New Study Suggests Climate Change Will Make Submarine Warfare More Complex
The impact of changing hydroacoustics is far-reaching, extending to military, commercial and scientific applications. It will have significant effects on underwater technologies that rely on sound, such as active and passive sonar, hydrophones, echo sounders, fish finders and sub-seafloor profiling devices.
My findings suggest that the changed environment will have positives and negatives for submarines. Thermal layers are likely to have a greater density differential with the cooler water below them compared to today. This means that submarines will be harder to detect when such a layer is present. However, because sound will travel further, when there’s no thermal layer they may be easier to detect.
Even as it potentially becomes much more difficult to hide in the open ocean, increased noise across the full acoustic spectrum, as well as increasing sound intensity overall, will likely make hiding in coastal shallows, littoral waters and archipelagos much easier.
The time involved in taking a submarine from concept to operations means that the Australian Defense Force needs to start planning for a changing environment now. Naval architects will need to consider material choices for both anechoic plating and hull construction, while marine engineers will need to consider improved dampening for the mechanical components that generate noise. Electrical engineers will need to begin designing next-generation sonars, sensors, processors and filtering techniques to improve their ability to detect hostiles amid very loud ambient noise.
Future submarines will almost certainly use embedded artificial intelligence and machine learning to process acoustic signal intelligence. The developers of these systems will need to take future acoustic conditions into account when assembling training datasets, or they may train an AI with a keen ear for today that won’t be suitable for tomorrow.
Picture this scenario. An Australian frigate is on patrol in the Coral Sea around 100 kilometers off the north Queensland coast when it receives intelligence that an enemy submarine is in the area. It pings the warm waters at 3,500 hertz with its sonar. Under conditions recorded in October 2023 by an Argo robot in the area, that sonar ping would be audible to a range of 28.5 kilometers. In 2100, the same sonar ping, in the same location, would be audible at 37.5 kilometers. When considering the circular area covered by the sonar in this scenario, that’s an increase of about 73%, from 637 square kilometers scanned in 2023 to 1,104 square kilometers in 2100.
More research is needed on this subject to understand the changing world that awaits us under the sea—especially considering the recent joint statement of AUKUS defence ministers about the important work to come in areas such as trilateral anti-submarine warfare and undersea vehicle launch and recovery.
My pilot study is a significant step towards understanding the effects of climate change on ocean hydroacoustics, but it has its limitations. We need more data, and future work should look to expand the dataset and modify the 2100 model to better align with today’s most advanced oceanographic models. Changes to the sea surface will also need to be factored in. The information we gain may make a significant difference to how we approach future warfare in the Indo-Pacific and will be an important part of maintaining a maritime capability edge. It may also provide insights that help Australia address two existential problems—climate change and our geostrategic circumstances.
Rhys Kissell is a systems engineer at defense engineering firm ADROITA. This article is published courtesy of the Australian Strategic Policy Institute (ASPI).
