It is very important for us to find out how climate changed in the past. Without knowing, we cannot predict how the future climate might behave. Global, systematic measurements of climatic variables have only been collected over the last few decades but we need to know how it varied through longer periods of time. We particularly need to know about this in the North Atlantic shelf seas which are currently experiencing accelerating climate change. The layers of ocean sediments in these regions contain the skeletons of microscopic organisms which can provide information about past climate. Benthic foraminifers in particular live in these shallow ocean habitats and their microscopic calcite shells accumulate through time providing a high resolution record of past environments. Communities of specific species (assemblages) are associated with the regional habitats of the shelf seas and this relationship is applied to similar assemblages found in time slices in the sediments (transfer functions). Forams also incorporate into their shells the physical and chemical signatures of the seawater in which they grow. This can be used as a geochemical 'proxy' to reconstruct the past environment in which they lived. All these past climate reconstructions are based on the assumption that the shells of a single species were constructed in the same range of environmental conditions. Using a unique DNA marker in living forams, we know that this is not always true. Individual morphospecies sometimes represent several distinct genetic types (genotypes) which may be adapted to different environments within a morphospecies range. It is highly likely that these are different species. Scientists are unknowingly analysing a mixture of different species because they look very similar (cryptic species). This will introduce noise and possible error into the data of both transfer function methods and geochemical proxies. To overcome this, we propose to genotype all the important benthic morphospecies used for past climate reconstruction throughout the regional habitats (biogeographic provinces) of the mid to high latitudes of the northeast Atlantic. We will sample these with the help of our four project partners from Norway and Iceland. We also have to bear in mind that these regions experience a wide range of environmental conditions as the seasons change. To address this, we will take samples from regions where seasonal studies are being carried to find out whether different genotypes appear as the environmental conditions change. Central to this study will be an extensive morphological investigation of shell shape to find out whether we can find subtle differences to help recognise the new genotypes in the modern ocean and most importantly, in the fossil record. We hope to genetically and morphologically define all important benthic morphospecies used for past climate reconstruction in the North East Atlantic to produce a unified classification scheme. From our high resolution sampling, we will be able to produce a new bioprovince distribution map for the present day northeast Atlantic/Arctic. We will discover whether 'generalist' species really occupy different bioprovinces or represent a series of different cryptic species with different ecologies. Finding identifiable new species will improve our understanding of how bioprovinces have migrated North/South as the glacial cycles have come and gone. Do different cryptic species appear in the same place as the seasons change? Their recognition would allow the exploration of seasonality in the fossil record. Do foram shells of the same species have a different shape in different environments? Confirmation will provide evidence of specific environmental conditions in the present day and in the past. This link between present and past also provides important clues about how extreme changes in these dynamic marine environments affect the survival of species and drive their evolution through time.

Copepod species of the genus Calanus (Calanus hereafter) are rice grain-sized crustaceans, distant relatives of crabs and lobsters, that occur throughout the Arctic Ocean consuming enormous quantities of microscopic algae (phytoplankton). These tiny animals represent the primary food source for many Arctic fish, seabirds and whales. During early spring they gorge on extensive seasonal blooms of diatoms, fat-rich phytoplankton that proliferate both beneath the sea ice and in the open ocean. This allows Calanus to rapidly obtain sufficient fat to survive during the many months of food scarcity during the Arctic winter. Diatoms also produce one of the main marine omega-3 polyunsaturated fatty acids that Calanus require to successfully survive and reproduce in the frozen Arctic waters. Calanus seasonally migrate into deeper waters to save energy and reduce their losses to predation in an overwintering process called diapause that is fuelled entirely by carbon-rich fat (lipids). This vertical 'lipid pump' transfers vast quantities of carbon into the ocean's interior and ultimately represents the draw-down of atmospheric carbon dioxide (CO2), an important process within the global carbon cycle. Continued global warming throughout the 21st century is expected to exert a strong influence on the timing, magnitude and spatial distribution of diatom productivity in the Arctic Ocean. Little is known about how Calanus will respond to these changes, making it difficult to understand how the wider Arctic ecosystem and its biogeochemistry will be affected by climate change. The overarching goal of this proposal is to develop a predictive understanding of how Calanus in the Arctic will be affected by future climate change. We will achieve this goal through five main areas of research: We will synthesise past datasets of Calanus in the Arctic alongside satellite-derived data on primary production. This undertaking will examine whether smaller, more temperate species have been increasingly colonising of Arctic. Furthermore, it will consider how the timing of life-cycle events may have changed over past decades and between different Arctic regions. The resulting data will be used to validate modelling efforts. We will conduct field based experiments to examine how climate-driven changes in the quantity and omega-3 content of phytoplankton will affect crucial features of the Calanus life-cycle, including reproduction and lipid storage for diapause. Cutting-edge techniques will investigate how and why Calanus use stored fats to reproduce in the absence of food. The new understanding gained will be used to produce numerical models of Calanus' life cycle for future forecasting. The research programme will develop life-cycle models of Calanus and simulate present day distribution patterns, the timing of life-cycle events, and the quantities of stored lipid (body condition), over large areas of the Arctic. These projections will be compared to historical data. We will investigate how the omega-3 fatty acid content of Calanus is affected by the food environment and in turn dictates patterns of their diapause- and reproductive success. Reproductive strategies differ between the different species of Calanus and this approach provides a powerful means by which to predict how each species will be impacted, allowing us to identify the winners and losers under various scenarios of future environmental changes. The project synthesis will draw upon previous all elements of the proposal to generate new numerical models of Calanus and how the food environment influences their reproductive strategy and hence capacity for survival in a changing Arctic Ocean. This will allow us to explore how the productivity and biogeochemistry of the Arctic Ocean will change in the future. These models will be interfaced with the UK's Earth System Model that directly feeds into international efforts to understand global feedbacks to climate change.

