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首页> 外文期刊>Journal of Physical Oceanography >Topographic Influence on Baroclinic Instability and the Mesoscale Eddy Field in the Northern North Atlantic Ocean and the Nordic Seas
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Topographic Influence on Baroclinic Instability and the Mesoscale Eddy Field in the Northern North Atlantic Ocean and the Nordic Seas

机译：地形对北大西洋北部和北欧海斜压不稳定和中尺度涡流场的影响

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摘要

A weak planetary vorticity gradient and weak density stratification in the northern North Atlantic and Nordic seas lead to time-mean currents that are strongly guided by bottom topography. The topographic steering sets up distinct boundary currents with strong property fronts that are prone to both baroclinic and barotropic instability. These instability processes generate a macroturbulent eddy field that spreads buoyancy and other tracers out from the boundary currents and into the deep basins. In this paper we investigate the particular role played by baroclinic instability in generating the observed eddy field, comparing predictions from linear stability calculations with diagnostics from a nonlinear eddy-permitting ocean model hindcast. We also look into how the bottom topography impacts instability itself. The calculations suggest that baroclinic instability is a consistent source of the eddy field but that topographic potential vorticity gradients impact unstable growth significantly. We also observe systematic topographic effects on finite-amplitude eddy characteristics, including a general suppression of length scales over the continental slopes. Investigation of the vertical structure of unstable modes reveal that Eady theory, even when modified to account for a bottom slope, is unfit as a lowest-order model for the dynamics taking place in these ocean regions.
机译：北大西洋北部和北欧海域的行星涡度梯度较弱且密度分层较弱，导致时均潮流受到底部地形的强烈引导。地形转向建立了具有强特性前沿的独特边界流，这些特性流容易引起斜压和正压不稳定。这些不稳定性过程产生了一个大湍流的涡流场，该涡流场将浮力和其他示踪剂从边界流扩散到深海盆地。在本文中，我们将斜压不稳定性在产生观测涡流中所起的特殊作用进行了比较，将线性稳定性计算的预测结果与非线性涡旋允许海洋模型后兆的诊断结果进行了比较。我们还将研究底部地形如何影响不稳定性本身。计算表明，斜压不稳定是涡旋场的一致来源，但是地形势涡度梯度对不稳定的增长有显着影响。我们还观察到了对有限振幅涡旋特征的系统地形影响，包括对大陆斜坡长度尺度的普遍抑制。对不稳定模式的垂直结构的研究表明，即使将Eady理论修改为考虑了底坡度，也不适合作为这些海洋区域中发生的动力学的最低阶模型。

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