Plantilla trabajo Geomorfo

7th EuroGOOS Conference

Lisbon, 28-30 October 2014

HF Radar Supporting Blue Growth in NW Europe: The Brahan Project Authors: W.R. Turrell (1), B. Berx (1), A. Gallego (1), S. Hughes (1), R. O’Hara-Murray (1), J. Sanchez (2), B. Pereira (2), A. Alonso-Martirena (2) (1)

Marine Scotland Science, 317 Victoria Road, Aberdeen, AB11 9DB, UK. Email: [email protected]

(2)

Qualitas Remos, Toronga, 31, Bajo, Madrid, 28043, Spain

Abstract: Blue growth must be obtained sustainably in European seas. Offshore oil and gas exploration continues to expand into deeper waters along the NW European shelf edge, and the competition for sea space on the European continental shelf is accelerating. At the same time national resources to monitor anthropogenic environmental impact are reducing. In order to expand our network of monitoring, in an environment of reducing resources, means we must regionally coordinate monitoring activities. Legislation such as the Marine Strategy Framework Directive (MSFD) requires single member states to coordinate environmental monitoring regionally. High Frequency (HF) radar, with its current expanding spatial range, provides an underpinning technology which can pull together regional monitoring efforts. The Brahan Project, using the Long Range SeaSonde HF radar system manufactured by CODAR Ocean Sensors measuring the speed and direction of ocean surface currents in near real time over a large region between Orkney and Shetland, has demonstrated the potential of HF radar technology in this key area of the NW European shelf seas. An operational network of HF radar deployments, between Faroe and Scotland, Scotland and Norway, and around the North Sea basin could provide the underpinning data supporting oil spill response, search and rescue response, renewable marine energy industries, prevailing conditions monitoring for the MSFD, as well as fundamental measurements that will aid the understanding of climatic change in the North Sea and Arctic Ocean. Here, the Brahan project is introduced, and a possible future expansion to include the key gateway areas of the Arctic and NW European seas is discussed. Keywords: MSFD, Operational Oceanography, Prevailing Conditions, Environmental Monitoring

1.

INTRODUCTION

High Frequency (HF) oceanographic radar is becoming a mature ocean monitoring technology that can contribute to a large range of marine end uses (e.g. Harlan et al., 2010). With HF radar, it is possible to remotely sense, from the shore or from offshore platforms, surface water movement (e.g. Paduan and Washburn, 2013), and properties of surface waves (e.g. Lipa and Nyden 2005). Secondary information about near-surface winds (e.g. Kirincich, 2013) may also be derived, as can information about vessel movement (e.g. Roarty et al., 2011). This paper introduces the technology using a demonstration deployment in Scottish waters; the Brahan Project. It then goes on to discuss how the technology might be applied to support blue growth in northwest Europe. 1.1. A Current Gap in European Marine Monitoring Before demonstrating the usefulness of HF radar, it is interesting to note the current deployment of operational radars in European waters. In a recent survey by the EuroGOOS HF Radar Team (Gorringe et al., 2014), of the 47 operational radar systems identified in Europe, none were located in northwest European waters, i.e. from Ireland, or the UK. In the North Sea only two operational radar installations were found (Figure 1).

Fig. 1. From Gorringe et al. (2014). Location of operational HF radar installations(red dots) located by the EuroGOOS HF Radar team in 2014. The absence of HF radar installations in NW European waters is highlighted.

The questions this map raises are, what services are being provided by the operational HF radars in southern Europe that are not available to northwest Europe, and how might these gaps be filled? 2.

THE BRAHAN PROJECT

In order to demonstrate the potential use of operational HF radar in the UK to a range of end users, QUALITAS Remos S.L., cooperating with CODAR Ocean Sensors Ltd., and Marine Scotland Science assembled a project team consisting of UK Government agencies (Marine Scotland, the UK


