Autocorrelation characteristics of surface ocean pCO2 and air-sea CO2 fluxes

Abstract

Understanding the variability and coherence of surface ocean pCO 2 on a global scale can provide insights into its physical and biogeochemical drivers and inform future samplings strategies and data assimilation methods. We present temporal and spatial autocorrelation analyses of surface ocean pCO2 on a 5 × 5 grid using the Lamont-Doherty Earth Observatory database. The seasonal cycle is robust with an interannual autocorrelation of ∼0.4 across multiple years. The global median spatial autocorrelation (e-folding) length is 400 250km, with large variability across different regions. Autocorrelation lengths of up to 3,000km are found along major currents and basin gyres while autocorrelation lengths as low as 50km are found in coastal regions and other areas of physical turbulence. Zonal (east-west) autocorrelation lengths are typically longer than their meridional counterparts, reflecting the zonal nature of many major ocean features. Uncertainties in spatial autocorrelation in different ocean basins are between 42% and 73% of the calculated decorrelation length. The spatial autocorrelation length in air-sea fluxes is much shorter than for pCO2 (200 150km) due to the high variability of the gas transfer velocity. © 2012 American Geophysical Union. All Rights Reserved.