Omitted from the 2007 IPCC Fourth Assessment Report on Climate Change was the potential contribution from ice sheets to global sea level. This reflected the level of uncertainty with respect to the ice dynamics (motion) and mass balance (snow and ice accumulation vs. snow and ice loss) of the extant ice sheets in Greenland and Antarctica. One potential key control on ice dynamics is glacier crevassing which can facilitate the routing of surface melt water to the ice sheet bed leading to increased sliding velocities on outlet glaciers. Additionally, crevassing controls the production of icebergs at marine terminating margins, through which the Greenland Ice Sheet disposes of ~50% and the Antarctic Ice Sheet almost all of their respective annual ice loss. Iceberg production (calving) may be through a combination of both bottom-up and top-down crevassing but atmospheric warming, by increasing the availability of melt water to fill surface crevasses, is likely to be the main driver of change, in the short term at least. Only recently have advances been made in the development of physics-based crevassing/calving relationships with incorporation into predictive numerical models. These advances are vital for improving our predictions for the response of the big ice sheets to future warming. However, only one study to date has tested these physics-based crevassing relationships and then only for shallow water-free crevasses. Given the current research focus on glacier crevassing, there is an urgent need to test crevassing models. To do this in the field is however challenging, due to difficulties of working in crevasse zones of glaciers, measuring the depth of what ultimately ends in a hairline crack at depth and associating the crevasse with the instantaneous stress/strain field. Project Partner DB has a project in preparation to deploy instrumentation for continuous water level monitoring in crevasses on Kronebreen, Svalbard. Geophysical imaging is currently problematic for example signal attenuation on 'warm' temperate glaciers, signal interference from adjacent crevasses in crevasse fields and obtaining the resolution to image the crevasse (crack) tip. Likewise controlling water-depth to force crevasse penetration would present significant challenges for example, the volume of water needed for filling a crevasse or connection with the englacial drainage system leading to water loss etc. Field monitoring of glacier crevassing is thus in its infancy. A modelling approach therefore represents an ideal way forward. However, lab-floor models are useless because the stresses relevant to crevasse propagation increase as a function of both the self-weight stress (gravity x ice density x ice thickness) and crack length i.e. the crevasse depth. The geotechnical centrifuge is a unique modelling tool which allows the magnitude self weight stresses to be reproduced, with stress equivalence between the prototype (real world) and the model by scaling down the dimensions in the model but 'enhancing' gravity. This is achieved by 'flying' (spinning) the model in the centrifuge such that an Nth scale model flown at N times gravity generates the same self-weight stress as the prototype. Scaling relationships are already established for all the parameters relevant to this study so no scaling issues are anticipated, but the standard modelling of models centrifuge technique will be employed to confirm this. Then a series of models will be run, replicating the stress levels experienced in a prototype glacier section ~50x80x50 m. Pre-cast crevasses will be filled with water to facilitate step-wise full-depth crevasse penetration allowing the current state of the art physics-based models to be tested. This project will provide a proof of concept which will facilitate further grant applications where more complex models (e.g. bottom-up and top-down) can be built and used to test and develop physical models.