Department of Energy and Climate Change, the UK Met Office, UK-IMON), oil companies (BP Exploration Operating Company Limited, Nexen Petroleum UK), and academia (International Centre for Island Technology, Heriot-Watt University). The geographical location for the demonstration, the sea area separating Orkney from Shetland (Figure 2), was chosen for a number of reasons. In terms of the scientific understanding of the oceanography of the northwest European continental shelf, the area is a key one. The Fair Isle Passage (the channel between Orkney and Shetland) is one of the principal entrances to the North Sea. It is stirred by strong semi-diurnal tides, resulting in intense tidal mixing and dispersion. Turrell et al. (1992) estimated that 12% of the inflow to the North Sea occurs through this Passage. A second important inflow occurs southwards along the east coast of Shetland, resulting in about 25% of the total North Sea inflow in the summer when it is forced by seasonal stratification (Turrell et al., 1992). A number of tidal fronts and seasonal jets are also present in the area (Hill et al., 2008), and the Continental Slope Current flows towards the north east, along the edge of the continental shelf to the west of Shetland. Additionally the Fair Isle Passage is one of the principal routes by which wind generated storm surges enter the North Sea from the west Scottish shelf. In terms of human activities, the area is heavily fished, there are oil and gas pipelines and offshore platforms both east and west of Shetland and Orkney, and the area is a vital shipping route out from and in to the North Sea from the west. In 1993, the grounding of the oil tanker MV Braer close to Sumburgh on the southern tip of Shetland showed the potential for shipping related pollution events in this harsh environment. Search and rescue (SAR) facilities operate both on Shetland and Orkney, and helicopter flights related to the oil industry fly from both island groups. There is current interest in the extraction of energy from the sea through both waves and tides in the area, and there is extensive aquaculture facilities along the west coast of Shetland. Due to the extreme environmental conditions, and the intensive human use of the area, few in situ measurements have been possible of ocean currents and waves, as maintaining traditional oceanographic moorings in this area has been difficult in the past. Hence there are a wide range of reasons to use this area for a demonstration of the potential of HF radar. 2.1 The Brahan Project Technical Set-Up Two long range 5MHz CODAR SeaSonde radars were provided to the project by CODAR and Qualitas Remos. They were installed close to the North Ronaldsay lighthouse, Orkney, and the Sumburgh Lighthouse, Shetland (Figure 2).

Lisbon, October 28 to 30, 2014

Fig. 2. An extracted 1-hour average (2000UTC, 7/9/14) image of current vectors observed using the long-range CODAR SeaSonde HF radar systems installed at the North Ronaldsay lighthouse, Orkney (lower red mast symbol) and at the Sumburgh lighthouse, Shetland (upper green mast symbol). Vectors are scaled by velocity, and also coloured (scale shown as inset – from www.thebrahanproject.com)

The SeaSonde systems were installed once land owner permissions, local authority planning permissions, and national authority EMF spectrum licences were obtained. Both sites are of high scenic value, and used extensively by the public, and hence the unobtrusive nature of the SeaSonde antennae was an important feature. For long range systems such as Brahan, two antennae were needed at each site, a transmit (4m) and a receive (5m). Both were simple mast structures with guy wires, and owing to their low power did not interfere with the public use of the adjacent areas. Both systems needed mains electrical power supplies, and connection to the internet. Power was available at both sites, but poor telecommunications at the Orkney site meant that a dedicated satellite phone link was installed there. Minimal civil works were needed at both sites, consisting of a concrete block under each antennae, and channelling for cables. Existing shelters were used for the system electronics, consisting of a small 19 inch rack installation. Installation of the systems were “turn key” operations, and no difficult technical issues were encountered on their installation or operation. The systems could be accessed remotely using the internet connections to check operation. Data was logged locally, as well as being transmitted to a central server located in Edinburgh. The HF radars measured the Doppler shift of radiated energy reflected from waves on the surface of the sea. The process of deriving currents is a complex one, and is handled by the accompanying electronics and software. The user can access the ocean energy spectra raw data, or simply use processed gridded vectors of ocean current (e.g. Figure 2). Data is normally averaged over a pre-set



period, depending on the needs of the user and the frequency of operation of the radar system. For Brahan, the system provides hourly outputs and the averaging period was initially set to three hours, but all raw data has been archived and hence other averaging periods can be re-calculated. The range resolution depends on the allocated bandwidth and the post-processing applied to the raw data, but in Figure 2 we have selected 5 km. In addition to the current data, the SeaSonde system also returns information on the surface waves in the illuminated sea area, such as significant wave height and period. However, it does this averaged over wider spatial areas than the highly-resolved current data.

