Combined impact of Greenland sea ice, Eurasian snow, and El Niño–Southern Oscillation on Indian and Korean summer monsoons

The combined impact of Greenland sea ice, Eurasian snow, and the El Nino-Southern Oscillation (ENSO) on the out-of-phase relationship between the Indian summer monsoon (ISM) and Korean summer monsoon (KSM) were investigated through numerical experiments. The results revealed that Indian and Korean summer rainfalls showed nonlinear responses to ENSO and Greenland sea ice forcing when the events co-occurred. Above-normal Greenland sea ice and a concurrent La Nina showed a distinct in-phase relationship with ISM and out-of-phase relationship with KSM. Below-normal and above-normal Greenland sea ice during boreal autumn surrounded the Greenland region with anomalous low pressure and high pressure, respectively. These were associated with a barotropic +west/-east or -west/+east dipole pattern, respectively, over Eurasia during the subsequent winter and spring seasons. Furthermore, these patterns led to positive and negative snow depth anomalies, respectively, over western Eurasia and the opposite snow tendency over eastern Eurasia during the subsequent spring. This variability in Eurasian snow patterns may play a crucial role in ISM and KSM. The co-occurrence of ENSO variability also generates high- and low-pressure anomaly patterns over the Indian Ocean that may be related to unfavourable or favourable ISM, respectively, while influencing the negative or positive phases of a Pacific Japan (PJ)-like teleconnection pattern that may be related to unfavourable or favourable KSM, respectively. Therefore, coexisting ENSO forcing may play a dominant role in ISM and KSM, but Greenland sea ice forcing and Eurasian snow variation intensify the out-of-phase relationship between ISM and KSM.