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The cloud feedback may result in amplification or damping of Arctic warming. Two common techniques used to diagnose the top‐of‐the‐atmosphere cloud feedback are the Adjusted Cloud Radiative Effect (AdjCRE) method and the Cloud Radiative Kernel (CRK) method. We apply both to CMIP5 and CMIP6 model data, finding that the AdjCRE calculated Arctic shortwave cloud feedback is twice as correlated with sea ice loss in CMIP5, and four times in CMIP6, as the CRK method. We find that the CRK method produces Arctic all‐sky residual percentages exceeding 20% in 15 of 18 models. We use the CRK method to decompose the feedback in CMIP5 and CMIP6 finding that its median value changed from negative to positive driven by a less‐negative cloud optical depth feedback. Despite its lack of closure, we conclude that the CRK method is better suited for Arctic SW feedbacks as it is less impacted by surface albedo changes. Plain Language Summary: The cloud feedback is the process by which cloud property changes in a warming climate can either further enhance warming or damp it. The Arctic is warming faster than the rest of the globe, and one of the largest sources of uncertainty in its climate projections is the cloud feedback. There are two popular methods to calculate the cloud feedback: the Adjusted Cloud Radiative Effect technique, and the Cloud Radiative Kernel technique. In this paper we compare the two methods in a suite of climate models by considering the extent to which changes in Arctic sea ice impact the cloud feedbacks. From this analysis we conclude that the Cloud Radiative Kernel method is less affected by sea ice loss. We then apply the Cloud Radiative Kernel technique to data from the two most recent generations of global climate models to investigate how polar day Arctic cloud feedbacks have changed between these generations. We find that the median value of these Arctic feedbacks is slightly positive in the newest generation of models, a change from slightly negative in the previous generation that is largely fueled by a weakening of the feedback associated with changes in cloud optical depth. Key Points: The Cloud Radiative Kernel method is less sensitive to surface albedo changes than the Adjusted Cloud Radiative Effect techniqueThe Cloud Radiative Kernel method provides poor radiative closure in a suite of global climate modelsThe median shortwave Arctic cloud feedback in recent climate models is slightly positive due to a weakened cloud optical depth feedback [ABSTRACT FROM AUTHOR]

Climate change is predicted to have dramatic effects on Arctic freshwater ecosystems through changes to the abiotic template that are expected to influence biodiversity. Changes are already ongoing in Arctic systems, but there is a lack of coordinated monitoring of Arctic freshwaters that hinders our ability to assess changes in biodiversity.To address the need for coordinated monitoring on a circumpolar scale, the Arctic Council working group, Conservation of Arctic Flora and Fauna, established the Circumpolar Biodiversity Monitoring Program, which is an adaptive monitoring program for the Arctic centred around four ecosystem themes (i.e., Freshwater, Terrestrial, Coastal, Marine). The freshwater theme developed a monitoring plan for Arctic freshwater biodiversity and recently completed the first assessment of status and trends in Arctic freshwater biodiversity.Circumpolar Biodiversity Monitoring Program–Freshwater has compiled and analysed a database of Arctic freshwater monitoring data to form the first report of the state of circumpolar Arctic freshwater biodiversity. This special issue presents the scientific analyses that underlie the Circumpolar Biodiversity Monitoring Program–Freshwater report and provides analyses of spatial and temporal diversity patterns and the multiple‐stressor scenarios that act on the biological assemblages and biogeochemistry of Arctic lakes and rivers.This special issue includes regional patterns for selected groups of organisms in Arctic rivers and lakes of northern Europe, Russia, and North America. Circumpolar assessments for benthic diatoms, macrophytes, plankton, benthic macroinvertebrates, and fish demonstrate how climate change and associated environmental drivers affect freshwater biodiversity. Also included are papers on spatial and temporal trends in water chemistry across the circumpolar region, and a systematic review of documented Indigenous Knowledge that demonstrates its potential to support assessment and conservation of Arctic freshwaters.This special issue includes the first circumpolar assessment of trends in Arctic freshwater biodiversity and provides important baseline information for future assessments and studies. It represents the largest compilation and assessment of Arctic freshwater biodiversity data to date and strives to provide a holistic view of ongoing change in these ecosystems to support future monitoring efforts. By identifying gaps in monitoring data across the circumpolar region, as well as identifying best practices for monitoring and assessment, this special issue presents an important resource for researchers, policy makers, and Indigenous and local communities that can support future assessments of ecosystem change. [ABSTRACT FROM AUTHOR]

Indigenous Peoples in the Arctic have for millennia relied on freshwaters for drinking water and freshwater species that comprise important subsistence harvests, which promotes a strong connection to the land and unique understanding of organisms and ecosystem processes and changes. Despite the importance of freshwater biodiversity and ecosystem services to Arctic Indigenous communities, there have been limited attempts to summarise available Indigenous Knowledge (IK) regarding Arctic freshwater systems and to understand how conservation can benefit from this knowledge base.This paper presents a systematic review of literature documenting circumpolar Arctic IK with a focus on freshwater biodiversity in Canada, Greenland, Fennoscandia (Norway, Sweden, and Finland), Russia, and the U.S.A. (Alaska). Standardised search terms and methodologies were used to locate relevant documents using Google Scholar and Google Advanced search engines. Thematic coding was used to identify freshwater biodiversity themes within the identified documents.Documented IK of freshwater biodiversity was found from all five geographic regions and included data on both species presence and habitat changes with potential to affect biodiversity. Canada had the highest number of relevant documents (n = 127), followed by the U.S.A. (Alaska; n = 116), Fennoscandia (n = 38), Russia (n = 27), and Greenland (n = 5). The number of relevant documents with IK published per year was highest in most recent years, from 2010 onwards, in all geographic regions.Fish represented the highest number of faunal observations with 59 species observed, approximately half of which were Salmonidae (29 species). Local‐scale assessment of fish diversity found observations of the highest number of species (11–25) in Alaska, and individual observations of 6–10 species were found throughout Alaska, mainland areas of Canada, and the Kola Peninsula in Russia. Documented IK also contributed new information on historical fish diversity and indicated local‐scale loss or gain of species. Such information is of vital importance to provide long‐term records of fish composition and abundance, especially when this information does not exist in other knowledge bases such as western science datasets.Indigenous Knowledge included observations of changes in freshwater and terrestrial habitat associated with a warming climate, such as: decreasing water levels and more draining/drying of lakes and rivers, a shorter period of ice cover (late freeze and early break‐up), decreasing ice thickness, and increasing occurrence of permafrost thaw and eroding banks. Such observations by those who actively rely on Arctic freshwater ecosystem services are important because they signify that change is occurring and that action is needed to mitigate the impacts on freshwater habitats and the biodiversity therein.This study demonstrates that previously documented IK provides valuable information towards determining freshwater biodiversity baselines and patterns of change in the circumpolar Arctic. However, these results do not sufficiently cover the depth and breadth of IK on freshwater biodiversity and ecology held by Indigenous communities. Further work incorporating Indigenous worldviews around freshwater ecology would provide context to the knowledge collected and a deeper understanding of Arctic circumpolar freshwater environments. [ABSTRACT FROM AUTHOR]