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South‐west Australia has been identified as a global hotspot for the occurrence of meteotsunamis. In this study, a numerical hydrodynamic model (Regional Ocean Modelling System) was configured to investigate the generation of meteotsunamis through propagating thunderstorms. A range of simulations were performed using realistic and synthetic atmospheric forcing to establish the sensitivity of meteotsunami wave heights and waveforms along different parts of the coast to variations in the propagation speed and bandwidths of propagating pressure jumps associated with the thunderstorms. When a pressure jump propagated from the north and north‐west quadrants with a speed (U) of 8–15 ms−1, both the Proudman and Greenspan resonances were possible mechanisms for the generation of meteotsunamis. However, the response changed for different bandwidths of the propagating pressure jump and resulted in different meteotsunami waveforms at the coast. When U> 15 ms−1, long waves were amplified initially through shoaling at the shelf slope, with Proudman resonance enhancing the wave heights at corresponding resonant depths on the shelf, and then propagated as free waves on the continental shelf. The waves were further amplified at the coast through refraction and shoaling effects and resulted in an elevation wave at the coast. Numerical simulations also indicated that edge waves can also be excited near the coast when the incoming free wave wavelengths were equal to or half the edge wave wavelength. The study provides observational and numerical evidence to suggest that the bandwidth of propagating air pressure jumps plays a major role in meteotsunami generation and their waveforms. The numerical simulation results show that meteotsunamis on the southwest Australian coast can be generated over a range of traveling pressure jump speeds and bandwidths, where Proudman resonance, Greenspan edge wave, refraction, and shoaling were responsible for the initial wave amplification. The simulations also revealed that resonance and shoaling amplification were determined by both the speed and bandwidth of the propagating pressure jumps. The pressure jump with constant translational speed can cause significantly different wave heights and waveform meteotsunami when the bandwidths were different. As the wave propagates southward with speeds of 15–28 ms−1, it undergoes subcritical, critical, and supercritical states over the shelf. The findings of this study provide preliminary guidelines for forecasting meteotsunamis generated by summer thunderstorms along the south‐west Australian coastline. A range of moving atmospheric pressure jump speeds were conducive to meteotsunami generation on the southwest Australian coastProudman resonance, Greenspan edge waves, refraction, and shoaling were responsible for the generation and amplification of meteotsunamisThe resonance and shoaling amplification were influenced by both the speed of propagation and the bandwidths of the pressure jumps A range of moving atmospheric pressure jump speeds were conducive to meteotsunami generation on the southwest Australian coast Proudman resonance, Greenspan edge waves, refraction, and shoaling were responsible for the generation and amplification of meteotsunamis The resonance and shoaling amplification were influenced by both the speed of propagation and the bandwidths of the pressure jumps

It has been ten years since Malaysia Airlines flight MH370 disappeared, and it remains one of the biggest aviation mysteries. Despite multiple searches, the main wreckage and bodies of the victims have not been found. The Malaysian government is considering another search, which would be conducted by Ocean Infinity. While debris from the plane has been found in the western Indian Ocean, the exact location of the crash site is still unknown. The proposed new search would use improved technology and could potentially bring closure to the families of the victims. [Extracted from the article]

