Protecting undersea infrastructure

Since 1982, the United Nations Convention on the Law of the Sea (UNCLOS) differentiates between the territorial waters of maritime countries, international waters, and Exclusive Economic Zones (EEZs). Limited to 12 nautical miles from a country’s coastline, territorial waters bestow full sovereign rights, but specific responsibilities for security are much vaguer under UNCLOS for the vast sections of undersea infrastructure intersecting international waters or the EEZs of multiple countries. Within its EEZ, a country has the right to maintain undersea infrastructure, but it is not legally entitled to restrict the military activity of other states. In international waters (alternatively called the High Seas), laws regulating both the protection of undersea infrastructure and military activity are even more ambiguous.

Harsh maritime conditions offer some coincidental protection. Many undersea communication cables connecting North America and Europe cross the mid-Atlantic where the average depth is approximately 3,600 metres. This makes it arduous but not impossible for a submarine to interfere. Harsh conditions may also cause cables to become damaged or malfunction without human interference, and so cable owners have built up a dense network of alternative cables to which data is routinely re-routed. This vast network – approximately 600 cables are globally active or planned; active cables are estimated to extend over a distance of 1.4 million kilometres – offers its own form of protection. In the Euro-Atlantic area, density ensures that hostile actors seeking to cause a serious, effective data outage must coordinate simultaneous aggression at multiple undersea cable nodes. A prepared maritime deterrence posture ensures that NATO can deter or respond to an attack like this. Risks of interference with undersea infrastructure increase in shallower waters proximate to coastlines. Shallow and/or rugged undersea topography may allow adversaries to escalate hybrid operations if deterrence is weak.

While NATO militaries have an operational advantage in the North Atlantic, Russia’s hybrid tactics can still target cracks where cooperation between EU and NATO members is less developed. Hybrid conflict is normally experienced below the threshold of direct aggression. If undeterred, it fosters insecurity, creating an environment that advantages the instigator.

As great power tensions escalate, Russia, China and other strategic competitors are poised to continue to utilise hybrid interference to challenge Western interests. Moscow and Beijing might acknowledge that the collective West, institutionally underpinned by NATO and the EU, have greater military and economic strength. Nevertheless, Russian and Chinese strategists understand that Western power can be weakened when gaps in security cooperation are targeted. Cooperation gaps between multiple stakeholders puts undersea infrastructure serving Euro-Atlantic democracies at risk.

Vulnerabilities with maritime infrastructure were starkly highlighted by sabotage to the Nord Stream pipelines in 2022, spurring the creation of NATO’s Undersea Infrastructure Coordination Cell (henceforth the Cell) in February 2023. Under the auspices of NATO’s international staff, the Cell will “map vulnerabilities, and coordinate efforts between NATO Allies, partners, and the private sector.” The Cell contributed to the NATO-European Union (EU) taskforce on resilience and critical infrastructure that reported its recommendations for enhanced EU-NATO security cooperation in energy, transport, digital infrastructure and space policies in June 2023.

Much undersea infrastructure is owned and/or operated by private companies, sometimes making the responsibility for security unclear between governments and commercial entities. Public-private partnerships are vital in reducing undersea vulnerabilities. The Cell is an important framework to bridge cooperation between governments and industry by combining information-sharing with technological, political and business expertise to support improved situational awareness against hybrid threats. The Cell assists NATO’s wider strategic response, for example, by supporting the Digital Ocean initiative under NATO’s Defence Investment Division, which prioritises technological innovation and interoperability. Technological innovation is vital when seeking to overcome many complex maritime security problems. Stronger dialogue with leading industries helps NATO to broaden its vision on the latest innovation trends and supports collaboration to advance maritime security technologies relating to sensors, surveillance, submersibles and undersea unmanned vehicles.

Across 32 Allied countries, NATO faces a multifaceted maritime security environment. While geopolitical tensions rose, the Nord Stream sabotage prompted concerns that similar incidents were set to spiral. Ongoing development of Joint Force Command (JFC) Norfolk improves operational coordination for northern NATO members across land, sea, air and cyber domains. NATO must balance this with support for southern members at risk from destabilisation in neighbouring regions connected by maritime zones that facilitate flows in narcotics, illicit weapons and organised crime.

Governments in Northern Europe play prominent roles in the EU’s and NATO’s responses to Russia’s conventional military aggression in Ukraine. Russia retaliates against the EU and NATO in different hybrid ways. Efforts to create insecurity have included frequent escalations in airspace violations by Russian military aircraft “flying dark” – without a transponder code visible to civilian air traffic control. More disruption around civilian aviation is now experienced in Northern Europe with GPS jamming from Russia’s western regions. Mirroring patterns in the Baltic Sea region, the UK and Ireland have encountered multiple hybrid incidents proximate to maritime EEZs. Since 2015, the Royal Air Force (RAF) has regularly scrambled to intercept Russian military aircraft approaching the UK’s controlled airspace. Reports have identified Russian Tu-95 and Tu-142 aircraft, bombers doubling as maritime patrol aircraft, indicating the wider manoeuvres that might also be taking place, with submarines conducting drills in the sea below.

