This project will assess the reproducibility of geochemical records of Sr/Ca ratios and oxygen isotopes in sclerosponges, both within single skeletons and from specimens collected from the same location. This research is considered exploratory because although there is no information at present as to the error that can be placed on the geochemical signals measured in the skeleton of sclerosponges, these proxies are potentially very important as they can provide high-resolution information of water mass characteristics over the past 500-700 years. The information obtained from this SGER will enable the PI to constrain the propagated error produced when computing salinities from combined geochemical data. These data are critical for determining whether reconstructions of North Atlantic salinities from sclerosponges are real or below analytical uncertainty. Once these errors have been established, it will then be possible to determine whether or not salinity variations in the Atlantic can be reconstructed from this biological archive over the past 500 years and longer. The broader impacts of this project include support of a PhD student's research and the first ultra high-resolution measurement of Atlantic gyre salinity and temperature during periods such as the Little Ice Age and the Medieval Warm Period.
