[1] A Porites coral from New Ireland (2.5 S, 150.5 E), at the heart of the Pacific warm pool, records variations of Ba/Ca back to the early 1820s. The New Ireland Coastal Undercurrent, which flows along the north coast and transports high-nutrient thermocline waters, is thought to be the main source of the Ba enrichment observed in the coral during El Niño. Between the 1850s and the 1960s, freq...