A multidisciplinary study of Holocene sediment records from Hjort Sø on Store Koldewey, Northeast Greenland

Two sediment cores of 70 and 252 cm length were recovered from Hjort Sø, a small lake on Store Koldewey, Northeast Greenland, and studied with a multidisciplinary approach in order to reconstruct the local environmental history and to test the relevance of proxies for paleoenvironmental information. The basal sediments from the longer core are dominated by clastic matter, which was likely deposited during deglaciation of the lake basin. These clastic sediments are overlain by gyttja, which is also present throughout the shorter core. AMS radiocarbon dating was conducted on plant macrofossils of 11 samples from the gyttja in both cores. A reliable chronology was established for both cores, which dated the onset of organic accumulation at 9,500 cal. year BP. The Holocene temperature development, with an early to mid Holocene thermal maximum, is best reflected in the grain-size composition. Nutrient availability was apparently low during the early Holocene and led to low productivity in the lake and its vicinity. From ca. 7,000 cal. year BP, productivity in the lake increased significantly, probably induced by external nutrient input from goose excrements. From this time, micro- and macro-fossil remains reflect relatively well the climate history of East Greenland, with a cooling during the middle Holocene, the medieval warming, and the Little Ice Age. The amount of organic matter in the sequence seems to be more affected by lake ice cover or by nutrient supply from the catchment than by temperature changes. The record from Hjort Sø thus reveals the difficulties in interpreting sedimentary records from high arctic regions.     

Vegetation impacts soil water content patterns by shaping canopy water fluxes and soil properties

Soil water content is a key variable for biogeochemical and atmospheric coupled processes. Its small‐scale heterogeneity impacts the partitioning of precipitation (e.g., deep percolation or transpiration) by triggering threshold processes and connecting flow paths. Forest hydrologists frequently hypothesized that throughfall and stemflow patterns induce soil water content heterogeneity, yet experimental validation is limited. Here, we pursued a pattern‐oriented approach to explore the relationship between net precipitation and soil water content. Both were measured in independent high‐resolution stratified random designs on a 1‐ha temperate mixed beech forest plot in Germany. We recorded throughfall (350 locations) and stemflow (65 trees) for 16 precipitation events in 2015. Soil water content was measured continuously in topsoil and subsoil (210 profiles). Soil wetting was only weakly related to net precipitation patterns. The precipitation‐induced pattern quickly dissipates and returns to a basic pattern, which is temporally stable. Instead, soil hydraulic properties (by the proxy of field capacity) were significantly correlated with this stable soil water content pattern, indicating that soil structure more than net precipitation drives soil water content heterogeneity. Also, both field capacity and soil water content were lower in the immediate vicinity of tree stems compared to further away at all times, including winter, despite stemflow occurrence. Thus, soil structure varies systematically according to vegetation in our site. We conclude that enhanced macroporosity increases gravity‐driven flow in stem proximal areas. Therefore, although soil water content patterns are little affected by net precipitation, the resulting soil water fluxes may strongly be affected. Specifically, this may further enhance the channelling of stemflow to greater depth and beyond the rooting zone.     

Fish assemblages in coastal lagoons in land-uplift succession: The relative importance of local and regional environmental gradients

The assemblages of young-of-the-year fish were studied in coastal lagoons in an archipelago with post-glacial land-uplift, which affects environmental gradients at local and regional scale, i.e. lagoon habitat isolation and archipelago position, respectively. The categorisation of 40 undisturbed lagoons into nine habitat types based on habitat isolation and archipelago position was supported by clear relationships with spring temperature and total fish abundance. Rutilus rutilus, breams (Abramis/Blicca sp.) and Perca fluviatilis were the most abundant and frequently occurring species. The fish assemblage differed among the nine habitat types. Rutilus rutilus, P. fluviatilis and breams were discriminating species in the majority of habitat types with low physical harshness, whereas Alburnus alburnus and Gasterosteus aculeatus increased their contributions in habitat types with high physical harshness. Rutilus rutilus and breams were thus common in lagoons with high habitat isolation situated in the inner archipelago. These lagoons were characterised by warm water and high vegetation coverage. Gasterosteus aculeatus was restricted to lagoons with low habitat isolation and exposure and low vegetation coverage, situated in the outer archipelago. Perca fluviatilis had the widest distribution of all species. The coverage of two macrophytes, Potamogeton perfoliatus and Zannichellia palustris, and salinity matched best the distance among habitat types. These habitat characteristics, as well as the fish abundances and assemblages differed most across the habitat types in the outer and mid archipelago zones and in the lowest habitat isolation. These patterns suggest that the structuring effect of habitat isolation increases along the archipelago gradient as differences between local and regional conditions increase. In the inner archipelago, overall low physical harshness induces homogeneous conditions and the habitat isolation is less important here than in the other zones. We suggest that this difference in the relative importance of the two gradients depending on the level of respective gradient ultimately forms these heterogeneous coastal habitats in a successional landscape. Rutilus rutilus and P. fluviatilis were responsible for large parts of the assemblage patterns. Although sympatric due to similar habitat requirements, differences in dispersal capability, competitive ability and predation vulnerability may add explanation to detected differences in distribution and abundance in these two species in an open system. Our results also stress the structuring role of vegetation in terms of total coverage and species composition, as these two aspects of macrophyte diversity may act as complementary habitat modifiers across gradients of physical harshness.     

