Interactions between stationary waves and ice sheets: linear versus nonlinear atmospheric response
Interactions between stationary waves and ice sheets: linear versus nonlinear atmospheric response
复制标题
驻波和冰盖之间的相互作用：线性与非线性大气响应
DOI：
10.1007/s00382-011-1004-6
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发表时间：
2012
期刊：
影响因子：
4.6
通讯作者：
M. Löfverström
中科院分区：
文献类型：
--
作者：
J. Liakka;J. Nilsson;M. Löfverström
本研究利用一个耦合线性和完全非线性干燥大气原始方程模式的热力冰盖模式，研究了地形强迫大气驻波与大陆尺度冰盖之间的相互作用。重点放在驻波引起的消融如何反馈到冰盖上。模拟是在理想化的“北美”大陆上，胚胎冰块演化成平衡的冰盖。在耦合到线性大气模式下，平衡冰盖主要由驻波波长与纬向大陆范围之比控制。当这一比率接近2时，冰盖的质心向东移动，其形状大致让人想起LGM的Laurentide冰盖。然而，对于与大陆范围相当的波长，冰缘在中部大陆向赤道延伸很远，但在东部海岸附近向极地移动。值得注意的是，与非线性大气模式的耦合产生的平衡冰盖实际上与非耦合模拟中获得的冰盖相同，即具有纬向南缘的对称冰盖。因此，大气响应的线性程度应该控制地形强迫的驻波能在多大程度上重组冰盖的结构。如果驻波响应是线性的，目前的结果表明，过去冰盖的空间重建可以提供一些关于盛行的纬向平均大气环流的信息。
This study examines the mutual interaction between topographically-forced atmospheric stationary waves and continental-scale ice sheets using a thermomechanical ice-sheet model coupled to a linear as well as a fully-nonlinear dry atmospheric primitive equation model. The focus is on how the stationary-wave induced ablation feeds back on the ice sheet. Simulations are conducted in which an embryonal ice mass, on an idealised “North American” continent, evolves to an equilibrium ice sheet. Under the coupling to the linear atmospheric model, the equilibrium ice sheet is primarily controlled by the ratio between the wavelength of the stationary waves and the zonal continental extent. When this ratio is near two, the ice sheet has its center of mass shifted far eastward and its shape is broadly reminiscent of the Laurentide ice sheet at LGM. For wavelengths comparable to the continental extent, however, the ice margin extends far equatorward on the central continent but is displaced poleward near the eastern coast. Remarkably, the coupling to the nonlinear atmospheric model yields equilibrium ice sheets that are virtually identical to the ones obtained in uncoupled simulations, i.e. a symmetric ice sheet with a zonal southern margin. Thus, the degree of linearity of the atmospheric response should control to what extent topographically-forced stationary waves can reorganise the structure of ice sheets. If the stationary-wave response is linear, the present results suggest that spatial reconstructions of past ice sheets can provide some information on the zonal-mean atmospheric circulation that prevailed.