Decade-Long Isotopic Analysis (18O & 2H) of Daily Precipitation in the Malaya Peninsula: Understanding the Complex Hydrometeorology

The Malaya Peninsula, uniquely positioned between the South China Sea to the east and the Indian Ocean to the west presents a unique geographic vantage point for the study of ocean-ocean and ocean-atmosphere-land interactions, particularly in the context of climate change. Its proximity to the Indo-Pacific Warm Pool (IPWP) makes the region a critical nexus where global temperature rise intersects with significant ocean-atmosphere processes, such as Hadley and Walker circulations, El Niño-Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), and Madden–Julian Oscillation (MJO). These processes and their teleconnections play a pivotal role in shaping the regional climate, profoundly influencing rainfall patterns and freshwater availability in the peninsula.  In our research, we conducted a decade-long analysis of oxygen and hydrogen isotopes in daily rainfall samples collected from Krabi, Thailand, a region situated in the northern Malaya Peninsula. Krabi faces the Andaman Sea and is characterized by a tropical monsoon climate. The region's climate is predominantly influenced by the North-South migration of the Intertropical Convergence Zone (ITCZ), which governs the patterns of summer and winter monsoonal rainfall. The diverse topography of Krabi plays a critical role in local weather patterns, potentially intensifying the complexity of the region's dual monsoon system. The time series analysis of isotopic data brings to light three distinct patterns superimposed over the daily variability. There's a clear seasonal cycle, primarily driven by changes in moisture sources, indicating shifts in atmospheric moisture transport with the seasons. Additionally, multi-year patterns suggest the influence of complex ocean-atmospheric processes, likely reflecting teleconnections between the Western Pacific and Indian Oceans. Intriguingly, we also observed a long-term trend of isotopic depletion without corresponding changes in rainfall volume, hinting at the potential impacts of ocean warming and broader climate change. This study underscores the importance of understanding the nuanced interplay of land, ocean, and atmospheric systems in regional rainfall dynamics. It has significant implications for regional climate models and paleoclimatic research. It highlights the sensitivity of the Malaya Peninsula's climate to both local topographical features and global oceanic phenomena, offering crucial insights into the regional responses to ongoing global climatic changes.