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and related research questions that need to be addressed to support the ESE, and does so with sufficient specificity to allow an assessment of the supporting measurements.

The scope of the science questions considered here is affected by how “cryosphere” is defined. The committee elected to begin with the definition used by the WCRP's Climate and Cryosphere Program, which defines the cryosphere as that portion of the Earth containing sea ice, snow cover, permafrost, ice sheets, and glaciers (WCRP, 2000). The committee also included critical processes that influence surface energy, freshwater fluxes in the cryosphere, and carbon and trace gas exchanges at the atmospheric interface.

The committee wishes to emphasize that we did not create the basic science questions, but took the global science questions presented in the NASA ESE Science Plan and focused them on polar regions. The following science planning documents relevant to the polar regions were also used:

  • Science Plan for the WCRP Arctic Climate System Study (WCRP, 1994)

  • Science Plan for the WCRP Climate and the Cryosphere Programme (WCRP, 2000)

  • Science Plan for the NSF ARCSS Human Dimensions of the Arctic System (ARCUS, 1997)

The IPCC Working Group I and II contributions to the Second Assessment Report were also consulted (Houghton et al., 1996). The committee found that several cryosphere issues that we judged relevant to this study were not thoroughly addressed by the three science plans or IPCC reports. For these issues, we have formulated a few new subsidiary science questions, but these are still organized within the basic ESE framework. For each ESE question, a set of polar-specific questions, a rationale for the importance of studying the relevant phenomenon, and a short list of required measurements are given.

1 Issue No. 1: How are Polar Climate and the Biosphere System Changing?

1.1 Are changes occurring in the polar troposphere?

1.1a Is an acceleration or deceleration of the polar hydrologic cycle apparent in changes of polar precipitation rates in either hemisphere?

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