Kerry P. Black

Present and future prolonged drought impacts on a large temperate embayment: Port Phillip Bay, Australia

Observations of a large temperate embayment in Victoria, Australia, reveal a sustained climatic shift that occurred in response to a prolonged drought in the region during 1997–2009. Historically, the bay is fresher than the ocean with fresh outflow to the sea. However, the drought has caused substantially elevated salinity and temperatures above adjacent oceanic waters. The bays capacity to dilute and flush waste discharges to the ocean was also changed. Observed conditions have been numerically modelled with hydrodynamic and coupled lagrangian particle dispersion models to test differences in dispersion and exchange during historically fresher conditions and hypersaline bay scenarios. Further scenarios were tested for projected climate conditions which were similar to the recent drought responses in the bay. The models identified the effects on the circulation of the climatic shift including regions of increased vulnerability to extreme salinity in the bay, with some existing discharges concentrating in these regions of heightened vulnerability. Absolute salinity in the bay could reach critical levels of over 38xa0gxa0kg−1, in places, which may compromise bay ecology.

Transient wind‐driven coastal upwelling on a shelf with varying width and orientation

Abstract Cross‐correlations between along‐shelf wind stress and both along‐ and cross‐shelf currents within the central Bay of Plenty, New Zealand show the circulation during spring‐summer to be highly responsive to wind events. Current meter records indicate that upwelling‐favourable wind stresses generate upwelling dynamics in both mean and fluctuating senses. Both thermistor moorings and satellite inferred temperature data record the outcropping of this cool water following upwelling‐favourable wind stresses. The upwelling circulation provides an efficient mechanism for the periodic delivery of cool (c. <15°C), nutrient rich (NOx‐N >80 μg litre‐1) water to the coastal zone during spring. Historical wind forcing data suggest that the wind‐forced dynamics described were responsible for a major toxic algal bloom within the Bay of Plenty during 1992–93.

Debris dispersal modeling for the great Sumatra Tsunamis on Banda Aceh and surrounding waters

The Great Sumatra Tsunami on 26 December 2004 generated large amounts of debris and waste throughout the affected coastal region in the Indian Ocean. In Banda Aceh—Indonesia, the tsunami flows were observed carrying a thick muddy sludge that mixed with all kinds of debris from the destroyed buildings, bridges and culverts, vehicles, fallen trees, and other flotsam. This waste and debris was mostly deposited inland, but traveled both onshore and offshore. Numerical dispersal modeling is carried out to simulate the transport of debris and waste produced by the tsunamis during the event. The model solves the Lagrangian form of the transport/dispersion equations using novel particle tracking techniques. Model results show that understanding the pathway and distribution of the suspended materials and flotsam caused by tsunamis is important for a proper hazards mitigation plan and waste management action, and to minimize serious long-term adverse environmental and natural resources consequences.

Dynamics of a 3‐dimensional, baroclinic, headland eddy

Abstract Wave, current, and temperature measurements from the north side of Cape Rodney, northeastern New Zealand, over a 6‐week field programme, reveal the detailed internal dynamics of a baroclinic eddy. The measurements include water levels, currents, and water temperatures through the water column and seabed descriptions. A detailed calibration of a 3‐dimensional numerical model leads to further examination of the flow and density structure within the eddy, in plan and cross‐section. The eddy stretches c. 5 km along the northern side of the headland and is of the order of 1.5–2.0 km wide. The eddy currents are strongest near the bed and against the coast. The eddy is characteristically complex and vertical eddies readily form in parts of the water column during different phases of the tide, although these internal eddies rarely penetrate through the full depth. The dynamics near the surface and near the bed are significantly different and the structure of the eddy is often partitioned vertically and is strongly affected by wind.

Extreme Tsunami Run Up and Inundation Flows at Banda Aceh, Indonesia: Are There Any Solutions to this Type of Coastal Disaster?

Almost 3 years after the extreme 26 December 2004 tsunami event, which devastated the Banda Aceh region of Sumatra, certain coastal protection works have been planned and implemented. They comprise mainly of seawalls, breakwaters, and planting forest trees and mangroves as a wave-absorbing greenbelt. Numerical modeling of this catastrophic event was established to investigate the processes of tsunami propagation and inundation flows over the Banda Aceh coastal region, identify zones that had escaped devastation (as identified during the post event field survey) and assess possible types of coastal protection along the affected coasts. Results of the modeling showed that for protection against such a 2004-type event, huge structures ∼ 15 m high would be required, but are not economically feasible. However, mature mangroves stands may offer reasonable protection, and this option shows greater promise as an affordable solution.