Note that, since Antarctic ice is about 10X in mass Arctic ice, this means that from 1979-2012 there was a 1.1-1.15%/decade growth in the combined ice caps over this time period.
Continuing
the trends reported in AR4, there is very high confidence
that the Arctic sea ice extent (annual, multi-year and
perennial) decreased over the period 1979–2012 (Figure
TS.1). The rate of the annual decrease was very likely
between 3.5 and 4.1% per decade (range of 0.45 to 0.51 million
km2 per decade). The
average decrease in decadal extent of annual Arctic sea ice has been
most rapid in summer and autumn (high confidence), but the extent has
decreased in every season, and in every successive decade since 1979
(high confidence).
The extent of
Arctic perennial and multi-year ice decreased between 1979
and 2012 (very high confidence). The rates are very likely
11.5 [9.4 to 13.6]% per decade (0.73 to 1.07 million km2
per decade) for the sea ice extent at summer minimum (perennial ice)
and very likely 13.5 [11 to 16] % per decade for multi-year ice.
There is medium confidence from reconstructions that the current
(1980–2012) Arctic summer sea ice retreat was unprecedented and
SSTs were anomalously high in the perspective of at
least the last 1,450 years. {4.2.2, 5.5.2}
It is likely that
the annual period of surface melt on Arctic perennial sea
ice lengthened by 5.7 [4.8 to 6.6] days per decade over the period
1979–2012. Over this period, in the region between the East
Siberian Sea and the western Beaufort Sea, the duration of ice-free
conditions increased by nearly 3 months. {4.2.2}
There is high
confidence that the average winter sea ice thickness within
the Arctic Basin decreased between 1980 and 2008. The
average decrease was likely between 1.3 m and 2.3 m.
High confidence in
this assessment is based on observations from multiple
sources: submarine, electromagnetic probes and satellite altimetry;
and is consistent with the decline in multi-year and perennial
ice extent. Satellite measurements made in the period 2010–2012
show a decrease in sea ice volume compared to those made over the
period 2003–2008 (medium confidence). There is high confidence that
in the Arctic, where the sea ice thickness has decreased, the sea ice
drift speed has increased. {4.2.2}
It is very
likely that the annual Antarctic sea ice extent increased at a rate
of between 1.2 and 1.8% per decade (0.13 to 0.20 million
km2 per decade) between 1979
and 2012 (very high confidence). There was a greater
increase in sea ice area, due to a decrease in the
percentage of open water within the ice pack. There is high
confidence that there are strong regional differences in
this annual rate, with some regions increasing in extent/area
and some decreasing. There are also contrasting regions around the
Antarctic where the ice-free season has lengthened, and others where
it has decreased over the satellite period (high confidence). {4.2.3}
