Using oceanographic datasets to improve decision-making

NITECH ››› ENSURING ACCESS TO CRITICAL DATA

USING OCEANOGRAPHIC DATASETS

TO IMPROVE DECISION-MAKING

The current return to great power competition is establishing a new chapter for naval warfare, where the submarine force is expected to play a relevant role. In addition to their lethal destructive power, submarines create a tremendous amount of uncertainty for adversaries by exploiting their stealth capabilities and discreet surveillance on the battlefield. This uncertainty is a substantial element of the deterrent power of the submarine force, compelling surface naval forces to devote enormous resources and effort to detecting submarine threats. In Anti-Submarine Warfare (ASW) operations, naval units with different endurance and power are usually distributed among specific marine sectors to configure detection and search patterns. Underwater acoustics is the primary, but not the only, technology involved in conducting these ASW operations. The effectiveness of underwater acoustics is highly dependent on the intervening medium and its imposed limitations on sensor performance. Sonar-based detection, localization and tracking capabilities are heavily influenced by the acoustic propagation loss. The rapid and timely assessment of acoustic propagation loss is required to reduce the uncertainty induced by the variable nature of the marine environment. This environmental assessment provides

Water Sound sufficient and realistic environmental information to Speed Profile optimize sensor designs, signal processing and the configuration of detection and search patterns. Acoustic propagation loss is highly dependent on the sound speed profile (SSP) of the water column and the acoustic reflection properties and geometry of its surface and bottom boundaries. SSP, in turn, is mainly determined by the thermal stratification of the water column. Knowledge about the spatial and time variability of the underwater temperature enables commanders to estimate sonar ranges to decide the appropriate ASW tactics to optimize tracking and detection. Traditionally, hydrographic ships from the world’s navies navigated the oceans collecting oceanographic data to build climatologies. Due to the impact of climate change, the Centre for Maritime Research and Experimentation (CMRE) is currently contributing to the updating of these climatologies in strategic regions such as the Arctic Ocean and the Mediterranean Sea. The eXpendable BathyThermograph (XBT) and the Conductivity-Temperature-Depth (CTD) are the preferred probes for this collection of oceanographic data. XBTs

Underwater vehicle (AUV). NATO’s CMRE tests such systems to explore potential application in military operations. (PHOTO: CMRE)

Dr Alberto Alvarez Diaz, Principal Scientist at NATO’s Centre for Maritime Research and Experimentation (CMRE), highlights how advances in maritime autonomous systems have optimized ASW tactics and sonar accuracy through effective and efficient data collection

obtain information of the thermal structure as they freefall through the water column. The information is transmitted to the on-board processing system through a very thin wire. Eventually, at predetermined depths, the wire breaks and data collection is concluded. The on-board CTD probe integrates temperature, conductivity and pressure sensors within a metal frame called a rosette. This houses a series of water bottles that can be selectively closed at the desired water depths. The structure is lowered via an electromechanical cable through the water column, providing temperature and derived salinity profiles in real time. Recent technological advances in low-power, miniaturized electronics and robotics have contributed to the development of a new paradigm in observational oceanography.

AUTONOMOUS PLATFORMS

This paradigm assumes that the most effective and efficient way to oceanographically sample vast marine regions is through persistent and widely distributed networks of autonomous platforms using low-power probes. Thanks to these technological advances, CTD probes are now installed on autonomous platforms like profiling floats and underwater gliders, among others. The former move freely with the currents and perform diving cycles to outline oceanographic properties. The latter are torpedo-shaped platforms that use a wing configuration and a buoyancy engine for underwater movements and manoeuvres, generating sawtooth-like profiles of oceanographic variables. Both platforms transmit the oceanographic data in near-real time when they surface. CMRE has repurposed these commercial technologies to facilitate covert oceanographic sampling in disputed areas, where it may not be safe for manned platforms to venture. The collected oceanographic datasets are used to generate understanding and provide insights into current and future thermal stratification, among other applications. This information is extracted from the data, using numerical ocean models. These are software engines that integrate the fundamental equations of fluid motion over time to obtain current and future conditions of the marine environment.

Although ocean prediction models capture much of the complexity of the real ocean, their results tend to deviate from reality after some time. Data assimilation methods attempt to constrain models to reality by incorporating existing observations in the modelling process. Digital ocean models of certain marine regions are run at CMRE to support NATO ASW exercises. The amount of oceanographic data collection has been drastically increased in recent decades with the advent of new in situ sampling platforms and satellites.

It is becoming increasingly difficult for a human being to capture all the information content from the huge amounts of collected data. The use of artificial intelligence (AI) to extract useful information from oceanographic datasets is still in its infancy and largely unexplored. Attempts have been made at CMRE to improve data assimilation using deep learning techniques. The range of applicability of AI techniques has yet to be determined in this field.