Deep Sea Research Part I: Oceanographic Research Papers ( IF 2.4 ) Pub Date : 2020-11-12 , DOI: 10.1016/j.dsr.2020.103424 Alvarinho J. Luis , Kiledar S. Tomar , Ashutosh Prasad
This study addresses the hydrodynamics inferred from the expendable conductivity-temperature-depth (XCTD) observations carried out in the southwestern Indian Ocean sector of the Southern Ocean along two transects: the Lazarev Sea to Cape Town (track-1) and Cape Town to Prydz bay (track-2) during the austral summer of 2019. The vertical temperature and salinity structures revealed an eddy extending up to 44°S (45°S) on track-1 (track-2). South of the eddy, we encountered frontal zones extending to 53°S (59°S) on track-1(track-2). The frontal locations identified from XCTD and satellite-based sea surface temperature and absolute dynamic topography coincided, with the latter placed within the latitudinal limits identified from the XCTD data. Meandering of the Polar front (PF), the southern Antarctic Circumpolar Current (ACC) Front, and the Southern Boundary of the ACC was observed from 90 to 550 km southward. The Winter Water which was confined to the south of 50°S was detected at deeper depth (~350 m) on track-1, compared to a depth of 100 m on track-2, and its thickness varied from zero to 1.2 m on track-1 and from 0.5 to 2.5 m on track-2. The vertical thermohaline structure revealed the northward subduction of a mixture of Antarctic Surface Water and Subantarctic Surface Water up to 45.5°S and down to 500 (320) m on track-1 (track-2). The volume transport (relative to 1000 m) accounted for 87% of that estimated in the literature (90 ± 2.4 Sv) and 34.7 Sv across track-1 and -2, respectively. It was found that 70% of the volume transport was confined to the ACC frontal region and 26% of the total transport occurred in the 100–500 m slab. The cumulative heat and salt content was 2% and 1.2% higher between 39° and 66°S, compared to that estimated from 2008 data along track-1. We used a satellite-based absolute dynamic topography field, to trace out Agulhas current (AC) and its retroflection current, and eddies detached from the meanders. A higher dynamic topography gradient across the polar front facilitates enhanced transport. Sea surface temperature fields revealed that the meanders in the AC propagate southwest with an offshore extent of 30–300 km.
中文翻译:
2019南方夏季开普敦和南极之间the流点的水动力
这项研究解决了从沿印度洋西南部印度洋海域沿两个样带进行的消耗性电导率-温度-深度(XCTD)观测推导的流体动力学:这两个样带是:拉扎列夫海至开普敦(track-1)和开普敦至Prydz在2019年的夏季,该区域位于海湾2号轨道。垂直温度和盐度结构显示出一条涡流延伸至轨道1(轨道2)上的44°S(45°S)。在涡流以南,我们在第1轨道(第2轨道)遇到了延伸至53°S(59°S)的额叶区域。从XCTD和卫星海表温度以及绝对动态地形确定的正面位置重合,后者位于从XCTD数据确定的纬度范围内。极地前缘(PF),南极南极洲极地电流(ACC)前缘蜿蜒而行,在向南90至550公里处观察到了ACC的南边界。与轨道2上100 m的深度相比,在轨道1上更深的深度(〜350 m)探测到了局限于50°S以南的冬季水,其厚度在0到1.2 m范围内变化。轨道1和轨道2上的0.5至2.5 m。垂直的热盐结构揭示了南极地表水和亚南极地表水的混合物向北俯冲,在轨道1(轨道2)上,南极地表水和南极地表水的最高温度分别为45.5°S和低至500(320)m。相对于轨道1和-2的体积传输(相对于1000 m)分别占文献中估计的体积传输的90%(90±2.4 Sv)和34.7 Sv。研究发现,体积运输的70%限于ACC额叶区域,总运输的26%发生在100-500 m的平板中。在39°和66°S之间,累积的热量和盐分含量分别比2008年沿轨道1的数据估计的高2%和1.2%。我们使用了基于卫星的绝对动态地形场,以找出Agulhas电流(AC)及其回射电流,以及从弯道分离出来的涡流。越过极地前缘的较高的动态地形梯度有助于增强运输。海面温度场显示,AC中的河曲向西南传播,离岸范围为30-300 km。越过极地前缘的较高的动态地形梯度有助于增强运输。海面温度场显示,AC中的河曲向西南传播,离岸范围为30-300 km。越过极地前缘的较高的动态地形梯度有助于增强运输。海面温度场显示,AC中的河曲向西南传播,离岸范围为30-300 km。