Geoscience Reference
In-Depth Information
areaacontinuousrecordofwind,temperature,iceconcentration,andotherpertinent
fields.Inthissection,weusesuchatimeseriestomodelthesubsequentupperocean
conditionsstarting from observationsaboutnoon UT on 19 August2005 at Maud-
NESS Phase 1 station 91, and extending20 days. Station 91 was chosenbecause it
exhibitedthelowest“thermobaricbarrier”index(McPhee2000)oftheMaudNESS
phase1survey.The1-doceanforecastmodelaccountsforopenwater asstipulated
in the supplied ice concentration data (averaged in a 90km square centered on the
station site) by assuming that whenice is absent,the surface loses 200Wm
−
2
,and
that, provided this exceeds heat flux from ocean, it forms ice that migrates away
from the region (but leaves salt). The treatment is crude, but proved not very im-
portant since according to the imagery analysis, ice concentrations remained high
duringthemodelingperiod.Heatlossthroughtheicewas estimated byassuminga
one-layerice modelwith heat flux proportionalto the air-oceantemperaturediffer-
ence divided by the ice thickness. Thermal conductivity in the ice was assumed to
be 2Wm
−
1
K
−
1
. Surface momentum flux was estimated from MM5 surface wind
with a 10-m drag coefficient 0.0015. The time series synthesized from the MM5
nowcasts at the Station 91 site is summarized in Fig. 8.19. Throughoutthe period,
winds were moderate (by Southern Ocean standards) with an average temperature
around
14
◦
C.
−
MM5 Wind, Site Maud 91
15
a
10
5
0
232
234
236
238
240
242
244
246
248
250
Air Temperature
0
-
10
b
-
20
232
234
236
238
240
242
244
246
248
250
Ice Fraction
0.95
c
0.9
0.85
232
234
236
238
240
242
244
246
248
250
Day of 2005
Fig. 8.19
Environmental parameters extracted from the MM5 model output:
a
10-m wind speed;
b
2-m air temperature; and
c
iceconcentration
