NORTH ATLANTIC CARBON CYCLE RESPONSE TO CLIMATE VARIABILITY

• Main Authors: David J. Ullman, J. Ullman
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2008
• Subjects: North Atlantic; North Atlantic oscillation
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.686.9398; http://www.aos.wisc.edu/uwaosjournal/Volume6/theses/David_Ullman_MS_Spring_2008.pdf

Air-sea CO2 flux variability in the North Atlantic has been found to be small in a variety of ocean biogeochemical models and at least one atmospheric CO2 inversion study, yet the mechanisms that damp variability in this region of large net carbon uptake are poorly understood. A biogeochemical general circulation model was used to assess the impact of climate variability from 1980-2006 on the CO2 flux and surface pCO2 in the North Atlantic. Results show a strong correlation between flux and pCO2 variability. Two distinct mechanistic regions are found explaining general pCO2 variability: temperature driven versus dynamics (mixing) driven. Model output pCO2 was separated into its influences from dissolved inorganic carbon (DIC), alkalinity (ALK), phosphate, silicate, sea-surface temperature (SST), and sea-surface salinity (SSS) to assess the mechanisms driving pCO2 variability. These pCO2 influences were regressed onto the North Atlantic Oscillation (NAO) index and onto the first principal component of the pCO2 to assess the ii effects of the main modes of climate and carbon variability in the region on the carbon system. The NAO regression shows that while the effects of SST and ALK on pCO2 variability balance each other in the eastern subtropical gyre, DIC and SST effects balance in the subpolar gyre, such that the overall variability of pCO2 is small. Regression of the pCO2 components on the first PC shows that horizontal advection may also be important. Driving forces behind pCO2 variability are evaluated with regard to limited data from transect and time series observations.