Ressource pédagogique : Present-Day Geomorphological Changes in Polar Regions

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The landscape uniqueness of polar zone manifests itself in morphological traces of older glaciations and marine transgressions, areas of present-day glaciations, multi-year permafrost, multi-year snow covers, deglaciation processes variable in time and space and resulting in an expansion of ice-free 94 areas, multi-directional geosuccession, and finally in the various responses of the Arctic peoples to landscape changes and the growing human impact. The abrupt landscape changes taking place over a period shorter than the life span of a single generation can be due to a wide variety of natural causes, whether endogenous or exogenous, or to the increasing, multi-directed human activity. At present, however, their principal cause is believed to be climate change at a variety of spatial scales. The paper presents examples of contemporary changes of morphologic surfaces from all the territory of the Arctic and Antarctica. Among the most significant environmental changes noted in the polar regions, can be list the following: • air temperatures frequently exceeding the hitherto absolute maxima, • an increase in annual precipitation totals, first of all in the form of rain, also during the cold period, • cold periods becoming milder and shorter, • transitional periods becoming longer: spring coming earlier and autumn ending later, • a decrease in the thickness, persistence and area of the sea-ice cover, • an increase in the number of icebergs from intensively calving glaciers, • an increase in the temperature and a decrease in the salinity and density of ocean waters; changes in the thermohaline circulation, • an increase in the level of the world ocean, • intense ablation and rapid recession of the majority of polar glaciers, • a decrease in the area of nival covers, • intensive thawing of multi-year permafrost, mainly in continental parts, • changes in the water cycle manifested by an increase in the surface runoff in streams and a shortening of the period of freezing of streams and lakes, • an increase in the area of some wetlands and a decrease in others, • a northward shift of geoecological, including vegetation, zones, • changes in the carbon cycle in the geoecosystems manifesting themselves in an increase in biogenic carbon dioxide and methane, and • an increase in the frequency and magnitude of forest fires. All those symptoms of climate change affect the terrestrial geoecosystems of polar regions to a greater or lesser degree. The ever-growing role of rock geoecosystems, crucially dependent on glacier and nival geoecosystems, results from intensive glacier recession and the melting of permafrost and snow covers. The polar research to date and scenarios of development of polar regions indicate that the polar landscapes have been undergoing rapid changes recently.

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• Économie (330)
• Sciences de la Terre (550)

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