1988
Thickness of land-fast ice is monitored from coastal sites in
Arctic Canada, Svalbard and Siberia
8,15,16
. Most sites show
large variations among years and among decades. Data ex-
tending back to 1936 from sites off the coast of Siberia show,
in general, no significant trends up to 2000
8
. Consistent ob-
servations at Svalbard do not go that far back in time, but
monitoring during the last decade showed that during the
warmer-than-normal winters of 2005/2006 and 2006/2007
the land-fast ice in most Svalbard fjords was less extensive,
thinner and lasted for a shorter time than normal.
1990
The age of sea ice in the Arctic is also changing. Studies
show that in recent years there is a higher proportion
of younger ice to older ice than was observed in the late
1980s
6
(Figure 5.7).
Southern Hemisphere trends
In contrast to the Arctic, there are signs of a slight in-
2001
crease in the extent of annual mean sea ice over the
period 1979–2005 (+1.2 per cent per decade) based on
the NASA Team retrieval algorithm
18
. The IPCC
20
con-
cluded that this overall increase was not significant and
that there are no consistent trends during the period of
satellite observations. There are, however, indications
that sea ice may be increasing more at the period of
minimum coverage (March) than at the period of maxi-
mum sea-ice extent in September. There is also regional
variation (Figure 5.8) with an increase, for example, in
2005 the Ross Sea (+4.8 per cent per decade) and a loss in the
Bellingshausen Sea (–5.3 per cent per decade).
Age of sea ice (years)
0 - 2 Figure 5.7: Change in the age of ice on the Arctic Ocean, com-
paring September ice ages in 1988, 1990, 2001 and 2005. This
2 - 4
analysis is based on results from a simulation using drifting
4 - 6
buoy data and satellite-derived ice-concentration data
17
. The
darker the colour, the older the ice.
6 - 10+
Source: Based on Richter-Menge et al. 2006
6
70 GLOBAL OUTLOOK FOR ICE AND SNOW