NOVEL METHODS FOR QUANTIFYING SPATIO-TEMPORAL CHANGE IN GLACIATED AND SUBAQUEOUS ENVIRONMENTS

In many scientific fields, it is important to actively develop new approaches to monitoring and quantifying changes within different systems. Often adapting existing tools or applying techniques from alternative fields can greatly improve our ability to monitor spatial and temporal changes. In this dissertation, I present four studies aimed at demonstrating new innovative ways at improving our ability to observe and quantify changes occurring on glaciers, submerged cultural resources (SCRs) and supraglacial lakes by using technology such as Structure from Motion + Multi-view stereo photogrammetry (SfM) and ground penetrating radar (GPR) surveying combined with facies analysis. I have successfully reconstructed highly detailed 3D models of multiple large scale SCRs including the Home, Hetty Taylor and the Wisconsin using archival and newly acquired diver video footage. Comparison of digital measurement versus in situ measurements show low percent errors for most measurements, ranging fromWisconsin in order to generate two models, one from 2006 and one from 2015. Differencing the digital elevation models has allowed us to quantify and map the spatial distribution of changes occurring through site degradation. In addition, comparison of the orthomosaics has allowed for the visual identification of changes occurring at the SCR such as disappearance of objects, shifting of material and increased colonization of mussels. I have also applied the SfM technique to historical imagery of glaciers in the high-arctic, European Alps and the Himalaya in order to extract spatial information for periods where it may not exist or is limited in resolution. The digital elevation models extracted are of a high-resolution and have allowed for very detailed spatial change mapping. The SfM process was performed without a priori information and relied on GCP obtained from more recent high-resolution remote sensing datasets. Results show highly contrasting patterns of long term melt on both a regional and local scale. Lastly, I have used GPR surveying techniques on the frozen Spillway Lake, Ngozumpa glacier, Nepal, in order to improve our understanding of the supraglacial lake subaqueous environment. These surveys have allowed for the extraction of high-resolution bathymetric data as well as detailed information pertaining to lakebed debris distribution. Identification of two specific radar signal facies and observations of near shore sediment structures have allowed for the creation of a new updated conceptual model of supraglacial lake development, incorporating not only lateral expansion, but also deepening processes and lakebed dynamics

Stagnation and mass loss on a Himalayan debris-covered glacier: processes, patterns and rates

This research was supported financially by the University Centre in Svalbard (UNIS), National Geographic Society GRANT #W135-10, The Natural Environmental Research Council and the European Commission FP7-MC-IEF.The ablation areas of debris-covered glaciers typically consist of a complex mosaic of surface features with contrasting processes and rates of mass loss. This greatly complicates glacier response to climate change, and increases the uncertainty of predictive models. In this paper we present a series of high-resolution DEMs and repeat lake bathymetric surveys on Ngozumpa Glacier, Nepal, to study processes and patterns of mass loss on a Himalayan debris-covered glacier in unprecedented detail. Most mass loss occurs by melt below supraglacial debris, and melt and calving of ice cliffs (backwasting). Although ice cliffs cover only ∼5% of the area of the lower tongue, they account for 40% of the ablation. The surface debris layer is subject to frequent re-distribution by slope processes, resulting in large spatial and temporal differences in debris-layer thickness, enhancing or inhibiting local ablation rates and encouraging continuous topographic inversion. A moraine-dammed lake on the lower glacier tongue (Spillway Lake) underwent a period of rapid expansion from 2001 to 2009, but later experienced a reduction of area and volume as a result of lake level lowering and sediment redistribution. Rapid lake growth will likely resume in the near future, and may eventually become up to 7 km long.Publisher PDFPeer reviewe

Spatial variability of CO \u3c inf\u3e 2 uptake in polygonal tundra: Assessing low-frequency disturbances in eddy covariance flux estimates

The large spatial variability in Arctic tundra complicates the representative assessment of CO2 budgets. Accurate measurements of these heterogeneous landscapes are, however, essential to understanding their vulnerability to climate change. We surveyed a polygonal tundra lowland on Svalbard with an unmanned aerial vehicle (UAV) that mapped ice-wedge morphology to complement eddy covariance (EC) flux measurements of CO2. The analysis of spectral distributions showed that conventional EC methods do not accurately capture the turbulent CO2 exchange with a spatially heterogeneous surface that typically features small flux magnitudes. Nonlocal (low-frequency) flux contributions were especially pronounced during snowmelt and introduced a large bias of -46 gCm-2 to the annual CO22 budget in conventional methods (the minus sign indicates a higher uptake by the ecosystem). Our improved flux calculations with the ogive optimization method indicated that the site was a strong sink for CO2 in 2015 (82 gCm2). Due to differences in light-use efficiency, wetter areas with lowcentered polygons sequestered 47% more CO2 than drier areas with flat-centered polygons. While Svalbard has experienced a strong increase in mean annual air temperature of more than 2K in the last few decades, historical aerial photographs from the site indicated stable ice-wedge morphology over the last 7 decades. Apparently, warming has thus far not been sufficient to initiate strong ice-wedge degradation, possibly due to the absence of extreme heat episodes in the maritime climate on Svalbard. However, in Arctic regions where ice-wedge degradation has already initiated the associated drying of landscapes, our results suggest a weakening of the CO2 sink in polygonal tundra

