5.3. What is the terrestrial OC burial efficiency of Bute
Inlet and how does it compare with other fjords?
Comparison between OC river input (23 ± 5 Kt OC/yr) and terrestrial OC
burial rate in Bute Inlet (11.7 to 16.3 Kt OC/yr), suggests that Bute
Inlet has a terrestrial OC burial efficiency ranging between 50 and 70
% (60 ± 11 % on average) when estimated over decennial and centennial
timescales, respectively.
No study has closed budgets between river sources and fjord sediments
before, so it is not possible to compare this value with other river-fed
fjords. However, we can compare our results in Bute Inlet with previous
fjord studies, by normalizing OC burial rates to the Bute Inlet’s total
surface area. By doing so, the burial of terrestrial OC in Bute Inlet
ranges between 72 and 100 t C/km2/yr. This range lies
between previous estimates of OC fluxes of 57 to 107 t
C/km2/yr in Scottish and Irish fjords that were
described as having heterogeneous seafloors (Smeaton and Austin, 2020).
Importantly, our results from Bute Inlet suggest that fjords
characterised by sandy turbidity current systems may bury over three
times more terrestrial OC compared to previous global estimates based on
muddy cores from fjords without any identified turbidity current
channels (22 t C/km2/yr; Smith et al., 2015, Cui et
al., 2016).