Twenty three million square kilometres of northern-hemisphere land - one quarter of the total land area - is permafrost. This permanently frozen ground stores twice as much carbon as the atmosphere contains, with a significant fraction of this carbon as methane. Formation and thawing of permafrost is therefore a significant positive feedback in the climate system, removing greenhouse gas as Earth cools, and releasing it, in periods such as today, when the planet is warming. Permafrost also exerts a strong control on ecosystems and biodiversity, and it underpins human infrastructure (buildings and transport links) in many high-latitude settings. A significant body of research exists (and continues) into active permafrost processes in the modern environment, but assessing the long-term behaviour of permafrost has proved more difficult. We do not yet have a clear idea of how the temperature of high-latitude continental regions responds to changing of global climates through time, nor of the extent of permafrost in different climate states. Such information is important for future planning in today's permafrost regions, and for our general understanding of high-latitude carbon and climate systems. How do the major permafrost regions of the northern hemisphere respond to global climate change such as orbital variation or the progressive cooling of the planet during the Plio-Pleistocene? And what role might permafrost have in these amplifying these changes through its carbon feedbacks on climate? Here we propose to use carbonates formed in caves (speleothems) to assess the extent of permafrost in the world's largest area of permafrost - Siberia. Speleothems require water to form so, when the ground is frozen year-round, do not grow. The presence or absence of speleothems therefore constrains the extent of permafrost through time. We have been working on a sequence of three caves which stretch from the modern edge of the permafrost-free zone near Irkutsk at 52oN, northwards through patchy permafrost and to the edge of continuous permafrost at 60oN. This work has yielded a detailed reconstruction of the permafrost history during the last 450 ka, showing thawing of the permafrost in each warm interglacial period in the south. In the north (60oN) the permafrost remained stable except during the interglacial period 390-430 ka ago when global conditions were warmer than present. We propose to continue the reconstruction of the permafrost history beyond the ~500 ka limit of the U-Th dating method in these caves, and to add a fourth cave in the centre of the continuous permafrost region at 64oN. Using a newly proven U-Pb dating ability, we will date periods of speleothem growth during the Plio-Pleistocne to assess the time, as the planet cooled after the warmth of the Pliocene, that permafrost conditions initiated in Siberia. And we will constrain the changing extent of permafrost during the variable climates of the Pleistocene. By comparing these records with information about climate elsewhere, we will learn how the high latitude northern continents respond to global climate change, particularly during periods warmer than today. To understand how the cave temperatures in each location related to annual mean temperatures above the caves will require a campaign of monitoring in our study caves. We will conduct this work in close collaboration with Russian colleagues from the Russian Academy of Sciences and the well-established Siberian caving community. We will also use our connections in Russia to ensure that new information we learn is provided to stakeholders in regions that will be impacted by changing permafrost in the future.

One of the regions where current global warming is most pronounced is Siberia and the Russian Far East (SRFE). Inconveniently, this is also one of the regions with least coverage of climate records in international databases. As a consequence, it is extremely difficult to analyse and understand the spatial and temporal variations of climate change in SRFE that can provide context for past changes and current warming trajectories, and data are inadequate for syntheses that can aid evaluation of simulations of past climate-an important way to assess how well models perform at projecting the future, whether it be the impact on communities and ecosystems of forest fires or the fate of carbon currently stored in soils and peatlands. The lack of records from SRFE partly reflects that there are few well established, multi-year international collaborations between Russian institutes and international partners. While scientists at Russian institutes have access to large datasets and field sites and have high-quality staff conducting laboratory analyses, they often have less access to the latest analytical approaches and data quality control protocols-or indeed the language fluency currently required for high-impact international publications and data syntheses. This can generate an imbalance of influence within projects and lead to one-sided and/or short-term scientific interactions that do not have long-term direction and coherence. We will address both the science and science culture issues via a network of researchers from the UK and six institutes of the Russian Academy of Sciences in SRFE. Partners in this network have already expressed a strong interest to work together and pool resources to (1) synthesise existing data, (2) learn new methods, and (3) together create new high-quality records of climate and environmental change in this and future research projects. Our network is called DIMA ("Developing Innovative Multi-proxy Analysis"), because we will use multiple new approaches to get climate information from sediment records (proxies) to reconstruct climate change. Our partnership-building and collaboration have several aims. First an extant dataset that described past vegetational change, which has not yet reached an international audience, will be analysed by the DIMA groups to create value-added features (e.g., data formulated for climate-vegetation modelling exercises) prior to publication. Second, we will collect samples to apply a method new to this region for reconstructing past temperatures from insect remains in lake sediments; this will be underpinned by UK-based training of Russian collaborators in the use of the latest laboratory and statistical procedures during a month-long visit of three colleagues from SRFE to the UK. It will involve collecting modern reference samples and generating a high-quality long temperature record from western Siberia as proof-of-concept for an expanded programme. Project leader van Hardenbroek is a specialist in this field. The two selected Russian Project Partners have considerable experience in organising field campaigns and laboratory analysis and will provide the necessary personnel, support and infrastructure. The new data and the experience gained during this project will place the DIMA team in a competitive position to apply for larger collaborative project; the highly motivated team will be geared up to generate long-term climate records across SRFE, produce a high-quality regional temperature synthesis, and develop collaborations with, for example, groups using data compilations to explore climate-vegetation model performance (co-I Edwards current collaboration). This proposal addresses the UK government's expressed need for developing and maintaining strong science ties with key countries, including Russia and strengthening international collaborations outside Europe post-Brexit.