The Atlantic Ocean's conveyor belt circulation is a fundamental component of the global climate system, transporting heat from low to high latitudes, and thus warming Northern Europe. The strength of this circulation is thought to have varied abruptly in the past, giving rise to rapid climate changes of more than 10 degrees C in a decade during the last glacial period. Changes of this nature today would have a severe impact on society, so we want to know more about the sensitivity of this circulation. In order to do this, we will study intervals of rapid climate and circulation change in the past. To better understand these past circulation changes we will reconstruct the concentration of radiocarbon in surface and deep waters in the North Atlantic Ocean. This is known as a radiocarbon reservoir age, and it is highly sensitive to the rate of ocean circulation. Therefore, by reconstructing reservoir ages, we can tell how quickly the ocean was circulating during intervals of rapid climate change. We also need to know what the reservoir age was in the past if we want to use radiocarbon as a dating tool, to tell the age of geological and archeological objects and events. Radiocarbon can be thought of as a stopwatch for a geological sample. For a marine sample, however, there is already some time on the clock when we press go. This extra time before starting the clock is the reservoir age, and we must know what it is in order to accurately tell geological time. By reconstructing reservoir ages, we will therefore improve understanding of rapid circulation and climate change, and also improve the most important dating tool used in earth and archeological sciences. To reconstruct radiocarbon reservoir ages we need to measure the radiocarbon content of a sample, and also to know its age independently, so we can work out what was already on the clock when the sample formed. To do this we will make radiocarbon measurements on shells taken from sediment cores from the North Atlantic, and pair them with a range of exciting new techniques that can tell their age. Firstly we will look for layers of volcanic ash in the sediment cores, which we can date using their argon content, and match to precisely dated ash layers in ice cores and on Iceland. Secondly we can look at changes in sea surface temperature records, and match these to the same events that are precisely dated in ice cores. Thirdly we will use the concentration of thorium in sediments to tell how much sediment accumulated between these ash and temperature tie points. Fourthly, we will combine all this information using statistical modelling, which will also provide a good measure of the uncertainty in our results. This work will create maps of reservoir ages and how they changed in the North Atlantic over the last 10 to 50 thousand years, with a special focus on times of rapid climate change. To help us link the reservoir ages to different circulation regimes, we will use a climate model that can simulate radiocarbon. We will make this model's ocean circulation operate in different ways, and see which circulations best match our data. This will allow us to better understand how ocean circulation changed in the past to cause rapid climate change, and improve confidence in how ocean circulation may operate in the future. Finally, we will package our reservoir age maps into a tool that can be used by earth scientists and archeologists to improve their radiocarbon dating.

