TY  - JOUR
A1  - Herman, Frederic
A1  - Braun, Jean
A1  - Deal, Eric
A1  - Prasicek, Gunther
T1  - The response time of glacial erosion
JF  - Journal of geophysical research : Earth surface
N2  - There has been recent progress in the understanding of the evolution of Quaternary climate. Simultaneously, there have been improvements in the understanding of glacial erosion processes, with better parameter constraints. Despite this, there remains much debate about whether or not the observed cooling over the Quaternary has driven an increase in glacial erosion rates. Most studies agree that the erosional response to climate change must be transient; therefore, the time scale of the climatic change and the response time of glacial erosion must be accounted for. Here we analyze the equations governing glacial erosion in a steadily uplifting landscape with variable climatic forcing and derive expressions for two fundamental response time scales. The first time scale describes the response of the glacier and the second one the glacial erosion response. We find that glaciers have characteristic time scales of the order of 10 to 10,000 years, while the characteristic time scale for glacial erosion is of the order of a few tens of thousands to a few million years. We then use a numerical model to validate the approximations made to derive the analytical solutions. The solutions show that short period forcing is dampened by the glacier response time, and long period forcing (>1 Myr) may be dampened by erosional response of glaciers when the rock uplift rates are high. In most tectonic and climatic conditions, we expect to see the strongest response of glacial erosion to periodic climatic forcing corresponding to Plio-Pleistocene climatic cycles. Finally, we use the numerical model to predict the response of glacial systems to the observed climatic forcing of the Quaternary, including, but not limited to, the Milankovich periods and the long-term secular cooling trend. We conclude that an increase of glacial erosion in response to Quaternary cooling is physically plausible, and we show that the magnitude of the increase depends on rock uplift and ice accumulation rates.
Y1  - 2018
U6  - https://doi.org/10.1002/2017JF004586
SN  - 2169-9003
SN  - 2169-9011
VL  - 123
IS  - 4
SP  - 801
EP  - 817
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Prasicek, Günther
A1  - Herman, Frederic
A1  - Robl, Jörg
A1  - Braun, Jean
T1  - Glacial steady state topography controlled by the coupled influence of tectonics and climate
JF  - Journal of geophysical research : Earth surface
N2  - Glaciers and rivers are the main agents of mountain erosion. While in the fluvial realm empirical relationships and their mathematical description, such as the stream power law, improved the understanding of fundamental controls on landscape evolution, simple constraints on glacial topography and governing scaling relations are widely lacking. We present a steady state solution for longitudinal profiles along eroding glaciers in a coupled system that includes tectonics and climate. We combined the shallow ice approximation and a glacial erosion rule to calculate ice surface and bed topography from prescribed glacier mass balance gradient and rock uplift rate. Our approach is inspired by the classic application of the stream power law for describing a fluvial steady state but with the striking difference that, in the glacial realm, glacier mass balance is added as an altitude-dependent variable. From our analyses we find that ice surface slope and glacial relief scale with uplift rate with scaling exponents indicating that glacial relief is less sensitive to uplift rate than relief in most fluvial landscapes. Basic scaling relations controlled by either basal sliding or internal deformation follow a power law with the exponent depending on the exponents for the glacial erosion rule and Glen's flow law. In a mixed scenario of sliding and deformation, complicated scaling relations with variable exponents emerge. Furthermore, a cutoff in glacier mass balance or cold ice in high elevations can lead to substantially larger scaling exponents which may provide an explanation for high relief in high latitudes.
KW  - glacial equilibrium
KW  - steady state topography
KW  - glacial erosion
KW  - glacial buzzsaw
KW  - rock uplift-relief scaling
KW  - scaling relation
Y1  - 2018
U6  - https://doi.org/10.1029/2017JF004559
SN  - 2169-9003
SN  - 2169-9011
VL  - 123
IS  - 6
SP  - 1344
EP  - 1362
PB  - American Geophysical Union
CY  - Washington
ER  -