Assessing Rapid Climate Change During the Last Interglacial with a New Approach to Sea Level Reconstruction

Bill Curry, Geology & Geophysics
William Thompson, Geology & Geophysics

OCCI Funded Project: 2005

Collaborators:
Ken Sims - Woods Hole Oceanographic Institution
Allen Curran - Smith College
Brian White - Smith College

What are the primary questions you are trying to address with this research?
The purpose of this project is to document the history of Last Interglacial sea level in detail, in order to understand if interglacial climates are inherently more stable than glacial ones. Previous work by others has produced conflicting results. The details of sea-level change have been difficult to resolve because of significant problems with conventional methods of coral dating. We will use a promising new approach that results in more accurate ages. Preliminary results suggest sea level changes by tens of meters over cycles of several thousand years.

What is the significance of this research for others working in this field of inquiry and for the broader scientific community?
Rapid and substantial sea level change implies similar changes in global climate and continental ice sheets. Present ideas about rapid climate change often invoke surges of ice or melt water from large northern hemisphere ice sheets. If such changes were indeed occurring during the Last Interglacial, a time of minimum northern hemisphere ice, it will require a different explanation. Rapid fluctuations in ice sheets also present a challenge to those working on glacier dynamics. In addition, if the new approach to coral dating proves to be robust, it will lead to significant improvements in chronologies for the past 600,000 years, benefiting all who work in this interesting period.

What is the significance of this research for society?
Today’s interglacial climate appears to have been relatively stable over the last several thousand years, in sharp contrast to the most recent glacial period where rapid and substantial climate changes have been well documented. In light of the increasing human impact on Earth’s climate, it is important to understand whether our modern climate is inherently stable, or if it might be susceptible to rapid change.

When and where will this investigation be conducted?
The plan is to revisit key coral outcrops on Barbados and the Bahamas, to do high-resolution sampling and mapping. If detailed results from these two sites agree, it will build confidence in this new methodology and add to our understanding of Last Interglacial sea level and climate change. In both locations, previous mapping and dating provides a solid foundation for focusing detailed sampling efforts.

What are the key tools or instruments needed to conduct this research?
In addition to a sledgehammer and chisel, which are the sampling instruments of choice for coral outcrops, the isotopic analysis for dating will be done at the WHOI Inductively Coupled Plasma Mass Spectrometry Facility. The instrument, a Neptune ICP-MS, has the required precision to generate high-quality coral ages.

Relevant publications:
Thompson, W. G., and S. L. Goldstein (2005). "Open-System Coral Ages Reveal Persistent Suborbital Sea-Level Cycles." Science 308: 401-404.
Thompson, W. G., et al. (2003). "An Open-System model for the U-series age determinations of fossil corals." Earth and Planetary Science Letters 210: 365-381.

Biography
Bill Thompson is presently an Ocean and Climate Change Institute Postdoctoral Scholar at WHOI. His PhD work on coral dating and sea level was done at the Lamont Doherty Earth Observatory of Columbia University, where he developed a new approach to U/Th coral dating. Undergraduate work and a Masters thesis on sea level variability during the Late Holocene and metal contamination in salt marshes was completed at Wesleyan University. Bill was born in landlocked Ann Arbor, Michigan, but grew up on the Connecticut shore of Long Island Sound. After a twenty-year career as a musician and entrepreneur, he returned to school with the intention of studying molecular biology, but quickly gravitated to the Geology department. Bill and his new wife, author Jamie Callan, currently live in a converted boathouse on Eel Pond in Woods Hole village. He spends his off hours fishing, cooking, and puttering around with his bonsai trees.

Originally published: January 1, 2005