In addition to the atmosphere, the global climatic system encompasses the global ocean and its sea ice cover as well as features on land that include glaciers, permafrost, rivers, and lakes. These system components continuously interact with each other. A number of studies identify patterns of such interaction, including Formation and Dynamics of Modern Climate of the Arctic regions (Alekseev et al., 2004), which provides recent qualitative patterns of polar-process interaction in the global climatic system. Its contributing authors stress that the "Arctic is quite a sensitive part of the global climatic system" (p. 4).
Influences on the polar climatic system include:
— Solar radiation, which is partly regulated by the ozone layer
— Transport of carbon dioxide and aerosols from other areas that influence the heat balance of the atmosphere and the underlying surface
— Heat and moisture fluxes from the atmosphere of low and temperate latitudes
— Horizontal heat and salt exchange with the global ocean
— River runoff and iceberg discharge
— Freezing and melting of sea ice
— Accumulation and melting of glaciers
— Permafrost processes
— Convection processes in polar-region waters, including deep and shelf convection
In order to understand Arctic ice cover, it is important to not only enumerate climate-shaping processes but also to estimate the role of their anomalies in climatic changes of different scale. Due to complex relationships among the processes governing climate, this problem is extremely complicated. Solutions to some of its complexities are considered in chapter 6 of this monograph. A brief review of approaches to the problem that are available in the literature is presented below.
Alekseev et al. (2004) consider the global impact on climate of the Arctic to be transferred primarily through atmospheric circulation, controlling the heat and moisture transfer to high latitudes and their fluctuations within the interannual variability range. In addition, fluctuations of large-scale atmospheric circulation influence the inflow of warm and saline water to the North European Basin and further to the Arctic Basin and are manifested in the changes in sea ice extent.
"An inverse impact of the Arctic on global climate change is connected with fluctuations of sea ice and fresh water export from the Arctic Ocean to the North Atlantic, which influence the total sea ice area change and the development of deep convective water sinking in the sub-Arctic and Arctic regions of the global ocean" (p. 7).
Because the formation of intermediate water in the North Atlantic depends on it, Nikiforov (2006) considers the overflow of dense, deep, near-bottom water across the Faroe-Shetland strait sill (Wyville-Thomson Ridge) to be significant in climate fluctuations. This overflow phenomenon influences the intensity of the Gulf Stream, determining the quantity and characteristics of warm Atlantic water flowing to the Arctic Ocean. Exchanges between the atmosphere and the Arctic Ocean are responsible for climatic fluctuations in the hydrometeorological ocean system regime.
Sea ice plays a large role in these exchanges, as has been observed by many scientists conducting both theoretical studies and data analysis, and discussed further in sections 1.2 and 1.3. The connection between sea ice (its thickness, area, and other parameters) and climate has long been recognized (Zakharov, 1996). The relationships of the ice thickness to the air temperature and other factors were described in the nineteenth century by Stefan (1891), and then confirmed by many empirical studies (e.g., Zubov, 1944). However, the existence of these relationships does not prove a climate-shaping role for ice, but only points to its dependence on climate.
The climate-shaping role of sea ice is determined by the presence of feedbacks (positive and negative) between the ice cover and processes at work in the atmosphere and hydrosphere. Sea ice influences climate on a variety of scales, from local to global. A brief review of the role of feedback mechanisms that determine the influence of ice cover on the global climatic system and its peculiarities in the Arctic is given below.
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