Abstract
Little is known about the long-term influence of periglacial processes on landscape evolution in cold areas, even though the efficiency of frost cracking on the breakdown of rocks has been documented by observations and experiments.
Cold-room laboratory experiments show that a continuous water supply and sustained sub- zero temperatures are essential to develop fractures in porous rocks (e.g. Murton, 2006), but the cracking efficiency for harder rock types under natural conditions is less clear.
However, based on experimental results for porous rocks, Hales and Roering (2007) proposed a model relating frost-cracking intensity to the mean annual air temperature (MAAT). The model integrates temperature variations in the subsurface following an annually oscillating surface temperature. Hales and Roering (2007) assumed that frost-cracking intensity is a simple function of the temperature gradient and the time span during which the conditions for frost cracking are fulfilled (i.e. a bedrock temperature between -8 and -3 °C and availability of water along a monotonous temperature gradient). Using this approach, Hales and Roering (2007) found a correlation between zones of intense frost cracking predicted by their model and the elevation of scree deposits in the Southern Alps, New Zealand. This result suggests a link between frost-cracking efficiency and long-term landscape evolution and thus merits further investigations.
Anderson et al. (2012) expanded this early model by including the effects of latent heat, daily temperature oscillations, snow cover, and transport limitations of water required to flow through cold bedrock. We have incorporated these elements into a numerical model and explored the sensitivity of frost-cracking rates to variations in MAAT and the thickness of regolith cover. This approach allows us to study the conditions under which a regolith cover is likely to accelerate frost cracking. We find that thin layers of regolith may accelerate erosion in cold regions where the presence of surface water drives bedrock cracking during the summer period.
The detailed sensitivity analysis also allows us to couple the frost-cracking model to a long- term landscape evolution model where surface elevation, sediment thickness, and air temperature evolve through time. This enables us to explore the spatial distribution of frost cracking in realistic landscapes, and to study the slow feedbacks between periglacial erosion, sediment transport, and the evolving topography.
References
Anderson et al. (2012). Rock damage and regolith transport by frost: an example of climate modulation of the geomorphology of the critical zone. Earth Surface Processes and Landforms.
Hales et al. (2007). Climatic controls on frost cracking and implications for the evolution of bedrock landscapes. Journal of Geophysical Research, 112(F2).
Murton et al. (2006). Bedrock fracture by ice segregation in cold regions. Science, 314(5802), 1127-1129. Keywords (max 5): Frost cracking, Landscape evolution, Modeling
Cold-room laboratory experiments show that a continuous water supply and sustained sub- zero temperatures are essential to develop fractures in porous rocks (e.g. Murton, 2006), but the cracking efficiency for harder rock types under natural conditions is less clear.
However, based on experimental results for porous rocks, Hales and Roering (2007) proposed a model relating frost-cracking intensity to the mean annual air temperature (MAAT). The model integrates temperature variations in the subsurface following an annually oscillating surface temperature. Hales and Roering (2007) assumed that frost-cracking intensity is a simple function of the temperature gradient and the time span during which the conditions for frost cracking are fulfilled (i.e. a bedrock temperature between -8 and -3 °C and availability of water along a monotonous temperature gradient). Using this approach, Hales and Roering (2007) found a correlation between zones of intense frost cracking predicted by their model and the elevation of scree deposits in the Southern Alps, New Zealand. This result suggests a link between frost-cracking efficiency and long-term landscape evolution and thus merits further investigations.
Anderson et al. (2012) expanded this early model by including the effects of latent heat, daily temperature oscillations, snow cover, and transport limitations of water required to flow through cold bedrock. We have incorporated these elements into a numerical model and explored the sensitivity of frost-cracking rates to variations in MAAT and the thickness of regolith cover. This approach allows us to study the conditions under which a regolith cover is likely to accelerate frost cracking. We find that thin layers of regolith may accelerate erosion in cold regions where the presence of surface water drives bedrock cracking during the summer period.
The detailed sensitivity analysis also allows us to couple the frost-cracking model to a long- term landscape evolution model where surface elevation, sediment thickness, and air temperature evolve through time. This enables us to explore the spatial distribution of frost cracking in realistic landscapes, and to study the slow feedbacks between periglacial erosion, sediment transport, and the evolving topography.
References
Anderson et al. (2012). Rock damage and regolith transport by frost: an example of climate modulation of the geomorphology of the critical zone. Earth Surface Processes and Landforms.
Hales et al. (2007). Climatic controls on frost cracking and implications for the evolution of bedrock landscapes. Journal of Geophysical Research, 112(F2).
Murton et al. (2006). Bedrock fracture by ice segregation in cold regions. Science, 314(5802), 1127-1129. Keywords (max 5): Frost cracking, Landscape evolution, Modeling
| Originalsprog | Engelsk |
|---|---|
| Publikationsdato | 2014 |
| Antal sider | 1 |
| Status | Udgivet - 2014 |
| Begivenhed | Eucop4: 4th European Conference on Permafrost - Évora, Portugal Varighed: 18 jun. 2014 → 21 jun. 2014 |
Konference
| Konference | Eucop4 |
|---|---|
| Land/Område | Portugal |
| By | Évora |
| Periode | 18/06/2014 → 21/06/2014 |