Fig. 4.
Sensitivity of the global heat budget to model resolution. Global maps of the annual-mean difference of a submesoscale vertical heat flux, b ocean surface temperature, c net air–sea heat flux, and d mixed layer depth between the 1/48° model and the 1/24° model (1/48° model minus 1/24° model). Values are spatially smoothed over 3° × 3° square boxes. The two models have identical setups except for the horizontal resolution. The model differences here are mainly caused by submesoscale at 10–20 km range. In most area of mid-latitudes, the 1/48° model exhibits upward heat transport at submesoscales larger than the 1/24° model, by ~4–10 W/m2 (a; about 14% larger, as in Supplementary Figure 5d). This results in a sea surface warming of ~0.06–0.3 °C (see b). This is ultimately compensated by a stronger upward ocean–atmosphere heat exchange (~4–10 W/m2, c vs a). The 1/48° model generally has a shallower mixed layer depth than the 1/24° model (see d). This is due to a stronger restratification in the 1/48° model (i.e., heat flux as in a) and is linked to most of the difference in sea surface temperature (see b). This is illustrated further in Supplementary Figure 4