg C/decade for the 1989 – 2003 period. This decadal variability is attributed to changing ventilation patterns associated with the North Atlantic Oscillation (NAO) and increasing release of anthropogenic carbon into the atmosphere. There are small changes in the uptake rate of CO₂ in the South Atlantic for these time periods, but within the uncertainty. Several eddies are identified that transport 20% more anthropogenic carbon than the surrounding waters in the South Atlantic showing the importance of eddies in transporting anthropogenic carbon. The uptake of carbon results in a decrease in pH of ~0.0021 ± 0.0007 yr^-1 for surface waters during the last 10 years, in line with the atmospheric increase in CO₂.