PP031-0002
A Coral Proxy-Model Comparison of 14-16th Century ENSO Event Variability
Friday, 11 December 2020
Poster
Jasmine Hunter1, Helen V Mcgregor1, Matthew Fischer2, Laurent S Devriendt3, Michael K Gagan4,5, Henri Wong2, Tara Clark4,6 and Colin D Woodroffe4, (1)University of Wollongong, Wollongong, NSW, Australia, (2)Australian Nuclear Science and Technology Organization, Kirrawee, Australia, (3)Royal Netherlands Institute for Sea Research, Den Burg, Netherlands, (4)University of Wollongong, Wollongong, Australia, (5)Australian National University, Research School of Earth Sciences, Canberra, Australia, (6)University of Queensland, Brisbane, Australia
Abstract:
The El Niño Southern Oscillation (ENSO), originating in the Pacific, accounts for one of the largest sources of interannual climatic variation globally. Understanding the mechanisms behind ENSO is vital to assess 20th century ENSO variability in the context of natural variation. Over the last millennium, the frequency and amplitude of ENSO events has varied over interdecadal to centennial timescales. The 14-16th
centuries appear to represent a period of transition from relatively warm conditions to a cooler period (Little Ice Age) in several reconstructions. However, the spatial extent of this change, as well as its impact on ENSO activity, is still uncertain, due in part to the scarcity of proxy records, and uncertainties in climate model simulations of ENSO. Recent work on El Niño event development has focused on the modern period, and the impact of future climate change. Our extension of this timeseries into the past millennium provides a baseline for how El Niño events develop during different periods of ENSO activity.
We present two Porites spp. Coral ẟ18O and Sr/Ca records for Kiritimati Island (central Pacific) and combine them with published coral data to analyse past ENSO variability. Composites of Individual El Niño events in the modern and fossil coral records reveal differences in the pattern of their growth and decay in the central Pacific versus the western Pacific. The coral reconstructions are compared to ẟ18O and Sr/Ca-SST coral proxy-system model output from the Last Millennium Ensemble of the isotope-enabled Community Earth System Model version 1 (LME iCESM1). Across the fossil ẟ18O and Sr/Ca records, a total of 24 El Niño events were identified, with an average central Pacific SST anomaly of +0.8°C. An increase in event amplitude can be seen in the 20th century compared to the 1400-1600s. Overall, this study characterises ENSO event behaviour in the 14-16th centuries across the Pacific, and identifies changes in ENSO intensity captured in the coral proxy and LME iCESM reconstructions for this period.
