Geoscience Reference
In-Depth Information
λ
p
=
η
∗
p
2
u
∗
p
/ |
at
z
p
)andwith
.TheideahereisthatanEkmanlayerwillformin
the upper pycnocline,forced by the stress and buoyancyflux (
f
|
w
b
p
)
at the inter-
face between the well mixed layer and the stratified fluid below. For typical Arctic
densitystructure,the pycnoclineisstrongenoughthat
1
−
1
w
b
p
+
Λ
∗
R
c
u
∗
p
2
Λ
∗
→
|
f
|
η
∗
p
2
=
R
c
u
∗
p
2
w
b
p
|
f
|
and
R
c
L
p
.
When meltingoccursfollowinga periodwhenthe well mixedlayer is relatively
deep, a seasonal pycnocline forms as in Fig. 5.17b. The depth of this intermediate
layer
λ
p
→
κ
(
z
p
)
depends on the turbulence scales determined by the surface flux condi-
tions. If this layer is shallow and the newly formed seasonal pycnocline is weak,
then
η
∗
p
2
may be close to unity, in which case turbulent exchange in the Ekman
layer formedbelow
z
p
will be similar to what it would be withoutthe intermediate
pycnocline.Inthesurfacelayer,
λ
followsMonin-Obukhovsimilarity(althoughfor
realistic values of
the dimensionless shear within the surface layer departsfrom
1byonlya fewpercent.)
WhenfreezinginjectssaltintotheIOBL,turbulencescalesareenhancedandthe
scaleoftheenergy-containingeddieswillapproachasignificantfraction
µ
∗
(
c
ml
)
ofthe
depthof thewell mixedlayer (Fig. 5.17c).Consequently,
λ
increaseswith distance
2
fromtheboundaryfollowingaMonin-Obukhovfunction
(
λ
=
κ
|
z
|
(
1
−
ζ
)
)
untilit
reachesavalue
c
ml
z
p
,whichitretainsuntilthepycnoclineisencountered.LeadEx
resultsindicatedthat
c
ml
∼
κ
.
References
Busch, N. E. and Panofsky, H. A.: Recent spectra of atmospheric turbulence. Quart. J. R. Met.
Soc., 94, 132-147 (1968)
Deardorff, J. W.: Numerical investigation of neutral and unstable planetary boundary layers. J.
Atmos. Sci., 29, 91-115 (1972)
Edson, J. B., Fairall, C. W., Mestayer, P. G., and Larsen, S. E.: A study of the inertial-dissipation
method for computing air-sea fluxes. J. Geophys. Res., 96, 10,689-10,711 (1991)
Hinze, J.O.:Turbulence, Second Edition.McGraw-Hill,New York (1975)
McPhee, M. G.:On the turbulent mixing length inthe oceanic boundary layer. J. Phys. Oceanogr.,
24, 2014-2031 (1994)
McPhee, M. G.: Physics of early summer ice/ocean exchanges in the western Weddell Sea during
ISPOL, Deep-Sea Res., II, doi:10.1016/j.dsr2.2007.12.022, in press (2008)
McPhee,M.G.andMartinson,D.G.:TurbulentmixingunderdriftingpackiceintheWeddellSea.
Science, 263, 218-221 (1994)
McPhee, M. G. and Smith, J. D.: Measurements of the turbulent boundary layer under pack ice. J.
Phys. Oceanogr., 6, 696-711 (1976)
McPhee, M. G. and Stanton, T. P.: Turbulence in the statically unstable oceanic boundary layer
under arctic leads. J. Geophys. Res., 101, 6409-6428 (1996)
Morison, J. H., McPhee, M. G., and Maykut, G. A.: Boundary layer, upper ocean, and ice obser-
vations in the Greenland Sea marginal ice zone. J. Geophys. Res., 92, 6987-7011 (1987)
Morison, J. H. and McPhee, M. G.: Lead convection measured with and autonomous underwater
vehicle. J. Geophys. Res., 103, 3257-3281 (1998)