Ocean bathymetry and mantle convection: 2. Small‐scale flow
Ocean bathymetry and mantle convection: 2. Small‐scale flow
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DOI：
10.1029/jb093ib09p10481
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发表时间：
1988-09
影响因子：
--
通讯作者：
G. Davies
中科院分区：
文献类型：
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作者：
G. Davies
数值模型表明，低层岩石圈边界层的不稳定性并不能阻止岩石圈下沉，因此不能解释所谓的老海底变平现象。无论如何，旧海底沉降的缓慢更好地被视为一种扰动，可能是由于羽流。此外，如果边界层的不稳定性，或任何形式的上地幔对流，输送了大部分的热量从老海底出现，将有普遍的，大幅度的局部测深，重力和大地水准面异常。除了扩张中心附近的一些低振幅、线性大地水准面异常之外，此类异常从未令人信服地与冷却岩石圈和热点轨迹的影响区分开来。水平尺度小于板块尺度的地幔对流的唯一模式，有相当明确的证据是热点羽流和一些可能的近脊边界层不稳定性。热点传输不到地球热通量的10%，其他小尺度模式可能不太重要。
Numerical models demonstrate that a boundary layer instability of the lower lithosphere does not stop the lithosphere from subsiding, and so it cannot explain the so-called flattening of old seafloor. The slower subsidence of the old seafloor is in any case better seen as a perturbation, probably due to plumes. Furthermore, if a boundary layer instability, or any mode of upper mantle convection, transported most of the heat emerging from old seafloor, there would be pervasive, large-amplitude local bathymetrie, gravity, and geoid anomalies. Such anomalies have never been convincingly differentiated from the effects of the cooling lithosphere and hotspot tracks, except for some low-amplitude, linear geoid anomalies near spreading centers. The only modes of mantle convection with horizontal scales less than those of plates for which there is reasonably clear evidence are hotspot plumes and some possible near-ridge boundary layer instabilities. Hotspots transport less than about 10% of the Earth's heat flux, and other small-scale modes are probably less important.