Buoyant marine plastic debris has become a serious problem affecting the marine environment. To fully understand the impact of this problem, it is important to understand the dynamics of buoyant debris in the ocean. Buoyant debris accumulates in “garbage patches” in each of the subtropical ocean basins because of Ekman convergence and associated downwelling at subtropical latitudes. However, the precise dynamics of the garbage patches are not well understood. This is especially true in the southern Indian Ocean (SIO), where observations are inconclusive about the existence and numerical models predict inconsistent locations of the SIO garbage patch. In addition, the oceanic and atmospheric dynamics in the SIO are very different from those in the other oceans. The aim of this paper is to determine the dynamics of the SIO garbage patch at different depths and under different transport mechanisms such as ocean surface currents, Stokes drift, and direct wind forcing. To achieve this, we use two types of ocean surface drifters as a proxy for buoyant debris. We derive transport matrices from observed drifter locations and simulate the global accumulation of buoyant debris. Our results indicate that the accumulation of buoyant debris in the SIO is much more sensitive to different transport mechanisms than in the other ocean basins. We relate this sensitivity to the unique oceanic and atmospheric dynamics of the SIO. Plastic pollution of the oceans is a serious problem. To better understand how big the problem is, it is important to know how plastics move in the oceans and where they end up. Floating plastics move with ocean currents, waves, and wind. Because these interact with each other in complex ways, the exact movement of plastic in the ocean is hard to predict. From observations and computer simulations, it is known that plastic collects in subtropical “garbage patches” in the Pacific and Atlantic oceans, but it is not clear if this also happens in the Indian Ocean. The aim of this paper is to determine the different influences of ocean currents, waves, and wind on the development of a garbage patch in the Indian Ocean. Because we cannot track plastics, we use data from over 22,000 GPS‐tracked drifting buoys that have been released worldwide in the oceans since 1979 to simulate the movement of plastic. Our results show that waves and wind prevent a garbage patch forming in the Indian Ocean. Because large amounts of plastic waste probably enter the Indian Ocean, an important question for follow‐up research is what happens to these plastics if they do not collect in a garbage patch. The subtropical Indian Ocean garbage patch is very sensitive to different transport mechanismsSensitivity to different transport mechanisms is likely a result of the unique Indian Ocean dynamicsThe surface Indian Ocean garbage patch is located to the west of the basin and is highly dispersive

Sediment transport equations often consider a mean velocity threshold for the initiation of sediment motion and resuspension, ignoring event‐based turbulent burstingprocesses. However, laboratory experiments have suggested that near‐bed sediment resuspension is influenced by intermittent turbulent coherent structures. In the field, accessibility constraints for deployment of easily operated equipment has largely prevented further identification and understanding of such processes, which may contribute to resuspension in the marine environment. Field experiments were conducted on the Northwest Slope, Australia, under conditions where the mean current velocities were below the estimated and measured time‐averaged critical velocity to investigate the relationship between near‐bed turbulent coherent structures and sediment resuspension. Results indicate that sediment resuspension occur even when velocities are below the estimated and measured mean critical values. The majority of turbulent sediment flux is due to ejection and sweep events, with lesser contributions from up‐acceleration and down‐deceleration (vertical flow) events. Spectral and quadrant analysis indicated the anisotropic and intermittent nature of Reynolds stresses, and wavelet transform revealed a group of turbulent bursting sequences associated with sediment resuspension. These observations, in flow conditions where resuspension was not expected to occur based on mean threshold concepts, reveal that intermittent turbulent events control sediment resuspension rather a single time‐averaged critical velocity. This highlights the need of considering turbulence as a significant factor in sediment resuspension and should be further investigated for inclusion into future sediment transport modeling. In this paper, investigation from deep‐water (~375 m) field measurements were carried out, showing that in deep water conditions, fluid turbulent bursting phenomena plays a significant role in resuspending sediment, even for low‐flow conditions under which transport equations (based on a time‐averaged critical velocity) predict no transport. The finding of this study allows us advance the understanding of the near‐bed sediment resuspension process for developing improved sediment transport equations and models in the future. In deep ocean systems, sediment resuspension occurs even when mean velocities are below the time‐averaged critical velocityOn the continental slope, sediment flux is largely controlled by ejection and sweep turbulent eventsWavelet transforms indicated turbulent bursting associated with intense sediment resuspension

