Modelling the dispersal and settlement of drill cuttings

Drilling operations at sea produce a mix of fine rock fragments that need to be discharged into the ocean. While inert, these fragments (known as drill cuttings) can have sediments, contaminants and drilling fluids adhering to them. To help regulators and marine managers assess the potential impact of drilling operations, MetOcean Solutions is regularly engaged to model the dispersal and settlement of drill cuttings in the marine environment at locations all over the world. 

“Drill cuttings settle on the seabed, where they can cause adverse environmental impacts,” explains Oceanographer Remy Zyngfogel. “The oceanic discharge of drill cuttings occurs over specific time periods, but their dispersal and deposition are driven by random variables such as currents and turbulence.” 

“To determine where the drill cuttings end up on the seabed, we use a variety of methods and leverage the expertise of our multidisciplinary science team. This includes modelling the hydrodynamics of the region and simulating the trajectory and the settling of the drill cuttings to the seabed. Regulators and marine managers require good knowledge of the likely footprint of  deposition and how thick the deposits will be at increasing distances from the drill site.”

Project Director Dr Brett Beamsley oversees the hydrodynamic modelling. “We use different models to produce the historical datasets needed for the studies,” advises Brett. “Oceanic and coastal currents vary according to synoptic and seasonal winds, tides and density differences. To account for this variability, and to provide robust statistical estimates of dispersal and deposition, we use historical data to recreate the actual oceanographic conditions, typically hour-by-hour for a 10-year period. We recreate these currents using the most appropriate model. For offshore studies, we use the Regional Ocean Modeling System (ROMS), whereas for smaller-scale studies at inshore sites SCHISM or Delft3D are used.” 
 

An example of 7-day mean surface current circulation and Sea Surface Temperature (°C) for the south-eastern region of Brazil.

An example of 7-day mean surface current circulation and Sea Surface Temperature (°C) for the south-eastern region of Brazil.

Remy uses the historical current dataset to determine the dispersal of drill cuttings. “Once we have the historical currents, we use a particle tracking model to trace the dispersal and deposition of drill cuttings for simulated discharges at different times of the year,” he explains. “Ocean currents vary with factors like seasonal winds and riverine discharges, so the depositional footprint will differ depending on which time of year the drilling is done. The size of fragments discharged into the sea depends on the rock type and the drill bit design. From an estimate of particle size, we can determine settling velocities - the finest fractions of the drill cuttings settle through the water column very slowly and become widely dispersed, whereas larger particles settle quickly and much closer to the discharge location.”

Example deposition thickness for drill cuttings discharged from a marine location. The spatial distributions of deposition thickness are color-coded with values in mm on each contour line in four zoom views: 100x100 km (top left), 10x10 km (top right), 1x1 km (bottom left) and 100x100 m (bottom right). The release site is indicated as a black cross. 

Example deposition thickness for drill cuttings discharged from a marine location. The spatial distributions of deposition thickness are color-coded with values in mm on each contour line in four zoom views: 100x100 km (top left), 10x10 km (top right), 1x1 km (bottom left) and 100x100 m (bottom right). The release site is indicated as a black cross. 

“The modelling represents what is likely to happen statistically, over long time periods. Naturally, for any given discharge, the drill cuttings will disperse according to the flow conditions at the time. For example, if discharge occurs during high current flows, the drill cuttings will be transported further, and the deposition will be more spread out. If current velocities are low at the time of discharge, the cuttings will accumulate closer to the discharge point.” 

Where pre- and post-drilling sediment samples have been taken, it is possible to verify the dispersal modelling. 

“We often use barium as a tracer,” explains Remy.  “Drill cuttings contain elevated concentrations of barium from the drilling fluids. This makes barium an ideal tracer of discharged cuttings. Seabed samples taken before and after drilling can be used to determine the change in barium concentration and thereby verify the modelled deposition of the cuttings.“

“The modelling provides a statistical representation of possible outcomes, taking into account the natural variety of current flow conditions. The modelled results typically show good agreement with observed barium levels, which means that operators and regulators can confidently use the modelling to determine the extent of potential adverse effects. This information is used both when applying for permits and post-permit, in the design of environmental monitoring programmes.” 

Contact us if you would like to discuss modelling the discharge of drill cuttings or historical current data for your drilling location.

Forecasting non-tidal water level in Port Phillip Bay, Australia

When Viva Energy Australia asked MetOcean Solutions to model water levels and storm surges in Port Phillip Bay (Victoria, Australia), we jumped at the challenge. With its large surface area, shallow depth and restricted entrance, resolving the hydrodynamics of Melbourne’s main coastal inlet required careful thought.

“Viva Energy is focussed on maintaining safe under keel clearance required for ships entering Port Phillip Bay,” explains Senior Oceanographer Dr Rafael Soutelino, the project leader. “The DUKC® system recently commissioned by the Victorian Regional Channels Authority is already delivering Viva Energy thousands of tons of extra cargo on every shipment, however, improved forecasting of non-tidal water levels has the potential to further increase safe vessel draughts and increase operational planning windows. Port Phillip Bay is a complex location subject to a variety of different forcings, and discerning the interaction between all the different influences on water level was crucial if we were to make accurate forecasts for their operations.

“The main issue for Viva Energy is negative storm surge when water depth is reduced due to the complex interplay between the meteorological and hydrodynamic processes. There are particular shallow patches and sand banks along the shipping channel, which can get too shallow for larger vessels to pass. Viva Energy required us to set up a robust forecast model for the Bay, generating alerts when water depths were likely to dip below safe levels. The detailed water level forecasts we produce will also be combined with recent observations and used in the DUKC® to provide improved planning advice to all port users.”

To generate accurate forecasts, the modelling had to include a variety of forcings, including the inverse barometric effect on water levels, the important phase lag effects caused by the constrained embayment, and the local and regional meteorological effects due to wind. The model also had to capture the behaviour of the progressive coastal-trapped waves that propagate eastwards across Australia’s extensive southern coastline.

“We used the Regional Ocean Modeling System (ROMS) for this work,” continues Rafael. “To translate the wide forcing into the local area of the Bay, we downscaled from a 5 km resolution parent domain covering most of the Australian South coast to a local 300 m resolution domain covering Port Phillip Bay. The model is forced by the ECMWF forecast winds, and has an external boundary condition prescribed by the Mercator solution.”  

