Ontdooicyclus

Ontdooicyclus is a concept in Dutch climate science used to describe cyclical thawing and refreezing processes in soils and shallow subsurface layers. The term combines ontdooien (to thaw) and cyclus (cycle). It refers to periodic changes in the phase state of pore water driven by temperature fluctuations, moisture, and solar radiation, rather than a single thaw event.

The cycle typically involves temperatures hovering around 0°C, with latent heat effects during phase changes, soil moisture redistribution, and changes in soil structure that affect porosity and hydraulic conductivity.

Geographically, ontdooicyclus is most relevant in periglacial and high-latitude or high-altitude environments, as well as in Arctic and boreal soils where seasonal thaw dominates. It also occurs in reclaimed lands or areas with seasonal ice cover.

Impacts include soil destabilization, frost heave, changes in drainage, and potential releases of stored carbon as soils thaw; these effects can influence infrastructure integrity and ecosystem productivity.

Measurement and modeling rely on in situ temperature and moisture sensors, soil temperature logs, and remote sensing of active layer thickness; models may incorporate phase-change dynamics, heat transfer, and moisture movement to simulate cycle intensity and frequency.

See also: thawing cycle, permafrost, frost heave, cryosphere, soil physics.