Multiscale Variability and the Comparison of Ground and Satellite Radar Based Measures of Peatland Surface Motion for Peatland Monitoring

Abstract

Peatland surface motion is highly diagnostic of peatland condition. Interferometric Synthetic Aperture Radar (InSAR) can measure this at the landscape scale but requires ground validation. This necessitates upscaling from point to areal measures (80 × 90 m) but is hampered by a lack of data regarding the spatial variability of peat surface motion characteristics. Using a nested precise leveling approach within two areas of upland and low-lying blanket peatland within the Flow Country, Scotland, we examine the multiscale variability of peat surface motion. We then compare this with InSAR timeseries data. We find that peat surface motion varies at multiple scales within blanket peatland with decreasing dynamism with height above the water table e.g., hummocks < lawn < hollows. This trend is dependent upon a number of factors including ecohydrology, pool size/density, peat density, and slope. At the site scale motion can be grouped into central, marginal, and upland peatlands with each showing characteristic amplitude, peak timing, and response to climate events. Ground measurements which incorporate local variability show good comparability with satellite radar derived timeseries. However, current limitations of phase unwrapping in interferometry means that during an extreme drought/event InSAR readings can only qualitatively replicate peat movement in the most dynamic parts of the peatland e.g., pool systems, quaking bog.

Blanket bog CO2 flux driven by plant functional type during summer drought

“…characterised by blanket bog and wet heath vegetation showing signs of active erosion (Hancock et al, 2018) and with peat depths ranging from 0.5 to 4.3 m (Avercamp et al, 2021) The lower altitude site Munsary (58 23 0 49.0 00 N, 3 20 0 26.5 00 W, approximately 100 m.a.s.l.) is located 30 km to the east of Knockfin and comprises low-lying blanket bog with peat depths between 2 and 5 m (Marshall et al, 2022). The mire expanse contains a wide range of micro-topographic elements such as hummock and hollows, with an extensive pool system in the centre (Smart, 1982) At each site, six replicated sampling plots were set up, with no more than one sampling plot within each 100 Â 100 m subsite to capture variation between different margin and centre microtopes (Figure 1) as identified by Marshall et al (2022).…”

Object oriented data analysis of surface motion time series in peatland landscapes

“…The coupling between ecohydrological condition and motion of the peat surface (Mahdiyasa et al, 2022;Marshall et al, 2022) make the characteristic time series of surface motion measured by the InSAR technique highly suited to quantifying peatland condition (Alshammari et al, 2018;Bradley et al, 2022). The InSAR signals that measure surface deformation are from the European Space Agency Sentinel-1A and Sentinel-1B satellites and are processed by Terra Motion Limited (Sowter et al, 2013) to generate a peatland surface motion time series.…”

“…To date, condition assessment of all UK peatlands has been impeded by the lack of cost-effective ways to monitor large and often remote areas of peatland. However recently the use of interferometry synthetic aperture radar (InSAR) signals (Sowter et al, 2013) to measure peatland surface motion has proved fruitful as a low cost alternative to taking ground measurements (Marshall et al, 2022). Recent literature has found peatland surface motion, a direct consequence of eco-hydrological change in the peatland, to be highly indicative of peatland condition (Alshammari et al, 2018(Alshammari et al, , 2020Marshall et al, 2022;Bradley et al, 2022).…”

“…However recently the use of interferometry synthetic aperture radar (InSAR) signals (Sowter et al, 2013) to measure peatland surface motion has proved fruitful as a low cost alternative to taking ground measurements (Marshall et al, 2022). Recent literature has found peatland surface motion, a direct consequence of eco-hydrological change in the peatland, to be highly indicative of peatland condition (Alshammari et al, 2018(Alshammari et al, , 2020Marshall et al, 2022;Bradley et al, 2022). InSAR calculates surface deformation for 80 × 90m 2 areas using Sentinel-1 satellites to produce surface motion time series.…”

Fresh Air for the Mire-Breathing Hypothesis: Sphagnum Moss and Peat Structure Regulate the Response of CO2 Exchange to Altered Hydrology in a Northern Peatland Ecosystem

“…It has been observed that Sphagnum dominated peatlands often undergo changes in surface height as a result of fluctuating water tables [21][22][23][24]. This following of the water table is often referred to as "mire-breathing" and is thought to be a method of self-preservation under water stress [25], which has been documented at scales of entire peatlands, with variations related to the height above water table of different peatland landforms [26]. In the traditional model, the collective peat surface expands as the water table position rises, raising the bog surface and increasing water storage.…”