Using structure-from-motion to create glacier DEMs and orthoimagery from historical terrestrial and oblique aerial imagery

Jordan R. Mertes acknowledges funding from Michigan Technological University and The Michigan Technological University 2016 Fall Finishing Fellowship. Lindsey Nicholson is supported by the Austrian Science Fund (FWF) Grant V309-N26.Increased resolution and availability of remote sensing products, and advancements in small-scale aerial drone systems, allows observations of glacial changes at unprecedented levels of detail. Software developments, such as Structure from Motion (SfM), now allow users an easy and efficient method to generate 3D models and orthoimages from aerial or terrestrial datasets. While these advancements show promise for current and future glacier monitoring, many regions still suffer a lack of observations from earlier time periods. We report on the use of SfM to extract spatial information from various historic imagery sources. We focus on three geographic regions, the European Alps, High-Arctic Norway and the Nepal Himalaya. We used terrestrial field photos from 1896, high oblique aerial photos from 1936 and aerial handheld photos from 1978 to generate DEMs and orthophotos of the Rhone glacier, Brøggerhalvøya and the lower Khumbu glacier, respectively. Our analysis shows that applying SfM to historic imagery can generate high quality models using only ground control points. Limited camera/orientation information was largely reproduced using self-calibrated model data. Using these data, we calculated mean ground sampling distances across each site which demonstrates the high potential resolution of resulting models. Vertical errors for our models are ±5.4 m, ±5.2 m and ±3.3 m. Differencing shows similar patterns of thinning at lower Rhone (European Alps) and Brøggerhalvøya (Norway) glaciers, which have mean thinning rates of 0.31 m a-1 (1896-2010) to 0.86 m a-1 (1936-2010) respectively. On these clean ice glaciers thinning is highest in the terminus region and decreasing upglacier. In contrast to these glaciers, uneven topography, exposed ice-cliffs and debris cover on the Khumbu glacier create a highly variable spatial distribution of thinning. The mean thinning rate for the Khumbu study area was found to be 0.54±0.9 m a-1 (1978-2015).PostprintPeer reviewe

A scale-dependent model to represent changing aerodynamic roughness of ablating glacier ice based on repeat topographic surveys

Turbulent fluxes make a substantial and growing contribution to the energy balance of ice surfaces globally, but are poorly constrained owing to challenges in estimating the aerodynamic roughness length (z0). Here, we used structure from motion (SfM) photogrammetry and terrestrial laser scanning (TLS) surveys to make plot-scale 2-D and 3-D microtopographic estimations of z0 and upscale these to map z0 across an ablating mountain glacier. At plot scales, we found spatial variability in z0 estimates of over two orders of magnitude with unpredictable z0 trajectories, even when classified into ice surface types. TLS-derived surface roughness exhibited strong relationships with plot-scale SfM z0 estimates. At the glacier scale, a consistent increase in z0 of ∼0.1 mm d−1 was observed. Space-for-time substitution based on time since surface ice was exposed by snow melt confirmed this gradual increase in z0 over 60 d. These measurements permit us to propose a scale-dependent temporal z0 evolution model where unpredictable variability at the plot scale gives way to more predictable changes of z0 at the glacier scale. This model provides a critical step towards deriving spatially and temporally distributed representations of z0 that are currently lacking in the parameterisation of distributed glacier surface energy balance models

Muddying the Picture? Forecasting Particulate Sources and Dispersal Patterns in Managed Catchments

Satellite imagery and climate change projections improve our ability to map and forecast sediment sources and transport pathways at high resolution, which is vital for catchment management. Detailed assessment of temporal and spatial changes in erosion risk are key to forecasting pollutant dispersal, which affects water treatment costs and ecology. Outputs from scenario modeling of the River Derwent catchment, Yorkshire, indicate clear spatial and temporal trends in erosion risk. These trends are not picked up by using traditional methods, which rely on static land use maps. Using satellite-derived maps show that lower resolution traditional land-use maps relatively underestimate erosion risk in terms of location of source areas and seasonal variation in erosion risk. Seasonal variation in agricultural practices can be assessed by incorporating bare land variation into models, which show that erosion risk is relatively overestimated if all agricultural land is assumed to have the same character. Producing seasonal land use maps also allows the assessment of temporal variation in rainfall, which in combination with climate change projections allows for adaptable management plans. The bias in gradient in modeling, which assumes that high gradients result in greater sediment erosion risk, show that traditional models underestimate the contribution of erosion risk in lowland areas. This is compounded by the absence of artificial drainages in topographic rasters, which increases connectivity in lowland areas. By producing end member scenarios, model outputs help to inform where catchment management should be targeted, and whether seasonal interventions should be implemented. This information is vital to communicate with landowners when they implement catchment management practices, such as sediment traps and earth bunds. Adaption of erosion risk modeling practices is urgently needed in order to quantify the impact of artificial interference in which human activity disrupts ‘natural’ sediment source-to sink configurations, such as integrating new pathways and stores due to land use change and management. Furthermore, integrating higher resolution catchment modeling and improved seasonal forecasts of pollutant flux to oceans will permit more effective interventions. This paper highlights single output erosion risk maps are not effective to inform catchment management

