Proxy-based 300-year High Arctic climate warming record from Svalbard

We used fossil Chironomidae assemblages and the transfer function approach to reconstruct summer air temperatures over the past 300 years from a High Arctic lake in Hornsund, Svalbard. Our aims were to compare reconstructed summer temperatures with observed (last 100 years) seasonal temperatures, to determine a potential climate warming break point in the temperature series and to assess the significance and rate of the climate warming trend at the study site. The reconstructed temperatures were consistent with a previous proxy record from Svalbard and showed good correlation with the meteorological observations from Bjornoya and Longyearbyen. From the current palaeoclimate record, we found a significant climate warming threshold in the 1930s, after which the temperatures rapidly increased. We also found that the climate warming trend was strong and statistically significant. Compared with the reconstructed Little Ice Age temperatures in late eighteenth century cooling culmination, the present day summer temperatures are >4 degrees C higher and the temperature increase since the 1930s has been 0.5 degrees C per decade. These results highlight the exceptionally rapid recent warming of southern Svalbard and add invaluable information on the seasonality of High Arctic climate change and Arctic amplification.Peer reviewe

Models of Arctic-alpine refugia highlight importance of climate and local topography

Projected climatic warming calls for increased attention to the identification of suitable refugia for the preservation of biota and ecosystems in changing high-latitude environments. One such way is the development of models for drivers of refugia. Here, we investigate the distribution and species richness of Arctic-alpine vascular plant species' refugia. The study is carried out in an environmentally variable area in N Europe, encompassing the northern boreal to the Arctic-alpine zone. We defined refugia as isolated 1 km x 1 km grid cells with multiple Arctic-alpine plant species occurrences outside their main distribution area and assessed the main environmental factors underlying their distribution and richness using cross-validated boosted regression tree modelling. In the modelling, we examined the effects of climatic, topographic, and geologic factors, and the connectivity of sites with refugia incrementally, i.e. first modelling climatic impact alone, then with separate additions of topographic, geologic and connectivity variables, concluding with a model including all predictor variables. The inclusion of slope and connectivity significantly improved model performance. Although climate has a central role in controlling the occurrence of refugia, topography provides important clues for recognizing heterogeneous locations that harbour refugia with suitable local thermal and moisture conditions. Results suggest considering refugia as, on the one hand, isolated pockets of suitable habitat, but on the other hand as potentially interconnected habitat networks. In general, our study demonstrates that the spatial patterns of refugia can be successfully modelled, but emphasizes a need for high-quality data sampled at resolutions reflecting significant environmental gradients.Peer reviewe

Arctic shrubification mediates the impacts of warming climate on changes to tundra vegetation

Peer reviewe

Consistency of use of plant stanol ester margarine in Finland

Abstract Objective: The aims of this study were to investigate the consistency of use of plant stanol ester margarine and to characterise consistent and inconsistent users. Design: A cohort of plant stanol ester margarine users was established based on 14 national surveys conducted by the National Public Health Institute in Finland between 1996 and 1999. A follow-up study questionnaire was developed and sent to 1294 users in 2000. Setting: Subjects who reported using plant stanol ester margarine in both the original survey and the follow-up study were classified as consistent users, and the rest as inconsistent users. Subjects: The study population consisted of 1094 subjects aged 18-87 years, 590 men and 504 women. Results: There were 357 (33%) consistent and 737 (67%) inconsistent users of plant stanol ester margarine in the study population. Consistent users were more likely to be men and to have a higher household income than inconsistent users. Both consistent and inconsistent users were predominantly middle-aged persons with a healthy lifestyle and diet as well as a history of cardiovascular disease. Healthfulness was the main factor affecting bread spread choice among 94% of the consistent users and 59% of the inconsistent users. Conclusions: The use of plant stanol ester margarine is more often inconsistent than consistent. There is nevertheless a relatively large subgroup of long-term users of plant stanol ester margarine. It is important to examine the health effects especially among these regular user

Biogeochemical cycling and ecological thresholds in a High Arctic lake (Svalbard)

