Browsing by Author "Else, Brent"
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- ItemOpen AccessAir-sea carbon dynamics in Baffin Bay: 2011-2021(2023-08) Nickoloff, Gina Mary; Else, Brent; Marshall, Shawn; Kimura-Hara, SusanaArctic waters play a disproportionately large role in oceanic CO2 uptake, but are most vulnerable to impacts of climate change. Due to the Arctic’s limited accessibility and remote nature, oceanic CO2 data is sparse to the extent that observation-based estimates of air-sea CO2 flux have only been derived for certain regions, leaving considerable uncertainty in the contribution of Arctic seas to global carbon budgets. Comprehensive description of surface-ocean CO2 dynamics in poorly-studied Arctic regions is needed to constrain Arctic and global carbon cycles, and to anticipate and document future change. In this thesis I provide such a novel description for the Baffin Bay region by examining the spatial and temporal distributions of surface-ocean partial pressure of CO2 (pCO2) while identifying its driving physical and biogeochemical controls, and by quantifying air-sea CO2 fluxes over the region during the open-water season. Utilising an extensive continuous underway ship-based pCO2 dataset accumulated over the last decade, 2011 to 2021, I report surface-ocean pCO2 over Baffin Bay (which in this definition includes Nares Strait and the Northwater Polynya) from June to October. Baffin Bay was highly favourable to uptake of atmospheric CO2 (70 to 130 μatm below saturation, depending on the year), but had substantial regional variability in pCO2 due to hydrography and ocean currents. Over the open-water season pCO2 exhibited a temporal pattern, increasing June to October but remaining undersaturated. Through comprehensive evaluation of Baffin Bay air-sea CO2 fluxes I show that it is a notably strong uptake region, even when compared to other North American Arctic regions. Baffin Bay had an average open-water-season flux of -7.3 mmol CO2 m-2 day1, which corresponds to an estimated carbon uptake of 11.9 Tg C year-1. Ice coverage in some regions served as a barrier to uptake, particularly in the northern portions of the study region. In the future, Baffin Bay is expected to remain a strong uptake region, with possible increased uptake as sea-ice loss lengthens the open-water season and summer wind speeds increase. This research fills a sizeable knowledge gap in Arctic oceanic carbon uptake, showing Baffin Bay is an exceptionally strong uptake region and providing insight into the variability of and drivers to surface-ocean pCO2.
- ItemOpen AccessAir-Sea CO₂ Cycling in Arctic Coastal Seas: Case Studies in the Canadian Arctic Archipelago and Hudson Bay(2020-08-10) Ahmed, Mohamed M. M.; Else, Brent; Papakyriakou, Tim; Belanger, Simon; Yackel, John; Dunfield, Peter; Hales, BurkeIn contrast to the open ocean, the sources and sinks for atmospheric carbon dioxide (CO₂) in the coastal ocean are source of large uncertainties when budgeting the global ocean carbon sink. This is mainly because of the different characteristics of coastal seas, and strong spatial and temporal heterogeneity. Furthermore, the coastal ocean has been substantially impacted by human activities (e.g., hydroelectric damming, overfishing, shipping, etc.) and is now considered one of the most sensitive parts of the marine environment to climate change. As a result, it is vital to study the carbon cycle and quantify the air-sea CO₂ fluxes in these regions to predict and understand how they may change in response to future climate change. In this thesis, I address this knowledge gap in two Arctic coastal seas by studying the spatial and temporal variability of surface water CO₂ partial pressure (pCO₂) and by quantifying air-sea CO₂ fluxes. Using continuous underway ship measurements of pCO₂, salinity, sea surface temperature, and chlorophyll a (Chl a) concentrations, we quantified the multi-annual variability of air-sea CO₂ exchange in the Canadian Arctic Archipelago and provided a baseline estimate of CO₂ sources and sinks in Hudson Bay during the spring and early summer seasons. Both study regions acted as a net oceanic sink with an average air-sea CO₂ flux of -7.7 and -7.2 TgC yr⁻¹ in the Canadian Arctic Archipelago and Hudson Bay, respectively. In the Canadian Arctic Archipelago, we estimated an increase in the atmospheric CO₂ uptake in the last four decades due to an increase in sea ice loss and higher wind speeds. In Hudson Bay, we observed a distinct spatial pattern in pCO₂ related to proximity from freshwater sources, with supersaturated pCO₂ (relative to the atmosphere) measured near river mouths, and undersaturated pCO₂ in offshore and ice-melt influenced waters. This thesis budgeted the CO₂ sources and sinks in a third of the Arctic shelf seas area (about 36%) and shows the importance of accounting for the spatiotemporal variability of coastal shelves to get better estimates of the carbon budget in the Arctic Ocean.
