| The recently proposed IDEMIX (Internal wave Dissipation, Energy and MIXing)
parameterisation for the effect of gravity waves offers the possibility to construct
consistent ocean models with a closed energy cycle. This means that the energy
available for interior mixing in the ocean is only controlled by external energy input
from the atmosphere and the tidal system and by internal exchanges. A central
difficulty is the unknown fate of meso-scale eddy energy. In different scenarios for that
eddy dissipation, the parameterized internal wave field provides between 2 and 3
TW for interior mixing from the total external energy input of about 4 TW, such
that a transfer between 0.3 and 0.4 TW into mean potential energy contributes to
drive the large-scale circulation in the model. The impact of the different mixing
on the meridional overturning in the North Atlantic is discussed and compared to
hydrographic observations. Furthermore, the direct energy exchange of the wave
field with the geostrophic flow is parameterized in extended IDEMIX versions
and the sensitivity of the North Atlantic circulation by this gravity wave drag is
discussed. |