The Impact of Deep Fjord Water Temperatures on the Ice Flow Velocities of Helheim Glacier, Greenland

Increasing ice flow velocities of marine terminating glaciers are often linked to rising ocean temperatures. Unfortunately, direct comparisons between glacier velocity and ocean temperatures are impeded by the fact that few oceanographic datasets span multiple years or contain temperatures at depth. Here, we use an oceanographic dataset collected in Helheim Fjord over several years (described in Straneo et al., 2011, Nat. Geoscience) in both shallow and deep waters. We compare the water temperatures at different depths with ice flow velocities that have been calculated from feature-tracking of LandSAT 7 and 8 images. Our results cover the period 2009–2013 and show both seasonal and inter-annual variability. We find that the velocity of Helheim glacier is likely influenced by the deep ocean water temperatures, namely the influx of warm Atlantic water, whereas water temperature at shallower depths do not have a significant influence on glacier speed. This is in contrast with findings from, for example, Svalbard. Our study demonstrates the need for multiple–year ocean datasets at different depths, if we are to disentangle the complex interactions between glaciers and ocean

Calibration and evaluation of a high-resolution surface mass-balance model for Paakitsoq, West Greenland

Modelling the hydrology of the Greenland ice sheet, including the filling and drainage of supraglacial lakes, requires melt inputs generated at high spatial and temporal resolution. Here we apply a high spatial (100 m) and temporal (1 hour) mass-balance model to a 450 km2 subset of the Paakitsoq region, West Greenland. The model is calibrated by adjusting the values for parameters of fresh snow density, threshold temperature for solid/liquid precipitation and elevation-dependent precipitation gradient to minimize the error between modelled output and surface height and albedo measurements from three Greenland Climate Network stations for the mass-balance years 2000/01 and 2004/05. Bestfit parameter values are consistent between the two years at 400 kg m–3, 2° C and +14% (100 m)–1, respectively. Model performance is evaluated, first, by comparing modelled snow and ice distribution with that derived from Landsat-7 ETM+ satellite imagery using normalized-difference snow index classification and supervised image thresholding; and second, by comparing modelled albedo with that retrieved from the MODIS sensor MOD10A1 product. Calculation of mass-balance components indicates that 6% of surface meltwater and rainwater refreezes in the snowpack and does not become runoff, such that refreezing accounts for 31% of the net accumulation

Basal conditions at Engabreen, Norway, inferred from surface measurements and inverse modelling

Engabreen is an outlet glacier of the Svartisen Ice Cap located in Northern Norway. It is a unique glacier due to the Svartisen Subglacial Laboratory which allows direct access to the glacier bed. In this study, we combine both sub- and supraglacial observations with ice-flow modelling in order to investigate conditions at the bed of Engabreen both spatially and temporally. We use the full-Stokes model Elmer/Ice and satellite-based surface-velocity maps from 2010 and 2014 to infer patterns of basal friction. Direct measurements of basal sliding and deformation of lower layers of the ice are used to adjust the ice viscosity and provide essential input to the setup of our model and influence the interpretation of the results. We find a clear seasonal cycle in the subglacial conditions at the higher elevation region of the study area and discuss this in relation to the subglacial hydrological system. Our results also reveal an area with an overdeepening where basal friction is significantly lower than elsewhere on the glacier all year round. We attribute this to either water pooling at the base, or saturated sediments and increased strain heating at this location which softens the ice further

Quality control of B-lines analysis in stress Echo 2020

Background The effectiveness trial “Stress echo (SE) 2020” evaluates novel applications of SE in and beyond coronary artery disease. The core protocol also includes 4-site simplified scan of B-lines by lung ultrasound, useful to assess pulmonary congestion. Purpose To provide web-based upstream quality control and harmonization of B-lines reading criteria. Methods 60 readers (all previously accredited for regional wall motion, 53 B-lines naive) from 52 centers of 16 countries of SE 2020 network read a set of 20 lung ultrasound video-clips selected by the Pisa lab serving as reference standard, after taking an obligatory web-based learning 2-h module ( http://se2020.altervista.org ). Each test clip was scored for B-lines from 0 (black lung, A-lines, no B-lines) to 10 (white lung, coalescing B-lines). The diagnostic gold standard was the concordant assessment of two experienced readers of the Pisa lab. The answer of the reader was considered correct if concordant with reference standard reading ±1 (for instance, reference standard reading of 5 B-lines; correct answer 4, 5, or 6). The a priori determined pass threshold was 18/20 (≥ 90%) with R value (intra-class correlation coefficient) between reference standard and recruiting center) > 0.90. Inter-observer agreement was assessed with intra-class correlation coefficient statistics. Results All 60 readers were successfully accredited: 26 (43%) on first, 24 (40%) on second, and 10 (17%) on third attempt. The average diagnostic accuracy of the 60 accredited readers was 95%, with R value of 0.95 compared to reference standard reading. The 53 B-lines naive scored similarly to the 7 B-lines expert on first attempt (90 versus 95%, p = NS). Compared to the step-1 of quality control for regional wall motion abnormalities, the mean reading time per attempt was shorter (17 ± 3 vs 29 ± 12 min, p < .01), the first attempt success rate was higher (43 vs 28%, p < 0.01), and the drop-out of readers smaller (0 vs 28%, p < .01). Conclusions Web-based learning is highly effective for teaching and harmonizing B-lines reading. Echocardiographers without previous experience with B-lines learn quickly.info:eu-repo/semantics/publishedVersio

Ice-flow velocity, Petermann Glacier, Greenland

Ice-flow velocity fields produced from optical feature tracking of Landsat data, using ImGRAFT toolbox. Data are provided in point NetCDF format along with a corresponding JPEG, a data timeline and example data structure are also provided. See attached documentation for detailed description of the data and corresponding terms of use

Ice-flow velocity from Jacobshavn, Kangerdlugssuaq and Petermann Glacier, Greenland

Ice-flow velocity fields produced from optical feature tracking of Landsat data, using ImGRAFT toolbox. Data are provided in point NetCDF format along with a corresponding JPEG, a data timeline and example data structure are also provided. See attached documentation for detailed description of the data and corresponding terms of use

Ice-flow velocity, Kangerdlugssuaq Glacier, Greenland

Ice-flow velocity fields produced from optical feature tracking of Landsat data, using ImGRAFT toolbox. Data are provided in point NetCDF format along with a corresponding JPEG, a data timeline and example data structure are also provided. See attached documentation for detailed description of the data and corresponding terms of use

Ice-flow velocity, Jakobshavn Glacier, Greenland

Ice-flow velocity fields produced from optical feature tracking of Landsat data, using ImGRAFT toolbox. Data are provided in point NetCDF format along with a corresponding JPEG, a data timeline and example data structure are also provided. See attached documentation for detailed description of the data and corresponding terms of use