Determination of Atlantic SSTs During the Maunder Minimum Using a New Multi-Element Paleothermometer


OCCI Funded Project: 2007


We propose to develop a new geochemical paleothermometer and apply it to reconstruct a 30-year proxy record of seasonally-resolved SSTs in the western subtropical Atlantic during the Maunder Minimum, a period of low solar activity that occurred between ~1645 and 1715 AD, that is associated with the coolest part of the Little Ice Age. Such proxy data offer the only means to extend our knowledge of ocean climate variability beyond the short instrumental record. Nevertheless, while a number of paleothermometers have been developed using the carbonate skeletons of marine invertebrates, such as corals and foraminifera, all are plagued by uncertainties arising from the influence of biological processes on skeletal chemistry (the so called “vital effects”).

Our work over the past two years has uncovered the mechanism responsible for “vital effects” in coral skeletons. This process that can be accurately modeled using element partitioning data from abiogenic precipitation experiments and the equations that govern Rayleigh fractionation. We are using this breakthrough to develop a new paleothermometer.Based on fundamental principles of element partitioning between seawater and CaCO3 and calibrated using partition coefficients determined from abiogenic precipitation experiments, our approach is a sharp departure from conventional paleothermometry.

The proposed work involves development of laser-ablation ICPMS protocols for multi-element, in situ analysis of coral skeleton.Laser-ablation ICPMS offers the potential for generating long, continuous records from corals with exceptionally high temporal resolution. Once our protocol is developed, we will target the skeleton of a massive brain coral that grew on Bermuda during the Maunder Minimum. These data will provide the first determination of SSTs in the western subtropical Atlantic during the coolest period of the past 1000 years, and enable us to assess the climate response to changes in solar activity.