The ROMS 2D model grid setup. The upper panel shows the parent 5 km domain. The lower panel shows three different zoom levels of the child nest bottom topography, grid nodes and connectivity between parent and child models.

The ROMS 2D model grid setup. The upper panel shows the parent 5 km domain. The lower panel shows three different zoom levels of the child nest bottom topography, grid nodes and connectivity between parent and child models.

Viva Energy provided a host of water level data for the model validation.

“Previous studies have shown that storm surges generated in the southwest of the Australian coast propagate eastwards toward Port Phillip Bay as coastal-trapped waves. On many occasions, that travelling patch of high water level is consistently re-intensified by the storm which is also propagating eastwards, providing the perfect set of ingredients for storm surge build up.”

A significant extra-tropical storm event in June 2014 caused a strong and extensive storm surge while propagating from west to east off the south coast of Australia. Water elevations relative to mean sea level are shown in red/blue shades and mean sea level pressure (HPa) in black contours.

A significant extra-tropical storm event in June 2014 caused a strong and extensive storm surge while propagating from west to east off the south coast of Australia. Water elevations relative to mean sea level are shown in red/blue shades and mean sea level pressure (HPa) in black contours.

The final model reproduced water level variations inside Port Phillip Bay very well, and MetOcean Solutions now runs an operational forecast for the location to help Viva Energy and the Port of Geelong safely manage shipping operations.

This work was carried out in collaboration with our science partners at MetraWeather and OMC International.

Southern Ocean wave buoy heading for Chile!

On Friday 28 July, New Zealand’s Southern Ocean Wave Buoy started drifting eastward with the ocean currents.  
 
"We're not exactly sure what happened," advises oceanographer Dr Peter McComb. "However it’s likely the compliant bungy section of the mooring failed under the extreme wave conditions down there. Since February 2017, the maximum wave heights have exceeded 10 m for 26% of the time, and there are very few places on our planet that energetic. At the start of the project there were many uncertainties. Would there be enough solar power to keep it alive during the deep south winter? Would the mooring survive the constant stresses and ride out the ferocious storms? Ultimately, we are very pleased to have succeeded in our goal of making almost 6 months of very detailed spectral measurements at this location in the sub-Antarctic.”

The HMNZS OTAGO deployed the buoy in February 2017 for a collaborative research project between the Defence Technology Agency and MetOcean Solutions. From the chilly waters just south of Campbell Island, the buoy has been sending back vital wave spectral data via a satellite link. These data will now be used by the New Zealand Defence Force to design the next class of patrol ships suited to the harsh Southern Ocean climate. MetOcean Solutions have a research project to develop a global wave model with improved performance in the Southern Hemisphere, and will use the data to verify the next generation of model physics. The wave data will also be made freely available to the international research community. The Southern Ocean is known to play an important role in the climate system - cycling heat, carbon, and nutrients. Waves modulate the air-sea fluxes and the swells generated in this region have far-reaching effects, contributing significantly to the wave climate in all the major ocean basins. 

Drift track and significant wave heights measured over the last 14 days.

Drift track and significant wave heights measured over the last 14 days.

Another positive outcome is the realisation that our research project is not over yet - the buoy continues to measure wave spectra and send its data via the satellite link as long as there is sufficient solar power.  

“Now we have a new and unique opportunity to make ongoing Southern Ocean wave measurements at the very extremity of the planets’ largest ocean – the Pacific. It’s highly valuable data for oceanographers," says Peter. “Conceivably, it might take over a year to reach Chile, which would make a fantastic and very significant dataset. Let’s hope there is enough sunlight to keep powering the system during this journey.”   

MetOcean Solutions plans to deploy another wave buoy at the Campbell Island site in February 2018, with the goal of establishing a long term sub-Antarctic wave monitoring station.

“The international ocean research community recognises the value of detailed wave spectra collected at this remote location,” notes Peter, “and Campbell Island is the perfect site to make baseline measurements for climate change studies as well improving our fundamental understanding of wave physics at a planetary scale. New Zealand can make a very practical contribution to global oceanography by making high quality, real-time measurements from this site. As a nation, we are very fortunate to have some Deep South real estate with a great harbour. It’s got a lot of potential for meaningful, long term research.” 

The buoy was deployed in February 2017.

The buoy was deployed in February 2017.

A real-time data solution supports drilling operations in Wellington Harbour

Griffiths McMillan JV (GMJV) is tasked by Wellington Water and the Greater Wellington Regional Council with drilling for a new water source for Wellington City, with the goal of providing an alternative supply in the event of a severe earthquake. GMJV approached Heron Construction Company to supply the jackup barge and support tug for the project. The target aquifer, however, lies beneath Wellington Harbour - just north of the Miramar Peninsula. A marine drilling rig is required for the operations, which means that operations are very sensitive to the wave conditions.

A marine drilling rig.

A marine drilling rig.

MetOcean Solutions has been supporting Heron Construction in their specialist marine activities with high resolution forecasting for the last decade. Managing director Greg Kroef says, “We rely on the forecast guidance from MetOcean Solutions wherever we are working in Australia and New Zealand. So, when the need arose in Wellington, we approached them for the best possible weather forecasting system for this site.”

The drilling job in the harbour requires very accurate predictions of wave height. However, the oceanographic conditions in Wellington Harbour present significant challenges for forecasting, with ocean swells entering from the south along with local seas generated by the infamous capital city winds.
 
Oceanographer Dr Peter McComb and his science team extensively studied the harbour dynamics for the recent harbour deepening project. “The drilling location is affected by both the southerly ocean swells and the short local wind seas,” explains Peter. “Our forecasting model has to deal with multiple and sometimes simultaneous sources of wave energy, plus discern how those waves refract and transform due to the shape of the seabed and the harbour tidal hydrodynamics.”

The wave buoy, framed by Wellington City

The wave buoy, framed by Wellington City

The operational SWAN wave model for Wellington Harbour has a spatial resolution of 80 m, and is one of nearly 200 forecasting domains that MetOcean Solutions run four times per day for various parts of the planet. This high-resolution model is coupled with the tidal hydrodynamics to capture the effects of the ebb and flood flows through the entrance on the waves, and it has spectral boundaries prescribed by a 3-stage nest into our global WAVE WATCH III wave forecast model. The model system produces the hour-by-hour wave conditions for the coming 7 days.  