A 15 year (2000–2014) simulation of the oceans around Australia, with the shelf‐scale model ozROMS, was used to estimate the mean, seasonal, and interannual variability of the surface and subsurface boundary currents and associated inflows. The simulation clarified some previous points of uncertainty and provided new information previously unknown and this is listed here. In the Indian Ocean, flow through the Timor Passage was linked to southeast Australia through the Holloway (HLC), Leeuwin (LC), South Australian (SAC), and Zeehan (ZC) Currents. The main inflows were from the Indonesian Throughflow and Eastern Gyral Current in the north whilst the central and southern branches of the South Indian Counter Current (SICC) provided major (>60%) inflows to the LC in the west. The HLC at North‐west Cape was at a maximum in April–May and its annual cycle accounted for 70% of the seasonal variance of LC, SAC, and ZC. In the Pacific Ocean, the northern branches of the South Equatorial Current were the main inputs to initiate the Hiri and East Australian (EAC) Currents flowing north and south, respectively, at ∼15°S. Inflow from the South Caledonia Jet to the EAC was ∼35%. The Flinders Current (FC) contributed to the Leeuwin Undercurrent (LU) directly as a northward flow and LU was enhanced from inflow from the subsurface southern SICC in the west (∼32–33°S). The majority of LU flowed westward offshore between 24 and 29°S while ∼25% continued northward to the northwest shelf. All Australian surface boundary currents systems were enhanced during the 2011–2013 La Niña. Major inflows to the Leeuwin Current and Leeuwin Undercurrent are provided by the South Indian Counter CurrentThe main inflow (65%) to the East Australian Current is through the northern branches of the South Equatorial CurrentAll Australian boundary current transport was enhanced during the 2011–2013 La Niña

The knowledge of regional wave regimes is critical for coastal zone planning, protection, and management. In this study, the influence of the offshore current regime on surface gravity waves on the southwest Western Australian (SWWA) continental shelf was examined. This was achieved by coupling the three dimensional, free surface, terrain‐following hydrodynamic Regional Ocean Modelling System (ROMS) and the third generation wave model Simulating WAves Nearshore (SWAN) using the Coupled Ocean‐Atmosphere‐WaveSediment Transport (COAWST) model. Different representative states of the Leeuwin Current (LC), a strong pole‐ward flowing boundary current with a persistent eddy field along the SWWA shelf edge were simulated and used to investigate their influence on different large wave events. The coupled wave‐current simulations were compared to wave only simulations, which represented scenarios in the absence of a background current field. Results showed that the LC and the eddy field significantly impact SWWA waves. Significant wave heights increased (decreased) when currents were opposing (aligning with) the incoming wave directions. During a fully developed LC system significant wave heights were altered by up to ±25% and wave directions by up to ±20°. The change in wave direction indicates that the LC may modify nearshore wave dynamics and consequently alter sediment patterns. Operational regional wave forecasts and hindcasts may give flawed predictions if wave‐current interaction is not properly accounted for. The knowledge of regional wave climates is critical for coastal zone planning, protection, and management. Large‐scale currents are known to alter wave conditions, however, minimal consideration has been given to the effect of offshore currents on the southwest Western Australian wave regime. The Western Australian offshore circulation is dominated by the Leeuwin Current (LC). The LC is a strong eastern boundary current that carries warm, low salinity water and features a large mesoscale eddy field. The LC is unique as it is the only pole‐ward flowing eastern boundary current in the world. Using state‐of‐the‐art numerical models, for the first time, the influence of the LC on Western Australian waves was studied and quantified. Wave heights increased (decreased) by ±25% when currents were opposing (aligning with) incoming waves and wave directions changed by up to ±20°. Changes in offshore wave height and direction may modify nearshore dynamics and consequently alter sediment patterns along the Western Australian coast. Operational wave simulations may give flawed predictions if wave‐current interaction is not properly accounted for. The Leeuwin Current, a pole‐ward flowing eastern boundary current in the Indian Ocean, modulates the southwestern Australian wave regimeIn areas of strong currents such as meanders and eddies significant wave heights are altered by up to ±25%Wave directions are modified by up to ±20° which may result in changes in nearshore dynamics

Understanding of measured and predicted waves has an impact on wave energy extraction, efficiency and economics and is therefore a focus for optimisation of Carnegie Wave Energy’s CETO technology. Improvements in weather prediction have enabled the generation of updated wave hindcasts by the National Oceanic and Atmospheric Administration (NOAA) and the Centre for Australian Weather and Climate Research (CAWCR). These were validated for Garden Island, Rottnest Island and Cape Naturaliste in south-west Australia for March to December 2009. The CAWCR data set provides a more extensive list of wave parameters as opposed to three-hourly major wave parameter sets (significant wave height (Hs), peak period (Tp) and peak direction (Dp)) provided by NOAA, and overall performed better. The CAWCR hindcast will form the underpinning data for the Australian Wave Energy Atlas Project, a CSIRO and Bureau of Meteorology project in which Carnegie is a collaborator.

