Faced with expectations of accelerated sea-level rise due to anthropogenic warming of the global climate system, decision makers, scientists and the general public have become increasingly concerned about potential risks to coastal communities and ecosystems. Gaining understanding of how changes in sea level may be linked to changes in climate is important in order to project future changes and possibly mitigate socio-economic impacts. In the northeastern United States geological records generally suggest sea-level rise of about 1 mm/year or less for the last few thousand years while instrumental records indicate rates of 2-3 mm/year over the past 150 years. The apparent discord between long-term and short-term records is often interpreted to indicate an increase in the rate of sea-level rise in the last few hundred years that may be the result of the warming global climate. Determining the timing of this apparent acceleration is crucial if we are to understand the relationship between sea-level changes and fluctuations in climate.
Intellectual Merit Many previous studies have exploited the narrow vertical habitat range of coastal wetland species to reconstruct past sea levels, but most lack the dating resolution to resolve historic sea-level changes. Well-constrained, high-resolution records of sea-level change are necessary if we are to be able to link the geologic record with the historic instrumental records. Reliable age estimates of sea-level indicators are necessary in order to establish a history of sea-level change for the historic period (last 400 years). Radiocarbon methods are useful in this interval, but large uncertainties associated with calibration for secular changes in atmospheric C-14 concentrations require that other dating methods also be employed to help reduce these uncertainties. Dated stratigraphic markers such as those attributable to anthropogenic landscape changes and pollution can provide important constraints on the age of sea-level indicators and can substantially reduce uncertainties associated with radiocarbon dating methods. Some recent attempts to reconstruct high-resolution records of sea-level changes in New England from coastal wetland sediments may suggest that the recent apparent increase in the rate of sea-level rise may have begun in the 17th or 18th century A.D., predating the climate warming of the last 150 years by several centuries. However, these studies have relied on non-basal samples that may have been displaced vertically by autocompaction of the peat column. Using an approach that recovers contiguous sections of basal marsh sediments deposited over a glacial erratic and a combination of radioisotopic and stratigraphic dating techniques, I have constructed a 1300-year sea-level chronology from Barn Island, Connecticut that indicates the recent acceleration in the rate of sea-level rise may have initiated in the late 19th century. Reproducing the results from Barn Island and other locations is critically important because changes in geomorphology that alter the tidal range at a site can introduce local changes of sea level. Here, I propose to use the approach described above to extend the instrumental record of sea-level change by attempting to replicate the results of this initial study at another site at Barn Island and two sites at Plum Island Marsh in northern Massachusetts. The results will provide critical insight into how sea level has changed over the last 1500 years and expand our understanding of the links between climate and sea-level change.
Broader Impacts Coastal resource managers and policy makers will be able to use the results of this study to make informed decisions regarding appropriate management practices and regulatory strategies. The results of this study would be extremely useful to stakeholders: coastal zone managers; habitat restoration groups; land managers; business interests concerned with managing risk; coastal property owners and coastal scientists. With billions of dollars and human lives at risk, I see this research as providing vital information for society. In addition, I am committed to helping train the next generation of geoscientists by providing them with practical, "hands on," interdisciplinary research experience and I plan to include a graduate student and at least one undergraduate in this project. I endeavor to recruit students from groups underrepresented in the geological sciences whenever possible. In addition, the geological and ecological lessons learned from this study, as well as the potential societal implications, will be integrated into undergraduate and graduate coursework including seminars and field trips. The results will be presented at a professional meeting and we will publish our findings in one or more peer-reviewed journals.
