Greenland Ice Sheet and sea-level response under climate change from AD 1600 to 2100

格陵兰冰盖的质量足以使全球海平面上升7米。目前，全球变暖导致的格陵兰冰盖质量损失是造成全球海平面上升的主要原因，到2100年可能使全球海平面上升几十厘米，尽管这一预测高度不确定。最近的大多数研究表明，地表质量平衡（定义为净固体降水减去从冰盖流出的地表融水）是21世纪格陵兰冰盖质量变化的主要部分；然而，我们对格陵兰冰盖在几个世纪时间尺度上的变化的认识和理解仍然存在重大差距。需要改进关于表面质量平衡随空间和时间变化的信息，以提高通过冰山崩解（称为冰动力学）计算冰盖流动和冰损失的计算机模型的可靠性。由于缺乏有约束的计算机模拟，特别是对过去50年左右的时间周期的模拟，目前对最近地表质量平衡变化的有限理解，传播到对未来总质量平衡（即地表质量平衡和冰动力变化的总和）的不可靠估计，从而对海平面上升的预估。目前大多数格陵兰冰盖表面质量平衡数据集不能追溯到1900年前后，而更复杂的表面质量平衡模式往往侧重于1960年以来相对较短的时期，因为不可避免地需要大量可靠、复杂的输入数据（例如与冰盖表面和大气之间的表面热量和能量流动有关的数据），而这些数据在1960年代之前通常是不可获得的。此外，对冰盖质量变化的冰动力部分的估计是基于冰输出与近期气候学的统计关系，这不太可能代表仪器前时期或未来。因此，迫切需要弥合在小冰期（约1600 - 1850年）和20 /21世纪之间的大气候变化期间对格陵兰冰盖-气候相互作用和海平面影响的理解方面的主要差距，以减少格陵兰冰盖变化在21世纪剩余时间内传播到全球海平面贡献的重大不确定性。我们的建议结合了广泛的模型、观察和科学专业知识，以解决这一关键的知识差距。该项目将利用尖端的气候和冰盖模型和数据集，对过去和未来的格陵兰冰盖表面质量平衡和动态冰变化进行估算，并对其中的不确定性进行数学评估。提出的工作的主要目的是生成1600年至2021年格陵兰冰盖的新的受限表面和完整质量平衡历史，以及格陵兰冰盖到2100年的质量平衡预测，并评估由此产生的对历史和未来全球海平面的贡献。格陵兰冰盖表面物质平衡的重建可追溯到1600年，在这一时期，这类记录在很大程度上是缺乏的，这将使现有已发表的表面物质平衡记录的长度增加四倍，并为更好地了解冰盖的历史和对气候变化的敏感性奠定基础。我们的方法提供了几个关键的方法改进——最显著的是它包括了所有主要的出口冰川，并确定了一系列最可能的结果——与之前预测格陵兰冰盖未来变化的尝试相比。我们将把我们的格陵兰冰盖表面质量平衡预估与我们的冰盖模拟工作的总质量平衡预估结合起来，计算地表质量平衡和冰动力在空间和时间上对总质量变化的相对贡献，并确定它们对1600-2100年间持续的人类驱动的气候变化的敏感性。

The Greenland Ice Sheet contains enough mass to raise global sea-level by seven metres. Greenland Ice Sheet mass loss arising from global warming is currently the main icy contributor to global sea-level rise and could contribute several tens of centimetres to global sea level by the year 2100, although this prediction is highly uncertain. Most recent studies show that surface mass balance (defined as net solid precipitation minus surface meltwater that runs off from the ice sheet) is the main part of 21st century Greenland Ice Sheet mass change; yet key gaps remain in our knowledge and understanding of Greenland Ice Sheet change at the multi-century timescale. Improved information on surface mass balance changes over space and time is needed to improve the reliability of computer models of ice-sheet flow and loss of ice via calving of icebergs (called ice dynamics). The present limited understanding of recent surface mass balance change resulting from the lack of constrained computer simulations, especially for time periods before the last 50 years or so, propagates through to unreliable estimates of future total mass balance (i.e. the sum of surface mass balance and ice dynamical changes) and therefore projections of sea level rise. Most current Greenland Ice Sheet surface mass balance datasets do not extend back before around 1900, while the more sophisticated surface mass balance models tend to focus on relatively short periods since 1960 due to unavoidable requirements of large amounts of reliable, complex input data (for example those relating to surface heat and energy flows between the ice sheet's surface and the atmosphere) which are typically unavailable before the 1960s. Also, estimates of the ice dynamic portion of ice-sheet mass change are based on statistical relationships of ice output with recent climatology, which is unlikely to be representative of the pre-instrumental period or the future. Therefore, bridging the major gap in the understanding of Greenland Ice Sheet-climate interactions and effect on sea-level during the large climate shifts between Little Ice Age (around 1600 to 1850) and the 20th/21st Century is urgently needed to reduce the significant uncertainty propagating through to the global sea-level contribution of Greenland Ice Sheet changes during the rest of the Twenty First Century. Our proposal combines a wide range of models, observations and scientific expertise to address this key knowledge gap.This project will produce estimates of past and future Greenland Ice Sheet surface mass balance and dynamic ice changes using cutting-edge climate and ice sheet models and datasets and mathematical evaluation of the uncertainties in these. The main aim of the proposed work is to produce a novel constrained surface and full mass balance history of the Greenland Ice Sheet from 1600 to 2021 and Greenland Ice Sheet mass balance projections to 2100, and to assess the resulting contribution to historical and future global sea-level. The reconstruction of the Greenland Ice Sheet surface mass balance back to 1600, for a period where such records are largely lacking, will quadruple the length of the existing published surface mass balance record, and form the basis of an improved understanding of the ice sheet's history and sensitivity to climate change. Our approach offers several key methodological improvements - most notably its inclusion of all the main outlet glaciers and determination of a range of most likely results - over previous attempts to forecast future changes in the Greenland Ice Sheet. We will combine our Greenland Ice Sheet surface mass balance projections with the total mass balance projections from our ice-sheet modelling work to calculate the relative contributions of surface mass balance and ice dynamics in space and time to total mass changes, and to determine their sensitivity to ongoing human-driven climate change during 1600-2100.