Geoscience Reference
In-Depth Information
is that the IOBL and atmospheric boundary layer have much in common, thus the
extensiveobservationalbaseavailablefortheatmosphereisapplicabletotheocean.
Similarity scaling of IOBL drag may help explain the formation of ice-edge
bands (McPhee 1983; Mellor et al. 1986). There is often a fairly abrupt front ob-
servedinoceantemperatureneartheedgeoftheicepackinmarginalicezoneslike
thatfoundintheGreenlandorBeringSeas.Whenoff-icewindsdrivethemainpack
across such a front, melting is rapid, and it is commonly observed that relatively
thinbandsoficedriftaway(downwind)fromthemainpack.Anexampleobserved
duringthe1983MIZEXprojectintheGreenlandSeamarginalicezoneisshownin
Fig.4.11.Weencounteredthisbandaftersailingsouthfromthemainpackforsome
distance in open water. While no environmental data are available from this site,
it is reasonable to assume that the southward drifting ice was in water well above
freezing. Suppose for example that
u
∗
0
∼
01ms
−
1
and
20 (corresponding
roughlyto a melt rate of 40cm per day). Then application of (4.34) and (4.35)im-
pliesthattheleadingedgeoftheicepackwouldtravelabout8-10kmperdayfarther
thansimilar icewithnomelting.Inthisview,theedgebandformsbecausewateris
cooledrapidlybehindtheadvancingice,soslowermeltingmeanslessstratification
and consequently ice following the leading edge moves slower. The width of the
bandprobablyreflects thesize of theinternalboundarylayerthatwouldformfrom
theleadingedge—whichisfarbeyondthescopeofthesimilaritytheory.
Alternative mechanisms for ice-edge band formation have been suggested, no-
tably wave radiation pressure on the trailing edge (Martin et al. 1983; Wadhams
1983). The photograph in Fig. 4.11 seems to indicate, however, that the following
edge feathersout, which would be more consistentwith the “slipperywater” effect
thanwaveradiationpressure.
0
.
µ
∗
∼
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