东南极Lambert冰川-Amery冰架系统着地冰/冰架相互作用过程研究

The ice sheet of East Antarctica may respond more rapidly to global climate change than previously assumed. Most of the contribution to sea level from melted ice occurs along the coastal perimeter of East Antarctica, where the slow moving ice sheet meets the ocean. An alternative mechanism of ice sheet melt to sea level is via large outlet glaciers which stream through deep and extensive basins that act like drainage channels.The outflux is controlled in part by the intrinsic resistance to flow provided by stresses at the bedrock or as internal shear. Also controlling the flow rate are gravitationaldriving forces and mechanical buttressingat the seaward margins provided by floatingice shelves. In this study, we perform perturbation experiments with a 3D ice flow model to study the dynamic response and interaction of the Antarctic grounded ice to ice shelf melting at the grounding line zones in the Lambert Glacier-Amery Ice Shelf System(LAS). Based on the informations (observations and modeling studies),we applied a 3D grounded ice/ice shelf model (with the bedmap in the grounding zone) of the Antarctic ice sheet the LAS with the data of the basal melting at the grounding line, by assuming that the effect of melting beneath ice shelf acts at grounding line. Analysis mechanism of the Lambert Glacier response to changes of ice shelf in conditions; reveal the mechanism the Lambert Glacier -Amery Ice Shelf system in East Antarcticaresponse to global changes;simulate ice sheet changes in the furture. This project will contributeto studythe issue" ice sheet mass banlance and sea level", which is the key scientific issues and priority areas in Antarctica.

东南极冰盖的快速变化研究是当前极地科学关注的热点与前沿问题。冰架融化速率的变化将导致内陆冰川外泄，南极冰盖物质损失增加，造成全球海岸线变化。本项目以东南极Lambert冰川下游、Amery冰架南端着地冰/冰架过渡区为研究对象，通过国际合作，基于动力学和热力学，利用大量遥感、模型计算和野外观测数据，构建该地区着地冰和冰架的耦合冰流动力模型；分析Lambert冰川下游的底部环境特征，阐明底部基岩环境对着陆冰-冰架的影响作用；建立过渡区域的3D各向异性冰流模型，理解着地冰/冰架的冰流动力过程；分析未来冰架变化条件下，着地冰的响应机制，揭示东南极Lambert冰川-Amery冰架系统对全球气候变化的响应。本项目将为极地领域的关键科学问题和优先研究主题"南极冰盖物质平衡与海平面"作出贡献。

开展南极Amery冰架最南端的冰厚度和Lambert-Amery冰架系统中部的物质平衡再分析。结果表明，Mellor和Fisher冰川基本处于平衡状态，而Lambert冰川处于正平衡，物质平衡值为4.2±2.3 Gt a-1。整个兰伯特冰川盆地大约处于正平衡。Amery冰架最近着地线附件的冰架底部融化速率为5.1±3.0 m a-1。上述结果与以前根据静水力学平衡推算冰厚度得出的结果存在巨大差异。构建了一个随时间变化的3D各向异性冰流模型，应用到Amery冰架南端着地线地区，选取了本世纪末可能出现的该冰架底部融化三个增大情景，模拟Lambert冰流盆地对Amery冰架底部不同融化情景的响应。结果表明，未来200年，冰厚度呈现不同的变化情况，在着地线附近显著减少或消融殆尽，而上游方向的影响较小，冰盖内部变化值小于0.01%。模型结果表明由海洋温度增加导致的冰架融化率增加对冰盖动力机制有着明显的响应作用。冰架融化速率在200年后达到20-200 m/a，将会造成着地线向上游方向后退120-240 km, 整个Lambert冰川盆地会损失3-6%的冰物质,并引起全球海平面上升0.2-0.5m。.开展了海洋驱动下冰架的变薄可加剧南极冰架的崩解和退缩研究。结果显示，2005-2011年间南极冰架崩解率为755±24亿吨每年，仅为1516±106亿吨每年底部消融率的一半。同时显示一些大的冰架正在扩张，而许多小的冰架正在退缩消失。观测到许多退缩冰架正在变薄，且由崩解导致的冰架净物质损耗量（302±27 亿吨/年）与由底部消融导致的冰架净物质损耗量（312±14 亿吨/年）相当。研究结果表明，海洋驱动下冰架底部消融增加的同时引发冰架崩解的加剧，这意味着冰架崩解可能在冰架退缩消亡中扮演着一个被忽视的角色，且崩解对海洋强迫比预期稳态下的估计更敏感。