The legacy of Brahan is a permanent archive of 12 months of high quality ocean radar data, from a key area of the northwest European shelf covering approximately 30,000 km2, available alongside an extensive in situ measurement data set. The data captured some severe weather, including extreme storm surges, as well as covering a full seasonal cycle of stratification, and stratification breakdown in the northern North Sea. The Brahan data set will now be used to support a range of studies and studentships. Where the Brahan Project was less successful was in stimulating user commitment to the system. We go on to discuss potential applications of HF radar technology in northwest Europe.

2.2 The Brahan Data Set

3. A NW EUROPEAN HF RADAR NETWORK

In Brahan, the first data was recorded at 0000 UTC 1/9/2013, and the last recorded at 0700 UTC 8/9/2014. Hence there were 8936 hours of operation, over 373 days. In that time, 8516 valid gridded hourly- averaged files were created, hence there was a data recovery of around 95%. The spatial range of the data did vary, principally with atmospheric conditions, and diurnally. However, Figure 2 shows the typical spatial extent of the data. With the configuration in Brahan, i.e. two radars either side of a channel, the pattern of illuminated sea is two lobes, one either side of the central line between the two radars. In Brahan, each lobe was approximately 150 km “long” perpendicularly to the central connecting line, and 100 km “wide”, hence the radars illuminated 30,000km2 of the adjacent seas. During the Brahan deployment period, the North Sea experienced some extreme storms, including the “Xaver” storm on the 5/6 December 2013 when tragically at least seven people were killed in northwest Europe, and there was extensive coastal flooding owing to storm surges.

Figure 1 reveals the absence of operational radar in northwest European waters. Figure 3 repeats Figure 1, but includes a hypothetical realisation of an operational observing system utilising less than 20 HF radar systems.

2.3 Brahan In-Situ Data Set Between May 2013 and December 2013 a variety of in situ instruments were deployed in the Brahan radar area on oceanographic moorings. These included single point current meters, and profiling (ADCP) current meters. In addition a number of drifting buoys were released in the area.

Fig. 3. A repeat of Figure 1, but with a hypothetical deployment of less than 20 HF radar systems (red dots) in northwest European waters. Red shaded areas indicate potential radar coverage. Black arrows show principal flows of oceanic water.

The maritime economy of the North Sea and Norway is estimated at €230 billion, employing 1 million people (EU Commission, 2012). The hypothetical network of Figure 3 would cost of the order of 0.003% the annual value of the region’s maritime economy. But how could European blue growth benefit from an HF radar network?

2.4 Brahan Project - Summary 3.1 The Modelling Community The year-long demonstration of HF radar in Scotland was hugely successful in one of its objectives, to demonstrate the technology. The two SeaSonde systems ran without any serious problems for one year. The installation was simple, and the operation virtually “plug-and-play”.

This may seem an odd “end user” to start with. However, many of the services below today increasingly rely upon accurate numerical models of the sea. We use models to predict tides, storm surges, spill dispersion, wreckage drift, nutrient budgets, impact of climate change, coastal flooding,


coastal erosion, and much more. A regional-scale network of HF radars is ideally suited to calibrate, validate, and improve through data assimilation the numerous operational models of our seas. 3.1 Offshore Industries Oil, gas, and offshore wind industries require many of the services below, such as SAR and spill response. However, they also specifically need engineering data when designing structures, realtime estimates of currents and waves when conducting offshore engineering work, and predictions to plan work. Regional scale HF radar, coupled with models, can provide this. Although the North Sea oil and gas industry is ageing, the new deepwater areas within our region, off the shelf edge north and west of the UK and Norway, all pose new environmental challenges. We have very few measurements from these areas compared to the North Sea, hence the regional network of HF radar would give vital information in these areas.


38% of all EU maritime cargo comes through the North Sea (EU Commission, 2012). A basin scale HF radar network could provide route planning and hence fuel saving facilities on a regional basis. In addition, the secondary information concerning vessel detection can help detect activities such as illegal fishing and drug trafficking (Roarty et al., 2011) 3.4 Search and Rescue Search and Rescue in northwest Europe is principally a national responsibility, and implemented on national scales (Figure 4). However, an improved European SAR model, using data assimilation from an HF radar network could benefit all maritime countries in the region. Within the United States for example, the Coastguard uses HF radar in their operational SAR programme, and has shown that this can reduce their target search area by 66% after 96 hours, compared to not using radar data (Harlan et al., 2010).

