Eddy-Induced Modulation of Turbulent Dissipation over Rough Topography in the Southern Ocean
Eddy-Induced Modulation of Turbulent Dissipation over Rough Topography in the Southern Ocean
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DOI：
10.1175/jpo-d-12-0222.1
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发表时间：
2013-11-01
影响因子：
3.5
通讯作者：
Waterman, Stephanie
中科院分区：
文献类型：
--
作者：
Brearley, J. Alexander;Sheen, Katy L.;Waterman, Stephanie
中尺度涡旋是海洋环流的普遍特征，但对其能量耗散的过程仍知之甚少。有一种假说认为，强烈的地转流与粗糙的海底地形的相互作用影响了涡流和内波之间的能量传递，这些波的破碎引起局部升高的耗散集中在海底附近。本研究使用水文和速度数据，从1年的系泊集群部署在南大洋来测试这一假设。系泊位于一个小的（类似于10公里）的地形障碍物以东的德雷克海峡在一个区域的高涡动动能，并配备了ADCP在2800米的深度，内波剪切方差和耗散率进行了计算。检查的ADCP时间序列显示向上传播的内波能量和显着的相关性（r = 0.45）之间的剪切方差水平和亚惯性近底流速度的优势。强近底流的周期与底部1500 m处涡流引起的界面形式应力的收敛增加相吻合。内波能量辐射的预测从理论上使用测量的近底流速，和波辐射的平均值（5.3 mW m（-2））是足够的支持从ADCP计算的耗散功率。辐射和耗散功率之间也观察到一个显着的时间相关性。鉴于南大洋普遍存在强涡流和粗糙地形，从涡流到内波能量的转移可能是关闭海洋能量收支的一个重要条件。
Mesoscale eddies are universal features of the ocean circulation, yet the processes by which their energy is dissipated remain poorly understood. One hypothesis argues that the interaction of strong geostrophic flows with rough bottom topography effects an energy transfer between eddies and internal waves, with the breaking of these waves causing locally elevated dissipation focused near the sea floor. This study uses hydrographic and velocity data from a 1-yr mooring cluster deployment in the Southern Ocean to test this hypothesis. The moorings were located over a small (similar to 10 km) topographic obstacle to the east of Drake Passage in a region of high eddy kinetic energy, and one was equipped with an ADCP at 2800-m depth from which internal wave shear variance and dissipation rates were calculated. Examination of the ADCP time series revealed a predominance of upward-propagating internal wave energy and a significant correlation (r = 0.45) between shear variance levels and subinertial near-bottom current speeds. Periods of strong near-bottom flow coincided with increased convergence of eddy-induced interfacial form stress in the bottom 1500 m. Predictions of internal wave energy radiation were made from theory using measured near-bottom current speeds, and the mean value of wave radiation (5.3 mW m(-2)) was sufficient to support the dissipated power calculated from the ADCP. A significant temporal correlation was also observed between radiated and dissipated power. Given the ubiquity of strong eddy flows and rough topography in the Southern Ocean, the transfer from eddy to internal wave energy is likely to be an important term in closing the ocean energy budget.