The response of Chesapeake Bay salinity to climate-induced changes in streamflow

Autoregressive statistical models of monthly salinity variations in the mainstem of Chesapeake Bay are developed for use in climate change applications. Observations of salinity and Susquehanna River flow from 1984 to 1994 are used to calibrate the models. Up to 93% of the variance in salinity is captured by these models, with the best fits occurring in the middle of the bay, where submonthly fluctuations due to river flow and oceanic currents are damped. Our salinity models use output from a climate-forced hydrological model under a doubling of present-day atmospheric CO₂. This coupling scheme predicts salinity changes between +3.5% and -27.5% near the mouth of the Susquehanna River, to between +0.1% and -0.7% near the ocean. These ranges demonstrate the uncertainty in climate model predictions, although three of the four scenarios used indicate increased Susquehanna River flow and therefore decreased salinity. In the highest flow scenario (a 32% annual increase) our results show that the bay's isohalines may recede by approximately 6.3 km (about 2% of the length of the bay) near the Susquehanna River, to as much as 55 km (about 17% of the length of the bay) near the middle bay. This shift implies that climate change may have consequences for organisms with low-salinity thresholds, including oysters and crabs.