Exceptionally high heat flux needed to sustain the Northeast Greenland Ice Stream
Exceptionally high heat flux needed to sustain the Northeast Greenland Ice Stream
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DOI：
10.5194/tc-14-841-2020
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发表时间：
2020-03-06
期刊：
影响因子：
5.2
通讯作者：
Nisancioglu, Kerim
中科院分区：
文献类型：
--
作者：
Smith-Johnsen, Silje;de Fleurian, Basile;Nisancioglu, Kerim
东北格陵兰冰流（NEGIS）目前消耗了格陵兰冰盖面积的10%以上，最近发生了重大的动态变化。因此，在评估格陵兰未来对海平面上升的影响时，准确地反映这一特征至关重要。目前，NEGIS是通过使用观测到的表面速度推断基础条件而在冰盖模式中再现的。这种方法有助于估计冰盖底部的条件，但不能用于估计基底阻力随时间的演变，因此它不能很好地代表未来气候变暖情景中冰盖的演变。NEGIS被认为是由靠近冰分水岭的地热热通量异常引起的，这是格陵兰岛在冰岛羽流上运动留下的。然而，冰盖下的热通量在很大程度上是未知的，除了从深冰芯钻探现场的一些直接测量。使用冰盖系统模型（ISSM），冰动力耦合到冰下水文模型，我们调查的可能性，启动NEGIS插入热通量异常与不同的位置和强度。在我们的模型实验中，最小热通量值为970 mW m（-2）位于东格陵兰冰芯项目（EGRIP）附近，需要在当地重现所观察到的NEGIS速度，使基础融化率与以前的估计一致。该值不能单独归因于地热热通量，我们建议热液循环作为高局部热通量的潜在解释。通过考虑高热通量和水对滑动的影响，我们在不使用数据同化的情况下成功地在冰盖模型中再现了NEGIS的主要特征。
The Northeast Greenland Ice Stream (NEGIS) currently drains more than 10% of the Greenland Ice Sheet area and has recently undergone significant dynamic changes. It is therefore critical to accurately represent this feature when assessing the future contribution of Greenland to sea level rise. At present, NEGIS is reproduced in ice sheet models by inferring basal conditions using observed surface velocities. This approach helps estimate conditions at the base of the ice sheet but cannot be used to estimate the evolution of basal drag in time, so it is not a good representation of the evolution of the ice sheet in future climate warming scenarios. NEGIS is suggested to be initiated by a geothermal heat flux anomaly close to the ice divide, left behind by the movement of Greenland over the Icelandic plume. However, the heat flux underneath the ice sheet is largely unknown, except for a few direct measurements from deep ice core drill sites. Using the Ice Sheet System Model (ISSM), with ice dynamics coupled to a subglacial hydrology model, we investigate the possibility of initiating NEGIS by inserting heat flux anomalies with various locations and intensities. In our model experiment, a minimum heat flux value of 970 mW m(-2) located close to the East Greenland Ice-core Project (EGRIP) is required locally to reproduce the observed NEGIS velocities, giving basal melt rates consistent with previous estimates. The value cannot be attributed to geothermal heat flux alone and we suggest hydrothermal circulation as a potential explanation for the high local heat flux. By including high heat flux and the effect of water on sliding, we successfully reproduce the main characteristics of NEGIS in an ice sheet model without using data assimilation.