On June 15 2006, the World Wildlife Federation (WWF) released a report called 'Killing them Softly', which highlighted concern over the accumulation and toxic effects of persistent organic pollutants present in Arctic wildlife, particularly marine mammals such as the Polar Bear. The Times newspaper ran a full-page article summarising this report and detailed 'legacy' chemicals such as DDT and polychlorinated biphenyls (PCBs), as well as the rise in 'new' chemical contaminants such as brominated flame retardents and perfluorinated surfactants, which are also accumulating in arctic fauna and adding an additional toxic risk. The high levels of these contaminants are making animals like the Polar Bear less capable of surviving the harsh Arctic conditions and dealing with the impacts of climate change. The work in this proposal intends to examine how these chemicals are delivered to surface waters of the Arctic Ocean, and hence the base of the marine foodweb. Persistent organic pollutants reach the Arctic via long-range transport, primarily through the air from source regions in Europe, North America and Asia, but also with surface ocean currents. The cold conditions of the Arctic help to promote the accumulation of these chemicals in snow and surface waters and slows any breakdown and evaporative loss. However, the processes that remove these pollutants from the atmosphere, store them in snow and ice and then transfer them to the Arctic Ocean are poorly understood, and yet these processes may differ depending on the chemcial in question. For example, some chemicals are rather volatile (i.e. they have a tendency to evaporate), so while they can reach the Arctic and be deposited with snowfall they are unlikely to reach the ocean due to ltheir oss back to the atmosphere during the arctic summer. On the other hand, heavier, less volatile chemicals, become strongly bound to snow and particles and can be delivered to seawater during summer melt. Climate change and a warmer world are altering the Arctic and affecting pollutant pathways. For example, the number of ice-leads (large cracks in the sea-ice that give rise to 'lakes' of seawater) are increasing. As a result, the pathways that chemical pollutants take to reach ocean waters are changing and may actually be made shorter, posing an even greater threat to marine wildlife. During ice-free periods, the ocean surface water is in contact with the atmosphere (rather than capped with sea-ice) and airborne pollutants can dissolve directly into cold surface waters. Encouragingly, there is evidence that some of the 'legacy' pollutants are declining in the arctic atmosphere, but many 'modern' chemicals are actually increasing in arctic biota and work is required to measure their input and understand their behaviour in this unusual environment. For example, in sunlit surface snow following polar sunrise (24 h daylight), some of these compounds can degrade by absorbing the sunlight, and in some cases, this can give rise to more stable compounds that subsequently enter the foodchain. Therefore, the quantity of chemical pollutant that is deposited with snowfall and the chemical's fate during snowmelt are important processes to address, especially to understand the loading and impact of these pollutants on the marine ecosystem. This project aims to understand these processes, and to understand which type of pollutants and their quantities pose the greatest threat to wildlife.

Global warming is melting many of Earth's glaciers, increasing the production of meltwater as the glaciers expire. In the worst-case scenario, up to 85% of glaciers will be lost by 2100, which will then mean the production of meltwater will decline drastically. About a billion people depend on rivers fed by glacier meltwater for water, and nutrients in glacial meltwater fertilize crucial ecosystems. This glacial meltwater contains bacteria and their products. We have found some of these products are made to protect bacteria against their viruses, and have proof that these same products have a second job in dissolving nutrients from rocks. Earlier research tell us the meltwater bacteria, their products and the nutrients are critical for important ecosystems in the land and sea fed by glacier meltwater. But we do not know how many of these three things will be released as the glaciers die, how they will interact and what this change in the supply of bacteria, products and nutrients will mean for ecosystems fed by glaciers that will disintegrate this century. Our proposal aims to address these three gaps in our knowledge. In this project we will go to valley glaciers on Svalbard in the High Arctic, in Austria in the European Alps, and Livingston Island at the tip of the rapidly warming Antarctic Peninsula to see how microbes and their products are released from glaciers. At each location we will collect samples from the glacier surface which will tell us how the microbes grow in the ice surface and how they are released. We will conduct experiments to reveal how the "arms race" between microbes and their viruses affects the delivery of microbes, their products and nutrients in the meltwater. We will also sequence the DNA of microbes living in the ice surface and meltwater to see who is living in this very large, but poorly understood and endangered habitat. We will use our fieldwork and lab analyses to inform models of how glaciers release their microbes, and what this means for downstream habitats. By doing this we will have a clear picture for the first time of how the loss of glaciers will release microbes, and what those organisms may do as they are washed out to important environments downstream of the glaciers.

