4.2.2 Improving HWR Predictions
Our results demonstrate that an OT below 4 m and a consistent exposure
of MI within the headwall were the most important factors in producing
the fastest rates of HWR at Peninsula Point. A simple index was created
to test if accounting for these two in-situ controls can improve
the prediction of HWR spatial variability across the site. Along the 20
transects that covered the MI surface model, we measured inland from the
2017 headwall position a distance equal to the 2016 to 2017 HWR. The
average ice elevation and the average OT along this distance were then
given a value based on the criteria in Table 2. These two values were
averaged and divided into the 2016 to 2017 HWR distance along each
transect to produce a predicted 2017 to 2018 HWR (green line labelled
MI). For example, consider a transect that recorded 5 m of retreat
between 2016 and 2017, but had no exposed ice and an overburden
> 4 m in both 2016 and 2017. If this transect is modelled
to have an exposure of ice and an OT < 4 m after 2017, using
Table 2, the predicted HWT from 2017 to 2018 would be 6.7 m (5 m divided
by 0.75).
These predictions were compared with similar metrics based on the
assumption that the headwall properties present in 2017 extended inland
(blue line labelled OBS), an extrapolation of the 2016 to 2017 HWR (red
line labelled EXT) and with the HWR of 7 m a-1 on
active retreating headwalls on Peninsula Point as described by Mackay
(1986) (pink line labelled MAC), and plotted together in Figure 10.
Table 2: Criteria and values used
to create the 2017 to 2018 HWR prediction