Discovery of a hypersaline subglacial lake complex beneath Devon Ice Cap, Canadian Arctic.

Subglacial lakes are unique environments that, despite the extreme dark and cold conditions, have been shown to host microbial life. Many subglacial lakes have been discovered beneath the ice sheets of Antarctica and Greenland, but no spatially isolated water body has been documented as hypersaline. We use radio-echo sounding measurements to identify two subglacial lakes situated in bedrock troughs near the ice divide of Devon Ice Cap, Canadian Arctic. Modeled basal ice temperatures in the lake area are no higher than -10.5°C, suggesting that these lakes consist of hypersaline water. This implication of hypersalinity is in agreement with the surrounding geology, which indicates that the subglacial lakes are situated within an evaporite-rich sediment unit containing a bedded salt sequence, which likely act as the solute source for the brine. Our results reveal the first evidence for subglacial lakes in the Canadian Arctic and the first hypersaline subglacial lakes reported to date. We conclude that these previously unknown hypersaline subglacial lakes may represent significant and largely isolated microbial habitats, and are compelling analogs for potential ice-covered brine lakes and lenses on planetary bodies across the solar system

The International Bathymetric Chart of the Arctic Ocean Version 4.0

Funder: The Nippon Foundation of Japan, grant Seabed 2030Funder: Open access funding provided by Stockholm UniversityAbstract: Bathymetry (seafloor depth), is a critical parameter providing the geospatial context for a multitude of marine scientific studies. Since 1997, the International Bathymetric Chart of the Arctic Ocean (IBCAO) has been the authoritative source of bathymetry for the Arctic Ocean. IBCAO has merged its efforts with the Nippon Foundation-GEBCO-Seabed 2030 Project, with the goal of mapping all of the oceans by 2030. Here we present the latest version (IBCAO Ver. 4.0), with more than twice the resolution (200 × 200 m versus 500 × 500 m) and with individual depth soundings constraining three times more area of the Arctic Ocean (∼19.8% versus 6.7%), than the previous IBCAO Ver. 3.0 released in 2012. Modern multibeam bathymetry comprises ∼14.3% in Ver. 4.0 compared to ∼5.4% in Ver. 3.0. Thus, the new IBCAO Ver. 4.0 has substantially more seafloor morphological information that offers new insights into a range of submarine features and processes; for example, the improved portrayal of Greenland fjords better serves predictive modelling of the fate of the Greenland Ice Sheet

Cortical Structure of Hallucal Metatarsals and Locomotor Adaptations in Hominoids

International audienceDiaphyseal morphology of long bones, in part, reflects in vivo loads experienced during the lifetime of an individual. The first metatarsal, as a cornerstone structure of the foot, presumably expresses diaphyseal morphology that reflects loading history of the foot during stance phase of gait. Human feet differ substantially from those of other apes in terms of loading histories when comparing the path of the center of pressure during stance phase, which reflects different weight transfer mechanisms. Here we use a novel approach for quantifying continuous thickness and cross-sectional geometric properties of long bones in order to test explicit hypotheses about loading histories and diaphyseal structure of adult chimpanzee, gorilla, and human first metatarsals. For each hallucal metatarsal, 17 cross sections were extracted at regularly-spaced intervals (2.5% length) between 25% and 65% length. Cortical thickness in cross sections was measured in one degree radially-arranged increments, while second moments of area were measured about neutral axes also in one degree radially-arranged increments. Standardized thicknesses and second moments of area were visualized using false color maps, while penalized discriminant analyses were used to evaluate quantitative species differences. Humans systematically exhibit the thinnest diaphyseal cortices, yet the greatest diaphyseal rigidities, particularly in dorsoplantar regions. Shifts in orientation of maximum second moments of area along the diaphysis also distinguish human hallucal metatarsals from those of chimpanzees and gorillas. Diaphyseal structure reflects different loading regimes, often in predictable ways, with human versus non-human differences probably resulting both from the use of arboreal substrates by non-human apes and by differing spatial relationships between hallux position and orientation of the substrate reaction resultant during stance. The novel morphological approach employed in this study offers the potential for transformative insights into form-function relationships in additional long bones, including those of extinct organisms (e.g., fossils)

Oceanic heat transport onto the Amundsen Sea shelf through a submarine glacial trough

Glaciers which drain the West Antarctic Ice Sheet (WAIS) into the Amundsen Sea are accelerating and thinning rapidly. These observations have been attributed to the regional oceanography whereby heat contained within Circumpolar Deep Water (CDW) drives the basal melting of floating glaciers. On the basis of new data we calculate that 2.8 terra-Watts (1012) of oceanic heat flow onto the continental shelf and toward the glaciers via a submarine glacial trough. This is enough to account for most of the basal melting in the entire region suggesting the ocean is supplying an excess of heat toward the Antarctic continent

Adaptation to bipedal gait and fifth metatarsal structural properties in Australopithecus , Paranthropus , and Homo

International audienc

Non-scaled values for cortical bone thickness (CBT) and second moments of area (SMA).

<p>Non-scaled values for cortical bone thickness (CBT) and second moments of area (SMA).</p

Penalized discriminant analysis (PDA) of standardized cortical bone thicknesses (CBTs).

<p>Due to differences in configurations resulting from hallucal abduction in chimpanzees and gorillas (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0117905#pone.0117905.g001" target="_blank">Fig. 1</a>), functionally equivalent cortices (columns in the color map) differ in anatomical correspondence (i.e., dorsal cortices of chimpanzee and gorilla hallucal metatarsals are comparable with medial cortices of human hallucal metatarsals, etc.). Rows of color maps along the top (PDF1 and PDF2) visualize the distribution of mean scaled CBT for interspecific comparisons. In the uppermost row (PDF1), boundaries (dashed yellow lines) superimposed on consensus maps (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0117905#pone.0117905.g003" target="_blank">Fig. 3A</a>) differentiate pixels with positive loading (red) from those with negative loading (blue) on PDF1. A positive loading for a given pixel indicates that a larger CBT value at that pixel increases the relative score on that discriminant axis. Similarly, a negative loading for a given pixel indicates that a larger CBT value at that pixel decreases the relative score on that discriminant axis. In the middle row (PDF2), boundaries (dashed black lines) superimposed on the same consensus maps differentiate pixels with positive loading (red) from those with negative loading (blue) for PDF2. Along the bottom, color maps (far left and far right in a red-blue colour scale) visualize pixel-wise loadings of 1^st and 2^nd penalized discriminant functions (PDF1 on the right and plotted on the horizontal axis of the centre scatter plot; PDF2 on the left and plotted on the vertical axis of the centre scatter plot). Note that white indicates the transition between positive and negative loadings (i.e., 0 loading by default). The bivariate scatter plot (bottom centre) presents the projection of each individual in the sample (<i>n</i> = 43; open symbols) into discriminant space via PDF1 and PDF2. Circles in the scatter plot indicate species means in discriminant space, effectively indicating group separation. Squares indicate subjects used in the training sample. Stars indicate test subjects. See the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0117905#sec002" target="_blank">methods</a> for an explanation of training versus test subjects. M—medial, D—dorsal, L—lateral, P—plantar.</p