Life thrives even on the sun-kissed surfaces of glaciers. But does life on ice survive in the darkened depths of Arctic winters and sediments? We know glacier surfaces are home to active microbial ecosystems. We know that in summer these photosynthesis-driven ecosystems fix carbon and darken ice as solar energy is converted to dark organic carbon. As a result, ecosystems on glaciers influence the fate of glaciers in our warming world. Until now, biogeochemists have assumed ecosystems on glaciers are only active when nourished with sunlight and nutrients in liquid meltwater in the brief melting season of summer. This constraint has framed our understanding of glacier surface ecology to the extent that the absence of evidence for active microbial processes on glaciers in winter has been considered evidence of their absence. But we now have year-round data which robustly challenges the assumption life is only active in summer. Our pilot data also reveals methane producers for the first time on ice surfaces. This project therefore tests the simple but powerful idea that glacier surface habitats are perennially active, resulting in unexpected sources of greenhouse gases. Our project proposes to address three interlinked major knowledge gaps in our understanding of glacier ecology. Firstly, we need to know what lives through the winter, secondly, we need to know what lives in thick accumulations of sediments on ice, and finally we need to know how the microbial life forms surviving through darkness influence carbon and nutrient cycles on glaciers. Our project's overall hypothesis is that glacier surfaces host light-independent microbial metabolic activities, thus allowing microbial activities in unexpected conditions with neglected contributions to nutrient cycles and greenhouse gas production. In this project we will go the High Arctic glaciers of Svalbard in every season to compare their microbial communities in the depths of polar night, the cold of the winter, the spring thaw and the height of summer. At each glacier we will collect samples for molecular analyses and measure microbial activities. We will conduct experiments to reveal how the microbes survive in these conditions, and how they interact with the carbon and nutrient cycles of the glaciers. We combine our fieldwork with carefully-controlled incubation experiments in cold labs in the UK, US and Norway. By doing this, we will have a clear picture for the first time of how life survives all seasons on Arctic glaciers and what this means for the ecology of Arctic glaciers as they face an uncertain future in the warming Arctic.

The impacts of climate change, and warming in particular, on natural ecosystems remain poorly understood, and research to date has focused on individual species (e.g. range shifts of polar bears). Multispecies systems (food webs, ecosystems), however, can possess emergent properties that can only be understood using a system-level perspective. Within a given food web, the microbial world is the engine that drives key ecosystem processes, biogeochemical cycles (e.g. the carbon-cycle) and network properties, but has been hidden from view due to difficulties with identifying which microbes are present and what they are doing. The recent revolution in Next Generation Sequencing has removed this bottleneck and we can now open the microbial "black box" to characterise the metagenome ("who is there?") and metatranscriptome ("what are they doing?") of the community for the first time. These advances will allow us to address a key overarching question: should we expect a global response to global warming? There are bodies of theory that suggest this might be the case, including the "Metabolic Theory of Ecology" and the "Everything is Everywhere" hypothesis of global microbial biogeography, yet these ideas have yet to be tested rigorously at appropriate scales and in appropriate experimental contexts that allow us to identify patterns and causal relationships in real multispecies systems. We will assess the impacts of warming across multiple levels of biological organisation, from genes to food webs and whole ecosystems, using geothermally warmed freshwaters in 5 high-latitude regions (Svalbard, Iceland, Greenland, Alaska, Kamchatka), where warming is predicted to be especially rapid,. Our study will be the first to characterise the impacts of climate change on multispecies systems at such an unprecedented scale. Surveys of these "sentinel systems" will be complemented with modelling and experiments conducted in these field sites, as well as in 100s of large-scale "mesocosms" (artificial streams and ponds) in the field and 1,000s of "microcosms" of robotically-assembled microbial communities in the laboratory. Our novel genes-to-ecosystems approach will allow us to integrate measures of biodiversity and ecosystem functioning. For instance, we will quantify key functional genes as well as quantifying which genes are switched on (the "metatranscriptome") in addition to measuring ecosystem functioning (e.g. processes related to the carbon cycle). We will also measure the impacts of climate change on the complex networks of interacting species we find in nature - what Darwin called "the entangled bank" - because food webs and other types of networks can produce counterintuitive responses that cannot be predicted from studying species in isolation. One general objective is to assess the scope for "biodiversity insurance" and resilience of natural systems in the face of climate change. We will combine our intercontinental surveys with natural experiments, bioassays, manipulations and mathematical models to do this. For instance, we will characterise how temperature-mediated losses to biodiversity can compromise key functional attributes of the gene pool and of the ecosystem as a whole. There is an assumption in the academic literature and in policy that freshwater ecosystems are relatively resilient because the apparently huge scope for functional redundancy could allow for compensation for species loss in the face of climate change. However, this has not been quantified empirically in natural systems, and errors in estimating the magnitude of functional redundancy could have substantial environmental and economic repercussions. The research will address a set of key specific questions and hypotheses within our 5 themed Workpackages, of broad significance to both pure and applied ecology, and which also combine to provide a more holistic perspective than has ever been attempted previously.