Peatland surface movements revealed by multi-temporal SAR interferometry: the case study of Clara Bog, Ireland
Abstract
Peatlands cover 3% of the global land surface but store approximately 30% of total soil carbon. Undisturbed peatlands typically act as net greenhouse gas (GHG) sinks; degraded peatlands act as significant GHG sources. Peatlands cover about 20% of the Irish landscape and store about 1-1.5 billion tonnes of carbon. Although over 90% of this peatland is considered degraded and a significant GHG emitter, it is currently not included in the national GHG emissions budget. Monitoring is required to obtain reliable GHG balance estimates and to assess the effectiveness of future peatland restoration efforts. In this work, we applied multi-temporal InSAR techniques to monitor Clara Bog (Ireland) an 8.4 km2, near-intact, raised peatland, parts of which are known to be subject to drainage-induced subsidence. SAR images acquired by the Sentinel-1A/B satellites during 05/2015-12/2018 were analyzed with SBAS and PS techniques to determine the spatial distribution and rates of movement of the peat surface. The results show that most of the peat is affected by subsidence with rates up to 1-2 cm/yr. Overall, the InSAR-derived rates of subsidence are consistent with longer-term (decadal) observations from past LiDAR and leveling surveys. In detail, the subsidence is characterized by complex trends in space and time that reflect heterogeneity of the peatland, particularly with respect to parameters such as ecotope and water level. The displacement time-series of the peat surface locally shows a good correlation with in-situ measurements of the water table level and with CO2 emissions measured at a flux tower, in particular during one extraordinarily dry three-month period in 2018. This case study supports the feasibility of multi-temporal InSAR techniques as a cost-effective tool to monitor peatland subsidence in temperate oceanic climate zones, and it raises the possibility of using InSAR to upscale in-situ GHG flux data onto regional or national levels.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B23L2513F
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0475 Permafrost;
- cryosphere;
- and high-latitude processes;
- BIOGEOSCIENCES;
- 4950 Paleoecology;
- PALEOCEANOGRAPHY