Geoscience Reference
In-Depth Information
8.2.2 Models Forced by Surface Velocity
A third model simulation of the same period (run Sep 14C) is identical to run
Sep 14A except that the dynamic stress interface boundarycondition was replaced
by the surface velocity boundary condition as in Section 7.2.2. The same value
(0.048m) was used for
z
0
. Apart from minor details the two simulations are sim-
ilar for exchanges at the interface (Fig. 8.12) as well as the rest of the IOBL. The
meanmodeledvaluesforfrictionvelocityoverthesimulationperioddifferbyabout
10% (if
c
10
is increased to 0.0025 they match). During winter there are often peri-
odswhentheiceclearlyrespondstowindforcing,butisalsoinfluencedbyinternal
stress gradients. In this case, provided the geostrophic (sea-surface tilt) velocity is
smallcomparedtoicevelocity,forcingtheIOBLwithicevelocityclearlyisabetter
strategythanforcingbywind(unlessice stress is known).
Especially during winter, a common consequence of internal ice forcing is that
inertial oscillation is severely damped even if the ice appears to be moving freely
in response to the wind (McPhee 1981). An obvious question then arises: would
the modeled response of the upper ocean be much differentif inertial oscillation is
absent? We performed a fourth simulation (run Sep 14D) of the September 14-22
periodwhichwasidenticaltorunSep14Cexceptthatsurfacevelocitywasspecified
Interface Friction Velocity
a
0.02
0.01
Sep 14C
Sep 14A
0
258
259
260
261
262
263
264
265
Basal Heat Flux
20
b
15
10
5
0
0
258
259
260
261
262
263
264
265
Day of 1998
Fig. 8.12
Comparison of interface friction velocity
a
and basal heat flux
b
for model run Sep 14C
(forced by surface velocity) and Sep 14A (forced by 10-m wind)
