影响坦帕湾水交换的三种因素

本文利用高分辨率数值模型,以2001年秋季为例,详细分析了影响坦帕湾水交换的三种因素:潮汐、河流和风。论文共设置了三组实验,驱动力分别为潮汐,潮汐和河流,潮汐、河流和风。模拟结果显示:只有潮汐作用时,由于坦帕湾潮汐较弱,潮程较短,坦帕湾与其临近海域的水交换主要发生在湾口附近;当潮汐和河流共同作用时,由于河流和湾口海水盐度的不同形成了水平密度梯度,在其产生的水平密度梯度力的作用下,坦帕湾形成了表层流向湾外、底层流向湾内的重力环流,从而加强了坦帕湾跟其临近海域的水交换;由湾内指向湾外方向(2001年秋季平均)的风应力加强了流向湾外的表层流,同时水位梯度力发生了反转,变成了由湾口指向湾顶,这加强了流向湾内的底层流,表层流和底层流的加强最终促进了坦帕湾跟其临近海域的水交换;在航道处,水深较深瑞利数较大,该处的重力环流较强,这使得相对于两侧的浅水区,航道处的水交换能力较强。此外,文章还分析了坦帕湾水交换的空间差异,在Old Tampa Bay的西侧和北侧,滞留时间最长,水交换能力最弱。为减少海洋生态灾害发生,今后应重点加强对该地区的生态环境保护。

THREE FACTORS AFFECTING THE FLUSHING IN THE TAMPA BAY

A validated high-resolution model is used to investigate the flushing of Tampa Bay in the autumn of 2001. To determine how the three factors, tides, rivers, and winds, impact the residence time of Tampa Bay, three experiments forced by tides; tides plus rivers; and tides plus rivers, plus winds are designed. For tides alone, the flushing of Tampa Bay is extremely weak due to the weak tide and short tidal excursion. Gravitational circulation associated with the buoyancy and momentum inputs sourced from estuaries is of importance for the establishment of classic estuarine circulation with a seaward surface flow and a landward subsurface flow, and hence the flushing of Tampa Bay. Winds are also a primary agent for the fully three-dimensional estuarine circulation of Tampa Bay, and could significantly enhance the flushing. The shipping channel is deeper than its both sides, suggesting that the Rayleigh number and gravitational circulation at channel are larger, resulting in a relative stronger flushing. The longest residence times are shown in the north and west Old Tampa Bay, suggesting that these areas should be vulnerable ecosystems which more efforts are needed to protect.