Paper No. 215-7
Presentation Time: 10:05 AM
ASSESSING THE FEASIBILITY OF STABLE OXYGEN ISOTOPES FROM OSTRACODE SHELLS AS PALEOCEANOGRAPHIC PROXIES FOR WATER MASS IN ARCTIC AND SUBARCTIC CONTINENTAL SHELF ENVIRONMENTS
Measurements of stable oxygen isotopes on calcitic valves of benthic ostracodes (δ18Oost) from the northern Bering and Chukchi Seas were used to examine ecological and hydrographic processes influencing ostracode and associated seawater δ18O values. Five cryophilic taxa were analyzed for δ18Oost values: Sarsicytheridea bradii; Paracyprideis pseudopunctillata; Heterocyprideis sorbyana; Heterocyprideis fascis; and the subarctic species Normanicythere leioderma. Controls on the stable oxygen isotope composition of ostracode calcite were investigated by first establishing species’ vital effects and then comparing ostracode δ18O to seawater δ18O values (that ranged from -2.7 to -0.5‰), CTD temperature (-1.7 to 8.7°C) and salinity (30-34) measured at sampling stations in the Bering and Chukchi Seas during the six summers of 2013-2018. Results from 297 δ18Oost measurements from 53 sites on the Bering and Chukchi Sea continental shelves are consistent with the temporal and spatial variation in δ18O values of continental shelf bottom water, as impacted by seasonality, regional hydrography, and physical processes (i.e., sea-ice melt and extent, vertical mixing, precipitation/evaporation). Regression statistics for δ18Oost values of two species showed correlations to temperature and salinity that may facilitate prediction of water-mass characteristics when applied to sediment core records. Specifically, a significant linear regression relationship was found between δ18Oostvalues of N. leioderma and P. pseudopunctillata and temperature (R2 = 0.67 and 0.52, respectively). A principal component analysis confirmed temperature as the main controlling factor in the δ18Oost values of all species except S. bradii, with samples of distinct water masses grouping together.