RAPID The Mass balance and freshwater contribution of the Greenland ice sheet: Numerical model and observational data

"The Mass balance and freshwater contribution of the Greenland ice sheet: a combined modelling and observational approach" project, which was a Natural Environment Research Council (NERC) RAPID Climate Change Research Programme project (Joint International Round - NE/C51631X/1 - Duration 1 Jun 2005 - 30 Nov 2008) led Prof Jonathan Bamber of the University of Bristol, with co-investigators at the Nansen Environmental & Remote Sensing Center, Norway, the Royal Netherlands Meteorology Institute and Dr MR van den Broeke, University of Utrecht, Netherlands.

The dataset quantifies how, where and when the Greenland ice sheet has fed fresh water through iceberg calving, subglacial melting and meltwater runoff into the surrounding ocean during the last half century.

This dataset collection contains precipitation, evaporation and run off model outputs.

The thermohaline circulation is a global ocean circulation, driven by differences in the density of the sea water that is controlled by temperature (thermal) and salinity (haline). In the north Atlantic, the thermohaline circulation transports warm and salty water to the north, where it, together with the North Atlantic Drift (the north-eastern most extension of the Gulfstream), contributes to the warm sea surface along the coast of western Europe and to the relatively mild European winters. From ice cores drilled in Greenland, there is evidence that rapid climate changes took place during the last glacial (the period roughly from 100,000 to 20,000 years before present): over a period of just several decades, northern European winter temperature dropped by as much as 10 degrees for periods typically lasting 1000 years. The present explanation is that large, pulse-like freshwater fluxes (probably from icebergs that originated from the continental ice sheets) were released into the north Atlantic where they weakened or shut down the thermohaline circulation. In a warmer greenhouse climate, it is also likely that the freshwater flux into the north Atlantic will increase; using a scenario of doubling CO2 within the next 70 years, most atmospheric models predict an increase in precipitation in high latitudes. One of the great uncertainties in these projections is the role of the Greenland ice sheet, which is situated in the middle of the area of interest. We know so little about the variability in its meltwater production and its sensitivity to regional warming that its contribution to the problem of the north Atlantic thermohaline circulation is often ignored, in spite of the fact that the Greenland ice sheet contains enough water to rise global sea level by 6 m! In this proposed research we quantifyed in detail how, where and when the Greenland ice sheet has fed fresh water through iceberg calving, subglacial melting and meltwater runoff into the surrounding ocean during the last half century. The melting and runoff was calculated using a coupled snow - atmosphere model that is run over Greenland at very high resolution (11 km in the horizontal), which took about 1 year on a supercomputer to run!

Rapid Climate Change (RAPID) was a £20 million, six-year (2001-2007) programme for the Natural Environment Research Council. The programme aimed to improve the ability to quantify the probability and magnitude of future rapid change in climate, with a main (but not exclusive) focus on the role of the Atlantic Ocean's Thermohaline Circulation.

格陵兰冰盖的质量平衡与淡水资源贡献：结合模型模拟与观测方法的科研项目，该项目由布里斯托尔大学的约翰逊·贝默教授领导，联合挪威的南森环境与遥感中心、荷兰皇家气象研究所以及荷兰乌德勒支大学的M.R.范登布罗克博士共同参与。该项目属于自然环境保护理事会（NERC）快速气候变化研究计划（RAPID Climate Change Research Programme）项目（联合国际圆桌 - NE/C51631X/1 - 持续时间：2005年6月1日至2008年11月30日）。该数据集量化了在过去半个世纪中，格陵兰冰盖如何、何地以及何时通过冰山崩解、冰下融化和融水径流向周边海洋输送淡水。该数据集集合了降水、蒸发和径流的模型输出。热盐环流是全球海洋环流，由海水密度差异驱动，密度由温度（热力）和盐度（盐度）控制。在北大西洋，热盐环流将温暖且盐度高的海水输送到北方，与北大西洋漂流（墨西哥湾流的最东北端延伸）共同促进了西欧沿海的海面温暖以及相对温和的欧洲冬季。在从格陵兰钻取的冰芯中，有证据表明，在最后冰川时期（大约100,000年至20,000年前）发生了快速的气候变化：在短短几十年内，北欧冬季温度下降了多达10度，通常持续1000年。目前的解释是，大型的脉冲状淡水通量（可能来自大陆冰盖起源的冰山）被释放到北大西洋，它们削弱或关闭了热盐环流。在一个更暖的温室气候中，北大西洋的淡水通量也很可能增加；使用未来70年内CO2翻倍的场景，大多数大气模型预测高纬度地区降水增加。在这些预测中，格陵兰冰盖的作用是一个巨大的不确定性。我们对它的融水产量变化及其对区域变暖的敏感性了解甚少，尽管格陵兰冰盖含有的水量足以使全球海平面上升6米！在本项拟议的研究中，我们详细量化了在过去半个世纪中，格陵兰冰盖如何、何地以及何时通过冰山崩解、冰下融化和融水径流向周边海洋输送淡水。融化和径流计算使用了在格陵兰以非常高的分辨率（水平方向为11公里）运行的耦合雪-大气模型，该模型在超级计算机上运行需要大约1年时间！快速气候变化（RAPID）是自然环境保护理事会的一项为期六年的（2001-2007年）价值2000万英镑的项目。该计划旨在提高量化未来快速气候变化概率和幅度的能力，主要但非唯一关注点是北大西洋热盐环流的作用。