|Benthic Foraminifera - Oxygen-18/Carbon-13|
Benthic foraminiferal oxygen and carbon isotopes (18O, 13C) are established water mass proxies with 13C related to carbon cycling and 18O related to the temperature and salinity. Many of our notions of ocean water mass reorganizations during the LGM originate from mapping benthic foraminiferal 18O and 13C due to their relatively wide geographical coverage across the world oceans (see e.g., Lynch-Stieglitz et al. 2007). Currently benthic foraminiferal 18O and 13C values from LGM sediments are available at about 800 sites from the World Ocean. Once this database has been reassessed for consistency it will provide a valuable benchmark for validating and refining climate models.
Improved species specific calibrations are needed through measurements of living specimens preferably at sites where seawater 18O and 13C are available. In order to provide the most meaningful data model comparisons, direct incorporation of individual proxies into models is desirable. In the case of 18O, inter-laboratory calibrations and adoption of uniform sample handling and preparation techniques and reporting standards (including number of shells, size fraction, specimen images, and treatment to remove organic matter, etc.) is crucial for reducing the systematic errors which limit the utility of the current dataset, vast as it may be. The development of better proxies for deep water temperature and more complete reconstructions of past ocean salinity would be very helpful towards expanding the use of 18O as a dynamic (density) tracer.