Abstract
Abstract. Advancements in radar technology are increasing our ability to detect Earth surface deformation in permafrost environments. In this paper we use satellite Differential Interferometric Synthetic Aperture Radar (DInSAR) to describe the growth of a large, relatively young pingo in the Tuktoyaktuk Coastlands. High-resolution RADARSAT-2 imagery (2011–2014) analyzed with the Multidimensional Small Baseline Subset (MSBAS) DInSAR revealed a maximum 2.7 cm yr−1 of domed uplift located in a drained lake basin. Satellite measurements suggest that this feature is one of the largest diameter pingos in the region that is presently growing. Observed changes in elevation were modeled as a 348 × 290 m uniformly loaded elliptical plate with clamped edge. Analysis of historical aerial photographs suggested that ground uplift at this location initiated sometime between 1935 and 1951 following drainage of the residual pond. Uplift is largely due to the growth of intrusive ice, because the 9 % expansion of pore water associated with permafrost aggradation into saturated sands is not sufficient to explain the observed short- and long-term deformation rates. The modeled thickness of ice-rich permafrost using the Northern Ecosystem Soil Temperature (NEST) was consistent with the maximum height of this feature. Modeled permafrost aggradation from 1972 to 2014 approximated elevation changes estimated from aerial photographs for that time period. Taken together, these lines of evidence indicate that uplift is at least in part a result of freezing of the sub-pingo water lens. Seasonal variations in the uplift rate seen in the DInSAR data closely match the modeled seasonal pattern in the deepening rate of freezing front. This study demonstrates that interferometric satellite radar can detect and contribute to understanding the dynamics of terrain uplift in response to permafrost aggradation and ground ice development in remote polar environments. The present-day growth rate is smaller than predicted by the modeling and no clear growth is observed at other smaller pingos in contrast with field studies performed mainly before the 1990s. Investigation of this apparent discrepancy provides an opportunity to further develop observation methods and models.
Highlights
Pingos are conical ice-cored hills that grow in the permafrost environment (Mackay, 1998 and references within)
Pingo-like features have been observed on Mars using the High Resolution Imaging Science Experiment (HiRISE) camera on board the Mars Reconnaissance Orbiter (Dundas et al, 2008; Burr et al, 2009; Soare et al, 2014)
Mackay on genesis and growth of pingos has provided tremendous insight into the landscape forming processes associated with permafrost aggradation and ground ice development (e.g., Mackay, 1977, 1979, 1987, 1990, 1992, 1997, 1998)
Summary
Pingos are conical ice-cored hills that grow in the permafrost environment (Mackay, 1998 and references within). R. Mackay on genesis and growth of pingos has provided tremendous insight into the landscape forming processes associated with permafrost aggradation and ground ice development (e.g., Mackay, 1977, 1979, 1987, 1990, 1992, 1997, 1998). Rapid lake drainage, caused either by coastal erosion or thermal erosion of ice wedges, exposes the lake bottom to subfreezing air temperatures (Fig. 1, Mackay, 1992) This initiates the process of permafrost aggradation into the unfrozen lake-bottom sediments. A closed system is formed when the residual pond freezes to the bottom In this case, increasing pressure derived from pore water expelled during permafrost aggradation into the surrounding lake bottom can heave the relatively small area of thin permafrost beneath the residual pond to initiate pingo growth. Availability of high-resolution SAR data from the newer RADARSAT-2 satellite and advanced processing methodology allowed us to map a very largediameter pingo that has not been recognized by field investigations in the Tuktoyaktuk Coastlands and, for the first time, monitor intra-annual pingo growth rate with high temporal and spatial resolution over a period of 4 years
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