Quantitative evaluations of ocean circulation and meridional themohaline transport in the Indian sector of Antarctic

本研究的目的是对我们的观测资料进行分析，首次成功地获得南极印度段向北流动的南极底水体积输送的季节变化。从2003年2月到2005年1月，作为与澳大利亚CSIRO的一个国际联合项目，我们在克尔格伦高原东南海岸的8个站点部署了当前系泊系统。我们的初步数据分析表明，该地区在大陆架斜坡和远近海的洋流方向完全相反；前者为西北流，后者为东南流。因此，该地区的水循环系统大致由作为西部边界流的向北流动和由于气旋再循环而形成的向南流动组成。在本研究中，我们还利用SSMI微波数据推导了南极底水形成区沿海冰裂带的海冰厚度分布。通过数据分析和热收支计算，我们还成功地绘制了沿海冰融区海冰产量的分布图。根据我们的研究，南极海冰产量最大的地区是罗斯海。然而，罗斯海沿岸冰融带的海冰产量在20世纪90年代至2000年代期间减少了约30%；这可能导致最近南极底水变新鲜的趋势。虽然我们还没有进行所有的数据分析，但我们将在不久的将来定量地提出南极印度洋部分的水循环系统。

The purpose of this study is to make an analysis of our observational data in which the seasonal variability of volume transport for the northward flowing Antarctic Bottom Water in the Indian sector of the Antarctic could be successfully obtained for the first time. We have done the deployment of the current-mooring systems at 8 stations off the southeastern coast of the Kerguelen Plateau for two years from February 2003 to January 2005, as an international joint project together with CSIRO in Australia. Our primary data analyses have shown that this region has completely reverse current direction over the continental shelf slope and the far offshore; the former is northwestward flow while the latter is southeastward flow. Therefore, the water circulation system in this region is approximately composed of the northward flow as a western boundary current and southward flow due to the cyclonic recirculation.In this study, we have also derived the sea-ice thickness distribution in the coastal polynyas where are the formation areas of the Antarctic Bottom Water, using the SSMI microwave data. From the data analyses and heat-budget calculation, we also have successfully made the mapping of the amount of sea-ice production in the coastal polynyas. According to our study, the area of the largest amount of sea-ice production in the Antarctic is Ross Sea. However, the amount of the sea-ice production in the coastal polynyas of the Ross Sea decreases about 30% during the period from 1990's to 2000's; this may lead to the recent trend of the freshening of the Antarctic Bottom Water.Although we did not yet make all the data analyses, we will propose water circulation system in the Indian Ocean sector of the Antarctic quantitatively, in the nearfuture.