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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Andrieslombaardite, RhSbS, a new platinum-group mineral from the platiniferous Onverwacht Pipe, Republic of South Africa

A hundred years after the discovery of the Merensky Reef in 1924, it is appropriate to present the new mineral andrieslombaardite in honour of Andries Frederik Lombaard who was instrumental in its discovery. Andrieslombaardite, RhSbS, was first described as an unknown mineral from placer deposits associated with the Tulameen Alaskan-Uralian type complex, British Colombia, Canada (Raicevic and Cabri, 1976) but has since been reported from several other deposits including the platiniferous Driekop, Mooihoek, and Onverwacht pipes in the eastern Bushveld Complex, South Africa. The mineral and the name were approved by the Commission on New Minerals Nomenclature and Classification (CNMNC) of the International Mineralogical Association (IMA no. 2022-076) based on data in the co-type samples from Onverwacht and a co-type sample from the Yubdo stream, Birbir River, Ethiopia. Andrieslombaardite in the Onverwacht sample is a single 8 x 20 μm grain attached to laurite in a matrix of altered silicate and Fe-oxyhydroxide minerals. In the Yubdo samples, there are many grains of pale brownish gray andrieslombaardite up to 25 x 55 μm in size, included in Pt-Fe alloys, some associated with erlichmanite, and others attached to bornite and chalcopyrite. The reflectance values (R%) measured in air and in oil at the COM wavelengths are 48.3 and 33.0 (470 nm), 49.3 and 34.0 (546 nm), 51.0 and 35.9 (589 nm), and 51.8 and 36.7 (650 nm). The colour values x, y, Y, λd, and Pe in air are 0.317, 0.322, 50.3, 580, and 3.2, and in oil are 0.319, 0.324, 35.6, 579, and 4.5. The composition of andrieslombaardite is ideally RhSbS, but it contains variable amounts of Fe, Pt, Pd, and Ir that may substitute for Rh. The mineral is cubic with unit-cell dimensions of a = 6.0278(4) Å, V = 219.01(6) Å 3 and Z = 4. It was synthesised at 400 and 550°C using stoichiometric elemental amounts. It is a member of the cobaltite group. The mineralisation of the intrusive dunite pipes was probably introduced at high temperatures, under magmatic conditions. The primary assemblages were to a certain degree overprinted and redistributed by low-temperature hydrothermal fluids. The Pt-Fe alloys from Yubdo containing PGM inclusions such as andrieslombaardite in the Yubdo-Alaskan-type complex were formed at some post-magmatic stage owing to PGE remobilisation during hydrothermal or metamorphic episodes.

58 GEOSCIENCES↗
DOE OSTI2025

Cold-air outbreaks in the continental US: Connections with stratospheric variations

Mid-latitude Northern Hemisphere extreme cold events continue to occur despite overall winter warming trends. These events have been linked to weakened stratospheric polar vortex (SPV) states. In this study, we analyze both the upper and lower polar stratosphere for links to extreme winter cold and snow in the continental US, finding two SPV variations of interest. The first features an upper-level vortex displaced toward western Canada and linked to northwestern US severe winter weather. The second features a weakened upper-level vortex displaced toward the North Atlantic and linked to central-eastern US severe winter weather. Both variations feature lower-level stretched vortices and stratospheric wave reflection. Since 2015, a northwestward shift in severe winter weather across the US is concurrent with an increase in the frequency of the westward-focused variation relative to the eastward-focused variation and a shift to more negative phases of the El Niño–Southern Oscillation.

