Collaborative Research: Reconstructing Pacific Trade Wind Variability: Extending and Replicating a Promising New Coral Proxy

Global surface warming markedly slowed between 2000 and 2014, despite a continued increase in greenhouse gases in the atmosphere. Recent modeling and observation work suggests that this slowdown or “hiatus” in warming could be attributed to strong winds in the tropical Pacific. These strong winds mixed some of the heat into the subsurface ocean, leaving less heat to warm the atmosphere. Such decade-to-decade changes in wind strength (associated with natural variability in the Pacific) likely contributed to periods of both accelerated and reduced warming over the last 100 years. Thus, warming will likely accelerate in the coming decade(s) when the cycle reverses and trade-winds weaken once again. 

However, to date, our understanding of the link between global air temperatures and tropical Pacific wind strength has been limited by the sparse historical wind observations. This work will utilize the chemical fingerprints of these wind events captured in the skeleton of living and fossil corals from the central tropical Pacific to investigate wind variability – and it’s link to global air temperatures – across the past century and preindustrial era. This project will also extend the application of this novel wind archive, providing key groundwork for such records to be extended to additional sites and time periods. These natural archives of tropical Pacific wind strength over the recent past have the potential to dramatically improve our understanding of the impact of natural wind variability on the rate of global climate change.

Site map figure
Map of research sites. All islands have westerly facing lagoons, where westerly winds may remobilize Mn (white arrows), which may then be incorporated into corals on nearby reefs (star) [Figure credit: Hussein Sayani].
This project leverages a number of existing modern and fossil coral cores and a promising new coral proxy to further investigate tropical Pacific trade wind variability across changes in natural and anthropogenic forcing. Buiding off pioneering studies linking westerly wind anomalies and coral Mn/Ca at Tarawa Atoll, we calibrate and extend this new proxy across sites (Tarawa, Kiritimati, Butaritari, and Palmyra) and time periods (20th century and Little Ice Age/preindustrial) leveraging existing modern and fossil coral material.

The primary aims of this project are to:

  1. Quantify the link between westerly wind bursts, seawater and porewater Mn concentration and Mn/Ca in coral skeletons at Kiritimati Atoll
  2. Develop a robust, quantitative Mn/Ca-wind reconstruction over the 20th century from Kiritimati, Palmyra, Butaritari, and Tarawa Atolls
  3. Investigate the frequency of westerly wind burst events over the LIA to preindustrial period (1400-1850CE) using fossil coral archives

Collaborators

  • Dr. Jessica Carilli, SPAWAR Systems Center – Pacific
  • Dr. Hussein Sayani, postdoctoral researcher, Boston University
  • Dr. Kim Cobb, Georgia Tech
  • Dr. Helen McGregor, University of Wollongong