Lakes are a dominant feature of the Arctic landscape and a focal point of regional and global biogeochemical cycling. We collected a sediment core from a High Arctic Lake in southwestern Svalbard for multiproxy paleolimnological analysis. The aim was to find linkages between the terrestrial and aquatic environments in the context of climate change to understand centennial-long Arctic biogeochemical cycling and environmental dynamics. Two significant thresholds in elemental cycling were found based on sediment physical and biogeochemical proxies that were associated with the end of the cold Little Ice Age and the recent warming. We found major shifts in diatom, chironomid and cladoceran communities and their functionality that coincided with increased summer temperatures since the 1950s. We also discovered paleoecological evidence that point toward expanded bird (Little Auk) colonies in the catchment alongside climate warming. Apparently, climate-driven increase in glacier melt water delivery as well as a prolonged snow- and ice-free period have increased the transport of mineral matter from the catchment, causing significant water turbidity and disappearance of several planktonic diatoms and clear-water chironomids. We also found sedimentary accumulation of microplastic particles following the increase in Little Auk populations suggesting that seabirds potentially act as biovectors for plastic contamination. Our study demonstrates the diverse nature of climate-driven changes in the Arctic lacustrine environment with increased inorganic input from the more exposed catchment, larger nutrient delivery from the increased bird colonies at the surrounding mountain summits and subsequent alterations in aquatic communities.Peer reviewe

Can Topographic Variation in Climate Buffer against Climate Change-Induced Population Declines in Northern Forest Birds?

Increased attention is being paid to the ecological drivers and conservation measures which could mitigate climate change-induced pressures for species survival, potentially helping populations to remain in their present-day locations longer. One important buffering mechanism against climate change may be provided by the heterogeneity in topography and consequent local climate conditions. However, the buffering capacity of this topoclimate has so far been insufficiently studied based on empirical survey data across multiple sites and species. Here, we studied whether the fine-grained air temperature variation of protected areas (PAs) affects the population changes of declining northern forest bird species. Importantly to our study, in PAs harmful land use, such as logging, is not allowed, enabling the detection of the effects of temperature buffering, even at relatively moderate levels of topographic variation. Our survey data from 129 PAs located in the boreal zone in Finland show that the density of northern forest species was higher in topographically heterogeneous PAs than in topographically more homogeneous PAs. Moreover, local temperature variation had a significant effect on the density change of northern forest birds from 1981–1999 to 2000–2017, indicating that change in bird density was generally smaller in PAs with higher topographic variation. Thus, we found a clear buffering effect stemming from the local temperature variation of PAs in the population trends of northern forest birds

Can Topographic Variation in Climate Buffer against Climate Change-Induced Population Declines in Northern Forest Birds?

Increased attention is being paid to the ecological drivers and conservation measures which could mitigate climate change-induced pressures for species survival, potentially helping populations to remain in their present-day locations longer. One important buffering mechanism against climate change may be provided by the heterogeneity in topography and consequent local climate conditions. However, the buffering capacity of this topoclimate has so far been insufficiently studied based on empirical survey data across multiple sites and species. Here, we studied whether the fine-grained air temperature variation of protected areas (PAs) affects the population changes of declining northern forest bird species. Importantly to our study, in PAs harmful land use, such as logging, is not allowed, enabling the detection of the effects of temperature buffering, even at relatively moderate levels of topographic variation. Our survey data from 129 PAs located in the boreal zone in Finland show that the density of northern forest species was higher in topographically heterogeneous PAs than in topographically more homogeneous PAs. Moreover, local temperature variation had a significant effect on the density change of northern forest birds from 1981–1999 to 2000–2017, indicating that change in bird density was generally smaller in PAs with higher topographic variation. Thus, we found a clear buffering effect stemming from the local temperature variation of PAs in the population trends of northern forest birds

Bioclimatic atlas of the terrestrial Arctic

The Arctic is the region on Earth that is warming at the fastest rate. In addition to rising means of temperature-related variables, Arctic ecosystems are affected by increasingly frequent extreme weather events causing disturbance to Arctic ecosystems. Here, we introduce a new dataset of bioclimatic indices relevant for investigating the changes of Arctic terrestrial ecosystems. The dataset, called ARCLIM, consists of several climate and event-type indices for the northern high-latitude land areas > 45 degrees N. The indices are calculated from the hourly ERA5-Land reanalysis data for 1950-2021 in a spatial grid of 0.1 degree (similar to 9 km) resolution. The indices are provided in three subsets: (1) the annual values during 1950-2021; (2) the average conditions for the 1991-2020 climatology; and (3) temporal trends over 1951-2021. The 72-year time series of various climate and event-type indices draws a comprehensive picture of the occurrence and recurrence of extreme weather events and climate variability of the changing Arctic bioclimate.Peer reviewe