relevant work is already occurring within the science community, as described in the examples and case studies in Chapter 1.

WILL A RAPIDLY SHRINKING CRYOSPHERE TIP POLAR ECOSYSTEMS INTO NEW STATES?

Many of the workshop participants emphasized the need to quantify both the vulnerability and resilience of the polar ecosystems, including local communities and populations, in response to the rapidly shrinking cryosphere, and to understand the connectivity between the cryosphere and the global system. Changes in air temperature and precipitation patterns are altering the structure of the cryosphere, the hydrological cycle, fire regimes, and permafrost melting in the terrestrial system. Warming atmospheric and seawater temperatures over the western Arctic (Chukchi Sea and Canada Basin) and the western Antarctic Peninsula have dramatically reduced sea ice cover, changing air-sea interactions regionally and their connectivity to the global system.

The polar regions are poised to lose biodiversity as the result of air, sea, and land temperature changes and seasonal-to-total melting of sea ice, glaciers, and permafrost. Changes in biodiversity can be expected to result in altered biogeochemical processes, which can affect the overall production of the system. For example, a shift in dominance from krilleating Adelie penguins to fish-eating seals can alter the net efficiency of biogeochemical processing. If the dominant higher trophic animal is eating higher on the food chain (fish-eating seals) versus feeding lower on the food chain (krill-eating penguins), the system is less efficient as more total energy is used to get the same base level of food to the top predator, requiring more food at the base of the food chain.

Other impacts of a shrinking cryosphere include changes to subsistence life styles, resource exploration, and tourism. Coastal erosion is increasing as sea ice retreats and open water can degrade coastal regions and negatively impact human habitation. Increased potential for resource access and extraction may be realized as the open water season increases in length (Arctic Council, 2009). Traditional hunting methods and sites are changing with changes in weather, the landscape, and resource availability (e.g., Ford et al., 2008). Understanding ecosystem changes with climate forcing, their complexities, vulnerabilities, and feedbacks are considered important research frontiers in a world that continues to warm. Workshop participants stressed the important goal of coupling climate models with biogeochemical models in order to identify potential tipping points and associated tipping elements, transformational processes,



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