Air‐sea CO2 fluxes in the near‐shore and intertidal zones influenced by the California Current. Issue 10 (2nd October 2013) - Reimer, Janet J.
Abstract [1] The study of air‐sea CO2 fluxes (FCO2) in the coastal region is needed to better understand the processes that influence the direction and magnitude of FCO2 and to constrain the global carbon budget. We implemented a 1 year (January through December 2009) paired study to measure FCO2 in the intertidal zone (the coastline to 1.6 km offshore) and the near‐shore (∼3 km offshore) off the north‐western coast of Baja California (Mexico); a region influenced by year‐round upwelling. FCO2 was determined in the intertidal zone via eddy covariance; while in the near‐shore using mooring buoy sensors then calculated with the bulk method. The near‐shore region was a weak annual net source of CO2 to the atmosphere (0.043 mol CO2 m−2 y−1); where 91% of the outgassed FCO2 was contributed during the upwelling season. Sea surface temperature (SST) and ΔpCO2 (from upwelling) showed the strongest relationship with FCO2 in the near‐shore, suggesting the importance of meso‐scale processes (upwelling). FCO2 in the intertidal zone were up to four orders of magnitude higher than FCO2 in the near‐shore. Wind speed showed the strongest relationship with FCO2 in the intertidal zone, suggesting the relevance of micro‐scale processes. Results show that there are substantial spatial and temporal differences in FCO2 between the near‐shore and intertidal zone; likely a result of heterogeneity. We suggest that detailed spatial and temporal measurements are needed across the coastal oceans and continental margins to better understand the mechanisms which control FCO2, as well as reduce uncertainties and constrain regional and global ocean carbon balances.