Senior Theses 2006
Patrick Schwing (2006). Regional Climatology and Anthropogenic Impacts on Coastal Sedimentation Patterns: St. John, USVI
Faculty Advisor: Gregg Brooks
Eleven sediment cores collected in salt ponds surrounding St. John document the effect of regional climate (precipitation) on the recent increase of terrestrial sediment input attributed to anthropogenic activities. Sediment accumulation rates, determined by Carbon-14 dating, illustrate the natural, long-term (1000’s of years) evolution of the island. Increased terrestrial infilling rates in the last 100 years, determined by Lead-210 dating, are a result of increased human activity. Comparing the rate of terrestrial sediment introduced naturally (i.e. before human impact) to the current input rate demonstrates the drastic effect of human development on the island’s natural evolution.
This study explores regional climate as an additional control on the recent anthropogenically enhanced sedimentation rate. An event in the 210Pb record is evident in every core. This event is most likely a regional-scale precipitation event, possibly a tropical cyclone, which is indicated by the large increase in terrigenous accumulation rate than those located in a pristine basin. By using the Constant Initial Concentration (CIC) method, the 210Pb date of the event is determined to be 1989 (± 2 years). This date may correspond to Hurricane Hugo, which had reports of many mass-wasting events suggesting this might be the cause for such a sedimentary event. This date may also correspond to the highest peak in the North Atlantic Oscillation (NAO). This peak in the NAO index indicates an extremely high amount of precipitation in the winter of 1989 for St. John, and could also be the cause of such a sedimentary record. One or both of these could be the cause for the sedimentary event.
The regional climate, wet or dry, has been found to be a factor that influences the sedimentation rate due to human development. Work continues to determine the effect of regional climate on anthropogenic sedimentation rates. These results will allow for responsible management and development decisions, which will ultimately aid in eliminating a premature destruction of the natural coastal environment on St. John.