DETERMINING THE EFFICACY OF OCEAN QUAHOG SHELL OXYGEN ISOTOPES AS A MID-ATLANTIC BIGHT COLD POOL BOTTOM WATER TEMPERATURE PROXY

The Mid-Atlantic Bight Cold Pool, off the coast of New York and New Jersey, forms during late spring into summer and results in near-bottom water temperatures of less than 10℃ during the hottest months. Recent evidence of Cold Pool deterioration has raised concerns regarding the future of species dependent on the cool summer waters and the industry that relies on them. However, it is difficult to understand Cold Pool evolution due to an insufficient long-term instrumental record; the use of a bottom water temperature proxy is therefore necessary. One such potential temperature proxy is oxygen isotopes measured in absolutely-dated Arctica islandica (ocean quahog) shells at sub-annual to annual resolution.

Here we present preliminary oxygen isotope data measured in A. islandica shell samples collected in 2017 off the coast of Long Island, New York at 43 m depth dated to 1970. These data are compared to data collected by the CW Oleander, the Optimum Interpolation Sea Surface Temperature (OISST) gridded dataset (1983-present), and the EN4 dataset to determine the potential use of this proxy as a bottom-water temperature proxy. The CW Oleander, a shipping vessel, has recorded monthly water column temperatures across the shelf from New Jersey to Bermuda using expendable bathythermographs (XBTs) since 1977. The OISST dataset compiles sea surface temperatures from both in situ and satellite data at a 1/4° resolution. Oxygen isotope data are converted to temperature data using bottom water salinity from the EN4 dataset and previously published local salinity-oxygen isotope mixing lines. By investigating this proxy as a bottom water proxy in this region we hope to extend our understanding of cold pool temperature dynamics back 150 years to contextualize the changes seen today.