has led to drastic changes in forest ecosystems. Such changes can lead to potential shifts in bird and large mammal migration patterns. Likewise, changes in ocean pH, temperature, and circulation patterns can reach thresholds that will eventually alter plankton distribution and the migration patterns of marine fish and mammal populations. Once these thresholds are reached, biodiversity at the species and genetic levels will almost certainly be altered.
Methane hydrates: Methane hydrates are known to be abundant in marine sediments, particularly those associated with the continental shelves of the Arctic (Kvenvolden, 1988). As ocean temperatures warm, either directly or as the consequence of altered circulation patterns, the hydrates can become unstable and release significant amounts of methane, a potent green house gas, to the atmosphere (Sloan, 2003; Maslin, 2004). This marine efflux of methane can exacerbate warming at the global scale. For example, Shakhova et al. (2010) have recently suggested that atmospheric release of a small amount of methane from the East Siberian Arctic Shelf could lead to abrupt warming.
Southern Ocean biological production: Regional and global models indicate that heat transport and associated stratification of the Southern Ocean will change in response to climate forcing (Ganachaud and Wunsch, 2000; Boning et al., 2008). In concert with the prediction of amplified ocean acidification in south polar waters, it can be expected that these changes in the physical environment will influence the species composition and rate of primary production in the Southern Ocean. Such changes may alter the production of methane sulfonic acid, a potent cloud nucleator, to the atmosphere, and change the sequestration of atmospheric carbon dioxide and transport to the deep ocean. Such physical and biochemical processes influencing changes in biological production are also being studied regionally in the Arctic Ocean.
The rapid warming of the Arctic is potentially leading to rapid shifts in productivity, habitat, and biodiversity that are likely to have profound implications for northern ecosystems and for the globe. Macroecology, the subfield that deals with the study of relationships between organisms and