Science & Technology - Other Topics↗
DOE OSTI2024

AmeriFlux CA-Mer Ontario - Eastern Peatland, Mer Bleue

This is the AmeriFlux version of the carbon flux data for the site CA-Mer Ontario - Eastern Peatland, Mer Bleue. Site Description - The Mer Bleue peatland is primarily a large ombrotrophic bog located in the Ottawa River Valley, 10 km east of Ottawa, Ontario, Canada (45.40º N lat., 75.50º W long.). Mean annual temperature is 6.3ºC ranging from -10.5ºC in January to 21.0ºC in July. Mean annual precipitation is 943 mm, 268 mm of which falls during the summer months (Environment Canada; climate normals). Peat began to form approximately 8500 years ago, but the bog phase began later, about 6400 years ago (Lafleur et al., 2003; Richard, pers. comm.). The peat depth now ranges from 2 m at the edge to >5 m in the middle. Beaver ponds are found at the lagg margin of the bog. The bog is dominated by plant communities comprised primarily of the ericaceous shrubs Chamaedaphne calyculata (L.) Moench, Ledum groenlandicum Oeder, and Kalmia angustifolia L. Clusters of the deciduous shrub Vaccinium myrtilloides Michx. and the tufted sedge Eriophorum vaginatum L. are fairly common across the bog. The most common tree species found in the bog are Larix laricina (Duroi) K. Koch., Betula populifolia Marshall and Picea mariana (Miller) BSP occurring less frequently. In the poor fen, located to the north of the bog proper, community composition is primarily composed of the ericaceous shrubs listed above, including higher densities of K. angustifolia and Andromeda glaucophylla Link. The primary sedge in this area is Carex oligosperma Michx. All sites are dominated by an under story of bryophytes, mainly Sphagnum magellanicum Brid., Sphagnum capillifolium (Ehrh.) Hedw., and Polytrichum strictum Brid. in the bog, with Sphagnum papillosum Lindb., and Sphagnum fallax (Klinggr.) Klinggr. common in the wetter portions of the poor fen

Humphreys, Elyn↗
DOE OSTI2021

The North American Renewable Integration Study (NARIS): A Canadian Perspective

The North American electric power system is undergoing significant change, with renewable resources now contributing more generation than ever before. This transformation is poised to continue given decreasing technology costs and ambitious decarbonization goals at the federal, state, local, corporate, and consumer levels. The North American Renewable Integration Study (NARIS) aims to inform grid planners, utilities, industry, policymakers, and other stakeholders about challenges and opportunities for continental system integration of large amounts of wind, solar, and hydropower to support a low-carbon future grid. The National Renewable Energy Laboratory (NREL) conducted a detailed, continent-wide analysis with planning scenarios of transmission, generation, and demand to reach 80%–92% carbon reductions (from 2005) for the Canadian electric power system, and up to 80% reductions continent-wide. We used a suite of models to study future scenarios and gain insights, including potential impacts on costs, emissions, resource adequacy, and the specific technologies that help enable the transition to a low-carbon grid. Our analysis had a particular focus on the potential role of cooperation among the three North American countries and between regions within each country, and how transmission can support sharing of supply and demand diversity. The NARIS project began in 2016. This report describes a Canadian perspective in coordination with the Natural Resources Canada, and a companion report describes a U.S. perspective in coordination with the U.S. Department of Energy. NARIS was an extension of a previous body of work, including the Western Wind and Solar Integration Study, the Eastern Renewable Generation Integration Study, Interconnections Seam Study, and the Pan Canadian Wind Integration Study. NARIS analyzed the entire continent in detail while studying higher renewable generation than previous studies. The scenarios in NARIS were informed by the goals in the Mid-Century Strategies for the Paris Agreement in each country.

