Influences of Islands and Shoals on Coastal Water Properties, Flushing Time, and Dispersion Within Western Long Island S
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Influences of Islands and Shoals on Coastal Water Properties, Flushing Time, and Dispersion Within Western Long Island Sound Steven R. Deignan-Schmidt 1
&
Michael M. Whitney 1 & Yan Jia 1
Received: 15 October 2018 / Revised: 24 May 2020 / Accepted: 10 June 2020 # Coastal and Estuarine Research Federation 2020
Abstract Effects of islands and shoals on coastal water temperature and salinity, flushing time, and dispersion were quantified for a study area within the Western Long Island Sound, inshore of the Norwalk Islands. Analysis focused on a summer warming period in July 2015. Observations were used to force a realistic high-resolution hydrodynamic model nested within a larger domain model. Island and shoal effects were isolated through intercomparison of three model runs with islands and shoals (the natural configuration), without the islands, and without islands and shoals. With islands, there was cooler and saltier water along a band immediately inshore of the islands. With shoals, water was warmer and fresher between the coast and islands. The shoals influence occupied a larger area with higher magnitude water property differences than the island influence. The islands influence tidal residual currents by intensifying eddies and creating across-shore exchange through island passes. Islands reduce flushing time and shoals increase flushing time. The retention effect of the shoals dominates over the dispersive influence of the islands for 2 days after dye tracer release, but the effects offset each other for later times. Keywords Estuary . Temperature . Salinity . Island . Shoals . Flushing time . Dispersion
Introduction It is well-known that islands influence hydrodynamics, dispersion, and ecosystems in coastal waters (e.g., Wolanski et al. 1984a; Inoue and Wiseman Jr 2000; and Johnston and Read 2007). Wolanski et al. (1984a) and subsequent works (Furukawa and Wolanski 1998; Wolanski et al. 1996) studied observations and model results for Rattray Island (on the northeast Australian coast) to describe the dynamics of island wakes in shallow coastal waters. Wakes also have been studied around islands off the southern California coast (Dong and McWilliams 2007), in the Bristol and English Channels (Pattiaratchi et al. 1987), and in the Firth of Forth (in Scotland) (Neill and Elliott 2004), in Rupert Bay (connected to the Hudson Bay) (Ingram and Chu 1987), and in the Bay of Fundy (where wakes influence marine mammal distributions) (Johnston and Read 2007). Numerous study dynamics around Communicated by David K. Ralston * Steven R. Deignan-Schmidt [email protected] 1
Department of Marine Sciences, University of Connecticut, 1080 Shennecossett Rd, Groton, CT 06340, USA
idealized islands (e.g., Pingree and Maddock 1980, 1985; Estrade and Middleton 2010). Dong and McWilliams (2007) include a thorough review of the dynamics governing island wakes. These studies focus on island effects in isolation from interactions with other islands and coasts. Flow between islands can promote onshore/offshore exchange a
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