The subject of our study is the aurora borealis, or northern lights, which is an amazing natural lightshow in the sky, seen regularly at high latitudes such as northern Scandinavia, but rarely at the latitudes of the UK. We use the aurora as a diagnostic to find out many things about the environment around the Earth, mainly in the region of upper atmosphere called the ionosphere. That environment is made up of 'plasma' (ionised gas) often called the fourth state of matter, which makes up over 95% of the directly observable material in the cosmos. Yet it is strangely difficult to maintain and study within Earth's biosphere. The upper atmosphere provides an ideal natural laboratory for its study since there is no need to consider collisions of the plasma with container walls. The story of the aurora begins at the Sun, which is a continuous but very variable energy source, in the form of a plasma stream (the 'solar wind') which impacts on the Earth. We are interested in understanding the smallest scale auroral structures, and how the energy changes within them influence the large scale environment. To study the aurora, we use a special instrument which has three cameras looking at different 'colours' simultaneously. The proposed research is for studies of very dynamic and structured aurora at the highest possible resolution. The instrument is named ASK for Auroral Structure and Kinetics. It was designed to measure a small circle of 3 degrees in the 'magnetic zenith' i.e. straight up along the Earth's magnetic field. Particles from the Sun spiral along these imaginary magnetic field lines, and lose energy when they collide with atmospheric oxygen and nitrogen. The exact colour (or wavelength of the light) depends on how much energy the incoming particle started with, and what molecule or atom it hits. The ASK cameras help to unravel this complicated process by making very precise measurements in space and time of three emissions which have different physical origins. We will combine these optical measurements with measurements from special radar experiments, which are designed to use a technique known as interferometry to measure structures smaller than the beam width, and with accuracy of position and height better than has been possible to date. The radar imaging technology is new in the field of incoherent scattering radar and will be one of the cornerstones of a future project that is called EISCAT_3D. The technology employed is Aperture Synthesis Imaging Radar (ASIR). It is very similar to the technology used by radio astronomers (VLBI, Very Long Baseline Interferometry) to image stellar objects, and also has some similarity with the SAR (Synthetic Aperture Radar) technique used onboard airplanes and satellites to map the Earth's surface and other planetary surfaces. In the radio astronomy case the source itself spontaneously emits radiation that is collected by a number of passive antennas. In ASIR, the radar transmitter acts like a camera flash to illuminate the target (the ionosphere or atmosphere) and a number of antennas collect the scattered radiation exactly as in the radio astronomy case (or like the lens of a camera). From this point on, the two cases are essentially identical. To construct the image of the target, the cross-correlation between the signals is calculated from all different pairs of receivers. By using the radar imaging technique we will become the pioneers of this new technique in Europe.

Chlorophyte "snow algae" and Streptophyte "glacier algae" are found across the cryosphere, forming widespread algal blooms in snowpacks and on glacier ice surfaces during spring/summer melt seasons. These blooms hold significant potential to exacerbate the already rapid loss of snowpack and glacial ice resources driven by climate change because they establish albedo feedbacks that amplify melt. Their presence also leads to the construction of active microbial food-webs that provide important ecosystem functions, e.g. carbon sequestration, nutrient cycling and export of resources to down-steam systems. The algae themselves are also important analogs for what life was like on Earth during past mass glaciations, and for how life may exist on other frozen planets across our solar system. Driven by these series of novelties, the snow and glacier algal research community has significantly expanded over recent years, with active projects now spanning Arctic, Alpine and Antarctic regions of the cryosphere. To-date, however, research projects have tended to work in isolation, employing different methods for the analysis of blooms. This has prevented comparisons of findings between regions of the cryosphere and an overall appreciation for the global role and impacts of blooms at present. In turn, we cannot yet project the fate of snow and glacier algal blooms into the future under climate change, or back to the past during key periods of Earth's history. Yet the critical mass achieved in the snow and glacier algal research community also presents an opportunity to pool knowledge and resources, and align methods to drive the field to new achievements. The CASP-ICE project brings together leaders in the field of snow and glacier algal research (x2 UK investigators and x12 international partners) to undertake the foundational work needed to align efforts across the research community and unlock the next generation of science on snow and glacier algal blooms cryosphere-wide. Specifically, we will tackle the following four major tasks: 1. Define consistent methods for sampling and mapping snow and glacier algal blooms within field sites, so that datasets produced into the future will be completely comparable across different regions and times of sampling. 2. Apply these methods in study sites that the CASP-ICE team are currently working to produce the first set of standardized samples and maps of blooms for the community to work with. 3. Undertake the nuts-and-bolts validation of both laboratory-based methods for analyzing field samples as well as computational methods for integrating field measurements and mapping datasets with larger-scale satellite imagery that is needed to monitor blooms at global scales. 4. Establish a list of field sites that can form the backbone of an ongoing cryospheric algal bloom monitoring network and secure the funding to continue monitoring into the future. CASP-ICE will achieve these tasks through a series of networking and knowledge exchange activities as well as hands-on science. An initial workshop in spring 2024 will provide the platform to define best practice methods for the community and start talks on future network structure and direction. All partners will then undertake sampling and sample/data analysis across their respective study regions to produce the first fully validated datasets on snow and glacier algal blooms across the cryosphere. The protocols defined and datasets produced will be leveraged in subsequent funding bids that will be prepared during a series of networking visits and partner meetings led by the project PI, providing the support needed for ongoing monitoring of blooms into the future as climate change proceeds. CASP-ICE will provide the network and scientific foundation needed to tackle the large-scale questions about the role of cryospheric algal blooms in the Earth System at present, into the future under climate change, and back into the past.