Seasonally-Resolved Bivalve Proxies of Late Holocene Gulf of Maine Climate Variability
K. Kreutz, A. Wanamaker, H. Borns, and D. Introne,
Climate Change Institute and Department of Earth Sciences,
and P. Rawson and S. Fiendel, School of Marine Sciences

Understanding the mechanisms responsible for interannual to decadal-scale climate variability and their impact on Gulf of Maine (GOM) oceanography during the past millennium remains a basic research problem in the North Atlantic sector. Our research focuses on the links among spatial and temporal patterns of climate in the North Atlantic (e.g., the North Atlantic Oscillation [NAO] and Atlantic Multidecadal Oscillation [AMO]) and the oceanography in the GOM during the Late Holocene, specifically during the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA), by analyzing carbonate geochemistry (stable isotopes) and developing standardized growth increments (SGI) of mollusk bivalves Mytilus edulis and Arctica islandica. These animals provide annual growth of shell carbonate that can be sampled continuously and at high (sub-seasonal) resolution to develop proxy records of physical (temperature and salinity) and biological (nutrient/productivity) oceanographic conditions. To calibrate the derived proxy records, we have developed aquaculture techniques that allow animals to be grown under controlled temperature and salinity/∂ 18O water conditions at the UMaine Darling Marine Center, as well as use available oceanographic data to evaluate relationships between shell growth and productivity. Results (see figure with annually-averaged isotope and growth data) indicate warmer/less saline water in the GOM during the MCA, and colder/more saline water during the LIA. A change in both temperature and productivity at ~1400 AD may be related to larger-scale climate shifts observed in the North Atlantic and Europe. However, shells collected alive imply that the coldest conditions of the Late Holocene have occurred in the past ~100 years. We are currently analyzing additional chemical and growth data from fossil shells recovered from GOM sediment cores, with the goal of producing a continuous proxy data spanning the past 1000 years. Research results will contribute to a better understanding of interannual to decadal climate forcing mechanisms during the Late Holocene in the GOM, New England, and the North Atlantic.

climate forcing mechanisms during the Late Holocene in the GOM, New England, and the North Atlantic.