Geoscience Reference
In-Depth Information
6.4 Heat Flux Measurements and the Stanton Number
for Sea Ice
The first direct measurementsof heat flux in the IOBL were made duringthe 1984
MIZEX project in the marginal ice zone of the Greenland Sea using instrument
clusterscombiningfastresponsethermometersandsmallmechanicalcurrentmeters
capable of measuring into the inertial subrangeof the turbulentspectrum (McPhee
etal.1987).AsummaryoftheMIZEXheatfluxmeasurements(Fig.6.4)illustrates
thatingeneralthereareincreasingtrendsalongaxesrepresentingincreasingmixed-
layer temperature elevation above freezing, and increasing friction velocity. Note
thatthereisadistinctionbetween
T
0
andmixed-layerfreezingtemperature,
T
f
(
,
since if there is melting at the interface,
S
0
will be different from far-field (mixed-
layer)salinity.Consequentlywemakeadistinctionbetweenthedefinitionof
S
ml
)
α
h
and
abulkStantonnumber
w
T
0
u
∗
0
∆
St
∗
=
(6.10)
T
where
∆
T
=
T
w
−
T
f
(
S
w
)
. If we identify
T
w
with mixed (or mixing) layer tempera-
ture,
T
isnot.
Heat flux measurements were been made during several ice station experiments
followingMIZEX.Wehavefoundonanumberofoccasionsthatsolarradiationpen-
etrating into the water column can influence local measurements, and that caution
∆
T
isreadilymeasured,while
δ
150
120
90
60
30
0
20
0.32
15
0.24
10
0.16
5
0.08
0
0.0
Fig. 6.4
Summary of directlymeasured heat fluxand frictionvelocityaveraged inbinsfor alldata
from MIZEX 84 (From Mcphee 1992. Withpermission American Geophysical Union)