- ItemOpen AccessEffects of Seasonal Ice Coverage on the Physical Oceanographic Conditions of the Kitikmeot Sea in the Canadian Arctic Archipelago(Taylor and Francis, 2021-08-31) Xu, Chengzhu; Mikhael, Wahad; Myers, Paul G.; Else, Brent; Sims, Richard P.; Zhou, QiThe Kitikmeot Sea is a semi-enclosed, east–west waterway in the southern Canadian Arctic Archipelago (CAA). In the present work, the ice conditions, stratification, and circulation of the Kitikmeot Sea are diagnosed using numerical simulations with a 1/12° resolution. The physical oceanographic conditions of the Kitikmeot Sea are different from channels in the northern CAA due to the existence of a substantial ice-free period each year. The consequences of such ice conditions are twofold. First, through fluctuations of external forcings, such as solar radiation and wind stress, acting directly or indirectly on the sea surface, the seasonal ice coverage leads to significant seasonal variations in both stratification and circulation. Our simulation results suggest that such variations include freshening and deepening of the surface layer, in which salinity can reach as low as 15 during the peak runoff season, and significantly stronger along-shore currents driven directly by the wind stress during the ice-free season. The second consequence is that the sea ice is not landfast but can move freely during the melting season. By analyzing the relative importance of thermodynamic (freezing and/or melting) and dynamic (ice movement) processes to the ice dynamics, our simulation results suggest that there is a net inflow of sea ice into the Kitikmeot Sea, which melts locally each summer. The movement of sea ice thus provides a significant freshwater pathway, which contributes approximately 14 km3 yr−1 of fresh water to the Kitikmeot Sea, on average, equivalent to a third of freshwater input from runoff from the land.
- ItemOpen AccessEstimation of Glacier Surface Melt from Low-Elevation Station Data(2016) Rozek, Anne; Marshall, Shawn; Else, Brent; He, JenniferThere is a growing need to accurately model the extent that glacial melt and runoff are affected by climate change. Measurement and modelling of fields in a glacial melt model is difficult due to complex mountain terrain. The variance of meteorological fields between measurement locations and glaciers lacks precision as geographic and terrain differences render interpolation difficult and inaccurate. This project ameliorates this issue for the Canadian Rockies by calculating how melt model parameters vary between Haig Glacier and ‘reference stations’ in Calgary, the mountain parks, and NARR. Regression and correlation analyses determine which stations accurately predict conditions on Haig Glacier for critical variables. If a statistically strong relationship is present, a transfer function is calculated between the given sites for the given variable. This function is then used in a glacial melt model to determine the extent to which conditions on Haig can be predicted from more accessible locations.
