Joshua Allin, James E. Hunt, Peter J. Talling, Michael Andrew Clare, Ed Pope

Submarine canyons are one of the most important pathways for sediment transport into ocean basins. For this reason, understanding canyon architecture and sedimentary processes has importance for sediment budgets, carbon cycling, and geohazard assessment. Despite increasing knowledge of turbidity current triggers, the down-canyon variability in turbidity current frequency within most canyon systems is not well constrained.
NewAMS radiocarbon chronologies from canyon sediment cores illustrate significant variability in turbidity current frequency within Nazaré Canyon through time. Generalised linear models and Cox proportional hazards
models indicate a strong influence of global sea level on the frequency of turbidity currents that fill the canyon.
Radiocarbon ages from basin sediment cores indicate that larger, canyon-flushing turbidity currents reaching
the Iberian Abyssal Plain have a significantly longer average recurrence interval than turbidity currents that fill
the canyon. The recurrence intervals of these canyon-flushing turbidity currents also appear to be unaffected
by long-term changes in global sea level. Furthermore, canyon-flushing and canyon-filling have very different
statistical distributions of recurrence intervals. This indicates that the factors triggering, and thus controlling
the frequency of canyon-flushing and canyon-filling events are very different. Canyon-filling appears to be predominantly triggered by sediment instability during sea level lowstand, and by storm and nepheloid transport
during the present day highstand. Canyon-flushing exhibits time-independent behaviour. This indicates that a
temporally random process, signal shredding, or summation of non-random processes that cannot be discerned from a random signal, are triggering canyon flushing events.