Contrasting response of regional spring Arctic Sea ice variations on Indian summer monsoon rainfall

Abstract

Understanding the relationship between Arctic Sea Ice Concentration (SIC) and Indian Summer Monsoon Rainfall (ISMR) is crucial for analysing regional climate change. Present study investigates this connection using satellite observations and simulations from Coupled Model Intercomparison Project Phase 5 (CMIP5) and CMIP6 coupled climate models, focusing on external forcing from 1979 to 2021. Rotated Empirical Orthogonal Function (REOF) analysis identified the dominant mode (PC1) of ISMR, explaining 31.7% of the variance with significant regional variability. Singular Value Decomposition (SVD) analysis revealed a maximum covariance of 41.1% during spring between Arctic SIC observations and ISMR. Leading SVD correlations for the multi-model ensemble mean (MMEM) simulations of spring Arctic SIC were 30.6% (CMIP5) and 42.8% (CMIP6). Our results demonstrate a significant correlation between ISMR PC1 and observed Arctic spring SIC (r = -0.25, p < 0.10), particularly in the Central Arctic (r = 0.51, p < 0.01) and the Barents-Kara Sea (r = -0.39, p < 0.01). During the High Sea Ice Years (HSYs) in the Central Arctic, distinct pressure pattern centres developed extending from western Europe to the western Pacific Ocean and were linked to the circumglobal teleconnection (CGT) influence circulation. Anomalous highs over western central Asia and a strengthened easterly jet enhance rainfall in northwestern and peninsular India. Conversely, weakened jets and high-pressure systems during Low Sea Ice Years (LSYs) hinder the monsoon. This highlights the influence of upper atmospheric Rossby waves on circulation patterns. Similarly, during LSYs in the Barents-Kara Sea, the North Atlantic-Eurasia teleconnection wave train pattern and ridge formation over northwestern Europe affect the Indian monsoon's onset. North European geopotential height anomalies contribute to formation of these ridges and troughs, impacting wind patterns and thermodynamic instability, ultimately influencing rainfall distribution. This comprehensive study underscores the far-reaching impacts of seasonal Arctic changes on the ISMR, emphasising the critical role of climate teleconnections between Arctic SIC and the Indian monsoon. Our results suggest an improved understanding of regional Arctic SIC dynamics is vital for accurate ISMR predictions using future climate models.