Simulated cycles of East Asian temperature and precipitation over the past 425 ka

Records from a wide range of geological archives covering the last few glacial-interglacial cycles show large inconsistencies in the East Asian summer monsoon variability, which severely hampers our understanding of the evolution and potential mechanisms of the regional East Asian climate on orbital timescales. Here, we examine the simulated temperature and precipitation in East Asia based on a series of equilibrium simulations conducted for the past 425 ka, and we investigate the sensitivity of temperature and precipitation to potential forcings. Our simulations show that, in East Asia, the seasonal mean temperature is dominated by a ∼20-kyr cycle, and the annual mean temperature (AMT) is dominated by a ∼100-kyr cycle, which is consistent with previous modeling efforts and geological reconstructions. Additional sensitivity experiments indicate that the greenhouse gas concentration, in combination with the ice volume, is the dominant force for the variations of AMT in East Asia on orbital timescales. For the precipitation in East Asia, our equilibrium simulations and additional sensitivity experiments, together with comprehensive model-data intercomparison analysis, suggest that the cycles of simulated annual mean precipitation over East Asia are highly model-dependent, although the dominant ∼20-kyr cycle in summer precipitation appears to be a robust feature. Overall, the results highlight the large model uncertainty with regard to the relative roles of forcings in hydroclimate variations in East Asia on orbital time scales. There is, therefore, an urgent need to implement more realistic precipitation schemes in models in order to decrease the model spread in simulated precipitation.