Solar Irradiance Modulates the Asian Summer Monsoon—ENSO Relationship Over the Last Millennium

Abstract

The Asian summer monsoon (ASM) is teleconnected to the El Niño Southern Oscillation (ENSO), but this relationship is nonstationary and has shifted significantly in recent decades. Characterizing the drivers of such shifts is crucial for improving ASM prediction and extreme event preparedness. Paleoclimate records indicate a link between ASM strength and solar activity on multidecadal‐to‐centennial timescales, but 20th‐century data are too short to test mechanisms. Here we evaluate how solar irradiance influences the ASM‐ENSO relationship using last‐millennium paleoclimate data assimilation reconstructions and model simulations. We find that high solar irradiance weakens the ENSO‐East Asian summer monsoon (EASM) correlation, but strengthens the ENSO‐South Asian summer monsoon (SASM) correlation. Solar irradiance likely influences the strength of the ENSO‐EASM and ENSO‐SASM teleconnections via changes in the Western Pacific Subtropical High and the amplitude of ENSO events, respectively. We suggest a need for considering solar activity in decadal ASM rainfall predictions under global warming scenarios.

PDO and AMO Modulation of the ENSO–Asian Summer Monsoon Teleconnection During the Last Millennium

“…For example, Mehta and Lau (1997) proposed that solar irradiance could impact the ENSO-ISM relationship over multidecadal time scales, as a long-lived, above-normal irradiance anomaly would amplify the contrast in thermal conditions between land and sea, leading to an intensification of monsoon winds and above-normal rainfall over India. Recent paleoclimate evidence confirms this, suggesting that during periods of high total solar irradiance, the ENSO-ISM correlation is strengthened and the ENSO-EASM correlation is weakened (Du et al, 2023). In addition, Narasimha and Bhattacharyya (2010) showed ENSO connections with solar activity, and suggested that the influence of solar irradiance on the ISM is indirectly applied via the ENSO teleconnection.…”