Tidal variations of turbulence at a spring discharging to a tropical estuary

Abstract

[1] Measurements of velocity profiles and near-bottom temperature and pressure were used to determine turbulence properties at a point-source submarine groundwater discharge (brackish) in a tropical estuary. The turbulence properties estimated were Reynolds stress, turbulent kinetic energy production, and vertical eddy viscosity. , respectively) at low tides. Discharge of brackish water increased at low tides, relative to high tides, as indicated by vertical mean velocity and by mean velocity shear. These maxima were caused by decreasing hydrostatic pressure and likely increasing hydraulic head at the site of discharge. Increased turbulence at low tides was one order of magnitude larger than the turbulence caused elsewhere by tidal flows up to~2.5 m s À1 .

Salt intrusion at a submarine spring in a fringing reef lagoon

“…Jet discharge was dominated by tides, with semidiurnal oscillations in jet velocities that varied from quadrature to syzygy (Figures b and c). Maximum jet velocities and TKE occurred during low tides as the water pressure over the jet was least and vice versa, consistent with previous investigations [ Expósito‐Díaz et al ., ; Valle‐Levinson et al ., ; Parra et al ., ]. This section explains the influence of waves on the spring discharge first.…”

“…Extensive study of submarine springs, on the other hand, has only occurred recently [e.g., Expósito‐Díaz et al ., ; Peterson et al ., ; Valle‐Levinson et al ., ]. In karst topography, SGD can flow through submarine springs that provide a hydraulic connection between seawater and aquifer water.…”

“…Journal of Geophysical Research: Oceans PUBLICATIONS Some combination of these factors is necessary for salt intrusion to occur. Conditions that affect salt intrusion from the sea include: increased sea levels caused by storm surges [Hu et al, 2006;Smith et al, 2008], waves and wave setup [Parra et al, 2014;Li et al, 1999], sea level rise caused by climate change [Werner and Simmons, 2009;Vera et al, 2012;Gonneea et al, 2013], and tides [Taniguchi, 2002;Valle-Levinson et al, 2011;Exp osito-D ıaz et al, 2013]. Factors from land include: seasonal variations in groundwater recharge rates [Vera et al, 2012;Carretero et al, 2013], groundwater pumping rates from coastal communities' consumption [Santos et al, 2009;Ferguson and Gleeson, 2012;Carretero et al, 2013], and the composition of sediments and porosity of coastal regions [Bakhtyar et al, 2012].…”

“…Understanding the levels and variability of turbulence from point-source SGD is needed before determining its role on the ecosystems. However, the turbulence associated with submarine springs has been scantly studied [Exp osito-D ıaz et al, 2013;Parra et al, 2014]. Exp osito-D ıaz et al [2013] estimated the vertical structure of turbulent properties of a point-source SGD in a tropical estuary in the Yucatan Peninsula.…”

“…However, the turbulence associated with submarine springs has been scantly studied [Exp osito-D ıaz et al, 2013;Parra et al, 2014]. Exp osito-D ıaz et al [2013] estimated the vertical structure of turbulent properties of a point-source SGD in a tropical estuary in the Yucatan Peninsula. Results showed maximum zonal Reynolds stress components, turbulent kinetic energy (TKE) production, and vertical eddy viscosity at low tides when the greatest discharge rates were observed.…”