Sea
Ice
Extent
(
SIE
)
index
[
mln
km2
]
provides
a
quick
look
on
changes
in
sea
ice
in
the
____________________
.
It
provides
daily
,
consistently
processed
ice
extent
and
concentration
from
images
taken
by
Nimbus
7
satellite
since
1979
.
The
values
of
the
SIE
Index
are
calculated
by
summing
the
area
of
all
grid
cells
25x25km
with
15%
or
greater
ice
concentration
.
The
daily
index
shows
ice
extent
with
an
outline
of
the
typical
extent
for
that
day
based
on
a
30
-
year
(
1981
-
2010
)
____________________
.
Since
1979
winter
Sea
Ice
Extent
in
the
Arctic
has
____________________
about
3
percent
per
____________________
.
