BLACK and BLOOM: variations in the albedo of the Greenland Ice Sheet as a result of interactions between microbes and particulates.

人们越来越担心格陵兰冰盖（GrIS）表面发生了多少融化，以及这种融化将在多大程度上导致海平面上升。似乎融化量正在加速，对海平面上升的影响每年超过1毫米（2）。这一信息引起了世界各地政府决策者的关注，因为这对沿海和低洼地区人口稠密地区的生存能力构成了风险。目前有一个巨大的科学需要预测未来几十年内GrIS表面将发生的融化量（3），因为不确定性很高。目前用于预测温暖气候下融化量的模型在很大程度上依赖于确定积雪和冰面对入射太阳能的反射率。较白的表面被认为具有较高的反射率，反射较多的阳光，因而融化较少。较暗的表面吸收较多的阳光，因而融化较多。雪的温度如何随时间变化取决于许多因素，包括雪和冰的湿度。迄今为止被忽略的一个重要因素是生物学。湿雪和冰中的每一滴水都含有数千种微小的微生物，主要是藻类和蓝藻，它们被染色-它们有一个内置的防晒霜-以保护它们免受阳光照射。这些藻类和蓝藻对浮游生物有很大的影响，使其显著降低。它们还能将被降雪从空气中扫出的灰尘颗粒粘在一起。这些尘埃颗粒还含有来自工业活动和森林火灾的烟灰，因此，表面的有色微生物和深色尘埃的混合物产生了更深的冰盖。我们迫切需要更多地了解导致和限制色素微生物生长的因素。我们小组最近在格陵兰岛西南部冰盖表面最黑暗的区域进行的研究表明，最黑暗的区域拥有最多的细胞。如果这些藻类在冰盖表面的其他区域同样生长良好，那么整个冰盖的融化速度将非常快。一个主要的问题是，在气候变暖期间，将有更多的潮湿冰面供这些微生物生长，并且生长时间更长，因此微生物将在更大的面积上以更大的数量生长，降低每年发生的融化量。微生物所需的营养-植物食物-来自冰盖表面的冰晶和灰尘，人们担心冰雪中氮含量的增加可能有助于微生物的生长。该项目旨在成为第一个研究微生物在气候变暖中的生长和传播的项目，并将生物变暗纳入预测未来GrIS融化的模型中。参考资料1. Sasgen I和其他8人。格陵兰岛最近区域冰量损失的时间和起源。地球和行星科学快报，333-334，293-303（2012）。Rignot，E.，韦利科尼亚岛货车登布鲁克，M. R.，Monaghan，A. & Lenaerts，J.格陵兰和南极冰盖对海平面上升的加速贡献。地球物理学家。保留信函38，L05503，doi：10.1029/2011gl046583（2011）。Milne，G.一、Gehrels，W. R.，休斯角W. & Tamisiea，M. E.找出海平面变化的原因。Nature Geosci 2，471-478（2009）.

Concerns are growing about how much melting occurs on the surface of the Greenland Ice Sheet (GrIS), and how much this melting will contribute to sea level rise (1). It seems that the amount of melting is accelerating and that the impact on sea level rise is over 1 mm each year (2). This information is of concern to governmental policy makers around the world because of the risk to viability of populated coastal and low-lying areas. There is currently a great scientific need to predict the amount of melting that will occur on the surface of the GrIS over the coming decades (3), since the uncertainties are high. The current models which are used to predict the amount of melting in a warmer climate rely heavily on determining the albedo, the ratio of how reflective the snow cover and the ice surface are to incoming solar energy. Surfaces which are whiter are said to have higher albedo, reflect more sunlight and melt less. Surfaces which are darker adsorb more sunlight and so melt more. Just how the albedo varies over time depends on a number of factors, including how wet the snow and ice is. One important factor that has been missed to date is bio-albedo. Each drop of water in wet snow and ice contains thousands of tiny microorganisms, mostly algae and cyanobacteria, which are pigmented - they have a built in sunblock - to protect them from sunlight. These algae and cyanobacteria have a large impact on the albedo, lowering it significantly. They also glue together dust particles that are swept out of the air by the falling snow. These dust particles also contain soot from industrial activity and forest fires, and so the mix of pigmented microbes and dark dust at the surface produces a darker ice sheet. We urgently need to know more about the factors that lead to and limit the growth of the pigmented microbes. Recent work by our group in the darkest zone of the ice sheet surface in the SW of Greenland shows that the darkest areas have the highest numbers of cells. Were these algae to grow equally well in other areas of the ice sheet surface, then the rate of melting of the whole ice sheet would increase very quickly. A major concern is that there will be more wet ice surfaces for these microorganisms to grow in, and for longer, during a period of climate warming, and so the microorganisms will grow in greater numbers and over a larger area, lowering the albedo and increasing the amount of melt that occurs each year. The nutrient - plant food - that the microorganisms need comes from the ice crystals and dust on the ice sheet surface, and there are fears that increased N levels in snow and ice may contribute to the growth of the microorganisms. This project aims to be the first to examine the growth and spread of the microorganisms in a warming climate, and to incorporate biological darkening into models that predict the future melting of the GrIS. References1. Sasgen I and 8 others. Timing and origin of recent regional ice-mass loss in Greenland. Earth and Planetary Science Letters, 333-334, 293-303(2012).2. Rignot, E., Velicogna, I., van den Broeke, M. R., Monaghan, A. & Lenaerts, J. Acceleration of the contribution of the Greenland and Antarctic ice sheets to sea level rise. Geophys. Res. Lett. 38, L05503, doi:10.1029/2011gl046583 (2011).3. Milne, G. A., Gehrels, W. R., Hughes, C. W. & Tamisiea, M. E. Identifying the causes of sea-level change. Nature Geosci 2, 471-478 (2009).