Global Outlook for Ice & Snow

Arctic shelf ecosystems are likely to be more sensitive to climatic perturbations than those of temperate shelf areas because a greater degree of warming is expected and be- cause these ecosystems are characterized by comparatively simple food webs and low biodiversity (meaning that loss of one part of the food web has greater consequences). In the remainder of this chapter we discuss sea ice in rela- tion to ocean and climate processes, summarize the im- pacts of observed and projected changes on polar marine biodiversity and ecosystems, and look at how both the

physical ice changes and the changes in ice-related eco- systems are affecting human economies and well-being.

Sea ice as a dynamic, complex environment

When observers aboard a ship watch ice floes drifting through Fram Strait (the area between Greenland and Svalbard) they can assume that each piece of ice has a long history. Sea ice that ends up in Fram Strait (and most multi-year ice that exits the Arctic Ocean flows through Fram Strait) often originates from the Siberian

Albedo (% of radiation reflected)

100

Melting of sea ice

Dry snow

80

Wet snow

Bare ice

60

Increase in absorbed sunlight

Lowered albedo

New melt pond

40

Mature melt pond

20

Figure 5.11b: Schematic illustrating the ice–albedo feedback. In spring, the ice is snow-covered and there is very little open water. Most sunlight is reflected, but some is absorbed. This absorbed sunlight leads to melting, which in turn reduces the ice albedo and increases the amount of open water. This causes the albedo to further decrease, increasing the rate of heating and further accelerating melting. Source: Based on material from D.K. Perovich

Open water

0

Figure 5.11a: Albedos of basic thick sea-ice surface types. Source: Based on Pegau and Paulson 2001 28 ; Perovich and others 2002 29

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GLOBAL OUTLOOK FOR ICE AND SNOW