A Model for the Formation of Eskers
A Model for the Formation of Eskers
复制标题
DOI：
10.1029/2019gl082304
复制
发表时间：
2019-06-28
影响因子：
5.2
通讯作者：
Creyts, Timothy T.
中科院分区：
文献类型：
--
作者：
Hewitt, Ian J.;Creyts, Timothy T.
我们建立了一个数学模型，通过冰下充水隧道口附近沉积物的连续沉积来研究埃斯克形成。我们假设一个退缩的冰盖边缘，并规定融水和沉积物供应渠道化冰下排水系统。冰下水道的水动力学模型的横截面受冰壁融化、蠕动闭合和沉积物沉积的影响。携沙能力通常在下游增加，然后在边缘附近迅速下降，这表明大多数沉积发生在那里。这可能导致边缘附近的阻塞，这被增强的熔化所抵消，以保持通道开放。该模型表明，沉积速率的变化与泥沙供应大致平方和水通量成反比。对于给定的沉积物供应，该模型表明，埃斯克形成是最普遍的较小的渠道。更大的冰盖融化速率可能会产生更紧密的eskers，但横截面更小。
We develop a mathematical model for esker formation by the continuous deposition of sediments near the mouth of water-filled subglacial tunnels. We assume a retreating ice sheet margin and prescribe meltwater and sediment supply to a channelized subglacial drainage system. The hydrodynamic model for the subglacial channel has its cross section governed by wall melting, creep closure, and sediment deposition. Sediment-carrying capacity typically increases downstream, before decreasing rapidly near the margin, suggesting that most deposition occurs there. This can lead to choking near the margin, which is offset by enhanced melting to keep the channel open. The model shows that the deposition rate varies roughly quadratically with sediment supply and inversely with water flux. For given sediment supply, the model suggests esker formation is most prevalent in smaller channels. Larger ice sheet melt rates likely produce more closely spaced eskers, but with smaller cross sections.