3.2 Spill Response

3.5 Coastal Protection

Spill response starts at small space and time scales, with pollution possibly spreading tens of kilometres in a few days. However, an extended event such as a sea bed blowout, can last for months, with pollution extending to North Sea basin scales (Figure 4). It has been seen repeatedly that present day numerical models can fail to accurately predict the track and spread of spills, particularly in the challenging waters off the European shelf edge. Numerical models, coupled with a regional scale HF radar network, would provide Europe with the best protection and response infrastructure for regionallyimportant events, as well as more local national events.

Europe faces an increasing threat from coastal flooding owing to climate change. Storm surges coupled with sea level rise may well threaten our current coastal defences. Storm surge models used currently to manage coastal defence use technology and knowledge which has not changed for more than a decade. A regional scale HF radar network would bring coastal flooding modelling into a new era of real-time data assimilation. 3.6 Science This may not be an obvious end-user, but the basic scientific understanding of circulation, dispersion, mixing and ocean-atmosphere interactions would benefit hugely from a regional scale HF radar network, particularly as in our region we still have some areas where human activities such as fishing prohibit traditional measurement techniques, and data during extreme events such as storms is lacking. 3.7 Health of the Ocean - MSFD

Fig. 4. An analysis of the space and time scales involved in Search and Rescue (SAR), spill response and the provision of prevailing conditions information for Health of the Oceans (HOTO) assessments, such as required by the European Marine Strategy Framework Directive. Blue lower rectangle – information return from a single radar system such as employed in the Brahan Project, red upper rectangle – the increase in information provided by a regional network of radar.

3.3 Shipping

Finally, we consider the benefit of a northwest European regional HF radar network to Health of the Ocean assessments, such as the one enshrined in the EU Marine Strategy Framework Directive (MSFD). The MSFD requires European Member States to assess the health of their seas using 11 descriptors (Biological diversity, Invasive and non-native Species, Commercial fish and shellfish, Food webs, Eutrophication, Seabed integrity, Hydrography, Contaminants, Contaminants in food, Litter, Introduced energy – i.e. noise). Member States must


define what Good Environmental Status (GES) looks like for each of these descriptors for their seas, and also define quantitative indicators of health within each descriptor. The Directive gives Member States two more directions; they must coordinate the assessments regionally, and they must take into account “prevailing conditions” (EU Commission, 2008). In order to define basin scale targets for GES for nutrients and contaminants, transport of these materials through the open boundaries of the region are required. The flux of nutrients and plankton are needed in order to understand changes in food webs. Numerical models of the North Sea basin that will be used extensively for such studies, and for setting targets, need to accurately estimate transports through the open boundaries to the north (Orkney/Shetland, Shetland/Norway), east (Baltic) and south (Channel). A regional network of HF radar would enable these open boundary transports to be more accurately estimated, and validated. 3.8 A Regional Framework Finally, while basin scale surveys in the North Sea such as the International Bottom Trawl Survey (IBTS) provide a unifying framework for much of the biodiversity, food web and litter aspects of the MSFD, no such regional scale framework exists which can pull together operational oceanographic observations in the region, or provide the underlying physical support for all of the above end-users. A northwest European regional HF radar network would provide that organisational framework upon which much could be built. 4. SUMMARY The Brahan Project has demonstrated how multiple users can come together to implement an operational HF radar network in northwest Europe. The operating conditions we have here, including the wave climate, permits long ranges and reliability to be achieved. The ranges now possible, coupled with the geography of our region, means that a relatively small regional investment can provide multiple returns to European blue growth. What is now needed is an organisation to take the lead in coordinating such an initiative, and perhaps EuroGOOS, NOOS or EMODnet can help provide that leadership. Acknowledgements The authors wish to acknowledge the work of their colleagues from the Brahan Project team, including J. Dunn, N. Álvarez Rojas, G. Slesser, B. McLeod (Marine Scotland Science), P. Agostinho (Qualitas Remos), D. Woolf, K. Johnson (ICIT), M. Bell, J. Turton (UK Met Office), R. Bly, C. Grant (BP


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