Geology Reference
In-Depth Information
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Figure 10.26
Radarsat‐2 (a) SAR image over the Gulf of Bothnia acquired on 13, March 2011, (b) SAR‐based ice
concentration, (c) FMI ice chart ice concentration, and (d) the ASI algorithm ice concentration based on AMSR‐E
radiometer. The Radarsat image is © MDA [
Karvonen
, 2012, Figure 8, with permission from IEEE].
decadal decrease of ice extent in winter is not as much as
found in September when the most significant interan-
nual changes are observed. The reduction in Arctic sea
ice allows for more seasonal ice cover. This has caused a
reversal in the proportion of seasonal to perennial ice
coverage with seasonal sea ice now covering more than
two-thirds of the Arctic Ocean in late winter. Seasonal
ice is more susceptible to melting in the summer, which
enhances the probability of further reduction of the ice
extent.
Kwok et al
. [2009] reported that MY ice in the cen-
tral Arctic has decreased by more than 42% since 2005.
Ivanova et al
. [2014] calculated daily ice extent and area
in the Artic for 2012 using 11 passive microwave ice con-
centration algorithms. Graphs are shown in Figure 10.28,
which depicts the annual cycle of the ice area and extent.
The unique feature about these graphs is the multiple
sources of the methods used to generate them. The nearly
equal values from the 11 algorithms confirms the authen-
ticity of the results (this is the advantage of the inter-
comparison approach adopted in the afore-mentioned
study). The difference in sea ice area varies between 0.1
and 1.4 million km
2
with the maximum occurring in the
