Weakening Relationship Between Vegetation Growth Over the Tibetan Plateau and Large-Scale Climate Variability

Vegetation growth on the Tibetan Plateau is strongly affected by large-scale climate variability, particularly the Pacific Decadal Oscillation (PDO) and the North Atlantic Oscillation (NAO). However, potential temporal changes in both the direction and strength of relationships between regional vegetation growth and large-scale climate variability remain poorly understood. Here we quantify temporal changes in these relationships during 1982–2012, using satellite-derived normalized difference vegetation index, global ecosystem model simulations of net primary productivity, regional tree ring chronologies, and PDO and NAO indexes. We found consistent weakening relationships between mean growing-season (April–October) normalized difference vegetation index and both PDO and NAO. A similar pattern was also found in the temporal relationship between net primary productivity and PDO. Such weakening relationships were partly attributable to weakening regional summer atmospheric circulation and its causal effects on changes in hydrothermal conditions over the Tibetan Plateau. These findings highlight a varying coupling of regional vegetation growth to large-scale climate variability at the interannual/decadal scale during past decades, and this feature should be considered in future prediction of terrestrial vegetation growth in response to shifting climate regime.