Modelling Glacier and Ice Sheet Response to Climate Change

我的研究小组结合实地研究和数值模拟来研究冰川动力学和冰川气候过程。我的主要目的是提高对气候系统中冰川和冰盖的理解，以及它们在冰川学和气候模型中的表现。实地地点包括加拿大西部和北极地区、冰岛和格陵兰岛，我的建模工作跨越了一系列空间和时间尺度，从山地冰川对气候变化的响应到冰河时代冰盖和气候动力学的演变。本次“发现基金”周期提出的研究包含了这些不同的研究线索，但将重点放在加拿大西部山区冰原和格陵兰冰盖积累区的融水排水、再冻结和保留上，那里的雪是季节性雪的底层。融水再冻结和液态水储存在坚硬的含水层中形成内部积累，在系统内保持质量并减少冰川径流。尽管越来越多的证据表明，为了准确模拟冰川质量平衡、融水径流和海平面上升，需要了解冰川和冰盖响应气候变化的过程，但这一过程通常没有体现在冰川和冰盖响应气候变化的模型中。此外，融水滞留和再冻结会影响冰密度，这需要了解，以解释用于监测冰川和冰盖变化的机载和卫星测高数据。提出的研究目标是融水滞留的热力学和水文控制及其对冰川热状态、致密化、冰川物质平衡、融水径流和同位素地层学的影响。实地研究将在格陵兰岛南部的Dye2、育空地区圣伊莱亚斯山脉的Kaskawulsh冰川上部以及加拿大西部的哥伦比亚和Illecillewaet冰原进行。预计在每个地点进行一到两个实地季节，以获取浅冰芯（深度达50米），并研究在季节性雪和雪中挖掘的近地表坑（深度达5米）中的融水渗透和再冻结。这些坑将配备热敏电阻和时域反射仪（TDR）探头，以跟踪雪/雪的液态水含量和融水重新冻结时潜热释放的热信号。冰芯将提供融水渗透和冰层含量的更深层表征。在加拿大西部和北部，人们对岩石的深度和性质知之甚少。这些研究将为冰原特征提供原始数据，这将指导大规模冰原和冰盖建模的冰原模型的发展。除了水文和热力学外，还将分析稳定同位素（d18O, dD），以了解融水渗透和再冻结对稳定同位素地层学和温度测量的影响，为基于冰芯的气候重建提供支持。

My research group combines field studies and numerical modelling to study glacier dynamics and glacier-climate processes. My main aim is to improve the understanding of glaciers and ice sheets in the climate system and their representation in glaciological and climate models. Field sites include western and Arctic Canada, Iceland, and Greenland, and my modelling work is across a range of spatial and temporal scales, from mountain glacier response to climate change to the evolution of Ice Age ice sheets and climate dynamics. The proposed research over this Discovery Grant cycle contains each of these different research threads, but will focus on meltwater drainage, refreezing, and retention in the accumulation area of mountain icefields in western Canada and the Greenland Ice Sheet, where firn underlies the seasonal snow. Meltwater refreezing and liquid water storage in firn aquifers give internal accumulation, retaining mass within the system and reducing glacier runoff. This process is generally not represented in models of glacier and ice sheet response to climate change, despite growing evidence that firn processes need to be understood for accurate modelling of glacier mass balance, meltwater runoff, and sea level rise. Moreover, meltwater retention and refreezing impact firn density, which needs to be known to interpret airborne and satellite altimetry data that are used to monitor glacier and ice sheet change. The proposed research targets the thermodynamic and hydrological controls of meltwater retention and its implications for glacier thermal regime, densification, glacier mass balance, meltwater runoff, and isotope stratigraphy. Field studies will be conducted at Dye2 in southern Greenland, the upper Kaskawulsh Glacier in the St. Elias Mountains, Yukon, and the Columbia and Illecillewaet Icefields in western Canada. One to two field seasons are anticipated at each site, to acquire shallow ice cores (up to 50 m depth) and study meltwater percolation and refreezing in the near-surface pits (up to 5 m depth) excavated in the seasonal snow and firn. The pits will be instrumented with thermistors and time-domain reflectometry (TDR) probes, to track snow/firn liquid water content and the thermal signal of latent heat release as meltwater refreezes. The ice cores will provide a deeper representation of meltwater percolation and ice layer content. Little is known about the depth and properties of firn in western and northern Canada. These studies will offer primary data into firn characterization, which will guide the development of a firn model for large-scale icefield and ice sheet modelling. In addition to the firn hydrology and thermodynamics, stable isotopes (d18O, dD) will be analyzed to understand the impacts of meltwater percolation and refreezing on stable isotope stratigraphy and thermometry, in support of ice-core based climate reconstructions.