North Atlantic Climate Variability Over the Holocene: Preliminary Analysis of Bermuda Historical Weather Data and Stable Isotope Time Series from Bermuda Stalagmites

Bermuda, located in the center of the Sargasso Sea of the North Atlantic Ocean, is a unique laboratory for analyzing Holocene climate change. This subtropical area lacks a strong seasonal cycle, making it an ideal place to look for low-frequency cycles identified in observational records of North Atlantic climate. A preliminary statistical analysis of historical climate data, provided by the Bermuda Weather Service and spanning a period from 1852 to 2006, will be presented. Emphasis will be placed on the identification of cycles corresponding to such climate modes as the North Atlantic Oscillation (NAO) and the Atlantic Multidecadal Oscillation (AMO). To extend the record back farther than the observational period, it is necessary to identify and analyze paleoclimate proxies.

Carbonate caves on the island of Bermuda contain numerous speleothems, which have the potential to serve as extremely high-resolution (sub-decadal) recorders of climate change via the stable oxygen and carbon isotope concentrations contained in their crystalline form. Three stalagmites retrieved from caves in the Hamilton Parish region of Bermuda were dated by U-series methods and found to cover the last 4.7 thousand years. Time series of stable isotope (O-18 and C-13) data from these stalagmites will be presented, with interpretations of implications for the dominant modes of North Atlantic climate variability over the last 4.7 thousand years.