Listening to the Polar Ocean: The Sensor Networks Measuring Change Below the Ice

The polar oceans are among the least observed environments on Earth. Their remoteness, the presence of sea ice, and the extreme conditions they present to instrumentation have historically made sustained monitoring extremely difficult. But the past two decades have seen a revolution in ocean observing technology — autonomous floats, gliders, ice-tethered profilers, and acoustic monitoring systems that can collect data continuously in environments where ship-based surveys are impossible. These sensor networks are revealing the polar oceans in unprecedented detail — and documenting changes that are reshaping our understanding of global ocean circulation.

The Argo Float Network

The Argo programme has deployed over 4,000 autonomous profiling floats in the world's oceans — including an increasing number adapted for polar conditions. Each Argo float drifts at a depth of approximately 1,000 metres for 10 days before descending to 2,000 metres and then rising to the surface, measuring temperature and salinity throughout the water column. At the surface, it transmits its data via satellite before descending again for the next cycle. In polar regions, ice-capable Argo floats can detect the presence of sea ice from below and delay their surfacing until they reach open water, allowing them to operate year-round even in ice-covered areas.

Ice-Tethered Profilers in the Arctic Ocean

Ice-Tethered Profilers (ITPs) are autonomous instruments that are installed through holes in the Arctic sea ice and tethered to a surface buoy that drifts with the ice. A profiling instrument travels up and down a cable suspended beneath the ice, measuring temperature, salinity, and other properties through the upper 750 metres of the Arctic Ocean — typically twice per day. The data is transmitted via satellite in near-real-time from the surface buoy. ITPs have documented the warming of Atlantic Water intruding into the Arctic Ocean — a phenomenon that is contributing to sea ice loss by delivering heat from below to the base of the ice.