The Western Pacific Warm Pool (WPWP) is a component of the largest mode of inter-annual climate variability on the planet, El-Niño Southern-Oscillation (ENSO). Despite the importance of climate variability in the WPWP, the climatology of the region over the last three centuries is largely unknown. This project, involving researchers from the University of Texas at Austin, aims to produce the first sub-annually resolved, multi-century record of ENSO and WPWP climate variability utilizing corals from the Western Province, Solomon Islands. By measuring δ18O in three cores of the slow-growing coral species Diploastrea heliopora, the researchers seek to generate a record of sea surface temperature and hydrologic variability spanning the last three centuries in the WPWP. These records will enable assessment of changes in WPWP and ENSO variability from pre-industrial through modern times.
In terms of broader impact, funding supports education and training of a graduate student and an undergraduate student. The research will also develop a potentially important, high-resolution data series that would provide an observational basis for relating WPWP changes to global climate conditions and may find changes in the mean state of the WPWP and ENSO as a result of anthropogenic climate forcing in the modern era.
The western, tropical Pacific Ocean is strongly impacted by the El Niño Southern Oscillation, which is the largest source of interannual climate variability on earth. The objective of NSF award 1103430 (ENSO and West Pacific Warm Pool Climate Variability over the Last Three Centuries) was twofold: 1) to establish that geochemical variations in a massive, slow-growing honeycomb coral can be used as a proxy for variations in surface ocean temperature and salinity over the past 30 years; the common period of overlap between the coral and instrumental records; and 2) to use this relationship to generate a nearly three century-long record of surface-ocean variability that could be used to assess how ENSO has changed over the recent past. This study successfully met both of these objectives. Perhaps the most significant result of this research was the demonstration that ENSO activity in the early 18th century and 19th centuries is similar to and/or exceeds that in the late 20th century. Hence, the modern level of ENSO variability in the western, tropical Pacific Ocean, is not unprecedented over the last 300 years. The project formed the basis of the dissertation studies of a graduate student and provided training and research experience for an undergraduate student, both of whom were able to present their research at national scientific meetings. Indeed, the undergraduate student, who is a female from an underrepresented minority group, plans to further pursue her studies in graduate school.
