Mixing, hypersalinity and gradients in Hervey Bay, Australia

Abstract

Hervey Bay, a large coastal embayment situated off the central eastern coast 6 of Australia, is a shallow tidal area (average depth = 15 m), close to the continental 7 shelf. It shows features of an inverse estuary, due to the high evaporation rate (approx. 82 m/year), low precipitation (less than 1 m/year) and on average almost no freshwater 9 input from rivers that drain into the bay. 10The hydro-and thermodynamical structure of Hervey Bay and their variability are The investigation further shows that air temperature, wind direction and tidal regime 21 are mainly responsible for the stability of the inverse circulation and the strength of 22 the salinity gradient across the bay. 23Due to an ongoing drying trend, the occurrence of severe droughts at the central east 24 coast of Australia and therefore a reduction in freshwater supply, the salinity flux out 25 of the bay has increased and also the inverse circulation has strengthened. 26

Impact of climate variability on an east Australian bay

“…This study show, how these changes in Australian rainfall (short-term variability and trends) have influenced the hydrodynamics of Hervey Bay over the period from 1990 to 2008 and its implications for water quality and ecological response to inputs from the watershed and from the coastal ocean are discussed. This work is a continuation of ongoing research initiated to understand the hydrodynamics/physics of Hervey Bay (Ribbe 2006, Gräwe et al 2009). Hervey Bay (Fig.…”

“…The numerical computations are performed with the identical model setup as described in Gräwe et al (2009). For a detailed discussion of the model setup and for validation of the model results the interested reader is referred to their paper.…”

“…2). The thresholds to define hypersalinity ∂S = 2 · 10 −3 psu/km, inverse state ∂ρ = 0.01kgm −3 /km are taken from Gräwe et al (2009). Contrary to their setup the location of the transect is shifted 30 km to the north and is now aligned with the position of the Mary River Canyon.…”

“…Gräwe et al (2009) estimated the average velocity of this clockwise flow in the bay with about 2 cm/s. To understand the impact of the reduced freshwater supply, a time series of this residual flow is given in Fig.…”

Demonstration of Comparison Methods for Ocean Model Validation

“…Many papers are concerned with the validity of the ocean model on the sea surface, e. g. sea surface temperatures, salinities, and currents. Drifting buoys measuring temperature and conductivity [1,2], and synthetic aperture radar (SAR) data [1,[3][4][5][6] are easily accessible and therefore ideal for such validations. However, when ocean model outputs are used for e.g.…”