Is there a signal of sea‐level rise in Chesapeake Bay salinity?

Abstract

[1] We evaluate the hypothesis that sea-level rise over the second half of the 20th century has led to detectable increases in Chesapeake Bay salinity. We exploit a simple, statistical model that predicts monthly mean salinity as a function of Susquehanna River flow in 23 segments of the main stem Chesapeake Bay. The residual (observed minus modeled) salinity exhibits statistically significant linear (p < 0.05) trends between 1949 and 2006 in 13 of the 23 segments of the bay. The salinity change estimated from the trend line over this period varies from À2.0 to 2.2, with 10 of the 13 cells showing positive changes. The mean and median salinity changes over all 23 cells are 0.47 and 0.72; over the 13 cells with significant trends they are 0.71 and 1.1. We ran a hydrodynamic model of the bay under present-day and reduced sea level conditions and found a bay-average salinity increase of about 0.5, which supports the hypothesis that the salinity residual trends have a significant component due to sea-level rise. Uncertainties remain, however, due to the spatial and temporal extent of historical salinity data and the infilling of the bay due to sedimentation. The salinity residuals also exhibit interannual variability, with peaks occurring at intervals of roughly 7 to 9 years, which are partially explained by Atlantic Shelf salinity, Potomac River flow and the meridional component of wind stress.

Long-Term Trends in Chesapeake Bay Seasonal Hypoxia, Stratification, and Nutrient Loading

“…Freshwater flow explains some of the observed inter-annual variations in stratification; however, there is no evidence to suggest a long-term trend in spring freshwater flow to the Bay. We therefore explored other physical factors that influence stratification including wind (Goodrich et al 1987), temperature, and salinity (Hilton et al 2008;Preston 2004).…”

Temporal responses of coastal hypoxia to nutrient loading and physical controls

“…For example, recent modeling and data analysis suggest that sea level rise tends to cause increases in salt flux and bottom-layer salinity in Chesapeake Bay (Hilton et al, 2008), which could have increased stratification. Other evidence suggests an increase in the latitude of the north wall of the Gulf Stream since the 1980s (Taylor and Stephens, 1998) that may have reinforced the trend associated with sea level rise by causing an increase in salinity at the Bay mouth (Lee and Lwiza, 2008).…”

“…The direct effects include decreased solubility of O 2 in water and enhanced respiration rates, while indirect effects include changes in food webs resulting from spatial and temporal shifts in species distribution and abundance (e.g., Najjar et al, 2000Najjar et al, , 2009Pyke et al, 2008). In addition, long-term increases in relative sea level occurring in many coastal regions worldwide (Holgate and Woodworth, 2004) may result in elevated bottom water salinities (Hilton et al, 2008), thus potentially enhancing stratification and reducing ventilation of deep waters. Longterm increases or decreases in freshwater input caused by global climate change will influence coastal hypoxia in many coastal systems by increasing or decreasing (respectively) the stratification strength and nutrient delivery rate (e.g., Justić et al, 2003;Arnell, 1999).…”

Impact of accelerated future global mean sea level rise on hypoxia in the Baltic Sea

“…However, the impact of GSLR has never been quantitatively assessed. From other coastal seas like Chesapeake Bay a statistically significant increase of salinity due to past sea level rise was reported (Hilton et al 2008). In this study, for the first time the potential impact of past and accelerated future GSLR on stratification, phosphorus cycling and eutrophication is investigated using a coupled physical-biogeochemical model for the Baltic Sea Eilola et al 2009).…”