Intratidal and Subtidal Circulation in a Tropical Estuary during Wet Season: The Maroni, French Guiana

Abstract

Observations of water level, current velocity, river discharge, wind and salinity were collected in the Maroni estuary, on the border of French Guiana and Suriname during the wet season of 2018 to explore subtidal circulation patterns. Measurements are complimented by the application of analytical models with an aim to diagnose forcing mechanisms responsible for producing subtidal flows during the day of data collection and to extrapolate these findings to other time periods with variable wind and river forcing. Subtidal along-channel flows were found to be dominated by river discharge, with seaward directed velocities found throughout the channel section reaching 40 cm s − 1 . This pattern was altered with strong southwesterly winds, which produced and inverse gravitational circulation pattern despite the elevated river discharge. Secondary, or cross-channel flows, displayed a three-layer vertical structure in the main channel due to a combination of channel curvature and tidal asymmetry in the lateral baroclinic pressure gradient. The pressure gradient was produced by a salinity intrusion front that only manifested in the channel during flood tide. This is the first comprehensive study of tidal and subtidal flow dynamics in the Maroni estuary.

Dynamics of the Estuarine Turbidity Maximum Zone from Landsat-8 Data: The Case of the Maroni River Estuary, French Guiana

“…The estuary shows a converging plan shape, with tidal range amplification at about 8 km from the mouth [15]. Ross et al [16] identified an ebb channel at the west bank of the estuary (Suriname) and a flood channel at the east bank (French Guiana) ( Figure 1c). A mud bank started impinging on the mouth of the Maroni in 2011 ( Figure 1d) [36], and it is still migrating across the estuary.…”

“…During ebb tides, the ETM is well developed (Figure 6b,f) and is located in the area between the downstream islands (KP 20and KP 0). High values of SPM are observed at the west bank of the estuary, which has been identified as the ebb channel [16], especially for 2018, when the length of the ETM was considerably longer than that of 2014 (Figure 6b,f). This is consistent with the results of Jolivet et al [36]: the dominant direction of transport of sediments from this river is westwards along the Suriname coast.…”

“…Such tropical estuaries are commonly bordered by mangroves that trap sediments [6][7][8][9] and affect flushing rates [10,11], thus contributing to the dynamics of the ETM. Unfortunately, studies dealing with the ETM in tropical estuaries are relatively scarce when compared to those devoted to the study of estuarine hydrodynamics [12][13][14][15][16].…”

“…To date, several studies have been conducted on the Maroni River, representative of this second type, which was the focus of our study. The previous studies on the Maroni have been devoted to the geochemistry of suspended matter [33,34] and to hydrodynamic controls on sediment distribution patterns, notably at the mouth [15,16,35]. Although the latter studies have highlighted some of the hydrodynamic processes and sediment circuits, including sediment exchanges with the shoreline [36], the seasonal dynamics and processes involved in the ETM in seasonally variable estuaries such as the Maroni, and under the influence of mud banks from the Amazon, are still poorly known.…”

A remote sensing-based classification approach for river mouths of the Amazon-influenced Guianas coast

“…monitored in these river mouths (Orseau et al 2017;Sottolichio et al 2018;Ross et al 2019), modelled (Do Anh et al, 2020, and analysed through remote sensing (Abascal Zorrilla et al 2020).…”