Rapid anthropogenic changes in CO₂ and pH in the Atlantic Ocean: 2003–2014

Abstract

The extended multilinear regression method is used to determine the uptake and storage of anthropogenic carbon in the Atlantic Ocean based on repeat occupations of four cruises from 1989 to 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 ± 0.9 Pg C decade−1 from 2003 to 2014 compared to 1.9 ± 0.4 Pg C decade−1 for the 1989–2003 period. This decadal variability is attributed to changing ventilation patterns associated with the North Atlantic Oscillation 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 (3.7 ± 0.8 Pg C decade−1 versus 3.2 ± 0.7 Pg C decade−1). Several eddies are identified containing ~20% more anthropogenic carbon than the surrounding waters in the South Atlantic demonstrating the importance of eddies in transporting anthropogenic carbon. The uptake of carbon results in a decrease in pH of ~0.0021 ± 0.0007 year−1 for surface waters during the last 10 years, in line with the atmospheric increase in CO2.

Irminger Sea deep convection injects oxygen and anthropogenic carbon to the ocean interior

“…Carbon chemistry data on the other hand have only been systematically collected on a repeat basis since the early 1990s. As the time span of the record is extended, the strong response of ventilation and anthropogenic carbon storage in the Atlantic to variability in atmospheric forcing becomes more evident589. In particular, the observations presented here reveal a strong link between oceanic heat loss enhanced by numerous tip jet events, ventilation and anthropogenic carbon storage in the Irminger Sea, which is one of the deep water formation areas in the North Atlantic.…”

“…Furthermore, a series of papers have shown how reduced deep water formation in the subpolar North Atlantic from the mid-1990s to the mid-2000s affected ocean anthropogenic carbon storage rates678. A recent acceleration in anthropogenic carbon storage rates has been observed in the North Atlantic from 2003 to 2014 compared with the 1989–2003 period, attributed to changes in water mass ventilation as well as increasing atmospheric CO 2 concentration9. The frequency, duration and intensity of deep water formation in the North Atlantic subpolar gyre region is strongly related to atmospheric variability.…”

Ocean acidification over the next three centuries using a simple global climate carbon-cycle model: projections and sensitivities

“…Recent work suggests that the North Atlantic absorbed 50 % more anthropogenic CO 2 in the last decade compared to the previous decade, decreasing surface pH by 0.0021 (Woosley et al, 2016). Under RCP 8.5, Hector projects a decrease in lowlatitude pH of 8.17 in 1850 to 7.77 in 2100 and down to 7.5 by 2300, similar to CMIP5 (Table 5).…”

State of the Climate in 2016

“…The difference between the regression constants from the earlier and later datasets are then used to estimate the changes in ocean carbon independent of any changes in the water mass distributions. Using a similar approach for the Atlantic, Woosley et al (2016) showed that C anth storage increased from 5.1 to 8.1 Pg C decade −1 over the same time intervals. These results suggest that both increases in air-sea exchange of CO 2 at the surface as well as changes in ventilation within the ocean interior contribute to increased rates of uptake in the later decade.…”