Geoscience Reference
In-Depth Information
Fig. 6.12 a
Time series of heat flux to thick ice (darker shading) and heat flux into the ocean
from false bottoms (lighter). Average values are shown at right.
b
Aggregate Stanton number as a
function of areal coverage of false bottoms and fresh water (Adapted from Notz et al. 2003. With
permission American Geophysical Union) (see also Colorplate on p. 207)
across the false bottoms, they represent a source of heat for the upper ocean in
summer apart from absorbed solar radiation penetrating into the well mixed layer.
Depending on how ubiquitous false bottoms (or any freshwater/seawater interface
on the ice undersurface) are during the melt season, they may exert a powerful
influence on the total heat exchange between the IOBL and the pack ice. An ef-
fectiveaggregateStantonnumber
H
total
(
St
∗
)
eff
=
ρ
c
p
u
∗
0
∆
T
where
H
total
ρ
w
T
fb
and
A
fb
is theareafractionof
the undersurface covered by false bottoms or meltwater ponds, includes the com-
bined positive and negative fluxes to thick ice
w
T
0
+
c
p
=(
1
−
A
fb
)
A
fb
w
T
0
)
(
and from false bottoms
w
T
fb
)
(
. It falls rapidly with increasingfalse bottomarea. For the AIDJEX sim-
ulation,
St
∗
)
eff
isnearlyhalvedif theareafractionapproaches3/10.
False bottoms and other manifestations of underice melt water may have a sig-
nificantimpactonthemassbalance,andeventheforcebalance,oftheArcticpack.
Notz et al. (2003)reportedestimates of false-bottomarea fractionsrangingfrom at
least 10% (Jeffries et al. 1995) to over 50% (Hanson 1965). Jeffries et al. suggest
thattheoriginofplateletsintheArcticicecorestheyanalyzedderivedmainlyfrom
falsebottomformationoran “ice-pump”mechanism,andthatundericemeltponds
(
