Assessing Tropical Cyclone Records in 20th Century Stalagmites: Challenges, Limitations, and Opportunities in Proxy Development

Many stalagmites are highly sensitive to multiple environmental changes. Studies of modern cave systems have provided keys to deciphering the rich environmental history witnessed in the stalagmite code. In the effort to understand inter-annual to sub-seasonal stable isotope variations in stalagmites, my experience demonstrates the great value in combining multi-variable proxy analysis, calendar-year age models, and characterization of the modern cave environment. A deeper understanding of the drivers of stalagmite variations can result when stalagmite-specific data is coupled with historical studies of local weather and climate, land- and cave-use, and regional extreme events such as hurricanes and explosive volcanic eruptions. I present a case study to demonstrate the utility of this approach.

Having demonstrated that speleothem calcite oxygen isotope ratios are sensitive to tropical cyclone precipitation, stalagmites may be poised to break new ground in hurricane-climate research. To advance the study of hurricane-climate interactions, we must assess the utility of stalagmite isotopic records for reconstructing aspects of paleo-hurricane activity, such as landfall dates or frequency, storm intensity, and rainfall amount. I present initial assessments of the overall reliability of the stalagmite tropical cyclone proxy and the quality of various hurricane proxy signals given currently available data and sampling techniques. It is also vital to understand the conditions that limit the usefulness of stalagmites as storm recorders. The history of late 20th century tropical cyclone strikes and inter-stalagmite comparison together provide essential constraints on this application. I will also discuss the influence of potentially limiting factors on the resulting speleothem parameters and the implications of tropical cyclone infiltration for the fidelity of lower resolution speleothem paleoclimatology in affected regions.