Salinity information from hydro-sensitive, biogenic marine carbonate 18O records
Abstract
Stable oxygen isotope ratios in marine biogenic carbonates (18Ocarb, e.g., from corals, coralline algae, bivalves, sclerosponges) have greatly extended the instrumental record, providing invaluable information about climate variability and change from the tropics to high latitudes. These 18Ocarb records reflect seawater temperature and 18O (18Osw) at the time of calcification, which occurs sufficiently rapidly to permit reconstruction of sub-annual to annual variability over the lifetime of the organism. 18Osw is strongly related to salinity, as both are similarly impacted by hydroclimate processes such as precipitation, evaporation, and advection. Many studies have leveraged 18Ocarb and the tendency for temperature and salinity to covary constructively in the tropics (e.g., warm with wet or low salinity, and vice versa) to reconstruct changes in major modes of climate variability and responses to forcings. However, with limited networks of in situ seawater temperature, salinity, and 18O measurements, quantifying the relative contribution of temperature and 18Osw to 18Ocarb variability remains a large source of uncertainty. Here we use pseudo-carbonate 18O records modeled from temperature and salinity to identify sites where salinity contributes substantially to 18Ocarb variance. These hydro-sensitive 18Ocarb records are located predominantly in the Indo-Pacific Warm Pool, Caribbean Sea, Gulf of Mexico, and Aleutian Archipelago. Notably, we find that temperature and salinity vary destructively in 18Ocarb (i.e., warm with drier or higher salinity) in many regions for which high-resolution paleoclimate reconstructions have provided key constraints on ocean circulationthe eastern equatorial Pacific, the North Atlantic, and at depth. However, the inferred salinity variability at these sites is sensitive to uncertainties in the 18Osw-salinity relationship, emphasizing the need for a coordinated network of in situ salinity and 18Osw measurements.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFMPP14B..01T