Turbulence and Mixing in the Arctic Ocean's Amundsen Gulf

Scheifele Benjamin; Waterman Stephanie; Carpenter Jeffrey R.

摘要

This study uses CTD and microstructure measurements of shear and temperature from 348 glider profiles to characterize turbulence and turbulent mixing in the southeastern Beaufort Sea, where turbulence observations are presently scarce. We find that turbulence is typically weak: the turbulent kinetic energy dissipation rate epsilon has a median value (with 95% confidence intervals in parentheses) of 2.3 [2.2, 2.4] x 10(-11) W kg(-1) and is less than 1.0 x 10(-10) W kg(-1) in 68% of observations. Variability in epsilon spans five orders of magnitude, with indications that turbulence is bottom enhanced and modulated in time by the semidiurnal tide. Stratification is strong and frequently damps turbulence, inhibiting diapycnal mixing. Buoyancy Reynolds number estimates suggest that turbulent diapycnal mixing is unlikely in 93% of observations; however, a small number of strongly turbulent mixing events are disproportionately important in determining net buoyancy fluxes. The arithmetic mean diapycnal diffusivity of density is 4.5 [2.3, 14] x 10(-6) m(2) s(-1), three orders of magnitude larger than that expected from molecular diffusion. Vertical heat fluxes are modest at O(0.1) W m(-2), of the same order of magnitude as those in the Canada Basin double-diffusive staircase, however, staircases are generally not observed. Despite significant heat present in the Pacific Water layer in the form of a warm-core mesoscale eddy and smaller, O(1) km, temperature anomalies, turbulent mixing was found to be too low to release this heat to shallower depths.

机译：本研究使用来自348滑翔机轮廓的CTD和微观结构测量，以表征东南博福特海的湍流和湍流混合，其中湍流观察目前稀缺。我们发现湍流通常是薄弱的：湍流动能耗散速率εε均具有2.3 [2.2,2.4]×10（-11）W kg（-1）的中值值（括号中的95％置信区间），并且较少在68％的观察中，比1.0 x 10（-10）W kg（-1）。 epsilon的变异性跨越五个数量级，具有湍流是底部增强和通过半衰期潮汐调节的突发性。分层强烈，经常潮湿湍流，抑制十进性混合。浮力雷诺数估计表明，93％的观察结果中，动荡的十进性混合不太可能;然而，在确定净浮力通量的情况下，少量强烈湍流的混合事件在不成比例地是重要的。算术平均密度的二韵偏差为4.5 [2.3,14]×10（2）S（2）S（2）S（-1），大小大于分子扩散预期的数量级。垂直热通量在O（0.1）W m（-2）中适度，与加拿大盆地双扩散楼梯中相同的数量级，然而，通常未观察到楼梯。尽管太平洋水层中存在着暖核Mescle涡流和更小的形式的显着热量，但o（1）km，温度异常，发现湍流混合太低，不能释放这种热量以较浅。

Turbulence and Mixing in the Arctic Ocean's Amundsen Gulf

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