[1] Observations in undisturbed terrain within some regions of the Arctic reveal limited correlation between increasing air temperature and the thickness of the seasonally thawed layer above ice-rich permafrost. Here we describe landscape-scale, thaw-induced subsidence lacking the topographic contrasts associated with thermokarst terrain. A high-resolution, 11 year record of temperature and vertical movement at the ground surface from contrasting physiographic regions of northern Alaska, obtained with differential global positioning systems technology, indicates that thaw of an ice-rich layer at the top of permafrost has produced decimeter-scale subsidence extending over the entire landscapes. Without specialized observation techniques the subsidence is not apparent to observers at the surface. This "isotropic thaw subsidence" explains the apparent stability of active layer thickness records from some landscapes of northern Alaska, despite warming near-surface air temperatures. Integrated over extensive regions, it may be responsible for thawing large volumes of carbon-rich substrate and could have negative impacts on infrastructure.

In some regions underlain by ice‐rich permafrost, a consistent, long‐term increase in ALT under changing climatic conditions is not supported by observations. The apparent lack of ALT may be attributed to soil consolidation from thawing of the uppermost ice‐rich permafrost and subsidence of the ground surface. Four plots established in 1962 at Barrow, Alaska, were re‐instrumented in 2003 and surveyed annually using differential GPS technology, accompanied by active‐layer probing. Elevation change from 1962 to 2003 was within the interannual variability of the 2003–15 period, indicating net stability in the area. Over the 2003–15 period, however, all four plots experienced subsidence trends of 0.4–1.0 cm/year, resulting in a net elevation change of 8–15 cm. Warmer winters and increased snow depth during this period decreased the potential for frost heave. Warmer summers resulted in thaw penetration into the ice‐rich transient layer and ice wedges, leading to the net subsidence in recent years. Copyright © 2016 John Wiley & Sons, Ltd.

Technological advances in Differential Global Positioning Systems (DGPS), used in conjunction with specially designed survey targets, provide a means for accurately detecting frost heave and thaw settlement in cold environments, and for relating positions precisely in worldwide geodetic reference systems. Under ideal conditions, DGPS technology is capable of measuring vertical change of 1 cm or less. The inexpensive platform targets developed for this study were designed to support a DGPS antenna, to move in concert with the ground surface in response to changes within the active layer, and to function with minimal disturbance. The targets are unlikely to be affected adversely by flooding, cold weather, snow, or animal disturbance. Although the DGPS/target methodology can be strenuous and time consuming in comparison with traditional surveying methods, preliminary results indicate that it can be used to detect frost heave and thaw settlement at very fine resolution. Post‐processed rapid static carrier‐phase DGPS measured a mean value of vertical heave of 1 cm and mean subsidence of 4 cm during 2001–2002 at Prudhoe Bay, Alaska. Traditional profile leveling techniques confirmed these measurements. DGPS is a promising tool for measurement of periglacial phenomena, and is applicable over a wide range of spatial scale. Copyright © 2003 John Wiley & Sons, Ltd.