Using altimetry to help explain patchy changes in hydrographic carbon measurements

Keith B. Rodgers (1) , Robert M. Key (1) , Anand Gnanadesikan (2) , Jorge L. Sarmiento (1) , Olivier Aumont (3) , Laurent Bopp (4) , Scott C. Doney (5) , John P. Dunne (2) , David M. Glover (5) , Akio Ishida , Masao Ishii (6) , Andrew R. Jacobson (7) , Claire Lo Monaco (8, 9) , Ernst Maier-Reimer (10) , Herlé Mercier (3) , Nicolas Metzl (9, 8) , Fiz F. Pérez (11) , Aida F. Rios (11) , Rik H. Wanninkhof (12) , Patrick Wetzel (10) , Christopher D. Winn (13) , Yasuhiro Yamanaka

1 AOS Program - Atmospheric and Oceanic Sciences Program [Princeton]
2 GFDL - NOAA Geophysical Fluid Dynamics Laboratory
3 LPO - Laboratoire de physique des océans
4 LSCE - Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette]
5 WHOI - Department of Physical Oceanography
6 MRI
7 CIRES - Cooperative Institute for Research in Environmental Sciences
8 IPSL - Institut Pierre-Simon-Laplace
9 LOCEAN - Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques
10 MPI-M - Max Planck Institute for Meteorology
11 CSIS
12 AOML - NOAA Atlantic Oceanographic and Meteorological Laboratory
13 College of Natural and Computational Sciences

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

Domaines: Océanographie

Keith B. Rodgers, Robert M. Key, Anand Gnanadesikan, Jorge L. Sarmiento, Olivier Aumont, et al.. Using altimetry to help explain patchy changes in hydrographic carbon measurements. Journal of Geophysical Research. Oceans, 2009, 114, pp.C09013. ⟨10.1029/2008JC005183⟩. ⟨hal-00454463⟩