- ItemOpen AccessFlying Anemometers: Performance Assessment of a Miniaturized Sonic Anemometer for Measuring Wind from a Drone(2022-01-28) Wearmouth, Clay; Hugenholtz, Christopher; Else, Brent; Moorman, Brian; Ke, DuThis MSc thesis incorporates wind-tunnel testing and field trials to evaluate the performance of new miniaturized sonic anemometers for use onboard small aerial drones for meteorological measurements. Drones have received considerable attention as they provide a flexible vantage point for measuring in-situ atmospheric conditions. Specifically, drones equipped with miniaturized sonic anemometers may be suitable for measuring wind conditions in support of research and industrial emissions applications. These compact and lightweight anemometers are small enough to fit the restrictive payloads of small multirotor drones, however, mounting these sensors on a drone introduces several sources of error that have not been well documented. This noted, the objective of this MSc thesis is to evaluate the accuracy of wind measurements from a drone equipped with a miniaturized sonic anemometer. The research approach consisted of two stages. First, flight conditions and changes in pitch angle and yaw rotation were simulated from a fixed position in wind tunnel experiments to evaluate the anemometer’s measurement accuracy in the absence of aerodynamic effects from platform motion and rotors. Next, a rotor wash analysis was performed to measure the airflow disturbance generated by the drone’s rotors. These data were used to identify ideal locations for sensor placement where airflow is minimally disturbed. Results from wind tunnel testing indicate the anemometer systematically disturbs airflow when part of the sensor is upwind of the sampling volume. This interference impacts both wind speed and direction data. Results from the rotor wash testing revealed airflow is minimally impacted 50 cm above the rotors and wind direction is less affected over the upwind rotor pair. These relationships were investigated to optimally balance each factor to generate high quality in-situ atmospheric data from a miniaturized sonic anemometer mounted on a drone. Lastly, recommendations for flight tests are provided for future research. The outcome of this thesis research is a better-resolved understanding of wind measurement accuracy from drones using miniaturized sonic anemometers.
- ItemOpen AccessIce Nucleating Particle and Ion Characteristics of Arctic Aerosols(2021-08-22) Henschel, Colleen Leanne; Norman, Ann-Lise; Wieser, Michael; Else, BrentINPs are aerosol particles that allow for the formation of ice crystals in clouds at temperatures warmer than required for homogeneous freezing. These aerosols are particularly important for the formation of mixed-phase clouds, which are ubiquitous during the Arctic summer. In order to better understand the factors affecting the rapidly warming Arctic climate, this study investigates INP concentrations found in size-segregated aerosol, fog and precipitation samples collected in the Arctic during the summer of 2016. The key findings from this study include: (1) the initial droplet freezing temperature correlates with sea salt ion concentrations for fog samples and aerosol samples in the size range of 1.5-7.2µm diameter, (2) INP concentrations for aerosol samples decreased after both heating and filtering, but were still distinguishable from blank samples, indicating the presence of biological INPs and separable ice nucleating components, (3) the INP concentrations measured for co-collected seawater samples were similar overall, but were not consistent at the exact locations of collection, and (4) the important size range of aerosols acting as INPs varied by sample time and location.
- ItemOpen AccessMarine microbial communities capable of hydrocarbon biodegradation along shipping routes in the Kivalliq region of the Canadian Arctic(2022-06) Ji, Meng; Hubert, Casey; Gieg, Lisa; Harrison, Joe; Else, BrentThe extreme cold and icy marine environment in the Canadian Arctic is not well understood regarding its potential for biodegradation of oil spills. Reduced ice cover due to climate change has led to increased human activities, with attendant risks of oil and fuel spills associated with shipping traffic. This threatens the marine ecosystem and well-being of Canadians living in Arctic communities that rely on the ocean for food and cultural livelihood. Naturally occurring hydrocarbon-degrading bacteria within the marine microbiome have the potential to catalyze biodegradation of crude oil compounds, with previous studies showing cold-adapted oil-degrading bacteria inhabiting different marine biomes in the Canadian Arctic. However, the Kivalliq region in Nunavut, Canada, which has been impacted by increased vessel traffic in Hudson Bay in recent decades, has not been investigated in this regard. Determination of the baseline microbiomes in pristine ice, seawater and surface sediment was complemented by mock oil spill microcosms in seawater and sediment to assess biodegradation potential in the Kivalliq marine environment. Incubations of seawater or sediment amended with crude oil were monitored over a 21-week period using 16S rRNA gene amplicon sequencing, metagenomics, cell counting and hydrocarbon geochemistry. Analysis of microbial baselines showed little variability in diversity or taxa in similar marine biomes apart from sites with fresher water. Seawater microcosms demonstrated growth from putative hydrocarbon-degrading organisms corresponding to losses in alkane hydrocarbons. Alkane and polycyclic aromatic hydrocarbon losses and detection of associated genes for hydrocarbon degradation corresponded with appearances of putative hydrocarbonoclastic taxa in sediment microcosms. The Kivalliq marine microbiome’s potential to mitigate pollution effects associated with oil spills suggests that incorporating microbial diversity and microbiome assessments into monitoring environmental change will lead to improved efficacy of spill bioremediation strategies and preparation measures in the Arctic.