Forecast model result from MetOceanView showing the 13 July 2017 southerly storm waves penetrating Wellington Harbour. The X denotes the wave buoy location.

Forecast model result from MetOceanView showing the 13 July 2017 southerly storm waves penetrating Wellington Harbour. The X denotes the wave buoy location.

“However, just having a wave forecast model is sometimes not enough to ensure safe operations - especially in Wellington which is notorious for rapid changes in weather conditions,” continues Dr McComb. “So we decided to deploy one of our directional wave buoys near the drilling site to provide real-time monitoring of the wave conditions along with instant verification of the forecast accuracy.”

The wave buoy sends data ashore every hour so everyone involved can monitor the sea conditions in real time. See for yourself at:  http://wavebuoy.metocean.co.nz/wellington 

“When ingested into the MetOceanView forecasting system, we co-plot the measured and the forecast wave heights. This is the most honest representation of forecast accuracy, and allows users to gain confidence in the timing and the magnitude of the wave predictions. The recent storm from 13 July was a very energetic event, but we captured it perfectly from 3-4 days ahead.”   

The real-time wave buoy data shows the waves resulting from the storm in mid-July.

The real-time wave buoy data shows the waves resulting from the storm in mid-July.

Accurate wave forecast – the significant wave heights measured by the buoy were very close to those forecasted for the storm in mid-July.

Accurate wave forecast – the significant wave heights measured by the buoy were very close to those forecasted for the storm in mid-July.

MetOceanView ingests observations from over 10,000 sites every day, including 252 locations around New Zealand. 

For queries about ingesting site-specific data, contact enquiries@metocean.co.nz.

Dr Aitana Forcén-Vázquez joins MetOceanView support team

This week we welcome Aitana Forcén-Vázquez, our new Technical Support Liaison.

Originally from Spain, Aitana has a PhD in physical oceanography from Victoria University, and recently completed Postdoctoral research in Southern Ocean dynamics at NIWA in Wellington. In her new role, Aitana will be providing technical support to our marine forecast clients throughout New Zealand and worldwide.

"I am looking forward to engaging with the MetOceanView users," says Aitana. "Having spent substantial time in and on the ocean, I understand the challenges that weather poses for ocean-based industries. I’m really excited to be part of a team providing scientifically robust data in meaningful ways.”  

Aitana is based in our Raglan Office. 

SurfZoneView part of KiwiNet Awards

MetOcean Solutions is proud to be part of the KiwiNet Research Commercialisation Awards. Last week, we attended awards night, where shortlisted New Zealand innovators shared how they are bringing their ground-breaking research to market.

The Kiwi Innovation Network (KiwiNet) is New Zealand’s network of public research organisations, working together to transform scientific discoveries into marketable products and services. MetOcean Solutions and the Defence Technology Agency were nominated for SurfZoneView, a software tool which helps safely plan nearshore operations such as landing vessels, personnel or supplies.

Sally Garrett from the Defence Technology Agency with David Johnson.

Sally Garrett from the Defence Technology Agency with David Johnson.

"We are very honoured to be part of the event," states Technical Director Dr David Johnson. "It is fantastic to see the real-word ingenuity and problem-solving displayed by participants, and the great examples of partnerships between research and industry, We value our collaboration with the Defence Technology Agency, and are proud to have worked with them to come up with solutions to make the New Zealand Defence Force safer." 

View the award video below, visit our SurfZoneView webpage or read the SurfZoneView pdf.

Meet us at the NZ Marine Sciences Society Conference

MetOcean Solutions will be at the New Zealand Marine Sciences Society annual conference in Christchurch this week.

The conference, which is held 4-6 July at the University of Canterbury, has as its theme 'Mahi Ngatahi: Working together for better management into the future'. 

At the conference, Dr Brett Beamsley will present estuary modelling done for Otago Regional Council, and Dr Peter McComb will present the multi-agency Moana Project

For more information, visit the conference website: https://www.nzmss2017.org/

Storm watch helps safe management

Forecasts of wind and wave conditions are vital for effective and safe management of near- and offshore operations. MetOcean Solutions has developed a warning system based on ensemble forecasting, which allows us to provide warning of upcoming severe wind and wave conditions for up to 7-day horizons, thereby helping operators plan for safe and efficient management.

Accurate high-resolution forecasts of wave conditions at local scales can be done using nested or grid-refining models such as SWAN (Simulating WAves Nearshore). Such forecasts capture local wave transformation and dissipation, and can be done at a reasonable computational cost. However, at horizons beyond 2-3 days a forecast inevitably suffers from the onset of chaotic uncertainty that is a physical characteristic of the atmosphere-ocean system. 

Ensemble forecasting is a method that quantifies this uncertainty in longer-range forecasts, providing probabilistic guidance for management decisions. MetOcean Solutions can customise a forecast warning system for any offshore or nearshore location based on the 7-day forecast wind speed, significant wave height (Hs) and maximum individual wave height (Hmax). The method used to estimate extreme Hmax accounts for the long-term uncertainty of the severity of the environment and the short-term uncertainty of the severity of the maximum wave of a given sea state, complying with the International Organization for Standardization (ISO standards).

Example of Storm Watch programme. T indicates present time.

Example of Storm Watch programme. T indicates present time.

We use such ensemble forecasts to provide the best possible site-specific warning to clients of upcoming severe conditions, using pre-set thresholds to define the level of alert. 

Up to 60 wind and wave ensemble forecasts can be used to support a storm watch programme.  

An example of email alert is illustrated below. All components of the email can be customised upon request.
 

Example of Storm Watch alert email. 

Example of Storm Watch alert email. 

Storm watch guidance. Orange shading indicates when the alerting thresholds are exceeded. Wsp: windspeed. Hmax: maximum wave height. Hs: significant wave height. 90 PCTL: 90th percentile. 

Storm watch guidance. Orange shading indicates when the alerting thresholds are exceeded. Wsp: windspeed. Hmax: maximum wave height. Hs: significant wave height. 90 PCTL: 90th percentile. 

Wave height warnings. Red shaded area represents the incoming wave direction for which thresholds are exceeded.

Wave height warnings. Red shaded area represents the incoming wave direction for which thresholds are exceeded.

