Past and future dynamics of the Brunt Ice Shelf from seabed bathymetry and ice shelf geometry
Past and future dynamics of the Brunt Ice Shelf from seabed bathymetry and ice shelf geometry
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DOI：
10.5194/tc-13-545-2019
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发表时间：
2019-02-14
期刊：
影响因子：
5.2
通讯作者：
Vaughan, David G.
中科院分区：
文献类型：
--
作者：
Hodgson, Dominic A.;Jordan, Tom A.;Vaughan, David G.
最近布伦特冰架上裂缝的快速增长似乎标志着自1915年有记录以来最大的冰裂事件的开始。这项研究的目的是确定这一产犊事件是否会导致布伦特冰架与床保持接触的新的稳定状态，或者从床上分离出来，这可能会使其加速流动或可能破裂。我们使用一系列地球物理数据来重建海底测深和冰架几何形状，检查布伦特盆地过去的冰盖结构，并定义布伦特冰架和床之间接触的当今几何形状。结果表明，在过去的冰推进过程中，接地冰流可能从南部和东部聚集在布伦特盆地。随着冰的消退，它很可能被固定在至少三条以前的接地线上，这些接地线以地形高度和盆地两侧的横向山脊为标志。它们可能随后形成了冰架发育的支撑点。冰架的几何形状和测深测量表明，布伦特冰架的底部现在只与这些地形高点中的一个接触。这种接触被限制在小于1.3至3公里(2)的区域内，并导致了一个有助于保持冰架完整性的压缩状态。冰架吃水和水深高度之间的最大重叠为2-25米，这取决于在冰架底部下方突出的合并冰山龙骨的存在。冰架的未来取决于预期的产犊事件是否会导致冰架完全或部分失去与床的接触，以及随后的反应是否会在可预测的时间内导致冰架重新接地，或者由于接地线继承的特性而导致冰架结构完整性的丧失。
The recent rapid growth of rifts in the Brunt Ice Shelf appears to signal the onset of its largest calving event since records began in 1915. The aim of this study is to determine whether this calving event will lead to a new steady state in which the Brunt Ice Shelf remains in contact with the bed, or an unpinning from the bed, which could predispose it to accelerated flow or possible break-up. We use a range of geophysical data to reconstruct the sea-floor bathymetry and ice shelf geometry, to examine past ice sheet configurations in the Brunt Basin, and to define the present-day geometry of the contact between the Brunt Ice Shelf and the bed. Results show that during past ice advances grounded ice streams likely converged in the Brunt Basin from the south and east. As the ice retreated, it was likely pinned on at least three former grounding lines marked by topographic highs, and transverse ridges on the flanks of the basin. These may have subsequently formed pinning points for developing ice shelves. The ice shelf geometry and bathymetry measurements show that the base of the Brunt Ice Shelf now only makes contact with one of these topographic highs. This contact is limited to an area of less than 1.3 to 3 km(2) and results in a compressive regime that helps to maintain the ice shelf's integrity. The maximum overlap between ice shelf draft and the bathymetric high is 2-25 m and is contingent on the presence of incorporated iceberg keels, which protrude beneath the base of the ice shelf. The future of the ice shelf depends on whether the expected calving event causes full or partial loss of contact with the bed and whether the subsequent response causes re-grounding within a predictable period or a loss of structural integrity resulting from properties inherited at the grounding line.