Abstract: Machine learning is becoming increasingly important in scientific and technological progress, due to its ability to create models that describe complex data and generalize well. The wealth of publicly-available seismic data nowadays requires automated, fast, and reliable tools to carry out a multitude of tasks, such as the detection of small, local earthquakes in areas characterized by sparsity of receivers. A similar application of machine learning, however, should be built on a large amount of labeled seismograms, which is neither immediate to obtain nor to compile. In this study we present a large dataset of seismograms recorded along the vertical, north, and east components of 1487 broad-band or very broad-band receivers distributed worldwide; this includes 629,095 3-component seismograms generated by 304,878 local earthquakes and labeled as EQ, and 615,847 ones labeled as noise (AN). Application of machine learning to this dataset shows that a simple Convolutional Neural Network of 67,939 parameters allows discriminating between earthquakes and noise single-station recordings, even if applied in regions not represented in the training set. Achieving an accuracy of 96.7, 95.3, and 93.2% on training, validation, and test set, respectively, we prove that the large variety of geological and tectonic settings covered by our data supports the generalization capabilities of the algorithm, and makes it applicable to real-time detection of local events. We make the database publicly available, intending to provide the seismological and broader scientific community with a benchmark for time-series to be used as a testing ground in signal processing.

Abstract: Geochemical investigations using FTIR, ICP-AES and C-N analyses were carried out on a single-family semi-subterranean Inuit house in order to assess the contribution of Inuit domestic activities in the formation of cryosolic soils in a periglacial archaeological context (Kuuvik Bay, Nunavik, Canada). The geochemical elements data were analyzed using box plots and enrichment factors. The information was also summarized and visualized through principal component analysis (PCA). These complementary statistical approaches provided evidence of a moderate but identifiable and significant imprint of Inuit domestic activities on soil geochemistry. The box plots indicate moderate Ca, Mn, Cu and P enrichments and more noticeable Mg, Fe and S enrichments. These enrichment factors and the ICP-AES data show that samples from the peripheral wall and the tunnel entrance of the house and its vicinity are significantly enriched. While FTIR analysis highlighted the main soil element contents (e.g., organic and mineral components), ICP-AES analysis was used to further document variations in the background elements throughout the site. However, the obtained results do not allow us to undertake a spatial analysis of Inuit activities or to describe them in detail. In addition, the data highlight the difficulty of documenting the natural variability of element contents in cryosolic soils, especially in archaeological contexts. Cryo-pedological processes in the active layer as well as house cleaning and nutrient inputs resulting from Inuit occupations may have attenuated chemical signatures of previous Inuit domestic activities.

Abstract: The decline of sea-ice thickness, area, and volume due to the transition from multi-year to first-year sea ice has improved the under-ice light environment for pelagic Arctic ecosystems. One unexpected and direct consequence of this transition, the proliferation of under-ice phytoplankton blooms (UIBs), challenges the paradigm that waters beneath the ice pack harbor little planktonic life. Little is known about the diversity and spatial distribution of UIBs in the Arctic Ocean, or the environmental drivers behind their timing, magnitude, and taxonomic composition. Here, we compiled a unique and comprehensive dataset from seven major research projects in the Arctic Ocean (11 expeditions, covering the spring sea-ice-covered period to summer ice-free conditions) to identify the environmental drivers responsible for initiating and shaping the magnitude and assemblage structure of UIBs. The temporal dynamics behind UIB formation are related to the ways that snow and sea-ice conditions impact the under-ice light field. In particular, the onset of snowmelt significantly increased under-ice light availability (>0.1–0.2 mol photons m–2 d–1), marking the concomitant termination of the sea-ice algal bloom and initiation of UIBs. At the pan-Arctic scale, bloom magnitude (expressed as maximum chlorophyll a concentration) was predicted best by winter water Si(OH)4 and PO43– concentrations, as well as Si(OH)4:NO3– and PO43–:NO3– drawdown ratios, but not NO3– concentration. Two main phytoplankton assemblages dominated UIBs (diatoms or Phaeocystis), driven primarily by the winter nitrate:silicate (NO3–:Si(OH)4) ratio and the under-ice light climate. Phaeocystis co-dominated in low Si(OH)4 (i.e., NO3:Si(OH)4 molar ratios >1) waters, while diatoms contributed the bulk of UIB biomass when Si(OH)4 was high (i.e., NO3:Si(OH)4 molar ratios <1). The implications of such differences in UIB composition could have important ramifications for Arctic biogeochemical cycles, and ultimately impact carbon flow to higher trophic levels and the deep ocean.

Abstract: The Inuit of Qikiqtaaluk (Baffin Island) have developed a deep respect for their natural environment and are able to report not only changes in weather, ice, and natural resources but also changes in their communities as a result of climate change. The objective of this study was to shed light on how the impacts of climate change are currently perceived in the communities of Kanngiqtugaapik, Pangniqtuuq, and Qikiqtarjuaq. In order to construct a shared knowledge base, we conducted qualitative video interviews and participated in a hunting camp with multigenerational and multigender Inuit hunters and fishers. First, Inuit continue to see the world in which they cohabit with other living things, particularly animals, as a world that they cannot control on their own—a world they must adapt to, passing learning from one generation to the next. Second, they report that changes in the ice have been among the major and most important transformations to have occurred in recent decades. Observations made by these local populations also indicate changes in hunted species, with fewer caribou and narwhal, more birds, insects, and fish, including from more southerly regions, and an uncertainty about polar bear populations. Seal hunting remains stable, and this meat is still the most popular and healthy food, physically and psychologically. Third, sociological and economic changes (e.g., lifestyle change, monetary economies, quotas), in addition to environmental changes (e.g., climate change, species change), have had a significant impact on food harvesting activities as well as food consumption in the region. A final perspective concerns the needs of the Qikiqtaaluk communities to further develop collaboration with scientists. This need for partnership is not only perceived as a scientific necessity but also recognized by Inuit as essential to their communities, with some local leaders ready to work toward a fruitful collaboration.

Abstract: Benthic organisms depend primarily on seasonal pulses of organic matter from primary producers. In the Arctic, declines in sea ice due to warming climate could lead to changes in this food supply with as yet unknown effects on benthic trophic dynamics. Benthic consumer diets and food web structure were studied in a seasonally ice-covered region of Baffin Bay during spring 2016 at stations ranging in depth from 199 to 2,111 m. We used a novel combination of highly branched isoprenoid (HBI) lipid biomarkers and stable isotope ratios (δ13C, δ15N) to better understand the relationship between the availability of carbon sources in spring on the seafloor and their assimilation and transfer within the benthic food web. Organic carbon from sea ice (sympagic carbon [SC]) was an important food source for benthic consumers. The lipid biomarker analyses revealed a high relative contribution of SC in sediments (mean SC% ± standard deviation [SD] = 86% ± 16.0, n = 17) and in benthic consumer tissues (mean SC% ± SD = 78% ± 19.7, n = 159). We also detected an effect of sea-ice concentration on the relative contribution of SC in sediment and in benthic consumers. Cluster analysis separated the study region into three different zones according to the relative proportions of SC assimilated by benthic macrofauna. We observed variation of the benthic food web between zones, with increases in the width of the ecological niche in zones with less sea-ice concentration, indicating greater diversity of carbon sources assimilated by consumers. In zones with greater sea-ice concentration, the higher availability of SC increased the ecological role that primary consumers play in driving a stronger transfer of nutrients to higher trophic levels. Based on our results, SC is an important energy source for Arctic deep-sea benthos in Baffin Bay, such that changes in spring sea-ice phenology could alter benthic food-web structure.