 |
| Titel |
Debris flow grain size scales with sea surface temperature over glacial-interglacial timescales |
| VerfasserIn |
Mitch D'Arcy, Duna C. Roda Boluda, Alexander C. Whittaker, João Paulo C. Araújo |
| Konferenz |
EGU General Assembly 2015
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250105946
|
| Publikation (Nr.) |
 EGU/EGU2015-5540.pdf |
|
|
|
|
|
| Zusammenfassung |
| Debris flows are common erosional processes responsible for a large volume of sediment
transfer across a range of landscapes from arid settings to the tropics. They are also
significant natural hazards in populated areas. However, we lack a clear set of debris flow
transport laws, meaning that: (i) debris flows remain largely neglected by landscape
evolution models; (ii) we do not understand the sensitivity of debris flow systems to
past or future climate changes; and (iii) it remains unclear how to interpret debris
flow stratigraphy and sedimentology, for example whether their deposits record
information about past tectonics or palaeoclimate. Here, we take a grain size approach
to characterising debris flow deposits from 35 well-dated alluvial fan surfaces in
Owens Valley, California. We show that the average grain sizes of these granitic
debris flow sediments precisely scales with sea surface temperature throughout
the entire last glacial-interglacial cycle, increasing by ~ 7 % per 1 Ë C of climate
warming. We compare these data with similar debris flow systems in the Mediterranean
(southern Italy) and the tropics (Rio de Janeiro, Brazil), and find equivalent signals
over a total temperature range of ~ 14 Ë C. In each area, debris flows are largely
governed by rainfall intensity during triggering storms, which is known to increase
exponentially with temperature. Therefore, we suggest that these debris flow systems are
transporting predictably coarser-grained sediment in warmer, stormier conditions. This
implies that debris flow sedimentology is governed by discharge thresholds and may
be a sensitive proxy for past changes in rainfall intensity. Our findings show that
debris flows are sensitive to climate changes over short timescales (≈¤ 104 years) and
therefore highlight the importance of integrating hillslope processes into landscape
evolution models, as well as providing new observational constraints to guide this.
Finally, we comment on what grain size represents in debris flow systems, and
evaluate the extent to which grain size is correlated with event size. If the effects
of past climate changes on debris flow stratigraphy are taken as a guide, future
warming is likely to result in intensified storms and larger, coarser debris flows. |
|
|
|
|
|
|