Date of Award

Summer 8-21-2015

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Quaternary and Climate Studies

Advisor

Karl J. Kreutz

Second Committee Member

Alan D. Wanamaker

Third Committee Member

Kirk A. Maasch, Neal R. Pettigrew

Abstract

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 centennial-scale

oscillations in AMOC variability, with increased strength of the AMOC after the Little

Ice Age.

Comments

As of 2002, Degree of Master of Science (MS) Quaternary and Climate Studies published under the auspices of the Climate Change Institute.

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