MetOcean Solutions can set up a storm watch programme for any location. For more information, or to discuss your site, contact us at enquiries@metocean.co.nz.

Meet us at Coasts & Ports 2017

Later this week, MetOcean Solutions will be at the 2017 Coasts & Ports Conference in Cairns, Australia. 

Project Director Dr Brett Beamsley and MetOcean Solutions' Australian representative Dr Alexis Berthot will both attend the conference. Brett will be presenting recent research on dredging plume dispersion.  

Running from 21 to 23 June, the Coasts & Ports Conference is the pre-eminent forum in the Australasian region for professionals to meet and discuss multi-disciplinary issues related to coasts and ports. This year the conference theme is 'Working with Nature', reflecting the need to design and operate projects from a perspective that places the natural environment at the forefront.

Geraldton Port - improving long wave predictions with real-time wave buoy data

“MetOcean Solutions has worked exceptionally hard to assist the Port of Geraldton with its surge problem. The product they now deliver is heavily relied on when scheduling shipping. The efficiencies gained in reduced labour costs to port users are significant, but is the contribution to safety that represents the greatest gain. In 2005 there were 242 parted ships lines at Geraldton. Following the developments in forecasting Long Wave effects at Geraldton, last year there were only 30 parted ships lines. This was the lowest number of parted lines since records have been kept. MetOcean Solutions is keeping Geraldton Port efficient, and port workers safe.”
Captain Ross Halsall, Acting Harbour Master, Port of Geraldton.

Observational wave data can help ports manage the onset of long wave events. In recent work for Geraldton Port (Australia), we improved our harbour long wave forecasts by integrating wave buoy data from two upstream locations into the short-range predictions.

Long (or infragravity) waves are created when swell waves interact with the coast and result in water level oscillations with periods much longer than the original swell waves. Long wave periods of 60-120 seconds are typical, and these are very problematic because their wavelength is similar to the size of ships. When such waves enter a harbour the moored vessels are energised, causing dangerous surging which can break lines and put personnel in danger. As a result, ports often have to close when long wave heights exceed a safe threshold.
 
Accurate forecasts of long wave height can help ports increase safety, reduce unwarranted closures and effectively plan for reopening. For the past 11 years, MetOcean Solutions has provided a specialist long wave forecasting service that ports and harbours throughout New Zealand and Australia have come to rely upon.   
 

Numerical simulation showing that the sea-swell climate in the vicinity of the Port of Geraldton is extremely complex, mainly due to the reef near the Port entrance.

Numerical simulation showing that the sea-swell climate in the vicinity of the Port of Geraldton is extremely complex, mainly due to the reef near the Port entrance.

“Our scientific research over many years provides the basis for a robust prediction system,” explains Senior Oceanographer Dr Severin Thiebaut. “We use a semi-empirical technique to establish the relationship between the offshore wave spectra and the long wave height at each berth in a port. It's a method that we have tested at more than 30 locations worldwide”. 
 
The forecast wave spectra is derived from the suite of global and regional numerical models run by MetOcean Solutions. Geraldton Port have been using these predictions to guide the harbour operations since 2007. Predictions have proved very reliable, but sometimes the arrival of a swell front may differ from the forecast by a few hours as the exact timing is difficult to resolve perfectly with a spectral wave model. To supplement the long wave forecasts, we developed a new technique using real-time wave buoy data to improve the short term predictions and better detect occasions with a sharp rise in long wave energy inside the harbour. 
 
‘“The goal is to ensure that our port clients are never surprised by weather events,” says Dr Thiebaut.  

The Department of Transport maintains wave buoys at Rottnest Island and at Jurien Bay, some 370 km and 170 km to the south of Geraldton, respectively. The live data from these buoys, updated at 30 minute intervals, are used to track the progression of swell up the west coast of Australia and provide harbour long wave predictions some 5-6 hours ahead.

Data from wave buoys at Rottnest Island and Jurien Bay help improve long wave predictions for Geraldton Port.

Data from wave buoys at Rottnest Island and Jurien Bay help improve long wave predictions for Geraldton Port.

“Using the live buoy data provides additional confidence to the standard forecasts. In particular, it allows us to accurately capture any rapidly rising long wave events. It also gives the port operators a better idea of when wave heights will decrease to safe working levels. Geraldton Port accesses the forecast information through the web-based MetOceanView platform and through their local environmental monitoring software. On the same plot we show the measured long waves at the berth along with the values that are forecast by our standard system plus those predicted by the buoys.” 
 

Comparison between measured and predicted significant long wave heights (Hslpw) in the Port of Geraldton in 2012 based on Jurien Bay real-time wave buoy data.

Comparison between measured and predicted significant long wave heights (Hslpw) in the Port of Geraldton in 2012 based on Jurien Bay real-time wave buoy data.

Contact us for a discussion of what we can do to help your port. Call +64 6 758 5035, email enquiries@metocean.co.nz or visit www.metoceanview.com.
 

SurfZoneView part of Defence Force training exercise

MetOcean Solutions joined the Defence Technology Agency (DTA) in a training exercise in Army Bay, Whangaparoa during May. As part of a larger trial involving the New Zealand Navy and Air Force, DTA were testing a wave buoy and integrating the data into the SurfZoneView beach landing software.

The field phase of Exercise Joint Waka was held at Army Bay and the inner Hauraki Gulf from 14-19 May 2017. It involved New Zealand Army vehicles, amphibious sealift vessel HMNZS CANTERBURY, and Royal New Zealand Air Force NH90 medium utility helicopters. The exercise sought to enhance the New Zealand Defence Force’s ability to deploy offshore to deal with any contingencies including humanitarian crisis, natural disasters and instability within our region.

Figure 1: HMNZS Canterbury

Figure 2: Amphibious vessel used for the landing exercise.

Developed in a collaboration between DTA and MetOcean Solutions, SurfZoneView allows the visualisation of beach landing conditions. Moving people and equipment from sea to land is one of the most complex tasks completed by the New Zealand Defence Force. Such operations are necessary when port facilities are not available, for example when providing natural disaster relief in New Zealand and the Pacific. The safety and success of shore landings are largely dependent on surf zone conditions, and SurfZoneView uses hydrodynamic modelling to provide a rapid and accurate assessment of the waves and currents at any location. Clear, easy-to-use maps of the nearshore conditions are displayed along with tools to assist with operational decision making.

