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(GRI)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)。由于人口稠密的沿海和低洼地区的生存面临风险，这些信息引起了世界各地政府政策制定者的关注。目前有很大的科学需求来预测未来几十年地球表面将发生的融化量(3)，因为不确定性很高。目前用于预测气候变暖时融化量的模型在很大程度上依赖于确定反照率，即积雪和冰面反射程度与到来的太阳能的比率。更白的表面据说有更高的反照率，反射更多的阳光，融化更少。较暗的表面吸收更多的阳光，因此融化得更多。反照率随时间的变化取决于许多因素，包括冰雪的湿度。到目前为止，一个被忽视的重要因素是生物反照率。湿冰雪中的每一滴水都含有数以千计的微小微生物，其中大部分是藻类和蓝藻，它们是有色的--它们有内置的防晒霜--以保护它们免受阳光的伤害。这些藻类和蓝藻对反照率有很大影响，显著降低了反照率。它们还将降雪从空气中卷走的尘埃颗粒粘合在一起。这些尘埃颗粒还含有工业活动和森林火灾产生的烟尘，因此表面的有色微生物和黑色尘埃的混合形成了较暗的冰盖。我们迫切需要更多地了解导致和限制有色微生物生长的因素。我们团队最近在格陵兰岛西南部冰盖表面最暗的区域进行的研究表明，最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生长得同样好，那么整个冰盖的融化速度将会非常快。一个主要的担忧是，在气候变暖期间，这些微生物将在更多潮湿的冰面上生长，并持续更长时间，因此这些微生物将在更大的区域内大量生长，从而降低反照率，增加每年发生的融化量。微生物需要的营养-植物食物-来自冰盖表面的冰晶和灰尘，人们担心雪和冰中氮含量的增加可能会促进微生物的生长。该项目的目标是第一次研究气候变暖时微生物的生长和传播，并将生物变暗纳入预测灰色系统未来融化的模型中。参考文献1。萨斯根一世和其他8人。格陵兰岛近期区域性冰块消融的时间和来源。地球和行星科学通讯，333-334,293-303(2012)2.Rignot，E.，Velicogna，I.，van den Broeke，M.R.，Monaghan，A.&Lenairts，J.格陵兰和南极冰盖加速对海平面上升的贡献。地球上的植物。莱特资源。38，L05503，DOI：10.1029/2011gl046583(2011年)。米尔恩，G.A.，盖瑞斯，W.R.，休斯，C.W.和Tamisiea，M.E.确定海平面变化的原因。《自然地理》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).