## 4 Discussion  
In this study, we illustrate the potential of multitemporal airborne and satellite imagery for modeling water table depth and NEE for an ombrotrophic peatland. These remotely sensed data provide opportunities for ongoing monitoring of peatlands at a range of spatial and temporal scales. Physical models of peatland C balance require inputs from in situ measurements--such as precipitation, temperature, incoming radiation, and wind speed, among others--for successful parameterization [54; 55]. While these variables are straightforward to collect for small spatial scales such as at individual eddy covariance towers, in situ measurements over large spatial extents are logistically unfeasible [56]. Estimations of the parameters are also possible from regional or global climate models, but this may introduce additional uncertainties for predictions of hydrological behavior and gas exchange at the ecosystem level by not taking into account the spatial heterogeneity of the system. Remote sensing observations can help bridge the gap between small spatial scale, in situ measurements of peatland processes, and ecosystem scale models. Long-term satellite archives further provide the opportunity for historical assessment or estimations of processes at locations without in situ measurements. New generation satellite imagery (e.g., Sentinel-2, Landsat 8 OLI) and airborne hyperspectral imagery allow for highly detailed image acquisitions from which to monitor the response of these ecosystems to both allogenic (e.g., climate) and autogenic factors (e.g., change in hydrology). The multitemporal model relating NDWI\({}_{1240}\) to water table depth illustrates the sensitivity of the narrowband index to both liquid water content in the vegetation and phenology. Mer Bleue has both deciduous and evergreen vascular plants and there are substantial seasonal variations in nitrogen and chlorophyll concentration in the vascular plants, but not in the mosses [9]. These changes can be seen in multitemporal imagery of the bog [9; 51]. With the depth of the water table position having been greater than 20 cm from the surface on the days the SASI HSI were collected over the period of study (2011-2016), the NDWI\({}_{1240}\) does not directly observe the position of the water table. The reflectance at these wavelengths is determined solely by the top 3-5 cm of the _Sphagnum_ canopy [57]. While other studies have used exposed surface water to infer the position of the water table across a peatland [58], the relationship here shows NDWI\({}_{1240}\) as a proxy for water table position. This is important for Mer Bleue because, other than during exceptionally wet periods, the water table remains below the surface of the hollows [20]. Water table depth is a subdued reflection of the surface microtopography [35], with a strong association to the vegetation community [1]. The magnitude of reflectance at 884.5 nm and 1238.6 nm are indicative of the moisture content in the superficial bog vegetation. As shown by [56],  
Figure 10: Spatial estimates of NEE from the resampled CASI HSI mosaics from 2016. Gray represents treed areas that have been masked out [31]. the magnitude of _Sphagnum_ reflectance can vary by as much as 50% in the SWIR region from saturated to dry samples. In particular, the characteristic peaks in reflectance centered between 799-900 nm and 1250-1330 nm in wet _Sphagnum_ are lost as the amplitude of the reflectance in NIR-SWIR increases with drying. Extrapolating the model beyond the range of the WT table depth investigated here should be done with caution because it is unknown if the NDWI\({}_{1240}\):WT relationship would remain with very high (i.e., water at surface of hollows) or low (\(<\)\(-\)43 cm) WT positions. However, at Mer Bleue, a very high WT is rare; it mostly remains below the surface of hollows. We found a lower correlation between microtopography and water table depth (Figure 6) than [1]. This is due to the spatial resolution (1 m) of the SWIR imagery and the degraded microtopography DSM (2 cm to 1 m).