Losing their Cool: are high-elevation heat exchanges warming Himalayan glaciers?

失去冷静：高海拔热交换会使喜马拉雅冰川变暖吗？

• 批准号: NE/Z000033/1
• 负责人: Duncan Quincey
• 金额: $ 107万
• 依托单位: University of Leeds
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2024
• 资助国家: 英国
• 起止时间: 2024 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FZ000033%2F1
• 关键词: Losing; their; Cool; elevation; heat

We recently discovered that over half of the ablation area of one of the world's highest glaciers, Khumbu Glacier, Nepal, comprises ice that is at the melting point. Moreover, ice within the upper ablation area has warmed by 2-3 degrees Celsius over the last 40 years and is out of equilibrium with local climate. Combined, these observations indicate that high-elevation Himalayan glaciers are unexpectedly vulnerable to 21st Century climatic warming, and approaching a tipping point beyond which greatly accelerated mass loss will occur. However, the processes that determine ice temperatures within this region remain poorly understood, making projections of future glacier change uncertain.The overarching aim of Losing their Cool (LtC) is to investigate the physical interactions between the atmosphere and the glacier surface at high-elevation (>6,000 m a.s.l.), providing insight into the snow and firn processes that prescribe Himalayan ice temperatures for the first time. The working hypothesis is that melting and refreezing within the accumulation area is sufficiently effective to raise firn-layer temperatures by several degrees prior to ice formation. To test this, LtC will collect the first robust and sustained measurements of firn conditions from Khumbu Glacier's accumulation area in the Western Cwm of Mount Everest. We will drill and instrument 20-25 m-long boreholes at elevations of 6,000-6,800 m a.s.l. to measure englacial firn and ice temperatures over a two-year period. We will also use a 360 degree camera to image the interior of the boreholes to characterise firn density and quantify the magnitude and frequency of previous re-freezing events. We will install automatic weather stations at elevations where they do not already exist, and take samples from the cores for collaborators working in relevant fields (e.g. biogeochemistry). We will use these empirical data to calibrate, and then validate, a numerical model that can simulate both the energy fluxes driving warming at the surface, and the consequent subsurface meltwater flow and refreezing processes. This will enable us to isolate the impact of meltwater re-freezing on ice temperature, and determine the extent to which this changes in a warming climate. Finally, we will simulate the whole glacier system, and track the evolution of ice temperatures with distance downglacier, to assess the extent to which firn processes can account for the unexpectedly high temperatures we previously observed in the glacier ablation area, as well as yield improved forecasts of ice loss up to 2100.This work will provide new understanding of firn processes that are relevant for all glaciers within similar settings world-wide. In particular it will improve the way we represent ice stiffness and processes of ice flow in dynamic glacier models. It will resolve outstanding debates in the literature about the possibility of net mass loss at the world's highest elevations, and indicate the extent to which other glaciers within the Himalaya may also comprise unexpectedly warm ice. Our work will provide insights into a rarely observed cryospheric zone that can inform agenda-setting reports such as those produced by the Intergovernmental Panel on Climate Change, as well as addressing, directly and indirectly, several key Sustainable Development Goals. We will further provide evidence for supporting agencies such as UNDP, and the Nepalese government, to help prepare for, and mitigate against, a now inevitable change in meltwater supply as climatic changes continue to impact this region.

最近，我们发现，世界上最高冰川之一的消融区域的一半以上，尼泊尔库姆岛冰川，包括在熔点上的冰。此外，在过去的40年中，上层消融区域内的冰升高了2-3摄氏度，并且与局部气候保持平衡。这些观察结果结合在一起表明，高海拔喜马拉雅冰川出乎意料地容易受到21世纪的气候变暖的影响，并接近一个转折点，将会发生极大的加速群众损失。 However, the processes that determine ice temperatures within this region remain poorly understood, making projections of future glacier change uncertain.The overarching aim of Losing their Cool (LtC) is to investigate the physical interactions between the atmosphere and the glacier surface at high-elevation (>6,000 m a.s.l.), providing insight into the snow and firn processes that prescribe Himalayan ice temperatures for the first time.工作假设是，在蓄能区域内进行熔化和重新冻结足够有效，可以在冰形成之前将FIRN层温度提高几个度。为了进行测试，LTC将从珠穆朗玛峰西部CWM的Khumbu冰川积累区域收集第一个强大而持续的FIRN条件测量。我们将在6,000-6,800 m A.S.L.的海拔高度钻和仪器20-25 m长。在两年内测量Eng-Racial Firn和ICE温度。我们还将使用360度摄像机对钻孔的内部进行成像，以表征FIRN密度并量化以前的重新冻结事件的幅度和频率。我们将在尚不存在的高程中安装自动气象站，并从核心中采集样本，以用于在相关领域工作的合作者（例如，生物地球化学）。我们将使用这些经验数据来校准，然后验证，这是一个数值模型，可以模拟驱动地面上驱动变暖的能量通量，以及随之而来的地下熔体流量和重新冻结过程。这将使我们能够隔离融合水对冰温的影响，并确定这种变暖气候中这种变化的程度。最后，我们将模拟整个冰川系统，并跟踪距离距离距离底线的冰温度的演变，以评估FIRN过程可以考虑到我们先前在冰川消融区域中出乎意料的高温以及造福处的出乎意料的高温以及对冰上损失的预测提供了相关性的范围。特别是它将改善我们代表动态冰川模型中冰刚度和冰流的过程的方式。它将解决有关世界上最高海拔净质量损失的可能性的杰出辩论，并表明喜马拉雅省内其他冰川在多大程度上也可能构成出乎意料的温暖冰。我们的工作将提供有关少数观察到的Cryosperic区域的见解，该区域可以为议程制定的报告提供信息，例如政府间针对气候变化的小组成立的报告，以及直接和间接地解决一些主要的可持续发展目标。我们将进一步提供证据，以支持开发计划署和尼泊尔政府等机构，以帮助准备并减轻现在的融水供应不可避免的变化，因为气候变化继续影响该地区。