Reconstructing Bottom Water Temperature Distributions on the Mid-Atlantic Continental Shelf

The Cold Pool on the Mid-Atlantic continental shelf is a recurring summer feature of cold, dense bottom water that supports the long-lived bivalve Arctica islandica (ocean quahogs). Shell growth in this species records bottom water temperature (BWT), providing an archive spanning decadal to centennial timescales. This study combines shell-derived temperature proxy records with spatial modes of BWT variability obtained using simulated BWT distributions from VIKING20X (1980-2019) to reconstruct past BWT fields. The BWT reconstructions show variability in the extent of the Cold Pool, which was 54,300 km2 from 1980 to 1999 and reduced to 46,481 km2 in 2000. Concurrent with reduction in size the bottom water temperature of the Cold Pool increased from 2000 to 2019 by 0.234°C per year. Comparison of these decadal trends in Cold Pool extent and summer temperatures with the North Atlantic Oscillation index showed a statistically significant inverse relationship. The Cold Pool expands by approximately 20% in response to the positive phase of the NAO cycle and shrinks in size by approximately 9% in response to the negative phase of the cycle. These responses of the Cold Pool modify the habitat that is available to ocean quahogs, linking climate variability to benthic ecosystem.