- ItemOpen AccessMeltwater Retention and Refreezing Processes in Glacier Snow and Firn(2020-01-14) samimi, samira; Marshall, Shawn; Else, Brent; MacFerrin, Michael; Moorman, Brian J; Pietroniro, Alain; Rennermalm, Asa KGlacier mass losses from all the regions of the world are a strong indication of global warming. The sum of glacier and ice sheet contributions is the dominant source of global sea level rise over the past two decades, and mass loss from the Greenland Ice Sheet is increasing due to significant increases in surface melt and runoff. A fraction of summer meltwater is retained as liquid water or refrozen ice as meltwater percolates into cold (sub-zero) underlying snow and firn, which helps to reduce the summer runoff. However, there are challenges to quantifying both infiltration and refreezing of meltwater in heterogeneous snow and firn and to understanding the spatial variability of these processes. In this study, I introduce a new method to continuously monitor meltwater infiltration and refreezing in snow and firn, applying Time Domain Reflectometry (TDR) measurements of dielectric permittivity as an indirect measure of snow/firn liquid water content. To my knowledge, this is the first application of TDR to studies of ice sheet hydrology. I developed and conducted field experiments on Haig Glacier in the Canadian Rocky Mountains and at DYE-2, Greenland, including in situ measurements of the evolution of subsurface temperature and liquid water content through a summer melt season. My studies aim to advance understanding of meltwater infiltration and refreezing processes in supraglacial snow and firn. In addition, my field data can help the modelling community to build more accurate models of firn hydrology in the percolation zone of glaciers and ice sheets, in support of glacier mass balance modelling.
- ItemOpen AccessMethanotrophic Bacteria and Biogeochemical Cycling in an Oil Sands End Pit Lake(2016) Haupt, Evan; Dunfield, Peter; Voordouw, Gerrit; Gieg, Lisa; Strack, Maria; Else, BrentThis study examined for the first time the microbial community and biogeochemical cycling of methane and oxygen in Base Mine Lake, the reclamation site of a former tailings pond in the Athabasca oil sands region of Northern Alberta. Base Mine Lake represents the first large-scale demonstration of the “water-capped end pit lake” approach to tailings pond reclamation, with the ultimate goal of transitioning the lake into a natural, self-sustaining ecosystem. The oxygenated upper portion of the lake is home to aerobic hydrocarbon degrading bacteria, including a diverse population of methane oxidizing bacteria, whose activity, dispersion, and community composition is greatly influenced by seasonal variation. The majority of methanotrophs in the lake belong to the class Gammaproteobacteria, although Alphaproteobacteria methanotrophs make up a relatively large percentage of methanotrophs during summer stratification. Methanotroph abundance and potential for methane oxidation are relatively high during periods of turnover or partial mixing in the lake, and decrease during stratification.
- ItemOpen AccessNumerical Investigation of Diapycnal Mixing in the Kitikmeot Sea, Canadian Arctic Archipelago(2022-09) Afsharipour, Yasaman; Zhou, Qi; Else, Brent; Huang, WendyThe Kitikmeot Sea, located in the southern Canadian Arctic Archipelago, has particular features distinguishing it from the northern parts of the Archipelago. Substantial ice-free period, massive freshwater input from rivers, limited water exchange due to its surrounding narrow straits and shallow sills, can influence the local ocean dynamics, in particular, the mixing and transport in this sea. In this thesis, diapycnal mixing is investigated by analyzing the output data from a numerical simulation of the Kitikmeot Sea, with 1/12◦ horizontal resolution, during years 2003 to 2019. Mixing strength has been quantified in terms of diapycnal diffusivity values derived from a volume-averaged advection-diffusion equation for fluid density. Spatial and temporal variability of mixing in the Kitikmeot Sea is investigated. Furthermore, the contributions from a number of energy sources to the mixing process have been estimated in order to identify the main driving mechanism for mixing. Investigation of the temporal variability in diffusivity reveals seasonal patterns which can be attributed to the annual cycle of sea-ice coverage. It was found that wind stirring and convection due to sea-ice forming and sea-surface cooling make significant energy contributions to mixing in the Kitikmeot Sea.
