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Assessing the lateral and vertical extent of permafrost is critical to understanding the fate of Arctic ecosystems under climate change. Yet, direct measurements of permafrost distribution and temperature are often limited to a small number of borehole locations. Here, we assess the use of co‐located shallow temperature and electrical resistivity tomography (ERT) measurements to estimate at high‐resolution the distribution of permafrost in three watersheds underlain by discontinuous permafrost. Synthetic modeling shows that co‐located temperature and ERT measurements allow for supervised classification schemes that provide 60% higher accuracy compared to unsupervised methods. Linking resistivity and size of the identified permafrost bodies to surface observations, we show that tall vegetation (>0.5 m) and gentle slopes (<15°) are related to warmer and smaller permafrost bodies, and a more frequent occurrence of taliks. Plain Language Summary: To better understand how the Arctic may be changing due to climate warming, we need to understand the distribution of permafrost in the subsurface. Although the temperatures of the ground can be measured in boreholes, only a small number of boreholes exist to do these measurements. Here, we use machine learning to link measurements of temperature and of the electrical resistivity of the ground to obtain detailed distributions of permafrost in the subsurface. Connecting the properties of permafrost with observations above ground, we show that south facing slopes, tall vegetation, and gentle slopes relate to warmer and smaller permafrost bodies. Key Points: High‐resolution estimation of permafrost distribution and depth over large spatial extent is obtained using geophysical and temperature dataMachine learning using co‐located temperature and resistivity measurements improve estimates of permafrost thicknessPermafrost depth and temperature varies with surface cover and slope angle [ABSTRACT FROM AUTHOR]

The delivery and burial of terrestrial particulate organic carbon (OC) in marine sediments is important to quantify, because this OC is a food resource for benthic communities, and if buried it may lower the concentrations of atmospheric CO2 over geologic timescales. Analysis of sediment cores has previously shown that fjords are hotspots for OC burial. Fjords can contain complex networks of submarine channels formed by seafloor sediment flows, called turbidity currents. However, the burial efficiency and distribution of OC by turbidity currents in river‐fed fjords had not been investigated previously. Here, we determine OC distribution and burial efficiency across a turbidity current system within Bute Inlet, a fjord in western Canada. We show that 62% ± 10% of the OC supplied by the two river sources is buried across the fjord surficial (30–200 cm) sediment. The sandy subenvironments (channel and lobe) contain 63% ± 14% of the annual terrestrial OC burial in the fjord. In contrast, the muddy subenvironments (overbank and distal basin) contain the remaining 37% ± 14%. OC in the channel, lobe, and overbank exclusively comprises terrestrial OC sourced from rivers. When normalized by the fjord's surface area, at least 3 times more terrestrial OC is buried in Bute Inlet, compared to the muddy parts of other fjords previously studied. Although the long‐term (>100 years) preservation of this OC is still to be fully understood, turbidity currents in fjords appear to be efficient at storing OC supplied by rivers in their near‐surface deposits. Plain Language Summary: Plants on land use CO2 from the atmosphere to produce organic carbon, which promotes their growth. Rivers transport organic carbon to the sea, where it is either eaten by fauna or buried in the seafloor, thus decreasing atmospheric CO2 levels on Earth over thousands to millions of years. Fjords are recognized as global organic carbon sinks; trapping 18 million tons of organic carbon in their seafloor sediments each year. However, the complex morphology of fjord seafloors was not considered in the calculation of this organic carbon flux. In this study, we determine the distribution and abundance of terrestrial organic carbon across a fjord (Bute Inlet, Canada), which contains a submarine channel network terminating onto a large accumulation of sand (called a lobe). We show that 62% of the organic carbon supplied by the two rivers connected to the fjord is buried across the fjord; the majority of this carbon being held in the lobe. In total, Bute Inlet buries at least 3 times more organic carbon per unit of surface area than other fjords previously studied. Submarine channels in fjords thus appear to promote the storage of land‐derived organic carbon in the seafloor, potentially impacting CO2 levels and food resources for marine fauna. Key Points: Bute Inlet, a river‐fed fjord incised by turbidity currents, has a contemporary terrestrial organic carbon burial efficiency of 62% ± 10%Sandy surficial deposits are responsible for 63% ± 14% of the total terrestrial organic carbon burial budget in Bute Inlet, but only cover 17% of the seafloor areaGlobal estimates based only on the muddy parts of fjords may significantly underestimate organic carbon burial rates by a factor >3 [ABSTRACT FROM AUTHOR]

