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

人们越来越关注格陵兰冰盖（GrIS）表面的融化程度，以及这种融化将在多大程度上导致海平面上升(1)。融化的速度似乎在加快，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国政府决策者的关注，因为人口稠密的沿海和低洼地区存在生存风险。由于不确定性很大，目前有很大的科学需求来预测未来几十年GrIS表面将发生的融化量(3)。目前用于预测气候变暖情况下冰层融化量的模型在很大程度上依赖于反照率的测定，反照率是指积雪和冰层表面对入射太阳能的反射率。表面越白，反照率越高，反射的阳光越多，融化的越少。较暗的表面吸收更多的阳光，因此融化得更多。反照率如何随时间变化取决于许多因素，包括雪和冰的湿润程度。迄今为止被忽略的一个重要因素是生物反照率。在潮湿的冰雪中，每一滴水都含有成千上万的微小微生物，主要是藻类和蓝藻，这些微生物是色素的，它们有一种内置的防晒霜，可以保护它们免受阳光的照射。这些藻类和蓝藻对反照率有很大的影响，显著降低了反照率。它们还能将被降雪从空气中扫出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，色素微生物和表面的深色尘埃的混合产生了深色的冰盖。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暗的区域进行的研究表明，最暗的区域有最多的细胞。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很快增加。一个主要的担忧是，在气候变暖期间，会有更多的湿冰表面供这些微生物生长，并且生长的时间更长，因此微生物的数量会更多，生长的面积会更大，从而降低反照率，增加每年发生的融化量。微生物所需的营养物质——植物食物——来自冰原表面的冰晶和灰尘，人们担心冰雪中氮含量的增加可能会促进微生物的生长。该项目旨在首次研究微生物在变暖气候下的生长和传播，并将生物变暗纳入预测未来GrIS融化的模型中。引用:1。Sasgen I和其他8人。格陵兰岛近期区域冰块损失的时间和起源。2.地球科学进展，2011,33(4):555 - 557。Rignot， E., Velicogna， I., van den Broeke， M. R., Monaghan， A.和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。《科学通报》38，L05503, doi:10.1029/2011gl046583(2011). 2。Milne, g.a., Gehrels, w.r., Hughes, c.w.和Tamisiea， m.e.确定海平面变化的原因。地球科学进展，23(2),471-478（2009）。

[See lead application]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. References:1. 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).