ocean sensors — Innovative ocean sensors are being developed to provide unprecedented insights into the marine carbon cycle, aiding scientists in understanding climate change impacts. Researchers funded by the EU are spearheading this initiative, focusing on monitoring previously inaccessible areas of the ocean to enhance knowledge of marine ecosystems.
Ocean sensors: Oceans: The Earth’s Climate Regulators
The world’s oceans play a crucial role in regulating the climate by absorbing significant amounts of heat and carbon dioxide (CO2). According to EU data, these waters absorb roughly one-third of human-made CO2 emissions annually. However, the challenge remains in accurately tracking how and where this absorption occurs, as existing observational data is limited.
Gaps in Current Monitoring Methods
Traditionally, scientists have relied on commercial ships and fixed moorings for ocean chemistry measurements. Unfortunately, this approach provides insufficient coverage, with direct observations covering only about 3% of the ocean, as noted by Janne-Markus Rintala, a Finnish marine scientist affiliated with the Integrated Carbon Observation System (ICOS). Rintala pointed out, “Sometimes it looks like we know much more than we do, because models give the impression we have monitored everywhere.” This highlights the urgent need for improved data collection methods.
Expanding Observational Capacity
To address these gaps, Rintala is leading an international team dedicated to enhancing ocean observation capabilities. Their objective is to develop sensors capable of functioning beyond conventional shipping routes and deep within the ocean, allowing continuous monitoring of carbon levels over extended periods. This ambitious project is part of an EU-funded initiative named GEORGE, which is set to conclude in 2027.
The Development of Advanced Sensors
Central to this undertaking is the creation of the world’s first autonomous sensor designed to accurately measure total alkalinity throughout the ocean, from the seabed to the surface. Total alkalinity serves as a critical indicator for understanding the ocean’s carbon system, enabling scientists to estimate how much CO2 seawater can absorb and store.
Moreover, monitoring total alkalinity is vital in tracking ocean acidification, a phenomenon caused by rising CO2 levels that diminishes seawater pH and endangers marine life, particularly organisms like shell-building plankton and molluscs. Rintala emphasised the detrimental effects of ocean acidification, stating, “It can cause cascading effects that ripple up the food web.”
Innovative Approaches to Measurement
Previously, total alkalinity measurements were conducted by collecting seawater samples and analysing them in laboratories on land. Although this method yields valuable information, it is limited to specific locations and times. Socratis Loucaides, an ocean scientist at the UK’s National Oceanography Centre (NOC), advocates for a more comprehensive understanding of ocean carbon content, noting, “If we are interested in the carbon content of the ocean as a whole, we need to measure deeper.”
To achieve this, Loucaides and his team are pioneering a compact lab-on-a-chip sensor. This innovative device conducts a miniature chemistry experiment on board, mixing a seawater sample with a known acid and a colour-changing dye. A light-based sensor then measures the colour shifts to determine the alkalinity of the surrounding seawater.
Testing Under Extreme Conditions
Before deployment, the sensor underwent rigorous testing to ensure it can withstand extreme deep-sea conditions, including immense pressure. This testing occurred at a high-pressure facility in the UK, simulating depths of up to six kilometres. The sensor has since been trialled in various environments, ranging from shallow estuaries to deep underwater landers.
In a significant test, the sensor was deployed nearly 5,000 metres below the surface in the North Atlantic, mounted on a seabed lander positioned at the Porcupine Abyssal Plain Sustained Observatory. At such depths, real-time communication is unfeasible; thus, the sensor operates on batteries and stores data until the lander is recovered, with results expected in May 2026.
Future Directions for Ocean Research
Researchers aim to expand the lifespan of seabed sensors and lower deployment costs by utilising autonomous underwater vehicles for data collection. This broader initiative also seeks to access remote ocean regions and storm-prone areas, such as the Southern Ocean, through another research project called TRICUSO, which builds on the groundwork laid by GEORGE.
To facilitate their objectives, scientists are developing sensors that can be transported by various autonomous vehicles, including torpedo-shaped underwater gliders and wind- and solar-powered surface vessels. Some of these sensors will simultaneously measure multiple carbon-related parameters, while others will collect and preserve seawater samples for later analysis.
Transforming Ocean Measurement Networks
As climate change progresses, the establishment of a network of autonomous sensors holds the potential to transform scattered measurements into a comprehensive map of the ocean’s carbon cycle. Such data will not only indicate where the ocean is changing most rapidly but also identify regions nearing critical thresholds and the evolving capacity of the ocean to absorb carbon.
Rintala underscored the significance of expanding measurements, stating, “We’re facing enormous changes – and huge unknowns. To understand what’s happening, and how fast, we need many more measurements than we have today.” This ongoing research promises to provide essential insights into the health of our oceans and their role in regulating the global climate.
