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log 10 ε (W m -3 )
Figure 2.13 See colour plates version . Distribution of tidal dissipation in Wm 3 derived from
a numerical model of the global ocean. Note the large contrast ( 6 decades) in the magnitude
of dissipation between low dissipation in much of the deep ocean and high values exceeding
1Wm 3 occurring mainly in the shelf seas. Figure from (Green, 2010 ), with permission
from Springer.
LW
HW
HW
Moon
W
LW
M
M
Figure 2.14 In a frictionless ocean, upper picture, the Earth and ocean rotate inside the tidal
ellipsoid with the ellipsoid major axis directed along the line of centres towards the Moon.
Consequently there are two tides per lunar day with the high water (HW) occurring when the
Moon is overhead and at the nadir. In the lower picture, friction with the seabed pulls the
ellipsoid round in the direction of the Earth's rotation, ahead of the Moon. This frictional stress
between the ocean and the solid earth acts as a belt brake on the Earth's rotation, which is
gradually slowed with a loss of kinetic energy of rotation and an increase in the length of the day.
 
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