THIN-LAYER GRAVITY CURRENTS IN A SHALLOW ESTUARY

Abstract A 48-hour field study conducted at the nexus between Oso Bay and Corpus Christi Bay (Texas) shows the development of cyclic thin-layer gravity currents initiated during an ebbing tide by hypersaline water in Oso Bay. Although the gravity current is in shallow water (depth < 4 m) and daily wind speeds peak at 20 kph, the thin-layer stratification induced by the gravity current persists over multiple tidal cycles. Two kilometers from the origination of the gravity current, a region of hypoxic (low dissolved oxygen) water is observed over the duration of the study. Field study We might expect that an estuary of 3-4 m depth with daily wind speeds peaking at 20 kph should be vertically well-mixed and exhibit only horizontal salinity gradients. However, Corpus Christi Bay (Texas) is adjacent to the Laguna Madre estuary and Oso Bay, which are sources for underflowing hypersaline gravity currents. A cyclic, thin-layer gravity current was observed in a field study conducted over a 48 hour period during August 22-24, 2005 at the nexus of Oso Bay and Corpus Christi Bay. The study used a Eureka Manta water quality profiler to measure conductivity, temperature and dissolved oxygen (DO) at ten sampling stations shown i