Tonga’s only undersea cable was damaged after Saturday’s volcano-tsunami disaster, plunging the Pacific island into a communications blackout that could last for weeks.

In the wake of last weekend's volcanic eruption in Tonga, much of the diminutive Pacific island nation’s communication with its own population and the outside world remains at a standstill.

When the volcano at Hunga Tonga-Hunga Ha’apai – 65 km northwest of Tongan capital Nuku’alofa – erupted on Saturday, it sent ash plumes 30 km into the atmosphere and triggered a tsunami that reached as far away as Alaska.

In what is being called one of the most powerful eruptions in over thirty years, damage to critical infrastructure saw Tonga’s lone subsea cable snap, one which connects it to the rest of the world. Tonga does not have any inter-island cables.

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The 827 km long fibre-optic cable, which goes between Tonga and Fiji, connects to the Southern Cross Cable. It went live in 2013 and was jointly funded by the Asian Development Bank and the World Bank.

Once it was cut, Southern Cross Cables said the Tonga Cable went into single-end feed mode, meaning it was being powered from its landing site in Fiji but not from the Tongan end.

The chair of Tonga Cable, Samieula Fonua, said there were two cuts in the cable, but the government would not give repair operations any clearance until volcanic activity had ceased.

While some have access to satellite phones, most Tongans now have no way of communicating with family members abroad. It has also made it challenging for Tongan government officials and emergency services to coordinate relief activities on the island itself.

Experts expect the telecoms blackout to persist for two weeks, if not longer.

“Tonga’s situation is problematic as the site is a source of ongoing volcanic activity, and equipment availability is sparser than in other regions. As a result, there is unlikely to be a quick fix,” Dr Scott Edwards, a research associate in maritime security at Bristol University, told TRT World.

Adding to the uncertainty is that the precise nature of damage to the cable is unknown.

“If long sections are buried (such as by debris from underwater landslides that were triggered by the eruption event) this may mean that extra cable needs to be installed to connect the undamaged sections, which may add further time,” said Mike Clare, an environmental advisor to the International Cable Protection Committee (ICPC), a submarine cable non-profit organisation.

While a standard repair job takes two weeks on average, an estimated timeframe for the Tongan repair will depend on the extent of the change to the seabed and cable damage, Clare told TRT World.

“It’s very context dependent. Even in regions that have sufficient repair boats and replacement cables, repair can take weeks,” said Edwards, pointing to an example when an earthquake off Southern Taiwan in 2006 saw nine cables damaged that took 11 ships and six weeks to repair.

In comparison to states in the Asia-Pacific region equally vulnerable to natural disasters, Tonga’s problem is less its natural hazard vulnerability, and more so its infrastructural limitations.

“Other countries [have] multiple cables so that if one goes down there is another they can continue to use. Many of the small Pacific island states do not have these backups, relying primarily on one cable which means they are completely cut off when damage occurs,” Edwards explained.

Over 99 percent of all transcontinental digital traffic travels over undersea cables that crisscross the ocean floor. More than one million kms of high-tech cables form the backbone of global digital interconnectedness: without them, the Internet would not exist as it does today.

These cables are largely privately owned, often in partnership with other private companies, though some firms involved in cable management are state-owned or intergovernmental.

Clare said that around 100-200 faults occur on the global network of telecom cables on any given year, most of which occur in shallow water (less than 100m in depth) and are largely related to accidental human interference, such as snagging by fishing gear and damage from dropped anchors.

Meanwhile, cable faults relating to natural hazards, like earthquakes and underwater landslides, account for less than 10 percent of all cable faults recorded worldwide since 1959. Faults related to volcanic activity are even rarer.

Nevertheless, the ongoing Tongan episode is a reminder of the risks associated with the global submarine cable network and how fast it can go offline in the face of a natural disaster.

Mitigating risk

Submarine cables are laid in the shortest distance between two points on the Earth’s surface, along geographic locations that allow for easy placement. For this reason, a sizable number tend to be clustered in choke points like the Sunda Strait in Indonesia, the Suez Canal and the Hawaiian islands.

Inconveniently, many of these undersea cables happen to run in proximity to active volcanoes and regions impacted by earthquakes and tropical cyclones.

State of TeleGeography's Submarine Cable Map, July 2018.
State of TeleGeography's Submarine Cable Map, July 2018. (Romain Fontugne / )

“Providing 100 percent security is not always possible,” underlined Clare. He argued the solution is to have several cables installed over a wide diversity of routes and a sophisticated management system that enables the traffic to be almost instantaneously switched in the event of a cable failure.

“Submarine cable systems are designed to be very reliable and have several redundant features. Notwithstanding this, submarine cable operators are constantly monitoring the performance of their systems and looking for opportunities to improve the reliability of the network.”

Issues of natural hazard risk have been the focus of several detailed scientific studies, and Clare said the submarine cable industry has regularly incorporated those findings when designing more resilient routes.

Given the vulnerabilities of the network, one step to mitigating risk can be to evaluate undersea cables in specific locations on the ocean floor and their resilience to various types of natural hazards.

But few countries have developed dedicated submarine cable-based seismic and tsunami monitoring systems to study the relationship between subsea seismic events and their potential impacts on human populations, or to facilitate early warning of tsunamis using real-time data.

For now, there is no consistent information sharing between different authorities, which further prevents collective global risk measurement from taking place.

“Different regions and cables have different authorities – some better equipped to evaluate risk than others,” said Edwards.

A core challenge to the protection of undersea cables is that the UN Convention on the Law of the Sea (UNCLOS) regulations – which establishes legality for all marine and maritime activities – lack precision in covering cables under the high sea.

“In addition, undersea cables are owned and operated by global business conglomerates that often involve a complex thicket of multi-ownership,” Edwards said, adding that international law on how such businesses operate, lay, maintain and repair cables is unclear.

“Cables do not fall under full sovereignty or ownership of any particular country or entity.”

Is a diversification strategy needed?

Diversifying methods of communication is another approach governments and telecom companies can pursue as part of managing natural hazard risk, like using more satellite-based systems.

Back in 2019, Tonga cable suffered a similar situation when a pair of cable cuts and a 12-day outage followed. The nation shortly signed a 15-year deal with Singaporean broadband operator Kacific for satellite connectivity.

While satellite systems can be a beneficial backup in dire circumstances, they aren’t a viable solution on their own.

“In the Tongan case, we have seen volcanic ash interfere with satellite reception, which means it can also be impacted by the same natural disasters,” Edwards clarified.

Nor can they handle the same levels of data that their fibre-optic counterparts do. “Cables carry 99 percent of digital communications because they are the fastest, cheapest, and most efficient means.”

Clare agreed. “The data-carrying capacity of subsea telecom cables exceeds that of satellite links by many orders of magnitude, providing accompanying savings to end users in the cost of consuming international data.”

That said, the ICPC maintains that satellite can be a valuable substitute for those locations worldwide that are reliant on a single cable connection (like Tonga), as well as for reaching remote inland communities and providing efficient broadcast services like TV.

The right approach, then, is one that sees cable-based and satellite-based systems as “complementary technologies rather than life-for-like alternatives,” Clare concluded.

Source: TRT World