We investigate the effect of doping on the mechanisms of carrier escape from intermediate states in delta-doped InAs/GaAs intermediate band solar cells. The intermediate states arise from InAs quantum dots embedded in a GaAs p-i-n junction cell. We find that doping the sample increases the number of excited-state carriers participating in a cycle of trapping and carrier escape via thermal, optical, and tunneling mechanisms. However, we find that the efficiency of the optically-driven carrier escape mechanism is independent of doping and remains small. [ABSTRACT FROM AUTHOR]

Climate change is causing rapid changes of Arctic ecosystems. Yet, data needed to unravel complex subsurface processes are very rare. Using geophysical and in situ sensing, this study closes an observational gap associated with thermohydrological dynamics in discontinuous permafrost systems. It highlights the impact of vegetation and snow thickness distribution on subsurface thermohydrological properties and processes. Large snow accumulation near tall shrubs insulates the ground and allows for rapid and downward heat flow. Thinner snow pack above graminoid results in surficial freezing and prevents water from infiltrating into the subsurface. Analyzing short‐term disturbances, we found that lateral flow could be a driving factor in talik formation. Interannual measurements show that deep permafrost temperatures increased by about 0.2°C over 2 years. The results, which suggest that snow‐vegetation‐subsurface processes are tightly coupled, will be useful for improving predictions of Arctic feedback to climate change, including how subsurface thermohydrology influences CO2 and CH4 fluxes. Plain Language Summary: When permafrost thaws, water can flow quicker through the ground, creating a very complex subsurface flow system. In this study, we gain detailed insight into these complex processes by measuring the electrical resistivity of the ground daily. Our results show that the type of vegetation and the snow pack that accumulates on it in winter control the temperatures of the ground, and therefore also how water flows. Above tall shrubs snow accumulates much more than above grass. Therefore, temperatures below shrubs are warmer and water and energy from snowmelt and rain can flow through the ground quickly, while colder temperatures below the grass prevent this rapid flow. Longer term dynamics show us that the temperature of permafrost at about 10 m depth increased by 0.2°C over a period of 2 years. The results of this study should be useful for improving predictions of Arctic feedback to climate change. Key Points: Transitional permafrost systems evolve through complex infiltration pathways and energy fluxes, including lateral flowSnow pack and vegetation distribution play major role in permafrost thermohydrological responsesMonitoring shows spatially variable thermohydrological responses and intra to inter‐annual dynamics in discontinuous permafrost systems [ABSTRACT FROM AUTHOR]

Submarine channel systems convey terrestrially derived detritus from shallow-marine environments to some of the largest sediment accumulations on Earth, submarine fans. The stratigraphic record of submarine slope channels includes heterogeneous, composite deposits that provide evidence for erosion, sediment bypass, and deposition. However, the timing and duration of these processes is poorly constrained over geologic time scales. We integrate geochronology with detailed stratigraphic characterization to temporally constrain the stratigraphic evolution recorded by horizontally to vertically aligned channel-fill stacking patterns in a Nanaimo Group channel system exposed on Hornby and Denman Islands, British Columbia, Canada. Twelve detrital zircon samples (n = 300/sample) were used to calculate maximum depositional ages, which identified a new age range for the succession from ca. 79 to 63 Ma. We document five phases of submarine-channel evolution over 16.0 ± 1.7 m.y. including: an initial phase dominated by incision, sediment bypass, and limited deposition (phase 1); followed by increasingly shorter and more rapid phases of deposition on the slope by laterally migrating (phase 2) and aggrading channels (phase 3); a long period of deep incision (phase 4); and a final rapid phase of vertical channel aggradation (phase 5). Our results suggest that ~60% of the evolutionary history of the submarine channel system is captured in an incomplete, poorly preserved record of incision and sediment bypass, which makes up <20% of outcropping stratigraphy. Our findings are applicable to interpreting submarine channel-system evolution in ancient and modern settings worldwide and fundamentally important to understanding long-term sediment dispersal in the deep sea. [ABSTRACT FROM AUTHOR]

Investigates persistent photoconductivity (PPC) and optical quenching (OQ) of photoconductivity (PC) in a variety of n-gallium nitride layers characterized by different carrier concentration, luminescence characteristics and strains. Study of the relation between PPC and OQ of PC by exciting samples with two beams of monochromatic radiation of various wavelengths and intensities.