Strengthening of the East Asian winter monsoon during the mid-Holocene

The change in the East Asian winter (December-January-February) monsoon (EAWM) during the mid-Holocene, approximately 6000 years ago, was investigated using all available experiments within the Paleoclimate Modelling Intercomparison Project (PMIP). As defined by regional-averaged meridional wind speed at 850 hPa, the mid-Holocene EAWM intensity was consistently stronger than that of the reference period in 38 out of the 42 models chosen for analysis, with an average strengthening of 14% across all models. In response to changes in the Earth's orbital parameters and atmospheric greenhouse gas concentrations, zonal and meridional land-sea thermal contrasts and sea-level pressure gradients were enhanced between the continent and the adjacent oceans of East Asia, leading to the strengthening of the mid-Holocene EAWM. In addition, there were uncertainties regarding the EAWM reconstructions and the effect of dynamic ocean and vegetation on the EAWM change during the mid-Holocene.