Flow dynamics and variability in the Delaware Estuary
Abstract
The mechanisms control tidally varying circulations and the density gradient between fresh and salt water are investigated in a wide, convergent estuary. This study integrates field observations and numerical simulations in the Delaware River estuary, which consists of a wide lower bay (maximum width 40 km), narrowing roughly exponentially to < 5 km in the upper estuary (around 150 km from the widest part). The COAWST Modeling System is utilized to evaluate the mechanisms control salinity intrusion and stratification. The salt intrusion shows much less sensitivity to discharge variability than more prismatic estuaries, with an exponent of -1/5 to -1/7, compared to -1/3 for prismatic estuaries. Both observations and model results show that the flow can be highly stratified (Δs>10psu) even during low discharge conditions, in contrast to prior designations of the Delaware as a "well-mixed" estuary. The stratification is stronger than other estuaries with the same values of the scaling parameters in the estuarine classification scheme [Geyer and MacCready 2014]. Stratification is enhanced by outflow in the channel associated with the Eulerian return flow balancing tidal Stokes transport on the shoals, as described by Li and O'Donnell [1997]. Moreover, the Simpson Number, which is proportional to the ratio of potential energy reductions due to straining to kinetic energy dissipation, shows a threshold value of 1 that separates stratified and unstratified conditions. This suggests that longitudinal straining is the important factor and lateral processes may play a role in controlling flow structure and density gradient of the Delaware River estuary. Funded by NSF.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMOS31E..07C
- Keywords:
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- 4544 Internal and inertial waves;
- OCEANOGRAPHY: PHYSICALDE: 4546 Nearshore processes;
- OCEANOGRAPHY: PHYSICALDE: 4558 Sediment transport;
- OCEANOGRAPHY: PHYSICALDE: 4560 Surface waves and tides;
- OCEANOGRAPHY: PHYSICAL