Seasonal modulation of the Asian summer monsoon between the Medieval Warm Period and Little Ice Age: a multi model study

Abstract

Instrumental and proxy records indicate remarkable global climate variability over the last millennium, influenced by solar irradiance, Earth's orbital parameters, volcanic eruptions and human activities. Numerical model simulations and proxy data suggest an enhanced Asian summer monsoon during the Medieval Warm Period (MWP) compared to the Little Ice Age (LIA). Using multiple climate model simulations, we show that anomalous seasonal insolation over the Northern Hemisphere due to a long cycle of orbital parameters results in a modulation of the Asian summer monsoon transition between the MWP and LIA. Ten climate model simulations prescribing historical radiative forcing that includes orbital parameters consistently reproduce an enhanced MWP Asian monsoon in late summer and a weakened monsoon in early summer. Weakened, then enhanced Northern Hemisphere insolation before and after June leads to a seasonally asymmetric temperature response over the Eurasian continent, resulting in a seasonal reversal of the signs of MWP-LIA anomalies in land-sea thermal contrast, atmospheric circulation, and rainfall from early to late summer. This seasonal asymmetry in monsoon response is consistently found among the different climate models and is reproduced by an idealized model simulation forced solely by orbital parameters. The results of this study indicate that slow variation in the Earth's orbital parameters contributes to centennial variability in the Asian monsoon transition.

The effects of orbital forcing on the East Asian Summer Monsoon for the past 450 kyr

“…MRI-CGCM has been widely used for future climate prediction (e.g., Kitoh, 2007;Ueda et al, 2006) and paleoclimate simulations (e.g., Braconnot et al, 2007a;Kamae et al, 2016Kamae et al, , 2017Kitoh et al, 2007;Ueda et al, 2011). The reproducibility of MRI-CGCM2.3 has already been studied by Yukimoto et al (2006) and indicates good agreement with observations in the distribution of surface air temperature and precipitation.…”

Summer monsoon over northeastern India during the last millennium

“…A multi‐model study by Kamae et al . (2017) shows more summer monsoon insolation during the MCA compared to LIA over the Indian subcontinent and NEI. Although the variability of ISMR during the LM has been is now being studied using models, no studies, including those mentioned above, on the NEI particularly from the modelling perspective.…”

“…A study by Polanski et al (2014) shows thermal gradients between the BoB and the Indian subcontinent drives the majority of the summer monsoon rainfall over NEI during the LM. A multi-model study by Kamae et al (2017) shows more summer monsoon insolation during the MCA compared to LIA over the Indian subcontinent and NEI. Although the variability of ISMR during the LM has been is now being studied using models, no studies, including those mentioned above, on the NEI particularly from the modelling perspective.…”

Variable monsoons and human adaptations: Archaeological and palaeoenvironmental records during the last 1400 years in north-western India

“…Though the timing of the onset of cooling conditions is still debated, this general chronology has allowed for archaeologists and historians to consider economic and social changes in Europe as a response to climate cycles (Aberth, 2012; Fagan, 2000). More recently, studies have focussed on the timing and impact of the ‘MWP’ and ‘LIA’ in Asia, in particular, the spatial distribution and forcing factors involved of fluctuations in the East Asian Summer Monsoon (Chen et al., 2015; Kamae et al., 2017). The onset of the ‘LIA’ in China from the mid-16th century has been linked to famines, north–south migrations and social unrest that had severe implications for the stability of the Ming and Qing Dynasties (Wu et al., 2018; Xiao et al., 2015).…”