14 SOLAR ENERGY↗
DOE OSTI2025

Potential quantum advantage for simulation of fluid dynamics

Numerical simulation of turbulent fluid dynamics needs to either parametrize turbulence—which introduces large uncertainties—or explicitly resolve the smallest scales—which is prohibitively expensive. Here, we provide evidence through analytic bounds and numerical studies that a potential quantum speedup can be achieved to simulate fluid dynamics using quantum computing. Specifically, we provide a lattice Boltzmann formulation of fluid dynamics for which we give evidence that low-order Carleman linearization is much more accurate than previously believed for these systems. This is achieved via a combination of reformulating the Navier-Stokes nonlinearity (u·$\triangledown$u) to lattice-Boltzmann nonlinearity (u 2 ) and accurately linearizing the dynamical equations, which effectively trades nonlinearity for additional degrees of freedom that add negligible expense in the quantum solver. Based on this, we apply a quantum algorithm for simulating the Carleman-linearized lattice Boltzmann equation and provide evidence that its cost scales logarithmically with system size compared with polynomial scaling in the best known classical algorithms. In this paper, we suggest that a quantum advantage may exist for simulating fluid dynamics, paving the way for simulating nonlinear multiscale transport phenomena in a wide range of disciplines using quantum computing.

42 ENGINEERING↗
NASA NTRS1984

Large Scale Winter Time Disturbances in Meteor Winds over Central and Eastern Europe

Daily zonal wind data of the four pre-MAP-winters 1978/79 to 1981/82 obtained over Central Europe and Eastern Europe by the radar meteor method were studied. Available temperature and satellite radiance data of the middle and upper stratosphere were used for comparison, as well as wind data from Canada. The existence or nonexistence of coupling between the observed large scale zonal wind disturbances in the upper mesopause region (90 to 100 km) and corresponding events in the stratosphere are discussed.

Greisiger, K. M.↗
NASA NTRS1986

An ecologic study of peat landforms in Canada and Alaska

The role of groundwater and surface runoff in controlling the water chemistry and development of peat landforms in northern Minnesota are described. The LANDSAT imagery taken duing spring break-up are particularly valuable in identifying potential zones of groundwater discharge. The vascular floras of raised bogs in eastern North Americas demonstrating the remarkabe uniformity of the ombrotrophic flora over broad geographic regions are described. The evolution of peat landforms in the major boreal peatlands of eastern America is examined. The LANDSAT imagery is used to determine the area of patterned to featureless peatlands, the area of ombrotrophic bog relative to minerotrophic fen, and the relative size and degree of streamlining of island landforms entirely composed of peat. Such measurements can be used to assess the role of climate, time, and hydrology in controlling the formation of peatland patterns across broad geographic regions.

Glaser, P. H.↗
DOE OSTI2025

AmeriFlux FLUXNET-1F CA-Mer Ontario - Eastern Peatland, Mer Bleue

This is the AmeriFlux Management Project (AMP) created FLUXNET-1F version of the carbon flux data for the site CA-Mer Ontario - Eastern Peatland, Mer Bleue. This is the FLUXNET version of the carbon flux data for the site CA-Mer Ontario - Eastern Peatland, Mer Bleue produced by applying the standard ONEFlux (1F) software. Site Description - The Mer Bleue peatland is primarily a large ombrotrophic bog located in the Ottawa River Valley, 10 km east of Ottawa, Ontario, Canada (45.40º N lat., 75.50º W long.). Mean annual temperature is 6.3ºC ranging from -10.5ºC in January to 21.0ºC in July. Mean annual precipitation is 943 mm, 268 mm of which falls during the summer months (Environment Canada; climate normals). Peat began to form approximately 8500 years ago, but the bog phase began later, about 6400 years ago (Lafleur et al., 2003; Richard, pers. comm.). The peat depth now ranges from 2 m at the edge to >5 m in the middle. Beaver ponds are found at the lagg margin of the bog. The bog is dominated by plant communities comprised primarily of the ericaceous shrubs Chamaedaphne calyculata (L.) Moench, Ledum groenlandicum Oeder, and Kalmia angustifolia L. Clusters of the deciduous shrub Vaccinium myrtilloides Michx. and the tufted sedge Eriophorum vaginatum L. are fairly common across the bog. The most common tree species found in the bog are Larix laricina (Duroi) K. Koch., Betula populifolia Marshall and Picea mariana (Miller) BSP occurring less frequently. In the poor fen, located to the north of the bog proper, community composition is primarily composed of the ericaceous shrubs listed above, including higher densities of K. angustifolia and Andromeda glaucophylla Link. The primary sedge in this area is Carex oligosperma Michx. All sites are dominated by an under story of bryophytes, mainly Sphagnum magellanicum Brid., Sphagnum capillifolium (Ehrh.) Hedw., and Polytrichum strictum Brid. in the bog, with Sphagnum papillosum Lindb., and Sphagnum fallax (Klinggr.) Klinggr. common in the wetter portions of the poor fen

