Upper-Ocean Eddy Heat Flux across the Antarctic Circumpolar Current in Drake Passage from Observations: Time-Mean and Seasonal Variability
Upper-Ocean Eddy Heat Flux across the Antarctic Circumpolar Current in Drake Passage from Observations: Time-Mean and Seasonal Variability
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DOI：
10.1175/jpo-d-19-0266.1
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发表时间：
2020-09-01
影响因子：
3.5
通讯作者：
Sprintall, Janet
中科院分区：
文献类型：
--
作者：
Gutierrez-Villanueva, Manuel O.;Chereskin, Teresa K.;Sprintall, Janet
涡热通量在南大洋经向翻转环流中发挥着重要作用，为德雷克海峡纬度地形上方和埃克曼层下方的极地热传输提供了唯一机制。模型和观测结果表明，德雷克海峡是南大洋少数几个热点之一，那里穿过南极绕极流（ACC）的涡流热传输得到增强。然而，量化这种传输及其空间分布和时间变化仍然是一个悬而未决的问题。这项研究使用独特的上层海洋温度和速度横断面的 20 年时间序列，以前所未有的水平分辨率，将涡流热通量量化为 ACC 流线的函数。涡流热通量是使用时均流线和时变流线来计算的，以隔离跨 ACC 的动态重要热通量分量。随时间变化的流线提供了跨 ACC 分量的最佳估计，因为它们跟踪 ACC 前沿的移动和蜿蜒。深度积分（0-900 m）跨流涡流热通量在亚南极锋南侧（20.10 +/- 0.05GWm(-1)）向极地方向最大，并向南减小，在极地锋中变得统计上不显着，表明亚南极锋以南的热辐合。该时间序列提供了一个难得的机会来探索涡流热通量的季节性循环。极地锋区的向极涡流热通量在南半球秋冬季节增强，表明涡流驱动的上升流存在季节性变化，从而导致经向翻转环流。
Eddy heat flux plays a fundamental role in the Southern Ocean meridional overturning circulation, providing the only mechanism for poleward heat transport above the topography and below the Ekman layer at the latitudes of Drake Passage. Models and observations identify Drake Passage as one of a handful of hot spots in the Southern Ocean where eddy heat transport across the Antarctic Circumpolar Current (ACC) is enhanced. Quantifying this transport, however, together with its spatial distribution and temporal variability, remains an open question. This study quantifies eddy heat flux as a function of ACC streamlines using a unique 20-yr time series of upper-ocean temperature and velocity transects with unprecedented horizontal resolution. Eddy heat flux is calculated using both time-mean and time-varying streamlines to isolate the dynamically important across-ACC heat flux component. The time-varying streamlines provide the best estimate of the across-ACC component because they track the shifting and meandering of the ACC fronts. The depth-integrated (0-900 m) across-stream eddy heat flux is maximum poleward in the south flank of the Subantarctic Front (20.10 +/- 0.05GWm(-1)) and decreases toward the south, becoming statistically insignificant in the Polar Front, indicating heat convergence south of the Subantarctic Front. The time series provides an uncommon opportunity to explore the seasonal cycle of eddy heat flux. Poleward eddy heat flux in the Polar Front Zone is enhanced during austral autumn-winter, suggesting a seasonal variation in eddy-driven upwelling and thus the meridional overturning circulation.