## 6 Discussion  
### Uncertainties  
Several components in this study are associated with uncertainties, though a detailed quantification of these uncertainties remains difficult due to a lack of appropriate data for comparison at this point. First, the remote sensing data represents, like in any other remote sensing study, a snapshot in time that reflects specific environmental conditions on the ground. Comparison with climate data from the Kotzebue climate station for the times of image acquisition indicated that the images were not taken in or directly after periods of unusual weather events and the image data seems generally representative for the observation periods. Second, NDVI and backscatter may be scale-dependent, and a comparison between these parameters should ideally be done at the same pixel resolution. In our case, no suitable high-resolution data was available for the time of the TSX acquisitions, and we therefore chose Landsat data for NDVI closest to the TSX acquisition date. Though the Landsat data is from earlier in the growing season than our TSX images, the present general patterns of NDVI still provide a valuable insight into basin-wide vegetation distribution and phenology that are useful for interpreting TSX backscatter results.  
Eventually, some uncertainty in this study arises from the relatively low number of samples for radiocarbon dated basins. In our study, several basins were dated by radiocarbon dating of basal  
Figure 7: DTLB of different age classes located in the northern Seward Peninsula (Modern: **(a)** 9 yrs old, **(b)** 29 yrs old; Young: **(c)** 403 \(\pm\) 55 cal\(\cdot\)yr\(\cdot\)BP, **(d)** 294 \(\pm\) 15 cal\(\cdot\)yr\(\cdot\)BP; Medium: **(e)** 1471 \(\pm\) 60 cal\(\cdot\)yr\(\cdot\)BP, **(f)** 770 \(\pm\) 35 cal\(\cdot\)yr\(\cdot\)BP; Old: **(g)** 2719 \(\pm\) 40 cal\(\cdot\)yr\(\cdot\)BP, **(h)** 2567 \(\pm\) 80 cal\(\cdot\)yr\(\cdot\)BP; Modern basin ages from [PERSON] _et al._[43] and radiocarbon dates from [PERSON] _et al._[10]). All images show bands 4-3-2 (near-infrared, red, green) and are in same scale. Image C is from Quickbird © DigitalGlobe; all others are from IKONOS © GeoEye. Vegetation appears in shades of pink with darker color representing high biomass. Water appears dark bluish or black, and bare or sparsely vegetated soil appears in shades of light blue or grey.  
terrestrial peat in a single core from a central portion of the basin [10]. These locations were considered to be representative for the entire basin based on aerial image and field analyses. Arguably, there may be heterogeneity in drained lake basins based on geological and hydrological history that also could affect the timing of peat accumulation. Only cost-intensive, additional radiocarbon dating could provide detailed insights in these particular uncertainties. However, radiocarbon basal peat dates of overlapping neighboring basins indicate that the method is suitable, as the ages of these basins were generally in agreement with their geomorphological position towards each other. [PERSON] _et al._[10] and [PERSON] _et al._[12] address some of the issues related to basin sampling and basin age determination in more detail. Due to a relatively small available sample size of basins with known age, we also were not able to explore general differences between upland and lowland basins. While lowland basins have low topography and a lower drainage gradient, upland basins usually have a steeper drainage gradient, likely resulting in different succession patterns of post-drainage soil moisture, vegetation and permafrost development. We suggest that some of the heterogeneity in our dataset results from mixing these two types of basins.