The RACE project addresses the impacts of rapid climate and environmental changes in the Arctic on infrastructure and pan-Arctic and regional population dynamics. By using best available datasets from in-situ and satellite observations and reanalyses together with climate model simulations under CMIP6 RACE will develop improved regional assessments of Arctic Social Indicators, which will be further used for the projections of population dynamics factors as well as demographic and life quality trends of Arctic communities. For the first time results of large-scale climate diagnostics and projections will be used and translated into social indicators and further into demographic variables by using socioeconomic and demographic models, thus providing accurate regional projections of the Arctic population dynamics which presently are routinely relaying exclusively on economy forecasts. The RACE work packages include accumulation and pre-processing of the available climatic, environmental, and socio-economic data for the last decades, which allows for the quantitative assessment of climate and environmental changes in the Arctic critical for the industrial activities and human well-being. They will be used for the development of regional population dynamics umbrella scenarios under different climate change scenarios and associated projections for environment and infrastructure. Of a special importance will the analysis of feedbacks between environmental factors, infrastructure and social indicators and case studies which will identify regions/cities at risk of rapid rates of mortality, net migrations, changes of population structure. RACE scientific results and deliverables will consist of databases of climate and environmental changes in the present and future climate, assessments of their impact onto community well being, projections of climate-mediated pan-Arctic and regional population dynamics and resulting recommendations on future sustainable development of the Arctic communities. RACE results will provide input of immediate relevance for the ongoing IPCC 6th Assessment Report, for Arctic Council Assessments and to the national Climate Change and Sustainability Reports and thus will help to define and implement the growing factor of a changing environment in building strategies for the social-economic development in the Arctic and pan-Arctic regions in the 21st century.

As the global climate warms, thawing permafrost may lead to increased greenhouse gas release from Arctic and Boreal ecosystems. Scientists agree that this permafrost-climate feedback is important to the global climate system, but its magnitude and timing remains poorly understood. The overall aim of COUP is to use detailed understanding of landscape-scale processes to improve global scale climate models. Better predictions of how permafrost areas will respond to a warming climate can help us understand and plan for future global change. In recent years much scientific progress has been made towards understanding the complex responses of permafrost ecosystem to climate warming. Despite this, large challenges remain when it comes to including these processes in global climate models. Permafrost ecosystems are highly variable and studies show that very detailed field investigations are needed to understand complexities. Because global scale models cannot run at such high-resolutions, we propose an approach where local landscape-scale field studies and modelling are used to identify those key variables that should be improved in global models. We will carry out careful field studies and high-resolution modelling at field sites covering all pan-Eurasian environmental conditions. The system understanding gained from this will then be used to (1) scale key variables so they are useful for global models and (2) improve a new global climate model. In the final step, the improved global climate models will be run to quantify the impact of thawing permafrost on the global climate. Datasets produced in COUP will be freely available online so that they can be used by other scientists and help improvement of all global climate models. COUP is designed to maximise synergies with ongoing projects. Much of the needed data and system understanding was generated in other research programmes.