and meters to decades and ocean basins also remains a large challenge facing climate-ecosystem models.
Workshop participants emphasized that polar regions and lower latitude ecosystems are parts of a coupled Earth system. For many ecosystem processes, changes in one component elicit responses from other components, which can further alter other system components. This cascade of bi-directional connectivity makes atmosphere-ecosystem interactions among the most complex in the natural world (NRC, 2007). These responses and interactions become even more complex with the involvement of human actions as broad ecosystem drivers. Given the complexity of these interactions and the feedbacks involved, participants stressed that breakthroughs will require effective collaboration among a wide range of sciences and long-term ecosystem monitoring, as well as involvement of multiple funding agencies.
Studies to date have shown unequivocally that climate change has produced many direct regional impacts at the poles (IPCC, 2007b). Polar regions are expected to be primary drivers of the global climate system because of the strong modification of the surface-energy budget through snow and ice cover, which is tightly coupled to the global circulation of the atmosphere and the ocean. The global implications and associated feedbacks of these polar impacts are difficult to define, and require long-term on-site monitoring and experimentation, in concert with coupled modeling efforts, to resolve. Participants noted that such efforts should focus on the construction of scenarios that cross many scales, a dynamic that we currently have little quantitative knowledge of.
Workshop participants discussed a number of processes and phenomena (including those identified in Anisimov et al. ) that may have bi-directional feedbacks on the global system:
Atmospheric variation: Changes in the polar energy sink region exert a strong influence on the mid- and high-latitude climate by modulating the strength of the sub-polar westerlies and storm tracks (Dethloff et al., 2009). Disturbances in the wintertime Arctic sea-ice and snow cover may induce perturbations in the zonal and meridional planetary wave-train from the tropics over the mid-latitudes into the Arctic. Consequently, Arctic processes can feed back on the global climate system via an atmospheric wave bridge between the energy source in the tropics and the energy sink in the polar regions.