Humphreys, Elyn [Carleton University]↗
NASA NTRSDate not supplied

Long-range Transport of Siberian Biomass Burning Emissions to North America During FIREX-AQ

Biomass burning from wildfires is a significant global source of aerosol and trace gases which impact air quality, tropospheric and stratospheric composition, and climate. During the summer of 2019, wildfire activity in central and eastern Siberia occurred during the Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) campaign conducted between July 24 and September 6, 2019. Ground-based lidar observations from the Autonomous Mobile Ozone Lidar for Tropospheric Experiments (AMOLITE) system in Alberta, Canada retrieved frequent anomalous ozone (O3) and aerosol lamina in the troposphere and lower stratosphere during this campaign. Data from NASA’s GEOS Composition Forecast (GEOS-CF) coupled chemistry meteorology model, TROPOspheric Monitoring Instrument (TROPOMI), Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), and ground-based insitu data were used to define the trans-Pacific and trans-Arctic transport pathway of Siberian biomass burning emissions resulting in the enhanced O3 and aerosol lamina observed by AMOLITE in western Canada. Siberian wildfires impacted North American air quality resulting in enhancements of hourly-averaged surface carbon monoxide (CO) (total CO >150 ppb) and fine particulate matter (PM2.5) (>20 μg m-3) in western Canada, however, minimal increases in surface-level O3 were measured as well as modeled by GEOS-CF. The impact in western Canada due to Siberian wildfires was much larger in the free troposphere, demonstrated by GEOS-CF and AMOLITE O3 lamina 30–40 ppb above background values and model-predicted PM2.5 lamina >30 μg m-3. In addition to tropospheric composition effects, the large wildfire activity in Siberia may have influenced the stratosphere as data from AMOLITE, CALIPSO, and GEOS-CF all suggested aerosol layers from the fires were located 13–18 km above ground level (agl). This study shows that the Siberian biomass burning emissions in the summer of 2019 impacted tropospheric/stratospheric composition in western Canada, and potentially could have influenced areas in the vicinity of FIREX-AQ airborne measurements, and future studies of FIREX-AQ chemical composition should consider how this long-range transport could have influenced the background trace gas and aerosol concentrations being investigated.

Biomass↗
DOE OSTI2021

Ferrotorryweiserite, Rh 5 Fe 10 S 16 , a New Mineral Species from the Sisim Placer Zone, Eastern Sayans, Russia, and the Torryweiserite–Ferrotorryweiserite Series