Visualizing flood risk,enabling participation and supporting climate change adaptation using the Geoweb: the case of coastal communities in Nova Scotia,Canada

Impacts of climate change have been observed in natural systems and are expected to intensify in future decades (IPCC in Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change IPPC, Geneva, 2014). Governments are seeking to establish adaptive measures for minimizing the effects of climate change on vulnerable citizen groups, economic sectors and critical infrastructure (Adger et al. in Global Environ Change 15(2):77–86, 2005. doi: 10.1016/j.gloenvcha.2004.12.005; Smit and Wandel in Global Environ Change 16(3):282–292, 2006. doi: 10.1016/j.gloenvcha.2006.03.008). Coastal areas are particularly vulnerable to changing conditions due to rising sea levels and storm event intensification that produce new flood exposures (Richards and Daigle in Government of Prince Edward Island, Halifax, Nova Scotia, 2011 http://www.gov.pe.ca/photos/original/ccscenarios.pdf). However, communities oftentimes lack access to locally-relevant climate change information that can support adaptation planning. This research introduces the use of a Geoweb tool for supporting local climate change adaptation efforts in coastal Canadian communities. The Geoweb tool (called “AdaptNS”) is a web-based visualization tool that displays interactive flood exposure maps generated using local climate change projections of sea level rise and storm surge impacts between the years 2000 and 2100. AdaptNS includes participatory features that allow users to identify and share specific locations to protect against present and future coastal flood events. By soliciting feedback from community members, AdaptNS is shown to support local adaptation through the provision of flood exposure visuals, as a platform for identifying adaptation priorities, and as an avenue to communicate local risks to external entities that could facilitate local adaptation initiatives (e.g. upper levels of government). Future Geoweb research directions include improving the visualization of climate change projection uncertainties, the expansion of informational and participation capabilities, and understanding the potential for long-term adoption of Geoweb tools in adaptation decision-making.     

The last glaciation of the Arctic volcanic island Jan Mayen

The volcanic island of Jan Mayen, remotely located in the Norwegian-Greenland Sea, was covered by a contiguous ice cap during the Late Weichselian. Until now, it has been disputed whether parts of the island south of the presently glaciated Mount Beerenberg area were ever glaciated. Based on extensive field mapping we demonstrate that an ice cap covered all land areas and likely also extended onto the shallow shelf areas southeast and east of the island. Chronological interpretations are based on K-Ar and ⁴⁰Ar/³⁹Ar dating of volcanic rocks, cosmogenic nuclide (³⁶Cl) surface exposure dating of bedrock and glacial erratics, and radiocarbon dating. We argue that ice growth started after 34 ka and that an initial deglaciation started some 21.5–19.5 ka in the southern and middle parts of the island. In the northern parts, closer to the present glaciers, the deglaciation might have started later, as evidenced by the establishment of vegetation 17–16 cal. ka BP. During full glaciation, the ice cap was likely thickest over the southern part of the island. This may explain a seemingly delayed deglaciation compared with the northern parts despite earlier initial deglaciation. In a broader context, the new knowledge of the Late Weichselian of the island contributes to the understanding of glaciations surrounding the North Atlantic and its climate history.     

Values,climate change,and implications for adaptation: Evidence from two communities in Labrador,Canada

Local material and symbolic values have to date remained underrepresented in climate change research and policy and this gap is particularly salient in places that have been identified as at significant risk from climate change. In such places, the dominant approach to understanding the effects of climate change has been centred on vulnerability; it has highlighted the social determinants of vulnerability and the differential and uneven distribution of effects. This approach cannot, however, illuminate the diverse and nuanced meanings people attach to specific aspects of their way of life, how the changing climate might affect these, and what this implies for adaptation. To address this gap, this empirical study uses the concept of values, defined as trans-situational conceptions of the desirable that give meaning to behaviour and events, and influence perception and interpretation of situations and events. We develop a set of values from 53 qualitative interviews in two remote communities in subarctic easternmost Canada. It draws on these values to frame how effects of climate change, specifically intangible and subjective effects, are felt, and how responses to them are imagined by those affected. The article argues that values are crucial in shaping perception of climate impacts and adaptation to them. Distinct values, such as tradition, freedom, harmony, safety, and unity shape different interpretations and meaning of impacts, and lead to distinct views on how to adapt to these. Conflicting and competing values can act as barriers to adaptation. The findings imply that adaptation research and policy need to address values explicitly if efforts for planned adaptation are to be perceived as legitimate and effective by those affected by the changing climate.     

Weighted model-based clustering for remote sensing image analysis

We introduce a weighted method of clustering the individual units of a segmented image. Specifically, we analyze geologic maps generated from experts’ analysis of remote sensing images and provide geologists with a powerful method to numerically test the consistency of a mapping with the entire multidimensional dataset of that region. Our weighted model-based clustering method (WMBC) employs a weighted likelihood and assigns fixed weights to each unit corresponding to the number of pixels located within the unit. WMBC characterizes each unit by the means and standard deviations of the pixels within that unit and uses the expectation-maximization algorithm with a weighted likelihood function to cluster the units. With both simulated and real data sets, we show that WMBC is more accurate than standard model-based clustering. Specifically, we analyze Magellan data from a large, geologically complex region of Venus to validate the mapping efforts of planetary geologists.