Geothermal flux and basal melt rate in the Dome C region inferred from radar reflectivity and heat modelling
Geothermal flux and basal melt rate in the Dome C region inferred from radar reflectivity and heat modelling
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DOI：
10.5194/tc-11-2231-2017
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发表时间：
2017-09
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影响因子：
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通讯作者：
O. Passalacqua;C. Ritz;F. Parrenin;S. Urbini;M. Frezzotti
中科院分区：
文献类型：
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作者：
O. Passalacqua;C. Ritz;F. Parrenin;S. Urbini;M. Frezzotti
抽象的。基础融化速率是寻找旧冰钻探地点时需要评估的最重要的物理量，它在很大程度上取决于地热通量（GF），而地热通量（GF）在东南极冰盖下却鲜为人知。鉴于潮湿的基岩比干燥的基岩具有更高的反射率，可以使用来自基岩的雷达回波来评估冰床界面的湿度。但是，由于基础条件取决于气候强制的传热，但厚冰滞后，因此基础冰目前可能被冻结，而过去通常会融化。因此，必须评估当前状况和过去状况之间的偏差风险。本研究的目的是评估 Dome C 区域的哪些位置在过去的任何时间都可以免受基底融化的影响，这需要评估 GF。我们使用逆向方法从雷达推断的湿床和干床分布中检索 GF。在过去 800 ka 内运行一维热模型，通过评估临界冰厚度（即允许当前基底融化局部分布的最小冰厚度）来限制 GF 值。然后推断出 80 km × 130 km 区域的 GF 区域图，具有南北梯度，值范围为 48 至 60 mW m−2。然后通过多项式函数模拟正演模型，以计算该区域空间可变基础熔化速率的时间平均值。三个主要次区域似乎没有基底融化，其中两个是因为上面有一层薄薄的冰，一个位于 Dome C 北部，因为GF 较低。
Abstract. Basal melt rate is the most important physical quantity to be evaluated when looking for an old-ice drilling site, and it depends to a great extent on the geothermal flux (GF), which is poorly known under the East Antarctic ice sheet. Given that wet bedrock has higher reflectivity than dry bedrock, the wetness of the ice–bed interface can be assessed using radar echoes from the bedrock. But, since basal conditions depend on heat transfer forced by climate but lagged by the thick ice, the basal ice may currently be frozen whereas in the past it was generally melting. For that reason, the risk of bias between present and past conditions has to be evaluated. The objective of this study is to assess which locations in the Dome C area could have been protected from basal melting at any time in the past, which requires evaluating GF. We used an inverse approach to retrieve GF from radar-inferred distribution of wet and dry beds. A 1-D heat model is run over the last 800 ka to constrain the value of GF by assessing a critical ice thickness, i.e. the minimum ice thickness that would allow the present local distribution of basal melting. A regional map of the GF was then inferred over a 80 km × 130 km area, with a N–S gradient and with values ranging from 48 to 60 mW m−2. The forward model was then emulated by a polynomial function to compute a time-averaged value of the spatially variable basal melt rate over the region. Three main subregions appear to be free of basal melting, two because of a thin overlying ice and one, north of Dome C, because of a low GF.