Ferrotorryweiserite, Rh 5 Fe 10 S 16 , occurs as small grains (≤20 µm) among droplet-like inclusions (up to 50 μm in diameter) of platinum-group minerals (PGM), in association with oberthürite or Rh-bearing pentlandite, laurite, and a Pt-Pd-Fe alloy (likely isoferroplatinum and Fe-Pd-enriched platinum), hosted by placer grains of Os-Ir alloy (≤0.5 mm) in the River Ko deposit. The latter is a part of the Sisim placer zone, which is likely derived from ultramafic units of the Lysanskiy layered complex, southern Krasnoyarskiy kray, Russia. The mineral is opaque, gray to brownish gray in reflected light, very weakly bireflectant, not pleochroic to weakly pleochroic (grayish to light brown tints), and weakly anisotropic. The calculated density is 5.93 g·cm –3 . Mean results (and ranges) of four WDS analyses are: Ir 18.68 (15.55–21.96), Rh 18.34 (16.32–20.32), Pt 0.64 (0.19–1.14), Ru 0.03 (0.00–0.13), Os 0.07 (0.02–0.17), Fe 14.14 (13.63–14.64), Ni 13.63 (12.58–14.66), Cu 4.97 (3.42–6.41), Co 0.09 (0.07–0.11), S 29.06 (28.48–29.44), and total 99.66 wt.%. They correspond to the following formula calculated for a total of 31 atoms per formula unit: (Rh 3.16 Ir 1.72 Pt 0.06 Ru 0.01 Os 0.01 ) Σ 4.95 (Fe 4.48 Ni 4.11 Cu 1.38 Co 0.03 ) Σ10.00 S 16.05 . The results of synchrotron micro-Laue diffraction studies indicate that ferrotorryweiserite is trigonal; its probable space group is $R\bar{3}m$ (#166) based on its Ni-analog, torryweiserite. The unit-cell parameters refined from 177 reflections are a = 7.069 (2) Å, c = 34.286 (11) Å, V = 1484 (1) Å 3 , and Z = 3. The c:a ratio is 4.8502. The strongest eight peaks in the X-ray diffraction pattern derived from results of micro-Laue diffraction study [d in Å(hkil)(I)] are 2.7950 ($20\bar{2}5$) (100); 5.7143 (0006) (60); 1.7671 ($22\bar{4}0$) (44.4); 3.0486 ($20\bar{2}1$) (39.4); 5.7650 ($10\bar{1}2$) (38.6); 2.5956 ($20\bar{2}7$) (37.8); 3.0058 ($11\bar{2}6$) (36.5); and 1.5029 ($4\bar{2}\bar{2}12$) (35.3). Ferrotorryweiserite and the associated PGM crystallized from microvolumes of residual melt at late stages of crystallization of grains of Os- and Ir-dominant alloys occurred in lode zones of chromitites of the Lysanskiy layered complex. In a particular case, the residual melt is disposed peripherally around a core containing a disequilibrium association of magnesian olivine (Fo 72.9–75.6 ) and albite (Ab 81.6–86.4 ), with the development of skeletal crystals of titaniferous augite: Wo 40.8–43.2 En 26.5–29.3 Fs 20.3–22.6 Aeg 6.9–9.5 (2.82–3.12 wt.% TiO 2 ). Ferrotorryweiserite represents the Fe-dominant analog of torryweiserite. We also report occurrences of ferrotorryweiserite in the Marathon deposit, Coldwell Complex, Ontario, Canada, and infer the existence of the torryweiserite–ferrotorryweiserite solid solution in other deposits and complexes.

58 GEOSCIENCES↗
NASA NTRS2011

SO2 Emissions and Lifetimes: Estimates from Inverse Modeling Using In Situ and Global, Space-Based (SCIAMACHY and OMI) Observations

Top-down constraints on global sulfur dioxide (SO2) emissions are inferred through inverse modeling using SO2 column observations from two satellite instruments (SCIAMACHY and OMI). We first evaluated the S02 column observations with surface SO2 measurements by applying local scaling factors from a global chemical transport model (GEOS-Chem) to SO2 columns retrieved from the satellite instruments. The resulting annual mean surface SO2 mixing ratios for 2006 exhibit a significant spatial correlation (r=0.86, slope=0.91 for SCIAMACHY and r=0.80, slope = 0.79 for OMI) with coincident in situ measurements from monitoring networks throughout the United States and Canada. We evaluate the GEOS-Chem simulation of the SO2 lifetime with that inferred from in situ measurements to verity the applicability of GEOS-Chem for inversion of SO2 columns to emissions. The seasonal mean SO2 lifetime calculated with the GEOS-Chem model over the eastern United States is 13 h in summer and 48 h in winter, compared to lifetimes inferred from in situ measurements of 19 +/- 7 h in summer and 58 +/- 20 h in winter. We apply SO2 columns from SCIAMACHY and OMI to derive a top-down anthropogenic SO2 emission inventory over land by using the local GEOS-Chem relationship between SO2 columns and emissions. There is little seasonal variation in the top-down emissions (<15%) over most major industrial regions providing some confidence in the method. Our global estimate for annual land surface anthropogenic SO2 emissions (52.4 Tg S/yr from SCIAMACHY and 49.9 Tg S / yr from OMI) closely agrees with the bottom-up emissions (54.6 Tg S/yr) in the GEOS-Chem model and exhibits consistency in global distributions with the bottom-up emissions (r = 0.78 for SCIAMACHY, and r = 0.77 for OMI). However, there are significant regional differences.

