Reconstructing Late Holocene Hydrographic Variability of the Gulf of Maine

• Main Author: Whitney, Nina Millicent
• Format: Text
• Language: unknown
• Published: DigitalCommons@UMaine 2015
• Subjects: Arctica islandica; isotopes; Gulf of Maine; paleoclimate; paleoceanography; Climate; Geochemistry; Oceanography; North Atlantic
• Online Access: https://digitalcommons.library.umaine.edu/etd/2247; https://digitalcommons.library.umaine.edu/context/etd/article/3291/viewcontent/FINAL_THESIS_nwhitney.pdf

I present an annually resolved reconstruction of seawater temperatures in the western North Atlantic from 1695-1915. This paleoclimate record was constructed using oxygen isotopes measured in precisely dated Arctica islandica shells collected off of Seguin Island in the western Gulf of Maine. The temperature reconstruction was derived from this oxygen isotope time series using a modern d18Ow-salinity mixing line developed for coastal waters in the Gulf of Maine from water samples collected over the last decade. The d18Ow and salinity composition of these water samples indicate that coastal surface waters consist of a mixture of Scotian Shelf Water and Maine River Water. The properties of these coastal waters are significantly influenced by seasonal changes in local river discharge. The Gulf of Maine oxygen isotope record suggests centennial-scale oscillations in seawater temperatures and therefore in the strength and position of the major ocean current systems that influence Gulf of Maine water properties. This record indicates that recent warming seen in the Gulf of Maine is not yet outside the natural seawater temperature variability of the region and therefore cannot be unequivocally linked to anthropogenic climate change. The positive and negative correlations between the Gulf of Maine oxygen isotope record and seawater temperature records from the subpolar gyre region of the North Atlantic and the western North Atlantic, respectively, are similar in pattern to the modeled and observed influence of the Atlantic meridional overturning circulation (AMOC) on seawater temperatures in these regions. This similarity suggests a possible association between AMOC variability and seawater temperatures in the Gulf of Maine. The association indicates that seawater temperature reconstructions from oxygen isotopes measured in A. islandica shells collected in the Gulf of Maine could provide an annually resolved, precisely dated reconstruction of AMOC variability. The oxygen isotope record I present in this thesis suggests ...