Figure 8.6. Annual mean, zonally averaged oceanic heat transport implied by net heat flux imbalances at the sea surface, under an assumption of negligible changes in oceanic heat content. The observationally based estimate, taken from Trenberth and Caron (2001) for the period February 1985 to April 1989, derives from reanalysis products from the National Centers for Environmental Prediction (NCEP)/NCAR (Kalnay et al., 1996) and European Centre for Medium Range Weather Forecasts 40-year reanalysis (ERA40; Uppala et al., 2005). The model climatologies are derived from the years 1980 to 1999 in the 20th-century simulations in the MMD at PCMDI. The legend identifying individual models appears in Figure 8.4.