Figure 3: Dr Jamie Halla (left) and Theo Zlatanov (right) from DTA and Dr Rafael Guedes from MetOcean Solutions (centre) getting ready for the trial on the Canterbury ship.

Senior Oceanographer Dr Rafael Guedes was involved with the trial. “It is very hard to assess the beach conditions when you are out at sea. Wave breaking patterns and surf zone currents can change drastically over only a few tens of metres as they are influenced by local bathymetry. By the time a vessel is close enough to the shore to allow operators to judge conditions, it is often already impacted by the waves. SurfZoneView allows operators to visualise the conditions over a stretch of coastline, to help them decide where the best landing place is that day, or sometime in the near future.

Figure 4: It is very hard to assess nearshore conditions from sea.

“The surf zone conditions vary from day to day depending on wind direction, swell characteristics and general circulation. To model the surf zone, the software needs input data describing offshore conditions. These data can either come from forecasts or from real-time measurements such as those from a wave buoy.

Figure 5: Screenshot from MetOceanView showing the forecast site at the location where the New Zealand Defence Force wavebuoy was deployed.

“In this training exercise, we used both. DTA deployed a wave buoy to provide real-time conditions, and we also set up a high resolution forecast site for the location. We can set up a forecast site within an hour, rapidly making available reliable wind, wave and current predictions. The buoy data provides an accurate description of the local conditions, and the forecast allows us to predict how these conditions will change over time.

“During the training exercise, a local storm developed. Waves near the landing site rose to over 1.5 m in just a few hours, with wave periods progressively increasing and directions shifting from north-east to northerly. The development was tracked on SurfZoneView, allowing us to predict conditions around the shore landing site, and how these would change over time as the storm progressed.”

See the example maps of the maximum wave height predicted by SurfZoneView in Figure 7, during the events marked by the black vertical lines in Figure 6. Information from the model is automatically processed to define safety thresholds including whether it is safe to attempt landing on the shore. These thresholds can then form part of the information assessed by operational staff when making a go / no-go decision.

Figure 6: Forecast provided by MetOcean Solutions during the period of the exercise, showing significant wave height  (Hs) and peak wave period  (Tp). Black vertical lines show the events along the development of the storm chosen as input conditions for SurfZoneView. Significant wave height, Hs, is the average height (in metres) of the largest one-third waves. It approximately corresponds to the height of waves as estimated by a trained observer at sea. Peak wave period (Tp) is the wave period (in seconds) of the most energetic waves in a sea state.

Figure 7: As the storm progresses, landing conditions worsen. Example output for the two events highlighted in Figure 6, showing maximum wave height increasing around the landing location. Coloured line along the shoreline displays safety thresholds for the landing vessel. 

“Models are most accurate when we use the best possible input data," adds Rafael. "Wave buoys provide site-specific, accurate data very quickly. Using such buoys alongside SurfZoneView allows the New Zealand Defence Force to go to any location, deploy a buoy and within less than an hour access accurate data to help them land personnel and supplies safely. To aid operation planning, MetOcean Solutions can set up a site-specific forecast for anywhere in the world. This means that we can quickly generate a forecast for wherever SurfZoneView needs to be used, thereby providing the best possible support for the Defence Force and other users.

“We are grateful to be invited to participate in this training exercise. Testing it under real conditions provides important information on where the tool adds value operationally. Coincidentally, we also assisted the Italian Littoral Warfare Unit with similar tests in Sardinia during May, and gained valuable feedback. ”

Figure 8: Based on chart depth, wave height, tide level and wave setup, SurfZoneView displays safe water levels for vessels approaching the shore. Left: map displaying safety thresholds. Right transect (indicated on map) profiles for (top): maximum wave height, including cross-hatched area for breaking waves; and (bottom): water depth and corresponding safety thresholds.

SurfZoneView was developed in close collaboration with DTA, and several overseas navies have indicated interest in purchasing the software.

Nearshore renewable wave energy assessment in Mexico

In July 2016, the international wave power company Eco Wave Power commissioned MetOcean Solutions to provide wave statistics for a nearshore site in Cuyutlan, Manzanillo, on the west coast of Mexico.  

Figure 1: Model depths (top) and snapshot of modelled significant wave height (bottom) for a 0.05 degree SWAN domain for 01 January 2006. Extensions of child nests are shown by the black rectangles. Mean wave direction is shown by the arrows..

Figure 1: Model depths (top) and snapshot of modelled significant wave height (bottom) for a 0.05 degree SWAN domain for 01 January 2006. Extensions of child nests are shown by the black rectangles. Mean wave direction is shown by the arrows..

“Our company required wave statistics to assess whether it was feasible to install a wave power plant at the location”, says Eco Wave Power project manager Guillermo Sherwell. “An overview of the wave conditions is essential for the planning of offshore installations - it allows us to assess operability and identify potential hazards. The data also helps document important environmental conditions that may require further attention.”  

Dr Séverin Thiébaut from MetOcean Solutions was in charge of the project, while Dr Rafael Guedes led the wave model implementations. 

“We set up a multi-nest wave hindcast model to replicate the wave climate at the nearshore site,” explains Séverin. “We modelled the 2005-2014 period so that we could reproduce the ambient wave climate and reliably estimate the most extreme wave conditions that can occur in a 30-year period."

In consultation with the client, the team picked three nearshore sites representative of the proposed location of the wave power plant in water depths of 4, 6 and 8 m. Annual, seasonal and monthly wave analyses were carried out for these sites to extract ambient and extreme wave statistics to assess the design, workability and efficiency of the proposed wave power plant. . 

The Simulating WAves Nearshore (SWAN) model was used for the work. A 4-level nesting approach was applied to downscale wave spectra from a global model to the shallow nearshore locations of interest. Wind fields for the model were derived from the Climate Forecast System Reanalysis (CFSR), and tidal constituents from the Oregon State University Tidal Inverse Solution (OTIS). The site is prone to tropical cyclones, and a cyclone mask was used to remove tropical cyclone signatures from the hindcast metocean data.

The model outputs were used to calculate wave power, the rate at which energy is being transmitted. Fatigue analysis was assessed by estimating the total number of individual waves of varying height and period.

