<p>As a critical region sensitive to global warming, the ecosystem dynamics of the Tibetan Plateau are regulated by the interaction between the westerlies and monsoon circulation systems. Utilizing remote sensing observations, this study quantifies the relative contributions of three climatic zones (monsoon, transition, and westerlies) to the evolution of gross primary productivity (GPP) and identifies their respective climatic drivers. Results reveal that while the monsoon zone dominates the plateau-wide GPP for the mean state (86.07%), long-term trend (69.84%), and interannual variability (81.80%), its relative contributions to GPP changes (i.e., long-term trends and interannual variability) are proportionally lower than to the mean state. Conversely, both the transition and westerlies zones exhibit proportionally higher contributions to GPP changes relative to their mean-state contributions. Temperature is the primary driver of the long-term GPP increase across the Tibetan Plateau and its subregions, though with a weaker contribution rate (57.26%) in the transition zone compared with the monsoon (77.88%) and westerlies zones (71.35%). The interannual variability of GPP across both the entire plateau and its subregions is also dominated by temperature, yet process-based ecosystem models fail to replicate this dominant temperature control. Our study elucidates complex GPP-climate interactions under the westerlies-monsoon synergy, highlighting the imperative to improve model parameterization for accurately capturing interannual variability in alpine ecosystem dynamics.</p>