2005 Fiscal Year Final Research Report Summary
Effect in atmosphere-ocean changes reflected by frequent large breakups of landfast ice and ice shelf in the Antarctic
| Project/Area Number |
15510015
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Environmental dynamic analysis
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| Research Institution | National Institute of Polar Research |
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Principal Investigator |
USHIO Shuki National Institute of Polar Research, Division for Research and Education, Research Associate, 研究教育系, 助手 (50211769)
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| Project Period (FY) |
2003 – 2005
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| Keywords | Antarctic / sea ice / interannual variation / ice navigation / fast ice / pack ice / glacier ice tongue / ice shelf |
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| Research Abstract |
Antarctic fast-ice variation has been investigated using satellite images and ship's ice navigation logs, focusing on breakup phenomena in Lutzow-Holmbukta (Lutzow-Holm Bay). Although spatio-temporal scales for breakup events vary somewhat for each event, their commencement is generally in autumn and almost always in the same region. Specifically, the 1997/98 breakup event occurred over a wide area and continued for a long time after the initial breakup. Since then, breakups have repeated until 2004, and a total of 20 annual events have been detected since 1980. Moreover, information from icebreaker navigation logs shows that unstable fast-ice conditions frequently occurred in the 1980s and after the late 1990s. From the analysis of surface meteorological data and the offshore pack-ice distribution, anomalously shallow snow-cover depths and a peculiar retreat pattern of the ice edge are found to be factors that favor fast-ice breakup. The pack ice distribution controls the propagation
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of ocean swell inside the bay ; encroaching swells are likely to mechanically disintegrate fast-ice field during autumn prior to the annual formation of the protective pack-ice cover to the north. Less snow cover also leads to fast-ice weakening as the melt season progresses and broken floes are then transported offshore by prevailing southerly winds.
In this way, the patterns of landfast-ice breakup and formation/persistence likely exert an important influence on the dynamics and thermodynamics of outlet glaciers and also the inland ice sheet. To promote this study, field measurements linked with satellite remote sensing are required to detect glaciological responses to landfast-ice stability in the form of the changing flow characteristics of floating ice tongues and the elevation/thickness distributions of inland drainage basins. Satellite imagery with high spatial resolution is much useful for quantification of the tongue movement of the Shirase Glacier that flows inside Lutzow-Holmbukta. Less
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