A 50-year hydro-climatological assessment of climatic modes over the world’s major mountain ranges

The observed climate response and variability that has occurred over the five decades since 1960 of 13 largest global mountain regimes (i.e. the European Alps, Anatolia, Andes, Applach, Atlas, Australian, Brooks, Ethiopian, Himalaya, Kolyma, Rocky, Pyrenees, and Scandinavian) to climate variability. This study covers the period 1960-2013, with a particular emphasis on changes in air temperature and precipitation conditions and their joint modes. Results demonstrate that mountains of high-latitudes in the Northern Hemisphere (e.g. Brooks, Kolyma, and Scandenavia) experienced the largest trends of air temperature (0.24 – 0.45° C/decade). In contrast, changes in air temperature in mountains of the Southern Hemisphere (e.g. Australian and most of the Andes) and the subtropics (e.g. Ethiopian mountains) were generally weaker than those of the mid- and highlatitudes of the Northern Hemisphere. Notably, temperature changes were stronger in low- and mid-elevation regions (e.g. Alps, Pyrenees, Brooks, and Kolyma), compared to the most elevated regions (e.g. Himalaya and Andes). Precipitation exhibited heterogeneous changes, with pronounced decrease over the Alps, Pyrenean and Ethiopian mountains and conversely significant increase across the northern high-latitudes mountains (e.g. Scandinavian and Applach). Factor analysis was also used to identify common patterns of interannual variability among all mountain systems. Results suggest three components with distinctive temporal evolution that explain together 72.72% of air temperature variability. In contrast, the temporal evolution of annual precipitation was more heterogeneous, with six components accounting for 68.59% of precipitation variability. This study also accounted for the possible joint changes in air temperature and precipitation by assessing changes in four different climatic modes (i.e. warm and wet [WW], warm and dry [WD], cold and wet [CW] and cold and dry [CD]), Changes in air temperature, precipitation and their joint modes were further linked to a range of the key circulation patterns over the Northern and Southern Hemispheres, e.g. the Atlantic Meridional Mode [AMO], the Atlantic Multidecadal Oscillation [AMO], the Arctic Oscillation [AO], the Multivariate ENSO Index [MEI], and the North Atlantic Oscillation [NAO]. Results of this work can advances our knowledge of the role of climate variability and change in mountain environments, giving insights into their possible ramifications for different environmental and socioeconomic sectors (e.g. freshwater supply, hydropower generation, biodiversity conservation, …etc).

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