The Gulf of California is a source of carbon dioxide to the atmosphere

Abstract

Water exchange between the Gulf of California and the Pacific Ocean has a significant vertical component (VCWE). Surface (0–200 m) gulf water flows out into the Pacific Ocean and deep (200–600 m) water flows into the gulf. This is a mechanism that allows for the net input to the gulf of dissolved constituents whose concentrations increase with depth, including dissolved inorganic carbon (DIC). Two scenarios were used to estimate the net input of DIC from the Pacific into the gulf (DICNET INPUT) and to compare this net input with new phytoplankton production in the whole gulf (PNEW) in order to infer if the gulf is a sink or source of CO2. The average annual values of VCWE were 0.67 ± 0.10 Sv in the first scenario and 0.23 ± 0.02 Sv in the second scenario (1 Sv = 106 m3 s–1). After comparing DICNET INPUT with PNEW the result is that the gulf is a source of CO2 to the atmosphere in both scenarios, with an annual average out-gassing of (18.16 ± 6.14) × 1012 and (7.66 ± 2.65) × 1012 grams of carbon in the form of CO2 in the first and second scenarios, respectively. These values are equivalent to an average of 123.5 ± 41.8 and 52.1 ± 18.0 g m–2 yr–1, respectively. The value for the first scenario is higher than the highest value for the eastern equatorial Pacific as reported in the literature (~108 g m–2 yr–1), which leads us to conclude that the value for the second scenario is closer to reality. Key words: Gulf of California, water exchange with the Pacific, new phytoplankton production, CO2 flux from the gulf to the atmosphere.