The Ningaloo Current (NC) is a wind-driven, northward-flowing current present during the summer months along the continental shelf between the latitudes of 22 and 24S off the coastline of Western Australia. The southward flowing Leeuwin Current is located further offshore and flows along the continental shelf break and slope, transporting warm, relatively fresh, tropical water poleward. A recurrent feature, frequently observed in satellite images (both thermal and ocean colour), is an anti-clockwise circulation located offshore Point Cloates. Here, the seaward extension of the coastal promontory blocks off the broad, gradual southern shelf, leaving only a narrow, extremely steep shelf to the north. The reduction in the cross-sectional area, from the coast to the 50 m contour, between southward and northward of the promontory is ~80%. Here, a numerical model study is undertaken to simulate processes leading to the development of the recirculation feature offshore Point Cloates. The numerical model output reproduced the recirculation feature and indicated that a combination of southerly winds, and coastal and bottom topography, off Point Cloates is responsible for the recirculation. The results also demonstrated that stronger southerly winds generated a higher volume transport in the NC and that the recirculation feature was dependent on the wind speed, with stronger winds decreasing the relative strength of the recirculation.

The Perth Canyon is a focal feeding area for pygmy blue whales on the Western Australian coast. Studies aimed at elaborating oceanographic mechanisms within the canyon were conducted between 2002 and 2005. Strings of temperature loggers set around the canyon rim were used to examine the water column's response to climatological forcing, current meanders, upwelling and downwelling. Six moorings were positioned on a plateau in 500 m of water on the northern canyon rim, and one was positioned at the canyon head. Loggers were positioned to sample the whole water column, including the Leeuwin Current and Undercurrent. Moorings revealed spatial temperature differences between the plateau and canyon head. Observed temperature features ranged temporally from seasonal to <1 day. Seasonal changes in water temperature agreed with published Leeuwin Current studies: for example, mixed layer and stratification changes were apparent. Other observed temperature changes were related to Leeuwin Current movement and wind forcing such as the summer sea breeze and winter storms. Storms induced mixing, re-stratification, downwelling and upwelling as the wind changed direction and strength. Changes lasting a day were associated with diurnal sea breezes, internal waves and possibly solitary waves. Bottom loggers indicated that upwelling and downwelling events each occurred up to 20% of the time.

Temporal primary production dynamics were investigated off south-western Australia, where the summer upwelling regime of the Capes Current was compared with early winter conditions characterised by strengthened near-shore Leeuwin Current flow. Seasonal upwelling in this region sourced nitrate levels of ?1 ?m from the nutricline at the base of the Leeuwin Current's mixed layer, with total water column production reaching a maximum of ~950 mg C m-2 day-1 in the Capes Current. Stable isotope signatures of particulate matter indicated that productivity off south-western Australia was heavily reliant on nitrate as a nitrogen source, with mean ?15N ranging from ~4 to 5 ? under both upwelling and non-upwelling (winter) conditions. Unexpectedly, significant nutrient enrichment within the Leeuwin Current (up to 3.1 ?m nitrate) occurred during winter, likely as a result of the meandering Leeuwin Current flooding the inner shelf north of the study area and entraining relatively high-nutrient shelf waters in its southwards flow. However, early winter production under these nutrient-replete conditions (mean s.d. 310 105 mg C m-2 day-1) was significantly lower than in summer (695 140 mg C m-2 day-1) due to light limitation, both as a result of reduced surface irradiance characteristic of the winter months and significantly higher light attenuation within the water column as compared with summer conditions.

