Variability of Meridional Overturning Circulation and Heat Transport in the 1992-2007 ECCO2 Synthesis

The zonally-integrated meridional velocity and temperature fields of the Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2) high-resolution global ocean and sea ice data synthesis are used to investigate the Meridional Overturning Circulation (MOC) and associated heat transport over the period of 1992-2007. The ECCO2 data synthesis is obtained by least squares fit of a global ocean and sea-ice configuration of the Massachusetts Institute of Technology general circulation model (MITgcm) to the available satellite and in-situ data using a Green's function approach. The results show that the mean states of MOC and heat transport are in good agreement with observations and with estimates from other studies. Empirical Orthogonal Function (EOF) analysis shows that the variability in global MOC is dominated by the annual cycle with principal contribution from the Indo-Pacific Basin. The Atlantic component of the MOC is characterized by strong intraseasonal variability. On time scales longer than one year, the ECCO2 estimates show trend-like patterns in both global temperature and MOC fields but no apparent trend in the global heat transport. The heat transport in the Atlantic Sector is characterized by different trends over the first and second half of the estimation period.