Using altimetry to help explain patchy changes in hydrographic carbon measurements

20 páginas, 1 apéndice, 10 figuras.-- Keith B. Rodgers ... et al.
Here we use observations and ocean models to identify mechanisms driving large 11 seasonal to interannual variations in dissolved inorganic carbon (DIC) and dissolved 12 oxygen (O2) in the upper ocean. We begin with observations linking variations in upper 13 ocean DIC and O2 inventories with changes in the physical state of the ocean. Models are 14 subsequently used to address the extent to which the relationships derived from 15 short-timescale (6 months to 2 years) repeat measurements are representative of variations 16 over larger spatial and temporal scales. The main new result is that convergence and 17 divergence (column stretching) attributed to baroclinic Rossby waves can make a 18 first-order contribution to DIC and O2 variability in the upper ocean. This results in a close 19 correspondence between natural variations in DIC and O2 column inventory variations 20 and sea surface height (SSH) variations over much of the ocean. Oceanic Rossby wave 21 activity is an intrinsic part of the natural variability in the climate system and is elevated 22 even in the absence of significant interannual variability in climate mode indices. The 23 close correspondence between SSH and both DIC and O2 column inventories for many 24 regions suggests that SSH changes (inferred from satellite altimetry) may prove useful in 25 reducing uncertainty in separating natural and anthropogenic DIC signals (using 26 measurements from Climate Variability and Predictability’s CO2/Repeat Hydrography 27 program).