Figure 2: Density plot of the total significant wave height (Hs) vs the peak wave period (Tp) at one of the sites. The plot provides a visual representation of the total number of 3-hourly hindcast data (10 years) per Hs-Tp bin, normalised by the bin sizes to obtain a unit of m/s.

Figure 2: Density plot of the total significant wave height (Hs) vs the peak wave period (Tp) at one of the sites. The plot provides a visual representation of the total number of 3-hourly hindcast data (10 years) per Hs-Tp bin, normalised by the bin sizes to obtain a unit of m/s.

“We produced regional summary maps of the conditions,” explains Séverin. “These showed the spatial distribution of variables such as mean significant wave height for the total, swell and sea components, mean peak wave period, mean wave direction and wavelength.” (Illustrated in Figure 1). Joint probability occurrences of variables such as significant wave height and peak period were also included (as illustrated in Figure 2).

Figure 3: Annual wind rose plot for one of the sites. Sectors indicate the direction from which the wind is coming.

Figure 3: Annual wind rose plot for one of the sites. Sectors indicate the direction from which the wind is coming.

Wind statistics were also generated, including monthly and annual wind speed exceedance probabilities, joint probabilities of wind speed and direction and corresponding wind roses (illustrated in Figure 3). 

“Values such as the 99th percentile non-exceedance significant wave height (Hs) level is often used to assess the wave climate and structure design for energetic events. This denotes the significant wave height which is not exceeded for 99% of the time.” states Séverin. “Similarly useful are extreme metocean statistics like the return period values for wind and wave, i.e. the likely maximum that can occur within a specific extended duration.”

“We are very happy with the quality of the work,” states Guillermo Sherwell from Eco Wave Power. 
 

Monster wave measured by Southern Ocean Wave Buoy

Earlier today, MetOcean Solutions' wave buoy in the Southern Ocean recorded a whopping 19.4 m wave.

Senior Oceanographer Dr Tom Durrant is thrilled. "This is one of the largest waves recorded in the Southern Hemisphere," he explains. "This is the world's southern-most wave buoy moored in the open ocean, and we are excited to put it to the test in large seas."

Persistent westerly winds and unlimited fetch combine to make Southern Ocean waves among the biggest in the world. Sub-Antarctic waters are difficult to work in, and reliable wave data for the area is scarce. The buoy was deployed in a collaboration between the New Zealand Defence Force and MetOcean Solutions aiming to get valuable observations from this remote part of the ocean. Such observations will enable better forecasting and design of vessels built to withstand Southern Ocean conditions. Moored in a water depth of 150 m, the buoy is located within the New Zealand Exclusive Economic Zone, 11 km south of Campbell Island. 

"The buoy is performing extremely well so far," adds Tom. "Not only is it surviving these large waves, but it is making detailed recordings of extreme sea states in the Southern Ocean, a region rarely observed by in-situ instruments. During the depths of winter, Southern Ocean waves are enormous, with significant wave heights averaging over 5 m, and regularly exceeding 10 m. Individual waves can double that size. Accurate measurements of these conditions will help us understand waves and air-sea interactions in these extreme conditions. This, in turn, will lead to improvements in the models used to simulate the waves, providing better forecasts, both for the Southern Ocean and for the wider region. Waves generated in the Southern Ocean have far-reaching effects, contributing significantly to the wave climate in all the major ocean basins."

The Southern Ocean Wave Buoy data are freely available from MetOcean Solutions. View the data here or contact us by emailing enquiries@metocean.co.nz.

SurfZoneView finalist for KiwiNet Award

SurfZoneView was used by NZDF to support beach landings on a recent mission in Fiji.

SurfZoneView was used by NZDF to support beach landings on a recent mission in Fiji.

The New Zealand Defence Technology Agency (DTA) and MetOcean Solutions are finalists for the 2017 KiwiNet Research Commercialisation Award. The award is for the SurfZoneView tool, which was developed by MetOcean Solutions in partnership with the Defence Technology Agency (DTA) to support beach landing operations conducted by the New Zealand Defence Force (NZDF). The DTA is the main provider of research, science and technology support to the NZDF and the Ministry of Defence.

The KiwiNet award is New Zealand’s premier event celebrating the organisations and individuals that turn scientific discoveries into innovative products and services that will grow the New Zealand economy.

SurfZoneView is one of three finalists in the running in the MinterEllisonRuddWatts Research & Business Partnership category.

SurfZoneView is a tactical decision aid to support beach landings. Moving people and equipment from sea to land is one of the most complex tasks completed by the New Zealand Defence Force (NZDF). Amphibious operations are required when port facilities are not available, most commonly when supporting our neighbours in the Pacific or New Zealanders at home after natural disasters such as Cyclone Winston and the Kaikoura earthquakes. The safety and success of amphibious landings are largely dependent on surf conditions.

In humanitarian and disaster relief, safe and efficient transfer of people and equipment is required. SurfZoneView is a fast, reliable and simple software tool that can be used by command teams to plan and execute safe and efficient amphibious and nearshore operations. Based on hydrodynamic modelling, SurfZoneView allows a rapid assessment of the waves and currents at any coastal location. Clear, easy-to-use maps of the nearshore conditions are displayed, and tools are provided to assist with operational decision making.

In 2016, SurfZoneView won the Ministry of Defence Industry Awards of Excellence in the category 'Provision of a product to Defence for less than $15 million'. 

KiwiNet (the Kiwi Innovation Network) is New Zealand’s network of public research organisations, working together to transform scientific discoveries into marketable products and services.

The winners of the award 2017 KiwiNet Awards will be announced on 13th July 2017.

Read more about the nomination on the KiwiNet website.

The Moana Project - an atmosphere-ocean knowledge infrastructure for New Zealand

Expert oceanographers from New Zealand leading marine science organisations have joined forces in a proposal to improve our understanding of New Zealand ocean dynamics and the coastal zone. 

The proposal, detailed on the Moana Project website, was submitted to the Ministry of Business, Innovation and Employment's (MBIE's) Endeavour Fund in March this year. 

