Research of characteristics of turbulent mixing in the Prydz Bay with intrusion of modified circumpolar deep water
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摘要: 基于中国第28、29和31次南极科学考察中的CTD数据，利用Thorpe尺度方法计算了普里兹湾及其附近海域湍动能耗散率，分析了其分布特征，并对当地的水团结构进行研究。结果表明，普里兹湾及其附近海域中，前两个航次观测中次表层湍动能耗散率强度在陆架坡折区域达到最大。在水团分布方面，在第28和29航次中均观测到了变性绕极深层水陆架入侵现象，水团分别向上涌升至海表以下100 m和200 m深度，向南均可达到67.5°S处。普里兹湾陆架坡折区域次表层湍动能耗散率强度分布与当地水团结构存在良好对应关系。研究认为变性绕极深层水入侵陆架，会使该深度水体变得不稳定，发生水体交换现象，最终造成该区域湍流混合强度加强。Abstract: Based on the CTD data from the 28th, 29th and 31st Chinese Antarctic Expedition cruises, we calculated dissipation rate of turbulent kinetic energy by using Thrope scale method, and analyzed the distribution characteristics of the dissipation rate and the structure of water masses in the Prydz Bay and its adjacent waters. Results show that the subsurface dissipation rate intensity of turbulent kinetic energy in the first two cruises reach maximum on the shelf break of Prydz Bay. Moreover, we compared the distribution of water masses among the three cruises and found intrusion of the modified circumplar deep water into the shelf happened on the 28th and 29th cruises. The the modified circumplar deep water could reach the depth of 100 m and 200 m on the cruise of 28th and 29th, respectively, and can extend southward to 67.5°S. Furthermore, the distribution of subsurface dissipation rate of turbulent kinetic energy on the shelf break of Prydz Bay are well related to the structure of local water masses. Therefore, the intrusion of the modified circumplar deep water into the shelf could induce instability of the local waters, promote water exchange and finally enhance local turbulent mixing.
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图 1 普里兹湾及附近海域站位分布
a. 第28航次；b. 第29航次；c. 第31航次
Fig. 1 Location of the stations in the Prydz Bay and the adjacent sea
a. The 28th cruise; b. the 29th cruise; c. the 31th cruise
图 2 73°E断面湍动能耗散率垂直分布 （ε 的单位：W/kg）
a. 第28航次；b. 第29航次；c. 第31航次
Fig. 2 Vertical distribution of dissipation rate of turbulent kinetic energy on the 73°E section (unit of ε is W/kg)
a. The 28th cruise; b. the 29th cruise; c. the 31th cruise
图 3 67.25°S断面湍动能耗散率垂直分布（ ε 的单位：W/kg）
a. 第29航次；b. 第31航次
Fig. 3 Vertical distribution of dissipation rate of turbulent kinetic energy on the 67.25°S section (unit of ε is W/kg)
a. The 29th cruise; b. the 31th cruise
图 4 湍动能耗散率深度平均水平分布（ ε 的单位：W/kg）
a. 第28航次；b. 第29航次；c. 第31航次
Fig. 4 Horizontal distribution of dissipation rate of turbulent kinetic energy (unit of ε is W/kg)
a. The 28th cruise; b. the 29th cruise; c. the 31th cruise
图 5 73°E断面各站位位温、盐度和位势密度剖面
a−c. 第28航次；d−f. 第29航次；g−i. 第31航次
Fig. 5 Vertical profiles of potential temperature, salinity and potential density of stations on the 73°E section
a−c. The 28th cruise; d−f. the 29th cruise; g−i. the 31th cruise
图 6 67.25°S断面各站位位温、盐度和位势密度剖面
a−c. 第29航次；d−f. 第31航次
Fig. 6 Vertical profiles of potential temperature, salinity and potential density of stations on the 67.25°S section
a−c. The 29th cruise; d−f. the 31th cruise
图 7 第29和31次南极科学考察普里兹湾及附近海域T−S图
Fig. 7 T−S diagram during the 29th and 31st Chinese National Antarctic Research Expedition cruises in the Prydz Bay and the adjacent sea
图 8 73 °E断面温盐密分布
a−c. 第28航次；d−f. 第29航次；g−i. 第31航次
Fig. 8 Distribution of potential temperature, salinity and potential density on the 73°E section
a−c. The 28th cruise; d−f. the 29th cruise; g−i. the 31th cruise
图 9 67.25°S断面温盐密分布
a−c. 第29航次；d−f. 第31航次
Fig. 9 Distribution of potential temperature, salinity and potential density on the 67.25 °S section
a−c. The 29th cruise; d−f. the 31th cruise
图 10 67°S，73°E处的潮流流速时间序列
a. 第28航次；b. 第29航次；c. 第31航次。蓝色实线为观测时间点
Fig. 10 Time series of tidal flow velocity at 67°S, 73°E
a. The 28th cruise; b. the 29th cruise; c. the 31th cruise. The blue line denotes observation time
图 11 67°S，73°E处的潮高时间序列
a. 第28航次；b. 第29航次；c. 第31航次。蓝色实线为观测时间点
Fig. 11 Time series of tidal level at 67°S, 73°E
a. The 28th cruise; b. the 29th cruise; c. the 31th cruise. The blue line denotes observation time
图 12 73°E断面的混合层深度分布
a. 第28航次；b. 第29航次；c. 第31航次
Fig. 12 Distribution of mixing layer depth on the 73°E section
a. The 28th cruise; b. the 29th cruise; c. the 31th cruise
表 1 普里兹湾海域主要水团特征
Tab. 1 The characteristics of water masses in the Prydz Bay and the adjacent sea
水团名称 温度/℃ 盐度 夏季表层水 T≥−1.50 S<34.20 冬季水 T<−1.50 34.20<S<34.50 绕极深层水 0.50≤T≤2.00 34.50≤S≤34.75 陆架水 −1.9<T<−1.50 S>34.20 南极底层水 T<0 34.60<S<34.72 冰架水 T<−1.92 34.40<S<34.60 
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