Impact of surface melt and ponding on ice shelf dynamics and stability

冰架环绕着南极海岸线的一半，对南极冰盖的冰排放起着根本的控制作用。它们可以通过与海洋和大气的相互作用获得或失去质量。从长期来看，它们的演变和对冰盖的影响由海洋控制，但大气变暖的影响可能在短期内占主导地位，因为它为冰架突然崩溃提供了条件和机制。南极半岛的冰架最近发生了最大的变化，其大气变暖的速度比地球上其他任何地方都快。导致表面融化和积水的大气变暖已经与南极半岛冰架的崩溃有关-2002年拉森B冰架的丧失导致了显著的和持续的冰川加速，从内陆吸收地面冰，并导致海平面上升。毫无疑问，气候变暖将导致更多的冰架在很长一段时间内受到冰点以上温度的影响。更大的拉森B冰架的南方邻居拉森C每年都会经历表面融化和积水的时期，部分地区似乎正在接近拉森B冰架崩塌之前的积雪致密程度。然而，关于熔融和降雪致密化的时空模式，池塘的分布和大小，或者这些因素对流动和破裂的影响，人们知之甚少。因此，对冰盖质量平衡的关键控制还没有充分的了解。我们的项目将通过实地考察、遥感和数值模拟的综合计划来解决这个问题。我们将把重点放在拉森C冰架，它是一个大型冰架经历各种表面融化和积水条件的理想例子，而且很容易进行现场测量。利用钻孔摄像测量和监测仪器，以及地表地球物理，我们将获得急需的关于冰柱上半部分冰架上的密度和温度的新数据。我们将探索数百年前的冰层，以了解拉森C冰架融化和积水的历史。为了了解过去和未来融化和积水对冰架的影响，我们将开发一个耦合模拟，它将使用一个区域气候模式来预测地表融化和积水，并使用一个冰架数值模式来测试这种融水对流动和破裂的影响。这些模型将通过我们将收集的实地调查和遥感数据进行优化。结果将是迄今为止最准确的冰架模型，它将使我们能够充分了解融化和积水对冰架的影响，并预测拉森C冰架在下个世纪的未来演变。

Ice shelves fringe around half of the Antarctic coastline and exert a fundamental control on the discharge of ice from the Antarctic ice sheets. They can gain and lose mass through interactions with both the ocean and the atmosphere. In the long term their evolution and impact on the ice sheets is controlled by the ocean, but the effect of a warming atmosphere may dominate in the shorter term by providing the conditions and mechanisms for abrupt ice shelf collapse. The atmosphere on the Antarctic Peninsula, where ice shelves have recently undergone most change, is warming faster than anywhere else on Earth.Atmospheric warming leading to surface melt and ponding has already been implicated in the collapse of ice shelves of the Antarctic Peninsula - the loss of the Larsen B ice shelf in 2002 led to significant and ongoing glacier acceleration, draw-down of grounded ice from the interior, and contribution to sea level rise. There is no doubt that climate warming will lead to more ice shelves being subject to temperatures above freezing for significant periods. The much larger southerly neighbour of the Larsen B ice shelf, Larsen C, annually experiences periods of surface melt and ponding, and appears in parts to be approaching the level of firn densification that preceded the Larsen B collapse. Very little is known, however, about the spatial and temporal pattern of melt and firn densification, the distribution and size of ponds, or the impact of these factors on flow and fracture. A key control on ice sheet mass balance is therefore inadequately understood.Our project will address this issue through a combined program of fieldwork, remote sensing and numerical modelling. We will focus on the Larsen C Ice Shelf as an ideal example of a large ice shelf experiencing a wide variety of surface melt and ponding conditions, and which is readily accessible for field measurements. Using borehole camera survey and monitoring instrumentation, and surface geophysics, we will acquire much needed new data about the density and temperature across the ice shelf in the upper half of the ice column. We will probe layers of ice going back hundreds of years to understand the history of melt and ponding on Larsen C Ice Shelf. To understand the impact on the ice shelf of past and future melt and ponding, we will develop a coupled simulation which will use a regional climate model to predict surface melt and ponding and an ice shelf numerical model to test the impact of this meltwater on flow and fracture. These models will be optimised by data from fieldwork and remote sensing that we will collect. The outcome will be the most accurate model of an ice shelf to date which will allow us fully understand impact of melt and ponding on ice shelves and to predict the future evolution of Larsen C Ice Shelf over the next century.