Fig. 9: Profiles of mean absolute error calculated from each grid point
for the (a) globe and (b) North Atlantic ocean of potential temperature
(°C) for DJF 1985–2014 of the five ensemble members of the historical
AWI-CM simulation (in colors) and for DJF 1976–2005 of CMIP5
simulations (in black, each line representing one CMIP5 model, green
representing the MPI-ESM CMIP5 model). (c) and (d) as (a) and (b) but
for salinity (psu). The reference climatology is the Polar Science
Center Hydrographic Climatology (PHC, updated from Steele et al., 2001).
4.5 Sea ice
The general patterns of observed Arctic and Antarctic sea ice
concentration are well represented in AWI-CM over the last 30 years of
historical simulations (Figs. 10 and 11). Both Arctic and Antarctic sea
ice concentration are overestimated in late winter in the marginal ice
zones and underestimated in late summer in most areas. This hints to a
too pronounced annual cycle of sea ice cover which can also be seen in
the sea ice extent as shown in Fig. 15. Nevertheless, Arctic sea ice
extent and thickness are remarkably well represented especially over the
last few years (Figs. 15 and 16). While late winter Arctic sea ice
concentration biases are very similar to MPI-ESM, late winter Antarctic
sea ice concentration in MPI-ESM has a substantial negative bias
especially northeast of the Weddell Sea and a slight negative bias in
East Antarctic marginal seas (Müller et al., 2018, their Fig. 4) rather
than a slight positive bias. This difference is consistent with the
reduced Southern Ocean warm bias in AWI-CM compared to MPI-ESM.
(a) (b) (c)