Refinement and utilization of the marine climate proxy Arctica islandica: An ideal replication strategy for stable isotope studies and an investigation into the shell growth and hydrographic variability of Georges Bank (Northwestern Atlantic)

• Main Author: Ballew, Jared Daniel Brenzink
• Format: Text
• Language: English
• Published: Iowa State University Digital Repository 2018
• Subjects: Arctica Islandica; Georges Bank; Gulf of Maine; Paleoclimatology; Sclerochronology; Stable Isotope Geochemistry; Climate; Geochemistry; Geology; Oceanography; Paleontology; Arctic; Nantucket; Arctica islandica; North Atlantic; North Atlantic oscillation; Northwest Atlantic
• Online Access: https://lib.dr.iastate.edu/etd/16313; https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=7320&context=etd

This thesis presents two studies that discuss the further refinement and utilization of the marine climate proxy Arctica islandica. The first study uses a Monte Carlo simulation to examine the relationship between replication and uncertainty for climate reconstructions utilizing oxygen isotopes, carbon isotopes and temperature estimates (derived from the modified Grossman and Ku [1986] equation) from the climate proxy A. islandica. An uncertainty within the 95% confidence interval occurred when using two or three shells. An increase to four shells further reduced the uncertainty to within the 99% confidence interval. Studies that utilize stable isotope ratios from A. islandica shells should use at least two to four shells. Replication beyond four shells may not provide substantially improved results when considering the costs and time associated with these analyses. Results from this study also suggest that A. islandica biomineralize their shells in oxygen isotope equilibrium with the seawater, supporting findings from previous studies. The second study discusses the development of a near century-long shell growth chronology, using the marine bivalve A. islandica for Georges Bank (Northwest Atlantic). The purpose of this study is to determine whether shell growth is synchronous within this population, and determine what environmental factors may influence shell growth through time. The high expressed population signal and interseries correlation suggest the Georges Bank population exhibits synchronous growth. Comparisons revealed significant inverse relationships between the shell growth chronology and a short salinity record from the nearby Nantucket Lightship, the North Atlantic Oscillation/Arctic Oscillation indices, and Florida Current strength. These results suggest that shell growth at the study site broadly reflects hydrographic conditions in the Gulf of Maine and North Atlantic.