Details of the Moana Project are provided on www.moanaproject.org

Details of the Moana Project are provided on www.moanaproject.org

"New Zealand has one of the world’s largest oceans," says Prof Moninya Roughan, MetOcean Solutions' Chief Scientist who coordinated the proposal. "Our ocean provides vital social, cultural, economic and environmental benefits. To safeguard these benefits for future generations we need to understand how our ocean works. This understanding will help good management of our oceans in a future of global climate change."

The project brings together a team of leading oceanographers from New Zealand's top science organisations, who will work with international experts in the field. 

Science organisations involved include MetOcean Solutions, the Cawthron Institute, NIWA, and Auckland, Waikato, Otago and Massey Universities. The team will collaborate with international experts from Australia and the US. In addition, the Moana Project has support from a wide range of ocean-information end-users, including the New Zealand Defence Technology Agency, the fishing industry, New Zealand Aquaculture, the Ministry for Primary Industries and Waikato Regional Council.  

Dr Peter McComb will present an outline of the project at the New Zealand Marine Science Conference in Christchurch in July. 

MBIE is expected to make a decision on the funding in August 2017. 

News related to the project will be published on the Moana Project website

Peter McComb in Southern Ocean seminar at Valparaiso University, Chile

MetOcean Solutions is visiting Chile this week. 

As part of the visit, Managing Director Dr Peter McComb will give a seminar on Friday 5 May at Valparaiso University. The seminar will detail the Southern Ocean wave project, a collaboration between the New Zealand Defence Technology Agency and MetOcean Solutions. As part of the project, MetOcean Solutions helped deploy the world's southernmost moored wave buoy in February 2017.

Dr McComb is excited to share the Southern Ocean project with colleagues in Chile. 

"Southern Ocean waves are famously enormous. Created by persistent westerly winds and a large fetch of uninterrupted ocean, these waves present serious obstacles for any vessels operating in the area. Understanding the dynamics of the Southern Ocean can help us forecast wave conditions, which is important for any nation located close to the Antarctic. 

"As a world first, New Zealand has installed an open ocean wave buoy in the Southern Ocean which can measure the huge waves and provide essential data to help us understand the area. Data collected will be used to improve our models, enabling us create more reliable wave forecasts for the region. We are keen to share data with our Chilean colleagues to ensure that the world science community benefits as much as possible from the project."

The full abstract of the talk is provided below.

An improved wave spectral characterisation of the Southern Ocean
Tom Durrant*, Peter McComb* and Sally Garrett^

The Southern Ocean is the southernmost part of the global ocean and represents around 22% of the world's sea surface area. The combination of persistent westerly winds and the largely unbroken expanse of sea produces potentially enormous fetches, resulting in the Southern Ocean experiencing higher wave heights for longer periods than any other body of water. Due to the harsh ocean environment and remote location, it is also the least observed of any ocean body. While satellite altimeter data can be used to estimate the surface variance, the wave spectral characteristics cannot be measured remotely, and consequently the directional wave spectra Southern Ocean are poorly sampled and not well understood. Here, we present a project that aims to provide a quantitative assessment of the performance of recently implemented improvements of source term physics in WAVEWATCH III in the Southern Ocean, including an analysis of the relative importance of large scale ocean currents. A moored wave buoy at 53 degrees South is an important part of the project scope, and the deployment of this equipment and the data obtained since February 2017 will be presented and discussed.

*MetOcean Solutions. ^ New Zealand Defence Technology Agency

Check out the Southern Ocean wave buoy direct data feed.

Read the New Zealand Herald news article on the project.

Click here for further information about the buoy.  

University of New South Wales and CSIRO visit MetOcean Solutions

This week, MetOcean Solutions is hosting a workshop for researchers from the University of New South Wales (Australia) Coastal and Regional Oceanography Team and the Australian Commonwealth Scientific and Industrial Research Organisation (CSIRO). 

"The workshop will gather experts in physical oceanography from the three organisations as well as students, postdocs and early career scientists," explains Prof Moninya Roughan, the Chief Scientist at MetOcean Solutions. "It will be a great opportunity for us to exchange knowledge and establish collaborations on upcoming initiatives."  

The workshop, which runs from 24-28 April, includes a number of sessions dedicated to scientific writing as well as a series of short research seminars. Themes include meso-scale ocean circulation and oceanic eddies, as well as operational oceanography.

MetOceanView - making the offshore oil & gas industry safer and more efficient

Worldwide, a variety of offshore oil and gas companies use historical data from MetOceanView to understand the environment they work in. Packaged up in the site’s ‘hindcast app’, historical wind, wave and current data is summarised in an easy-to-access format that users can download and integrate into their operational planning.

“The offshore oil and gas industry needs access to reliable site data,” explains Senior Oceanographer Dr Rafael Guedes. “Nowadays, many data sources are available, and the industry needs a robust web platform where they can easily access, browse and download time-series from some of the best hindcast data sources available around the globe. To meet their needs, we set up a hindcast downloading app within our MetOceanView web service.”

Reliable data

The hindcast app provides access to an extensive compilation of data, going as far back as 1958 for some of the datasets.

“We host some of the most reliable global ocean and atmospheric reanalysis data sources in the world,” adds Dr Guedes. “These include NOAA’s CFSR V1 and V2, Hycom from the National Ocean Partnership Program (NOPP) and JRA-55 from the Japanese Meteorological Agency (JMA). In addition, we also provide MetOcean Solutions’ in-house WAVEWATCH III wave hindcast datasets.”

Gaining efficiency

Dealing with huge datasets is not easy, and to set up a useable service, practical obstacles had to be overcome.

“One common problem when accessing historical data is that the volume of data in gridded datasets can be very large,” says Dr Guedes. “For example, a subset of the HYCOM dataset we host comprises about 2.6 trillion individual data points for each variable. Reading long-term time-series from such enormous datasets can be very slow. To make a user-friendly service, we came up with an efficient process to speed up the reading, so that datasets that used to take more than two hours to download could be read in just five minutes.”

One-stop-shop for ocean data

The service works by hosting a range of reference datasets in our servers, giving the client access to unlimited data from all available global datasets as well as MetOcean Solutions’ wave and current model outputs.

“We provide a user-friendly map-based web interface where the user can inspect the different data sources and request time-series for any available grid location,” adds Dr Guedes. “The results are generated without human intervention and delivered within minutes in standard file formats, a link to which is sent directly to the user’s email.”

