气候变化领域集成服务门户(CCPortal): A Model for Thaw and Erosion of Permafrost Riverbanks

CCPortal

DOI	10.1029/2023JF007452
	A Model for Thaw and Erosion of Permafrost Riverbanks
	Douglas, Madison M.; Lamb, Michael P.
发表日期	2024
ISSN	2169-9003
EISSN	2169-9011
起始页码	129
结束页码	4
卷号	129 期号:4
英文摘要	How will bank erosion rates in Arctic rivers respond to a warming climate? Existing physical models predict that bank erosion rates should increase with water temperature as permafrost thaws more rapidly. However, the same theory predicts much faster erosion than is typically observed. We propose that these models are missing a key component: a layer of thawed sediment on the bank that buffers heat transfer and slows erosion. We developed a 1D model for this thawed layer, which reveals three regimes for permafrost riverbank erosion. Thaw-limited erosion occurs in the absence of a thawed layer, such that rapid pore-ice melting sets the pace of erosion, consistent with existing models. Entrainment-limited erosion occurs when pore-ice melting outpaces bank erosion, resulting in a thawed layer, and the relatively slow entrainment of sediment sets the pace of erosion similar to non-permafrost rivers. Third, the intermediate regime occurs when the thawed layer goes through cycles of thickening and failure, leading to a transient thermal buffer that slows thaw rates. Distinguishing between these regimes is important because thaw-limited erosion is highly sensitive to water temperature, whereas entrainment-limited erosion is not. Interestingly, the buffered regime produces a thawed layer and relatively slow erosion rates like the entrainment-limited regime, but erosion rates are temperature sensitive like the thaw-limited regime. The results suggest the potential for accelerating erosion in a warming Arctic where bank erosion is presently thaw-limited or buffered. Moreover, rivers can experience all regimes annually and transition between regimes with warming, altering their sensitivity to climate change. Large river systems flow through regions containing permafrost (permanently frozen ground), which stabilizes riverbanks. As the climate warms, Arctic riverbank erosion processes and rates might change, threatening the homes and livelihoods of communities living along permafrost rivers. Previous work determined that permafrost riverbank erosion can be limited by rates of permafrost thaw or sediment entrainment, whichever process is slower, but did not track heat transfer within the riverbank or the development of a layer of thawed sediment on the bank surface that can insulate permafrost. To address this knowledge gap, we developed a simplified numerical model for permafrost thaw, thawed sediment entrainment, and heat transfer within the thawed and frozen portions of the riverbank. We found that banks form thin layers of thawed sediment, which insulated permafrost and dramatically slowed thaw and erosion rates. For the case where the thawed sediment was unstable and failed past a threshold thickness, the thawed layer remained thin and bank erosion was sensitive to water temperature. Therefore, Arctic rivers may experience higher bank erosion rates as river water warms with climate change in locations where bank erosion occurs under thaw-limited conditions or due to periodic thawed sediment failure for a portion of the year. We developed a 1D model for permafrost riverbank erosion across the thaw- and entrainment-limited regimes When a thawed sediment layer develops, it tends toward a constant thickness where sediment entrainment and permafrost thaw rates balance Periodic thaw-layer failure produces bank erosion rates that simultaneously depend on sediment entrainment and permafrost thaw rates
英文关键词	permafrost; river; fluvial geomorphology; erosion; cutbank
语种	英语
WOS研究方向	Geology
WOS类目	Geosciences, Multidisciplinary
WOS记录号	WOS:001206012500001
来源期刊	JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/296331
作者单位	California Institute of Technology; Massachusetts Institute of Technology (MIT)
推荐引用方式 GB/T 7714	Douglas, Madison M.,Lamb, Michael P.. A Model for Thaw and Erosion of Permafrost Riverbanks[J],2024,129(4).
APA	Douglas, Madison M.,&Lamb, Michael P..(2024).A Model for Thaw and Erosion of Permafrost Riverbanks.JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE,129(4).
MLA	Douglas, Madison M.,et al."A Model for Thaw and Erosion of Permafrost Riverbanks".JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE 129.4(2024).