研究人员探究了北纬25°-90°范围内的超过69,000个源头流域盆地，以确定土壤的热状态是否在山坡(扩散)和河流(平流)侵蚀过程之间建立了平衡，这可以通过河道网络的密度(即排水密度)和凹凸地形(分别为山坡和河谷)的比例来证明。无论流域冰川历史、年平均降水量和地形如何，永久冻土区内的流域的排水密度都低于无永久冻土区的流域。
发现的证据表明，与温带地区相比，平流河流过程在永久冻土景观中受到抑制。冻土可能会抑制河道发育，研究人员预测气候变暖将降低切割阈值，从而促进永久冻土景观中河道网络的增长。研究强调，通过展示平流与扩散过程的平衡如何随着未来的变暖而改变，该团队深入地了解了将这些景观从碳封存转变为碳输出的机制。
据了解，高纬度地区的变暖加剧和冻土的快速融化威胁着永久冻土的碳储量。永久冻土的存在调节了土壤覆盖斜坡上的水渗透和流动以及沉积物运输，以不同于温带环境的方式影响斜坡上平流河流过程与扩散过程的平衡。这些塑造永久冻土景观的过程也通过温度、饱和度和斜坡稳定性，影响土壤覆盖斜坡上的碳储量，因此碳储量和景观形态测量应该密切相关。
附：英文原文
Title: Permafrost extent sets drainage density in the Arctic
Author: Del Vecchio, Joanmarie, Palucis, Marisa C., Meyer, Colin R.
Issue&Volume: 2024-2-1
Abstract: Amplified warming of high latitudes and rapid thaw of frozen ground threaten permafrost carbon stocks. The presence of permafrost modulates water infiltration and flow, as well as sediment transport, on soil-mantled slopes, influencing the balance of advective fluvial processes to diffusive processes on hillslopes in ways that are different from temperate settings. These processes that shape permafrost landscapes also impact the carbon stored on soil-mantled hillslopes via temperature, saturation, and slope stability such that carbon stocks and landscape morphometry should be closely linked. We studied ＞69,000 headwater basins between 25° and 90 °N to determine whether the thermal state of the soil sets the balance between hillslope (diffusive) and fluvial (advective) erosion processes, as evidenced by the density of the channel networks (i.e., drainage density) and the proportion of convex to concave topography (hillslopes and river valleys, respectively). Watersheds within permafrost regions have lower drainage densities than regions without permafrost, regardless of watershed glacial history, mean annual precipitation, and relief. We find evidence that advective fluvial processes are inhibited in permafrost landscapes compared to their temperate counterparts. Frozen soils likely inhibit channel development, and we predict that climate warming will lower incision thresholds to promote growth of the channel network in permafrost landscapes. By demonstrating how the balance of advective versus diffusive processes might shift with future warming, we gain insight into the mechanisms that shift these landscapes from sequestering to exporting carbon.
DOI: 10.1073/pnas.2307072120
Source: https://www.pnas.org/doi/abs/10.1073/pnas.2307072120