RECONSTRUCTING LATE HOLOCENE HYDROGRAPHIC VARIABILITY IN THE WESTERN NORTH ATLANTIC USING OXYGEN ISOTOPES FROM AN ANNUALLY RESOLVED ARCTICA ISLANDICA SHELL-BASED RECORD

Arctic climate is significantly influenced by several climate modes in the North Atlantic, including the North Atlantic Oscillation (NAO) and the Atlantic Multidecadal Oscillation (AMO), which in turn are linked with changes in the strength of the Atlantic Meridional Overturning Circulation (AMOC). Evidence from terrestrial paleoclimate proxies in the Arctic implies that these Arctic climate drivers have varied during the past millennium. However, relatively little is known about how they have affected ocean hydrography on annual to decadal timescales. Our work seeks to determine how the NAO, AMO and AMOC have influenced oceanic climate in the western North Atlantic by reconstructing annually resolved records of salinity and temperature in the Gulf of Maine over the past 300 years and comparing this hydrographic variability to oscillations in North Atlantic climate drivers.

Several hundred live and dead Arctica islandica have been collected in the central Gulf of Maine, near Seguin Island, at a depth of 38 meters. Twenty-eight of the shells from these specimens, which were targeted for geochemical analysis, have been crossdated into an annually-resolved master shell growth chronology extending to AD 1694. 201 oxygen isotope samples, from 12 crossdated shells, have been analyzed. These samples were measured with an annual resolution in shell increments that grew during AD 1695-1703, 1748-1838,1853-1873,1926-1944 and 1953-1990. The δ¹⁸O data have a mean of 1.255‰ and range from 0.483‰ - 2.099‰. These isotope values indicate a mean temperature in the Gulf of Maine over the last 300 years of 7.82°C, with a minimum annual temperature of 4.18°C and a maximum annual temperature of 11.11°C, assuming a mean annual salinity value before the instrumental record of 32.1 PSU.

Initial time series analysis of the isotope data will be presented. This analysis reveals a centennial scale oscillation in Gulf of Maine hydrographic properties. Additionally, associations of reconstructed Gulf of Maine seawater temperature trends with variability in North Atlantic climate drivers will be discussed, including the moderately strong negative correlation between Gulf of Maine seawater temperature and the strength of the AMOC.