- ItemOpen AccessOpen or Closed? Measurement Performance of Open- and Closed-Path Methane Sensors for Mobile Emissions Screening(2024-01-11) Billinghurst, Chandler Duran; Hugenholtz, Chris; Else, Brent; Du, Ke; Hugenholtz, ChrisGround-based vehicle systems are being increasingly used by industry, regulators, and service providers in the upstream oil and gas sector to measure methane emissions. However, the suite of methane sensors affixed to these systems is non-standardized and existing literature displays a scarcity of direct comparisons regarding their measurement performance. Gaussian dispersion models are often used to supplement measured data and derive estimates of emission intensity in screening applications based on data measured by these sensors. Existing literature indicates these models perform with considerable uncertainty. As such, equivalence of performance between existing vehicle-based emission screening systems is difficult to assess. To address this issue, field-based controlled release experiments were conducted to compare concentration data from an open- and closed-path sensor deployed in tandem onboard a vehicle. Performance of a forward Gaussian dispersion model was assessed relative to measured data from both sensors. 801 transects were driven through methane plumes dispersed downwind of a controlled emission source at various measurement distances and driving speeds, as well as a range of atmospheric conditions. Measurement performance was predicated on three primary descriptors of concentration data: the maximum concentration within each plume (maximum enhancement), plume width, and plume area (total methane sampled within the plume). Results showed that the measurement performances of both sensors were not equivalent. Relative to the open-path sensor, the closed-path sensor reported maximum enhancements that were ~40% smaller on average and plume widths that were ~42% larger on average, while measures of plume area displayed near 1:1 parity. Measurement discrepancies are largely explained by differences in sensor measurement frequency and intrinsic sampling mechanisms. Forward Gaussian dispersion model performance displayed uncertainties ranging from 12.3% to 1207.0%. The origin of this uncertainty is largely determined by generalizations of atmospheric stability and simplistic representations of downwind plume migration within the model.
- ItemOpen AccessResponse of the Arctic Marine Inorganic Carbon System to Ice Algae and under-ice Phytoplankton Blooms(2017) Whitehead, Jeremy; Else, Brent; Yackel, John; Gieg, Lisa; Mundy, C.J.Research on the inorganic carbon cycle in the Arctic winter to spring transition process has revealed that ice algae could play a role in the inorganic carbon cycling under sea ice. A ten-week case study was conducted near Qikiqtarjuaq, NU, Canada, in which dissolved inorganic carbon (DIC) and was collected from the water column. Samples were collected near the start of an ice algae bloom, and continued until early stages of an under-ice phytoplankton bloom. During the ice algae bloom period, there was no significant decrease in DIC or pCO2sw prior to sea ice melt. DIC fixation calculations show that previous studies may have overestimated the drawdown of DIC from ice algae, but that sloughing ice algae or an under-ice phytoplankton bloom can dramatically reduce DIC and pCO2sw. This case study provided insights that under-ice phytoplankton blooms are a more important biological mechanism preconditioning the Arctic surface mixed layer.
- ItemOpen AccessSnow Thickness Estimation on First-Year Sea Ice from Microwave and Optical Remote Sensing and Melt Modelling(2017) Zheng, Jiacheng; Yackel, John; Else, Brent; Michael, SiderisLate-winter snow thickness on first-year sea ice is estimated based on the duration of snowmelt. The study encompasses the late-winter to advanced-melt period. The beginning of snowmelt is detected using space-borne C-band microwave scatterometer measurements, and the end of snowmelt is detected using optical satellite measurements. The snowmelt duration is then used to invert a degree-day snowmelt model based on air temperature, and a melt coefficient is calibrated with in situ observations. The modelled snow thickness estimation is validated with distributed in situ measurements of snow thickness throughout Dease Strait, Nunavut, Canada. The mean snowmelt duration for the study sites is 24.6 ± 1.2 days, and the estimated mean snow thickness is 14.7 ± 3.0 cm. The overall performance of the model reveals a RMSE of 27.1% and a bias of 1.8%. The methodology shows promise, and it can easily be scaled up to estimate snow thickness on a regional basis.