Alkalinity in the south-eastern United States continental shelf waters

Abstract

The distributions of salinity, alkalinity and specific alkalinity, and the relationship between alkalinity and salinity in the south-eastern United States continental shelf waters, commonly known as the South Atlantic Bight, in April, 1985 indicate that the primary mixing process is between Gulf Stream water and shelf water. However, in the inner shelf the influence of the Cape Fear/Pee Dee Rivers and the Savannah River were also detectable. The influence of the outflows from the other rivers, which also drain into this Bight, was not as clearly evident. In the outer shelf, and over the shelf break, the presence of the altered (Gulf Stream) continental edge water was found. The mixture of shelf and Gulf Stream waters was characterized by a specific alkalinity of about 6·6 × 10 −2 meq l −1 ‰ −1. While the river waters were characterized by significantly lower salinity and specific alkalinity, the altered (Gulf Stream) continental edge water had only slightly lower salinity but a significantly lower specific alkalinity relative to the shelf water. The intrusion of offshore water over the shelf break onto the outer and middle shelves as a result of the meandering of the Gulf Stream has been recognized as one of the major contributors to the exchange of water between the shelf and the Gulf Stream. The distributions of specific alkalinity and salinity in the middle and outer shelves were consistent with the occurrence of such a process. Alkalinity/specific alkalinity may be a potentially useful complementary tracer for studying mixing processes in coastal areas where seawater mixes with outflows from multiple rivers.