Variability of Antarctic Intermediate Water south of Australia and its relationship with frontal waves

• Published in: Science China Earth Sciences
• Main Authors: Zhang LinLin, Yan XiaoMei, Sun Che, Hu DunXin
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2016
• Subjects: Antarctic Intermediate Water (Aaiw); Stream-coordinates; Frontal Wave; Eof; Antarctic; Southern Ocean; The Antarctic; Antarc*
• Online Access: http://ir.qdio.ac.cn/handle/337002/135875; https://doi.org/10.1007/s11430-015-0179-5

A streamfunction EOF method is applied to a time series of hydrographic sections in the Southern Ocean south of Australia to study water mass variations. Results show that there are large thermohaline variations north of the Subantarctic Front ( SAF) at 300-1500 dbar level, indicating upwelling and downwelling of the Antarctic Intermediate Water ( AAIW) along isopycnal surfaces. Based on the latest altimeter product, Absolute Dynamic Topography, a mechanism due to frontal wave propagation is proposed to explain this phenomenon, and an index for frontal waves is defined. When the frontal wave is in positive ( negative) phase, the SAF flows northeastward ( southeastward) with the fresh AAIW downwelling ( upwelling). Such mesoscale processes greatly enhance cross-frontal exchanges of water masses. Spectral analysis shows that frontal waves in the Southern Ocean south of Australia are dominated by a period of about 130 days with a phase speed of 4 cm/s and a wavelength of 450 km.