Russia’s plans for major naval drills on the southerly edge of Ireland’s EEZ in February 2022 received global attention shortly before Moscow began its full-scale invasion of Ukraine. Hybrid operations blur civilian and military domains. In April 2023, Ireland observed suspicious Russian-registered cargo and repair vessels with equipment capable of undersea damage in the Irish EEZ, where important transatlantic cables pass. This was followed by Russian warships manoeuvring in the same waters in May 2023. Commentators indicate that these exercises were to gauge Irish and UK reaction capabilities. Elsewhere in the North Atlantic, more suspicious Russian-registered commercial vessels have appeared guarded by armed “little blue men”. Russian oil tankers have shunted through European seas on long and environmentally precarious journeys transporting supplies to China and India. Working around Western sanctions, it is claimed that these vessels carry unusual communications equipment, heightening suspicions that the vessels are “listening posts” informing Russian hybrid activity.

Serious maritime incidents continue to affect the wider Nordic-Baltic region. According to police reports, an undersea data cable linking mainland Norway with its Arctic archipelago of Svalbard suffered human-made damage in January 2022. Commissioned in December 2019, the Balticconnector pipeline enhances gas supply security for Finland and Estonia. Damage to this pipeline was detected in October 2023. More damage to nearby undersea data cables connecting Finland and Estonia, the EE-S1 cable linking Estonia and Sweden, and a Russian-maintained cable, was soon discovered. Finnish investigators have so far communicated that this destructive spree was likely caused by a Hong Kong-registered vessel dragging its anchor along the seabed during a journey where it docked multiple times at Russia’s Baltic Sea ports. Parallel investigations in Estonia have corroborated early Finnish findings.

Whether the damage was caused on purpose or occurred by accident remains unclear. Either way, the Balticconnector incident underscores that critical undersea infrastructure can be disrupted by rudimentary means. NATO responded with “additional surveillance and reconnaissance flights” for its Baltic Sea Allies, by sending four mine hunters and by deploying Airborne Early Warning and Control (AWACs) and Uncrewed Aerial Vehicle (UAV) systems. Following repairs costing approximately EUR 40 million, the Balticconnector returned to service in April 2024. The episode lingers as a reminder to NATO members that stronger maritime security cooperation is vital against future hybrid interference.

After the Baltic states – Estonia, Latvia and Lithuania – restored independence in the early 1990s, these countries remained largely reliant on Russian-supplied energy. Over the past decade, undersea infrastructure has expanded between EU and NATO members in the Baltic Sea. This is gradually releasing Baltic and Nordic states from Russian energy dependence. With EU support, the Baltic states are synchronising their electricity grids with plans to disconnect from Russian and Belarusian supplies by 2025. An LNG terminal at Klaipėda has boosted Lithuania’s energy independence since 2014. Lithuania is also linked to Sweden via the undersea electricity connector, NordBalt, that opened in 2015, integrating Baltic and Nordic electricity markets.

When NordBalt was being installed on the seabed, Vilnius reported several instances of interference from Russian military vessels. Opened in October 2022, a partially undersea gas connector, Baltic Pipe, transports gas from the North Sea via Denmark to Poland. A further undersea electricity connector, LaSGo, is currently in development, promising to reinforce supplies between Sweden, its Baltic island of Gotland, and Latvia. This new infrastructure, much of it undersea, is generally positive for European security because it weakens Russia’s “energy weapon”. Nevertheless, having its influence stymied by the continued erosion of its energy monopoly, Moscow might now retaliate with sabotage. Infrastructural expansion increases risks of disruptive interference if vulnerabilities are not reduced, a challenge that renews responsibilities for EU and NATO members to reshape maritime cooperation.

While expanded undersea infrastructure transforms the Baltic Sea region, similar projects are also ongoing in the Black Sea. Russia has long aimed to control Black Sea infrastructure with undersea pipeline projects and data cables supplying other states in the region. These attempts to dominate through dependency are now being challenged. An undersea Black Sea electric cable and adjoining data cable linking Romania with partners Georgia and Azerbaijan is being planned. President of the European Commission Ursula von der Leyen has affirmed that the project will provide “clean, affordable and secure energy sources” for Black Sea countries. Expanded Black Sea infrastructure connecting Ukraine with EU and NATO members is likely to feature in plans for Ukraine’s post-war reconstruction. Like scenarios in the Baltic Sea, expanding undersea infrastructure under EU auspices increases connectivity to strengthen liberal political and economic order. It nevertheless creates new questions on how vulnerabilities are to be secured. Maritime security challenges are more severe around the Black Sea as its regional politics is less stable than in the Baltic region or North Atlantic.

NATO members can galvanise public and private networks to secure undersea infrastructure via NATO’s Critical Undersea Infrastructure Network, which convened for the first time in May 2024. Broader global networks are possible through partnerships with Australia, Ireland, Japan, Jordan and New Zealand, among others. Each partner perceives common strategic interests with NATO on protecting undersea infrastructure. Jordan’s economy relies on the Mediterranean’s dense undersea infrastructure. Dialogue on undersea infrastructure is prioritised in Ireland’s recently updated partnership with NATO. Innovative security solutions are essential for expanded data cable connections planned between Japan and some of its Pacific neighbours. For Australia and New Zealand, securing the Southern Cross data cable connecting both with the US is a vital aim. As undersea infrastructure continues to evolve, NATO’s recent adaptations mark an important milestone in its response to hybrid threats.