Data for safer operations

The hindcast app gives access to historical ocean temperature, current, elevation and wave data, as well as atmospheric parameters such as wind, temperature and precipitation.

“Accurate wave, wind and current information is essential for anyone operating offshore,” explains Dr Guedes. “Oil and gas companies use the hindcast data for a range of purposes, including determining the potential operational conditions for offshore locations and ensuring safety at sea.”

The hindcast data subscription service allows customers to browse map views of global datasets with descriptions of the variables that can be downloaded. Grid points show the exact location of each data point. Time-series are provided in either CF-compliant netCDF files or a format specially requested by the client. Wave hindcast data can be downloaded as time-series of spectral parameters or as two-dimensional, frequency-direction wave spectra. This allows a comprehensive description of the modelled wave field over the entire globe. For example, the spectra shed light on the multiple wave systems influencing wave conditions at a certain location and given time.

Making our clients’ life easier

This is the second year of delivering online historical metocean data services to Shell.  “We’ve found the global hindcast portal very valuable,” states Octavio Sequeiros, Shell Metocean Engineer. “Previously, to obtain data for a given location we had to create a specific purchase order for each request. Now, unlimited high quality historical data for any location are just a mouse-click away.

“The fast data download has made our planning easier, more efficient and cost-effective” continues Mr. Sequeiros. “The app is easy to use, and because it provides map layers along with the data grid locations, we can inspect areas and do a few queries before we decide to download time-series. Many summary statistics are shown in tile format, which means we can get a sense of the data before committing to downloads. We mostly use the time-series of wave parameters and wave spectra. On these, we run our own statistics in-house to obtain operational and design criteria for preliminary studies of new potential sites for oil and gas exploration. Our goal is to get workability predictions using accurate modelling.”

High level statistics from each of the datasets hosted by MetOcean Solutions is available via our MetOceanView interface.

Sea surface temperature snapshot from CFS dataset.

Sea surface temperature snapshot from CFS dataset.

Sea ice area snapshot from CFS dataset.

Sea ice area snapshot from CFS dataset.

Eastward wind snapshot from CFS dataset.

Eastward wind snapshot from CFS dataset.

Sea surface wave significant height snapshot from MetOcean Solutions’ dataset.

Sea surface wave significant height snapshot from MetOcean Solutions’ dataset.

Alexis Berthot representing MetOcean Solutions in Australia

We are very pleased to welcome Dr. Alexis Berthot, who will be representing MetOcean Solutions in Australia. Based in Sydney, Alexis's main focus will be looking after the company's Australian clients and providing solutions tailored to the local environment and requirements. 

Alexis’s academic and professional background is in physical oceanography and coastal science. Following an MSc in Marine Environmental Sciences from the University of Marseille, France, he completed a PhD in Physical Oceanography at the University of Western Australia. He has worked in coastal and ocean research and engineering consulting for over 15 years, as a principal numerical modeller, technical lead or project director. 

From his involvement with a wide range of coastal and maritime engineering projects, Alexis has gained extensive experience in hydrodynamic, wave, sediment transport and water quality modelling. 

“I have followed the development of Metocean Solutions since the company started," explains Alexis. "I have been continuously impressed by the high technical quality of the work, the innovative tools developed, and the team's enthusiastic approach when tackling new challenges. I am very excited to join the company and assist in making sure that all Australian companies and government agencies get the opportunity to have Metocean Solutions' great technical expertise and forward thinking solutions at their fingertips.” 

Alexis can be reached at a.berthot@metocean.co.nz or by calling +61 422 369 314.

Sea surges as ex-cyclone Debbie moves through

Heavy rains and surging seas plagued New Zealand as the remnants of cyclone Debbie moved  across the country this week.

“Storm surges occurred in different places across New Zealand as the storm moved through,” explains Senior Oceanographer Dr Rafael Soutelino. “We were lucky that the system moved through fast and did not coincide with large tides, otherwise the coastal flooding could have been a lot worse.”

Storm surges occur when the sea rises as a result of wind and atmospheric pressure changes associated with a storm. The surges build up over time and will worsen when a low pressure system lingers. 

“MetOcean Solutions forecast storm surges nationwide using a complex high definition 3D hydrodynamical model,” continues Rafael. “The model computes the atmospheric effects on coastal water levels. It combines this with baseline water levels generated by open ocean eddies and water column expansions and contractions caused by the spatially-variable vertical density distribution.

“Our modelling shows that as the storm progressed, it caused storm surges in different parts of the country. Although mostly mild, the storm surges were still high enough to cause coastal flooding in sensitive areas. 

The storm progresses: wind and rain (right) and storm surges (left) coincide as ex-cyclone Debbie passes over New Zealand.  

The storm progresses: wind and rain (right) and storm surges (left) coincide as ex-cyclone Debbie passes over New Zealand.
 

Storm surges up to 35 cm high occurred in a number of coastal locations around New Zealand.  

Storm surges up to 35 cm high occurred in a number of coastal locations around New Zealand.
 

“We were very lucky that the storm moved through so fast, and that it coincided with neap tides. Had it happened at spring tides, when the high tide levels are higher, flooding in the area could have been much worse. Our models show that at spring tide, the storm surge would have been high enough to almost match the measured river level after all the rain. In that scenario, the river would not have drained into the ocean as fast, which means the flooding would have been worse and lasted longer.”

Coastal flooding could have been much worse had the storm surge coincided with spring high tide at the Whanganui River mouth.

Coastal flooding could have been much worse had the storm surge coincided with spring high tide at the Whanganui River mouth.

Storm surge forecasts provide valuable information for for low-lying coastal locations, and these solutions are readily available to public authorities. 

“MetOcean Solutions’ New Zealand storm surge model has a resolution of 5 km. It’s the only operational hydrodynamical model for the country and we’ve been running it for more than five years now. During that time we have used it for oil spill and search and rescue modelling, and during the Rena disaster is provided essential guidance for the national response activities. We developed a similar model for the south coast of Australia, which has been operational for more than one year. This model is used by our Alliance partners OMC International in their specialist under keel clearance applications. 

“We run these types of models all over the world,” says Rafael - even in his home country of Brazil where the complex flows along the continental shelf are important to the offshore oil field operations.   

For further information about storm surge warnings and the New Zealand 3D hydrodynamical model, please contact us at enquiries@metocean.co.nz