Monitoring the Invisible: The Science and Technology of Permafrost Observation

Permafrost — ground that has remained frozen for at least two consecutive years — underlies approximately 25% of the Northern Hemisphere's land surface, spanning vast areas of Russia, Canada, Alaska, and the Nordic countries. Within it is locked an estimated 1.5 trillion tonnes of organic carbon — approximately twice the amount currently in the atmosphere. As Arctic temperatures rise, permafrost is thawing — releasing this stored carbon as CO₂ and methane. Monitoring the extent, temperature, and thaw depth of permafrost is therefore one of the most critical — and most technically challenging — tasks in climate science.

Borehole Temperature Networks

The primary method of monitoring permafrost temperature is the borehole — a hole drilled into the ground and equipped with a string of temperature sensors at multiple depths. The Global Terrestrial Network for Permafrost (GTN-P) coordinates a network of over 1,000 monitoring boreholes across the Arctic and alpine regions. These boreholes record temperature profiles that reveal not just current permafrost temperature but the rate of warming — and can detect the downward migration of the thaw front that indicates active permafrost degradation. The network shows that permafrost temperatures have been increasing across virtually all monitored regions, with warming rates of approximately 0.3°C per decade on average.

Satellite Detection of Permafrost Thaw

Satellite remote sensing is increasingly used to detect the surface expressions of permafrost thaw. Thermokarst — the irregular, hummocky terrain created when ground ice melts and the surface collapses — can be mapped from optical satellite imagery. Synthetic aperture radar (SAR) can detect ground surface deformation caused by permafrost thaw at millimetre precision using InSAR (interferometric SAR) techniques. Thermal infrared sensors can map ground surface temperature patterns that indicate the presence or absence of permafrost. Together, these satellite methods are allowing scientists to track permafrost dynamics across vast, inaccessible areas of the Arctic that cannot be monitored by ground-based networks alone.