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Heat Flux Modeling on Debris-Covered Glaciers

A one-dimensional heat flux model has been developed in this study to analyze changes in heat propagation within debris cover on a glacier and the subsequent melt. The model can accept data collected in situ for calculations of real modeled melt, and also synthetic data based on simple wave forms and debris physical characteristics. The model is based on the Crank-Nicolson finite difference method of solving the one-dimensional heat equation. It has been written and implemented using MATLAB 2007b. A GUI has also been developed to allow for quick visualization and model adjustment. Numerous hypothetical runs have been performed to test the limitations of the model and to determine the accuracy and performance of the model. The model has been used to study what differences arise when using the melt calculation method of assuming an average daily linear thermal gradient versus using a physically based model. From this it has been shown that under stable atmospheric conditions and a relatively thick (~>0.5m) debris layer, the linear method does produce results similar to the full physical model. However, during times of unstable atmospheric conditions, errors do arise as the internal heat storage begins to fluctuate rapidly. If using the linear method on thinner (~<0.5m) debris layers the errors grow in response to the underestimation of internal temperatures. Using the model to analyze the changes in heat flux with varying debris thicknesses, a relationship between the two has been found, such that the linearity of the temperature profile is inversely related to the debris thickness. From this, a secondary relationship has also been found where the magnitude of the thermal gradient is also inversely related to the debris thickness. A comparison of calculated melt based on the assumption of a linear thermal gradient with that of the actual model shows a decreasing error with depth up to ~0.6m. It has been found that with an increasing debris thickness two things happen which decrease the error between the two methods. Firstly the magnitude of the modeled thermal gradient, at or near the surface, has been shown to decrease by almost a factor of 4 in this case, reducing the error between the two methods within this region of the debris. Secondly, the values for modeled thermal conductivity at the debris-ice interface approach zero, thereby reducing the error between the two calculated melts in the lower regions as the debris thickens. The model has also been used in an attempt to replicate results from a previous laboratory study performed by Reznichenko et al. (2010) where under stable conditions in a lab setting, melt was calculated under debris layers of varying thicknesses. The results of the model have been used as a verification of the accuracy of the model. Using data from the 2010 melt season from Longyearbreen, melt calculations have been made using both the modeled and the linear thermal gradient method producing values of 0.54m and 0.47m respectively. A correction has been made to the melt calculated using the linear thermal gradient based on an analysis of the differences between the two gradients and a correlation with daily average surface temperatures. By applying this correction equation the final R2 between the melt values was increased to 0.98. An Østrem curve has also been created using the model and varying the debris thickness by sub-centimeter increments. Based on the model’s performance tests and ability to produce similar melt results as laboratory results, the Østrem curve is believed to be more accurate in its general shape rather than its magnitude. The model has also been used to study the effects of measuring melt below varying debris thicknesses during shorter time periods throughout the melt season and how this subsequently changes the resulting Østrem curve. Differences on the order of ~0.5m have been found using 10 day periods during the mid-beginning melt season, mid-peak and mid-end of the melt season

Ngozumpa Glacier Gokyo ice cliffs photographic surface model

Data files of a photographic surface model of three ice cliffs exposed on the surface of the Ngozumpa Glacier ( 27°57′N, 85°42′E), Nepal, near the village of Gokyo. Details of how the data were produced: 1160 full resolution JPEG images were used to make the difgital surface model (DSM) Photos were taken using Nikon D5000 with 100mm Tamron macro lens on 4th April 2016 7 ground control points (GCPs) within the captured scene were used to scale and georeference the DSM GCPs were measured using a Trimble XH6000 with Tornado antenna as rover and a Trimble Geo7X with Zephyr antenna as a local base station Agisoft Photoscan (v1.26) was used to make the DSM using a SfM-MVS workflow Point pairs appearing in only one image pair and havoing a reprojection error grreater than 0.5 pixels were removed Model optimization was done using default parameters of f, b1, b2, cx, cy, k1-4, p1 and p2 and, as the lens distortion plot showed no extreme skewing or distortion, these optimization settings were accepted. The dense point cloud was generated using the ‘High’ quality setting with ‘Aggressive’ point filtering. The dense point cloud was then used directly to generate the DSM and orthomosaic at resolutions of 0.046 and 0.023 m respectively. Description of files: GokyoIceCliffs_POINTCLOUD.txt: dense point cloud including the whole scene covered by the photographs. Format: x,y,z, text file, WGS 84 / UTM zone 45N. GokyoIceCliffs_DSM_0.04.tif: 0.046 m resolution digital terrain model derived from the dense point cloud covering the area of interest including the 3 sampled ice cliffs. Format: TIFF WGS 84 / UTM zone 45N. GokyoIceCliffs_ORTHO_0.04.tif: 0.023 m resolution orthophoto covering the area of interest including the 3 sampled ice cliffs. Format: TIFF WGS 84 / UTM zone 45N