Acta Oceanologica Sinica

, Volume 34, Issue 11, pp 92–101 | Cite as

Mesoscale characteristics of Antarctic Intermediate Water in the South Pacific

Article

Abstract

The Argo float observations are used to investigate the mesoscale characteristics of the Antarctic Intermediate Water (AAIW) in the South Pacific in this paper. It is shown that a subsurface mesoscale phenomenon is probably touched by an Argo float during the float’s ascent-descent cycles and is identified by the horizontal salinity gradient between the vertical temperature-salinity profiles. This shows that the transportation of the AAIW may be accompanied with the rich mesoscale characteristics. To derive the spatial length, time, and propagation characteristics of the mesoscale variability of the AAIW, the gridded temperature-salinity dataset ENACT/ENSEMBLE Version 3 constructed on the in-situ observations in the South Pacific since 2005 is used. The Empirical Mode Decomposition method is applied to decompose the isopycnal-averaged salinity anomaly from 26.8 σ θ –27.4 σ θ , where the AAIW mainly resides, into the basin scale and two mesoscale modes. It is found that the first mesoscale mode with the length scale on the order of 1 000 km explains nearly 50% variability of the mesoscale characteristics of the AAIW. Its westward-propagation speeds are slower in the mid-latitude (around 1 cm/s) and faster in the low latitude (around 6 cm/s), but with an increasing in the latitude band on 25°–30°S. The second mesoscale mode is of the length scale on the order of 500 km, explaining about 30% variability of the mesoscale characteristics of the AAIW. Its westward-propagation speed keeps nearly unchanged (around 0.5 cm/s). These results presented the stronger turbulent motion of the subsurface ocean on the spatial scale, and also described the significant role of Argo program for the better understanding of the deep ocean.

Keywords

mesoscale characteristics subsurface ocean Antarctic Intermediate Water (AAIW) Argo 

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Copyright information

© The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  1. 1.College of Ocean and Earth SciencesXiamen UniversityXiamenChina
  2. 2.Key Laboratory of Physcial OceanographyOcean University of ChinaQingdaoChina
  3. 3.Marine Monitoring and Forecasting Center of ZhejiangHangzhouChina
  4. 4.Key Laboratory of Marine Science and Numerical Modeling, the First Institute of OceanographyState Oceanic AdministrationQingdaoChina

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