Multiple Regimes and Low-Frequency Variability in the Quasi-Adiabatic Overturning Circulation
Multiple Regimes and Low-Frequency Variability in the Quasi-Adiabatic Overturning Circulation
复制标题
准绝热翻转环流的多态性和低频变化
DOI：
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
P. Cessi
中科院分区：
文献类型：
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作者：
C. Wolfe;P. Cessi
©2015美国气象学会。当内部混合很弱时，海洋可以支持在北半球和高纬度南绕极海峡中露出的等同轴上的半球间翻转环流。这个翻转的单体参与了盐平流反馈，抵消了北部高纬度地区由降水引起的地表清新。最终的结果是增加了两个半球之间共享的等轴线范围，这加强了翻转的环流。然而，如果北半球的降水量足够超过南半球的降水量，倾覆的单体就会坍塌，取而代之的是一个向相反方向循环的单体，其南端的终点是海峡的赤道方向。这个倒置的单元格比正向单元格更浅、更弱，并以扩散的方式维持。在有限的参数范围内，存在淡水滞回现象，并且同一强迫下存在多个倾覆区域。根据定义，这些多个区域对于有限幅度扰动是不稳定的，因为足够大的扰动可以影响从一个区域到另一个区域的过渡。这两个颠覆制度在数十年和多中心的时间尺度上都显示出明显的、几乎是周期性的温盐变化。这种年代际振荡表现为北半球环流，由地表温盐不稳定所驱动。多中心振荡具有半球间环状振荡的特征。这些振荡通过提供有限幅度扰动的内部来源来协调颠覆制度之间的过渡。随着扩散系数的减小，反向单元变得更弱，因此对给定的微扰幅度不太稳定。这会导致磁滞的宽度随着扩散系数的减小而减小。
© 2015 American Meteorological Society. When interior mixing is weak, the ocean can support an interhemispheric overturning circulation on isopycnals that outcrop in both the Northern Hemisphere and a high-latitude southern circumpolar channel. This overturning cell participates in a salt-advection feedback that counteracts the precipitation-induced surface freshening of the northern high latitudes. The net result is an increase in the range of isopycnals shared between the two hemispheres, which strengthens the overturning circulation. However, if precipitation in the Northern Hemisphere sufficiently exceeds that in the Southern Hemisphere, the overturning cell collapses and is replaced by a cell circulating in the opposite direction, whose southern end point is equatorward of the channel. This reversed cell is shallower and weaker than its forward counterpart and is maintained diffusively. For a limited range of parameters, freshwater hysteresis occurs and multiple overturning regimes are found for the same forcing. These multiple regimes are, by definition, unstable with regard to finite-amplitude disturbances, since a sufficiently large perturbation can affect a transition from one regime to the other. Both overturning regimes show pronounced, nearly periodic thermohaline variability on multidecadal and multicentennial time scales. The multidecadal oscillation is expressed in the North Hemisphere gyre and driven by a surface thermohaline instability. The multicentennial oscillation has the character of an interhemispheric loop oscillation. These oscillations mediate transitions between overturning regimes by providing an internal source of finite-amplitude disturbances. As the diffusivity is reduced, the reverse cell becomes weaker and thus less stable to a given perturbation amplitude. This causes the width of the hysteresis to decrease with decreasing diffusivity.
影响因子：
3.5
作者：
S. Waterman;K. Polzin;A. N. Garabato;K. Sheen;A. Forryan
通讯作者：
S. Waterman;K. Polzin;A. N. Garabato;K. Sheen;A. Forryan
存在涡流时翻转环流的多年代际变化
影响因子：
3.5
作者：
Huck T
通讯作者：
Huck T
机械驱动经向翻转环流与温盐强迫和多重平衡理论的协调
影响因子：
4.6
作者：
Johnson H
通讯作者：
Johnson H