Arctic shelf ecosystems are likely to be more sensitive to physical ice changes and the changes in ice-related eco-
climatic perturbations than those of temperate shelf areas systems are affecting human economies and well-being.
because a greater degree of warming is expected and be-
cause these ecosystems are characterized by comparatively Sea ice as a dynamic, complex environment
simple food webs and low biodiversity (meaning that loss
of one part of the food web has greater consequences). When observers aboard a ship watch ice floes drifting
through Fram Strait (the area between Greenland and
In the remainder of this chapter we discuss sea ice in rela- Svalbard) they can assume that each piece of ice has a
tion to ocean and climate processes, summarize the im- long history. Sea ice that ends up in Fram Strait (and
pacts of observed and projected changes on polar marine most multi-year ice that exits the Arctic Ocean flows
biodiversity and ecosystems, and look at how both the through Fram Strait) often originates from the Siberian
Albedo
(% of radiation reflected)
100
Melting of
Dry
sea ice
snow
80
Wet
snow
Bare ice
60
Increase in
Lowered
absorbed
albedo
sunlight
New melt
pond
40
Mature
melt
pond
20
Figure 5.11b: Schematic illustrating the ice–albedo feedback.
Open
In spring, the ice is snow-covered and there is very little open
water water. Most sunlight is reflected, but some is absorbed. This
absorbed sunlight leads to melting, which in turn reduces the
0
ice albedo and increases the amount of open water. This causes
the albedo to further decrease, increasing the rate of heating
Figure 5.11a: Albedos of basic thick sea-ice surface types. and further accelerating melting.
Source: Based on Pegau and Paulson 2001
28
; Perovich and others 2002
29
Source: Based on material from D.K. Perovich
76 GLOBAL OUTLOOK FOR ICE AND SNOW