Water table depth dynamics derived from optical remote sensing data in northern peatlands

Water table depth (WTD) is one of the key factors that affect the carbon balance in peatlands. Optical remote sensing can detect WTD indirectly through the estimation of surface moisture. In peatlands, WTD and surface moisture conditions are closely related through the strong capillary connection in the topmost peat layer. We took advantage of this strong connection and calculated the OPtical TRApezoid Model (OPTRAM) that relies on the assumption that short-wave infrared reflectance represents the surface moisture conditions. OPTRAM was calculated based on Sentinel-2 MSI and Landsat 8 OLI over selected northern peatlands in Finland, Sweden, Canada, the USA, and Estonia. This is the first study in which the advantages and shortcomings of OPTRAM estimation from Sentinel-2 MSI and Landsat 8 OLI data were discussed. We calculated OPTRAM in two ways: (i) using a manual parametrisation and (ii) utilising a recently developed automatic parameterisation in Google Earth Engine. Further, we analysed the impact of these two parameterisations on OPTRAM performance in various peatlands. Our findings provide an important insight into the global applicability of OPTRAM for monitoring moisture conditions in northern peatlands.