干旱区生态环境知识资源中心

Monthly cool-season salinity over the 1958 to 1991 period is analyzed for the Chesapeake Bay (CB), and the salinity variations are associated with low-frequency 500 hPa flow variations and with extremes of the Southern Oscillation (SO). Results identify a significant decrease in mean CB surface salinity, which is supported by similar trends in individual salinity subbasins occupying the northern extremes of the bay. Zonal (meridional) flow associated with the North Atlantic Oscillation (NAO) seems to be linked to below-(above-) normal CB salinity, while the Southern Oscillation Index (SOI) seems to be negatively correlated with CB salinity. Principal components analysis (PCA) reveals that the Pacific/North American (PNA) pattern is related to CB salinity, even though the PNA index is not. Within extreme El Nino months, the strongest association between CB salinity and PCA-derived circulation suggests that 500 hPa height features over the Great Plains may be linked to surface salinity in CB. By contrast, during La Nina months, height features over the Desert Southwest appear to be linked more directly to surface CB salinity. The results also suggest that 500 hPa flow patterns conducive to extreme precipitation in the northeastern United States are related to salinity variations in the northern bay. However, for the bay as a whole, and especially the southern portions of the bay, flow patterns favoring mean advective processes of CB and oceanic surface waters may be more important than those patterns relating to precipitation in contributing drainage basin areas. Results may be useful to environmental planners in the CB region.