| Autor: |
Douglas, Madison M., Miller, Kimberly Litwin, Schmeer, Maria N., Lamb, Michael P. |
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| Zdroj: |
Journal of Geophysical Research. Earth Surface; Aug2023, Vol. 128 Issue 8, p1-21, 21p |
| Abstrakt: |
Permafrost thaw is hypothesized to increase riverbank erosion rates, which threatens Arctic communities and infrastructure. However, existing erosion models have not been tested against controlled flume experiments with open‐channel flow past an erodible, hydraulically rough permafrost bank. We conducted temperature‐controlled flume experiments where turbulent water eroded laterally into riverbanks consisting of sand and pore ice. The experiments were designed to produce ablation‐limited erosion such that any thawed sediment was quickly transported away from the bank. Bank erosion rates increased linearly with water temperature, decreased with pore ice content, and were insensitive to changes in bank temperature, consistent with theory. However, erosion rates were approximately a factor of three greater than expected. The heightened erosion rates were due to a greater coefficient of heat transfer from the turbulent water to the permafrost bank caused by bank grain roughness. A revised ablation‐limited bank erosion model with a heat transfer coefficient that includes bank roughness matched our experimental results well. Results indicate that bank erosion along Arctic rivers can accelerate under scenarios of warming river water temperatures for cases where the cadence of bank erosion is set by pore‐ice melting rather than sediment entrainment. Plain Language Summary: Many rivers in the Arctic have banks made up of permanently frozen sand and ice (permafrost) that are susceptible to erosion when they thaw. To understand how bank erosion may change as the Arctic climate warms, we conducted laboratory experiments using a channel with an erodible frozen bank. We found that warmer river water and lower bank‐ice content produced faster erosion rates. In contrast, bank erosion was insensitive to the ground temperature. Bank erosion rates were three‐fold faster than predicted by existing theory. We attribute the faster‐than‐expected erosion to a greater transfer of heat from the river water due to bank roughness. Our results imply that warming river water may increase riverbank erosion rates in permafrost regions, threatening communities and infrastructure built along Arctic rivers. Key Points: Flume experiments with frozen, erodible riverbanks were used to test and revise theoryErosion rates were affected by hydrodynamically rough banks that change the rate of heat transferAblation‐limited bank erosion rates increase with warmer water and lower pore‐ice content and are insensitive to bank temperature [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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