Submarines, designed for stealth, and whales, the ocean’s largest inhabitants, share the same underwater domain. This creates a complex interaction point between naval operations and marine life conservation. The submarine’s silent running capability, which makes it an effective military asset, is also a threat to whales, which rely heavily on sound for navigation and communication. Naval forces face a dual challenge: maintaining operational security while mitigating the risk of collision and acoustic harm to marine mammals.
The Reality of Submarine-Whale Collisions
Submarines are not exempt from the risk of striking whales, though highly publicized incidents often involve large commercial freighters. Documented collisions between naval vessels and whales can be catastrophic due to the vessel’s displacement and speed, often resulting in serious injury or mortality. Modern submarines are engineered for “silent running” to avoid detection. This lack of engine and propeller noise means a whale’s passive acoustic sense, which might otherwise alert it to an approaching ship, is rendered ineffective.
Whale behavior further compounds this collision risk. Many species spend significant time at or near the surface for resting, socializing, or feeding, and migration corridors often overlap with common naval transit routes. Naval vessels, including submarines, typically operate at speeds of 8 to 15 knots. This speed is fast enough to cause lethal impact in the event of a strike, a possibility acknowledged by navies in their environmental impact assessments.
Acoustic Detection and Navigation Systems
A submarine’s primary tool for environmental awareness, including marine life, is its acoustic detection system. Submarines rely on passive and active sonar, though their use for whale avoidance differs from military applications. Passive sonar involves listening for sounds in the water, such as whale vocalizations, using sophisticated hydrophone arrays, including long towed arrays. This passive acoustic monitoring (PAM) helps classify and locate marine mammals by their specific calls.
Interpreting the underwater soundscape is complex, requiring operators to distinguish between military targets, natural phenomena, and marine mammals. Naval analysts have sometimes mistaken whale sounds for advanced technology, highlighting the difficulty of filtering the environment. Active sonar emits a sound pulse and listens for the echo, but it is typically avoided for routine collision avoidance due to its environmental impact and the need to maintain stealth. Specialized software is now being integrated into naval systems to automatically detect marine mammal vocalizations, turning acoustic data into actionable avoidance information.
Operational Protocols for Avoidance
Naval forces implement strict procedural rules to reduce the risk of collision and acoustic disturbance. These operational protocols start with time and area management, planning training exercises to avoid known whale migration routes or sensitive ecological areas like calving grounds. A dedicated watch team, known as Lookouts, is mandated to visually scan the surface for marine mammals when the vessel is transiting at or near the surface. These personnel are trained to identify whales and other protected species.
If a whale or aggregation is sighted, established protocols require the commanding officer to take immediate action, including maneuvering the vessel to maintain a required avoidance distance. In high-density areas, naval vessels may face mandatory speed reductions, often to 10 knots or less. This significantly reduces the probability of a lethal strike. The Navy also uses real-time alerts to notify vessels of large whale aggregations, allowing for proactive course changes.
The Broader Impact of Underwater Noise
Submarine operations impact the marine environment through anthropogenic noise, extending beyond the risk of physical collision. High-intensity, mid-frequency active sonar used for anti-submarine warfare is a particular concern because it is louder and more powerful than routine navigation systems. The sound waves from this military sonar can travel hundreds of miles, interfering with the biosonar and communication of many whale species. This acoustic interference disrupts essential biological functions, such as feeding, mating, and navigation, by masking their own calls or the sounds of prey.
Exposure to active sonar has been linked to severe behavioral changes in deep-diving species like beaked whales, including rapid surfacing that can lead to a form of decompression sickness. Navies attempt to mitigate this using a “soft start” procedure, gradually increasing sonar intensity to give marine mammals a warning and a chance to leave. However, the overall increase in background ocean noise from all naval and commercial activities presents a chronic stressor for whales.