Effects of Low Water Temperature on Longshore Sediment Transport on a Subarctic Beach, Hudson Bay, Canada

在亚北极海滩，哈德森湾和加拿大地区低水温对沿岸输沙的影响
作者：Arnaud Hequette and Patrick Tremblay
Department: University du Littoral Coted’Opale 32 Avenue Foch 62930 Wimereux, France
单 位： 法国滨海大学
Journal：Journal of Coastal Research
杂 志： 海岸研究杂志
Volumes：25
Date：January 2009
日 期：2009年1月
Page number：171–180
Key words: Longshore sediment transport, water temperature, fluid viscosity, subarctic beach, Hudson Bay.
关键词： 沿岸输沙，水温，流体粘度，亚北极地区海滩，哈德森湾
Abstract： Measurements of longshore sand transport, wave breaker height, longshore current velocity, and water temperature and salinity were carred out on a subarctic beach under varying water temperature conditions during summer and fall. Water temperature during summer varied from 9 C to17 C, while temperature ranged from 1.75 C to1.25 C during the fall experiments. During periods with low water temperatures, considerably higher rates in both bedload and suspended sediment transport were observed compared with the results obtained during summer with similar wave heights and current velocities. The increase in suspended sediment transport associated with low water temperatures is likely due to lower sediment fall velocities resulting from significant increases in fluid kinematic viscosity, which ranged from 1.1 to 1.37 10 6 m2 s 1 in summer and from 1.74 to 1.92 10 6 m2 s 1 in the fall. Less but still significant increase in bedload sediment transport in cold water is interpreted to be the result of temperature-induced variations in fluid viscosity that affect turbulence and boundary layer dynamics as well as bed configuration. Frazil ice occurred on some occasions during the fall experiments, but with the small number of samples collected when frazil ice crystals were present in the water column, it was not possible to establish a relationship between sediment transport rates and the presence or absence of ice. Our results nevertheless indicate that in cold climate regions extremely low water temperatures may cause a substantial increase of coastal sediment transport.
摘要：在夏季和秋季不同的水温条件下测量亚北极地区海滩的沿岸输沙，破波高度，沿岸流流速和水的温度与盐度。夏季水温从9℃到17℃，而秋季水温从1.75℃到1.25℃。在秋季的实验数据中，即使出现于夏季相似的波高、流速关系，但在推移质和悬移质输沙率上，低水温明显效率较高。引起这种现象的因素可能是水温的降低增加了流体的运动粘度，导致沉降速率下降而引起泥沙输移效率增加。夏季沉降速率为1.1至1.37*106m2s-1,秋季沉降速率为1.74至1.92*106m2s-1。少量的温度变化引起了流体粘度的变化，影响了湍流边界层动力学以及床面形态，从而仍然可以引起显著的推移质输沙变化。在某种情况下出现的冻结现象出现在秋季时间中，少数的样本中含有结晶水，液态水和结晶水的并存导致水沙关系较难确立。但我们的研究结果表明，在气候寒冷地区的较低的水温条件可能导致大量增加沿岸泥沙输移。
链接：http://www.bioone.org/doi/abs/10.2112/07-0906.1