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Figure 11.
Seasonal cycles during 2000-2010 and 2090-2100 of (a) surface downwelling longwave (LW) and shortwave
(SW) radiative fluxes and (b) all-sky net (incoming minus reflected) surface SW flux simulated by the NCAR CCSM3
model forced with SRES A1B scenario and averaged over the ocean north of 70°N. Decrease in surface incoming SW
due to changes in clouds is shown as “D SW (clouds).” Increase in the net SW due to surface albedo changes is shown
as “D SW (sfc albedo).”
of the low troposphere contributes to the large increase in
downwelling LW flux in winter and is the main factor re-
sponsible for increased downwelling LW flux during the
summer when clouds are optically thick (Figure 11a).
Figure 11b shows seasonal cycles of the Arctic Ocean sur-
face net SW fluxes during the first and last decades of the
21st century together with the contribution of the cloud and
surface albedo changes to the difference between the two
Table 1.
Differences in Cloud Fraction, Cloud Liquid Water Path, Surface Downwelling Long-
wave and Shortwave Fluxes, and Net Shortwave Flux Between the Last and First Decades of
the 21st Century Averaged Over the Ocean North of 70°N Predicted by the NCAR CCSM3
Model SRES A1B Scenario for Each Month
a
Month
Cloud (%)
LWP (g m
-2
)
DLF (W m
-2
)
DSF (W m
-2
)
Net SW (W m
-2
)
December
9
62
52
0
0
January
7
36
38
0
0
February
6*
34
33
0
0
DJF
7
44
41
0
0
March
2.5
29
30
-3
0.8
April
5
37
25
-15
2.2
May
2.5
14
14
-19
17
MAM
3
27
23
-12
6
June
4
5*
11
-24
24
July
3
4*
10
-16
17
August
5
25
17
-16
2
JJA
4
11
13
-19
14
September 3 26 21 -6 2
October 5 54 36 -1.5 0
November 9 56 49 0 0
SON 6 45 35 -2.5 0.8
a
Abbreviations are LWP, liquid water path; DLF and DSF, surface downwelling longwave and
shortwave fluxes, respectively; and SW, shortwave flux. Seasonal means are for December-
February (DJF), March-May (MAM), June-August (JJA), and September-November (SON).
All differences are significant at 95% level, except for those marked with asterisks.
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