Variability in ice motion and dynamic discharge from Devon Ice Cap, Nunavut, Canada

© The Author(s) 2017. Feature tracking of approximately annually separated Landsat-7 ETM+ imagery acquired from 1999 to 2010 and speckle tracking of 24-day separated RADARSAT-2 imagery acquired from 2009 to 2015 reveal that motion of the major tidewater glaciers of Devon Ice Cap is more variable than previously described. The flow of almost half (six of 14) of the outlet glaciers slowed over the observation period, while that of the terminus regions of three of 14 of the glaciers sped up in the most recent years of observation. The North Croker Bay Glacier of southern Devon Ice Cap showed the greatest variability in motion, oscillating between multi-year (three or more) periods of slower and faster flow and exhibited a pattern of velocity variability that is different from that of the rest of the ice cap's outlet glaciers. Comparisons between areas of dynamic variability and glacier bed topography indicate that velocity variability is largely restricted to regions where the glacier bed is grounded below sea level. Derived velocities are combined with measurements of ice thickness at the fronts of tidewater glacier to determine a mean annual (2009; 2011-15) dynamic ice discharge of 0.41 ± 0.11 Gt a-1 for Devon Ice Cap. The Belcher Glacier is becoming a larger source of mass loss via ice discharge.NERC (NE/K004999/1

Accurate and reliable quantification of total microalgal fuel potential as fatty acid methyl esters by in situ transesterification

In the context of algal biofuels, lipids, or better aliphatic chains of the fatty acids, are perhaps the most important constituents of algal biomass. Accurate quantification of lipids and their respective fuel yield is crucial for comparison of algal strains and growth conditions and for process monitoring. As an alternative to traditional solvent-based lipid extraction procedures, we have developed a robust whole-biomass in situ transesterification procedure for quantification of algal lipids (as fatty acid methyl esters, FAMEs) that (a) can be carried out on a small scale (using 4–7 mg of biomass), (b) is applicable to a range of different species, (c) consists of a single-step reaction, (d) is robust over a range of different temperature and time combinations, and (e) tolerant to at least 50% water in the biomass. Unlike gravimetric lipid quantification, which can over- or underestimate the lipid content, whole biomass transesterification reflects the true potential fuel yield of algal biomass. We report here on the comparison of the yield of FAMEs by using different catalysts and catalyst combinations, with the acid catalyst HCl providing a consistently high level of conversion of fatty acids with a precision of 1.9% relative standard deviation. We investigate the influence of reaction time, temperature, and biomass water content on the measured FAME content and profile for 4 different samples of algae (replete and deplete Chlorella vulgaris, replete Phaeodactylum tricornutum, and replete Nannochloropsis sp.). We conclude by demonstrating a full mass balance closure of all fatty acids around a traditional lipid extraction process

Gulf Stream Detection from SAR Doppler Anomaly

This work presents a Gulf Stream (GS) North Wall (GSNW) detection algorithm applicable to Sentinel-1 Radial surface Velocity (RVL) products derived from Doppler centroid analysis of synthetic aperture radar (SAR) data collected off the east coast of Canada from February 2017 to August 2017. Visual comparison of the extracted location of the GSNW (obtained by evaluating the peak RVL gradient in the azimuth direction), and the estimated location of the GSNW as determined by the U.S. Naval Oceanographic Office and a GSNW search region (GSNWSR), indicates that the algorithm is capable of detecting the GSNW in ∼80% of the cases evaluated. Results are dependent on the geophysical orientation of the GS across the SAR swath, such that the GSNW detector performed most reliably when the GS was oriented across the swath resulting in maximized surface velocities in the range direction. When the GS meandered, or when GS eddies appeared in the RVL data, the GSNW was often partially detected or detected multiple times, reducing confidence in the extracted location. It is anticipated that the results obtained using the Sentinel-1 RVL products will be applicable to SAR data from other platforms

Synergistic RADARSAT-2 and Sentinel-1 SAR Images for Ocean Feature Analysis

Using a case study approach, the utility of synergistic RADARSAT-2 (R2) and Sentinel-1 (S1) synthetic aperture radar (SAR) imagery is demonstrated for ocean feature signature analysis in the vicinity of the Gulf Stream. The R2 and S1 images considered are either spatially adjacent or spatially overlapping, and were quasi-simultaneously collected (i.e., within minutes of each other). Spatially adjacent R2 and S1 imagery allows ocean feature signatures to be delineated over large spatial areas, while spatially overlapping R2 and S1 imagery collected within short time intervals provides independent ‘looks’ at the same ocean features. This permits determination of the surface displacement of features, potentially leading to improved classification of the origin of ocean feature signatures (quasi-stationary features are likely related to sea surface temperature fronts, while mobile features are likely related to atmospheric conditions). Further, we demonstrate how the use of S1 Level-2 products (i.e. radial velocity datasets) can be leveraged as contextual data to improve the interpretation and classification of ocean feature signatures extracted from R2 imagery. Despite the straight-forward approach taken here, this work demonstrates that there are practical, real-world applications that would benefit from exploiting these on-going imaging opportunities in operational environments

The Utility of Sentinel-1 Data for Ocean Surface Feature Analysis in the Vicinity of the Gulf Stream

European Space Agency Sentinel-1 (S1) synthetic aperture radar (SAR) datasets are used to assess their suitability for ocean surface feature extraction in the vicinity of the Gulf Stream. A SAR ocean feature detection tool originally developed to extract and classify brightness fronts in RADARSAT-2 (R2) SAR imagery has been updated to extract and classify brightness fronts from S1 ground range-detected products. Results indicate that the features extracted from S1 datasets are largely consistent with those derived from R2. However, more features are extracted from S1 data and, in limited examples, there are differences in how features are classified. In addition, S1 radial velocity (RVL) products were compared with simulated RVL products created from modeled ocean current data. This comparison shows that the orientation and magnitude of the Gulf Stream in S1 RVL products is generally consistent with modeled results, but does indicate that some regions of the Gulf Stream (meanders and ocean eddies) are likely to present challenges for automatic extraction algorithms. Taken together, this research shows that S1 data have utility for ocean surface feature extraction and provide an additional dataset that can be exploited to expand ocean feature analysis over Canadian waters

Retreat Pattern of Glaciers Controls the Occurrence of Turbidity Currents on High-Latitude Fjord Deltas (Eastern Baffin Island)

International audienceGlacier and ice sheet mass loss as a result of climate change is driving important coastal changes in Arctic fjords. Yet limited information exists for Arctic coasts regarding the influence of glacial erosion and ice mass loss on the occurrence and character of turbidity currents in fjords, which themselves affect delta dynamics. Here we show how glacial erosion and the production of meltwaters and sediments associated with the melting of retreating glaciers control the generation of turbidity currents in fjords of eastern Baffin Island (Canada). The subaqueous parts of 31 river mouths along eastern Baffin Island were mapped by high-resolution swath bathymetry in order to assess the presence or absence of sediment waves formed by turbidity currents on delta fronts. By extracting glaciological and hydrological watershed characteristics of these river mouths, we demonstrate that the presence and areal extent of glaciers are a key control for generating turbidity currents in fjords. However, lakes formed upstream during glacial retreat significantly alter the course of sediment routing to the deltas by forming temporary sinks, leading to the cessation of turbidity currents in the fjords. Due to the different deglaciation stages of watersheds in eastern Baffin Island, we put these results into a temporal framework of watershed deglaciation to demonstrate how the retreat pattern of glaciers, through the formation and filling of proglacial lakes, affects the turbidity current activity of deltas