Isotopic spikes from tropical cyclones in surface waters: Opportunities in hydrology and paleoclimatology

The stable isotopic ratio of precipitation from tropical cyclones is very low compared to that of normal summer precipitation (Lawrence and Gedzelman, 1996). Tropical Storms Allison and Chantal made landfall in southeast Texas in the summer of 1989 and dumped large amounts of rain. Isotope ratios of surface waters measured at five different sites decreased markedly after the passage and remained low for a few weeks. The return of isotope values to normalcy following these storms varied from site to site reflecting differences among the hydrological environments. During other summers from 1985 to 1993 isotope ratios of rains were higher and in the normal range. Calculations using air temperatures and oxygen isotope measurements of the surface waters show that organically precipitated fresh water carbonate should have recorded the two oxygen isotopic spikes produced by Allison and Chantal at all five sites. This suggests that isotopic analysis of ancient fresh water fossil carbonate shells, fossil mammal teeth or tree rings might be used to document past tropical cyclone activity.