 |
| Titel |
Climatic forcing of erosion rates in space and time - examples from the central Andes and Himalaya |
| VerfasserIn |
Bodo Bookhagen, Manfred Strecker |
| Konferenz |
EGU General Assembly 2011
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250049394
|
|
|
|
|
|
| Zusammenfassung |
| The windward flanks of the central Andes and the Himalaya are characterized by steep
climatic and tectonic gradients. Here, orographic rainfall causes some of the wettest places on
Earth that are closely linked with intensified surface processes and high erosion rates.
However, the higher-elevation flanks of both orogens become progressively drier, until arid
conditions are attained in orogen interiors (i.e. the Tibetan and Altiplano-Puna
plateaus). Some of the world’s largest rivers with high sediment loads emerge from
these mountain belts, and understanding the relation between climate and erosion
is key in predicting mass fluxes, assessing the effects of climate variability and
long-term climate forcing of erosion on landscape evolution. In this study, we analyze
the effect of climatic gradients on erosion rates through new, cosmogenic nuclide
basin-wide erosion rates from the central Andes (n=40) and the western Himalaya
(n=30).
We make three key observations that underscore the importance of climatic parameters on the
voracity of surface processes in space and time. (1) First-order spatial erosion patterns can be
explained by a simple specific stream power (SSP) approach. Importantly, we explicitly
account for discharge by routing high-resolution, satellite-derived rainfall downstream. This
is important as the steep climatic gradient of both orogens results in a highly nonlinear (and
non-power law) relation between drainage area and discharge, one of the key assumptions for
deriving energy expenditure in fluvial systems. This simple, but robust approach allows us to
compare similarly steep catchments from wet, frontal with dry, internal parts of the orogens.
(2) The derived relation between SSP and basin-wide erosion rates indicates that
erosion (E) scales with E ~ SSP2 on cosmogenic-nuclide timescales. (3) The
use of late Pleistocene and Holocene sedimentary archives (lacustrine sediments
related to landslide damming of river valleys) from both regions furnishes valuable
information on the temporal variation of erosion rates. These records reveal that
arid, but steep landscapes with low present-day and millennial-scale erosion rates
may have increased sediment flux by an order of magnitude during wetter periods.
Overall, these findings underscore (1) the fundamental importance of climate-driven
processes in the long-term landscape evolution of tectonically active mountain belts;
(2) the importance of climatic forcing on sediment production, mass transfer, and
permanent vs. transient sediment storage in orogens; and (3) the importance of
climate variability in intensifying erosion and sediment-flux rates on millennial time
scales. |
|
|
|
|
|
|