Mechanical current meters deployed within the upper part of the water column, in regions of high wave energy, may measure current velocities inaccurately. A modified Aanderaa meter was compared in the field with the standard Aanderaa meter, with a propeller-type NBA meter and with OSCR (Ocean Surface Current Radar) measurements. Comparison was also made with the standard Aanderaa in a wave-simulating flume. The modified meter showed reduced susceptibility to overreading in the presence of waves, particularly under conditions of low current velocities. Graphs are presented to allow prediction of wave effects on both the modified and standard Aanderaa meters.

In coastal regions sheltered from the direct impact of swell- and storm-wave activity, locally generated wind waves, particularly those associated with strong sea-breeze activity, play a dominant role in controlling nearshore and foreshore processes. Field data collected from the Perth Metropolitan Coast (western Australia) during a typical summer sea-breeze cycle, are presented. It is demonstrated that the nearshore environment responds rapidly to an increase in wind speed (up to 12 m s−1) during the sea breeze, resulting in considerable changes to the nearshore hydrodynamics and morphology. Incident wave energy increased during the sea breeze and was associated with development of a wind-wave field with significant wave heights up to 0.9 m. Nearshore currents responded to this change in wave climate with the development of net offshore near-bed currents and a rapid increase in the mean longshore current from < 0.05 m s−1 to 1.0 m s−1 A 10-fold increase in suspended sediment concentration and a 100-fold increase in the longshore sand transport resulted from the effects of the sea-breeze system. Erosion of the beachface was coincident with the development of the wind-wave field. Sea breeze wave-driven water circulation also completely eroded beach cusps (wavelength 20–30 m), overwhelmed the rip current system associated with the beach cusps and suppressed the infra-gravity wave frequencies in the incident wave and swash record. The beach cusps reformed after the cessation of the sea breeze. It is demonstrated that the beachface is in a constant stage of adjustment to the incident wave energy through the diurnal sea-breeze cycle alternating between dissipative and reflective morphodynamic regimes. The results may be used to determine the impact of a medium-sized storm on the beachface. It is clear that the sea-breeze system plays a major role in controlling the nearshore and foreshore processes not only in this region, but also on other geographic locations where strong sea breezes are present.

Northwest cloudbands are tropical-extratropical feature that crosses the Australian continent originating from Australia’s northwest coast and develops in a NW-SE orientation. In paper, atmospheric and oceanic reanalysis data (NCEP) and Reynolds reconstructed sea surface temperature data were used to examine northwest cloudband activity across the Australian mainland. An index that reflected the monthly, seasonal, and interannual activity of northwest cloudbands between 1950 and 1999 was then created. Outgoing longwave radiation, total cloud cover, and latent heat flux data were used to determine the number of days when a mature northwest cloudband covered part of the Australian continent between April and October. Regional indices were created for site-specific investigations, especially of cloudband-related rainfall. High and low cloudband activity can affect the distribution of cloudbands and their related rainfall. In low cloudband activity seasons, cloudbands were mostly limited to the south and west Australian coasts. In high cloudband activity seasons, cloudbands penetrated farther inland, which increased the inland rainfall. A case study of the southwest Australian region demonstrated that, in a below average rainfall year, cloudband-related rainfall was limited to the coast. In an above average rainfall year, cloudband-related rainfall occurred further inland.

Tidal inlets in microtidal, wave-dominated coastal environments tend to close to the ocean seasonally. This obstructs navigation and could cause degradation of water quality in the estuary/lagoon connected to the inlet. Hence, engineering solutions are often implemented to prevent inlet closure. However, a prior knowledge of circulation and mixing processes within the estuary is crucial for the sustainability of any engineering solution. This paper attempts to provide insight into circulation and mixing characteristics of seasonally open estuaries based on the results of a field study undertaken at Wilson Inlet, a typical seasonally open estuary, in south-western Australia. Results of the study indicate that this type of estuary may have two distinct behavioural patterns, in winter and in summer. During winter, solar heating causes density stratification during daytime, and convective cooling causes overnight de-stratification; a horizontal cyclonic gyre is established during winter by the combined action of the Coriolis force and streamflow. During summer, strong sea breezes (~10 m s–1 ) cause vertical mixing during daytime, and convective cooling vertically mixes the water column at night. When the inlet is open, sea water propagates into the estuary during flooding tides unless streamflows are very high.