Lee, Chulkyu↗
NASA NTRS2012

Recent Upgrades to NASA SPoRT Initialization Datasets for the Environmental Modeling System

The NASA Short-term Prediction Research and Transition (SPoRT) Center has developed several products for its National Weather Service (NWS) partners that can initialize specific fields for local model runs within the NOAA/NWS Science and Training Resource Center (STRC) Environmental Modeling System (EMS). In last year's NWA abstract on this topic, the suite of SPoRT products supported in the STRC EMS was presented, which includes a Sea Surface Temperature (SST) composite, a Great Lakes sea-ice extent, a Green Vegetation Fraction (GVF) composite, and NASA Land Information System (LIS) gridded output. This abstract and companion presentation describes recent upgrades made to the SST and GVF composites, as well as the real-time LIS runs. The Great Lakes sea-ice product is unchanged from 2011. The SPoRT SST composite product has been expanded geographically and as a result, the resolution has been coarsened from 1 km to 2 km to accommodate the larger domain. The expanded domain covers much of the northern hemisphere from eastern Asia to western Europe (0 N to 80 N latitude and 150 E to 10 E longitude). In addition, the NESDIS POES-GOES product was added to fill in gaps caused by the Moderate Resolution Imaging Spectroradiometer (MODIS) being unable to sense in cloudy regions, replacing the recently-lost Advanced Microwave Scanning Radiometer for EOS with negligible change to product fidelity. The SST product now runs twice per day for Terra and Aqua combined data collections from 0000 to 1200 UTC and from 1200 to 0000 UTC, with valid analysis times at 0600 and 1800 UTC. The twice-daily compositing technique reduces the overall latency of the previous version while still representing the diurnal cycle characteristics. The SST composites are available at approximately four hours after the end of each collection period (i.e. 1600 UTC for the nighttime analysis and 0400 UTC for the daytime analysis). The real-time MODIS GVF composite has only received minor updates in the past year. The domain was expanded slightly to extend further west, north, and east to improve coverage over parts of southern Canada. Minor adjustments were also made to the manner in which GVF is calculated from the distribution of maximum Normalized Difference Vegetation Index from MODIS. The presentation will highlight some examples of the substantial inter-annual change in GVF that occurred from 2010 to 2011 in the U.S. Southern Plains as a result of the summer 2011 drought, and the early vegetation green up across the eastern U.S. due to the very warm conditions in March 2012. Finally, the SPoRT LIS runs the operational Noah land surface model (LSM) in real time over much of the eastern half of the CONUS. The Noah LSM is continually cycled in real time, uncoupled to any model, and driven by operational atmospheric analyses over a long-term, multi-year integration. The LIS-Noah provides the STRC EMS with high-resolution (3 km) LSM initialization data that are in equilibrium with the operational analysis forcing. The Noah LSM within the SPoRT LIS has been upgraded from version 2.7.1 to version 3.2, which has improved look-up table attributes for several land surface quantities. The surface albedo field is now being adjusted based on the input real-time MODIS GVF, thereby improving the net radiation. Also, the LIS-Noah now uses the newer MODIS-based land use classification scheme (i.e. the International Biosphere-Geosphere Programme [IGBP]) that has a better depiction of urban corridors in areas where urban sprawl has occurred. STRC EMS users interested in initializing their LSM fields with high-resolution SPoRT LIS data should set up their model domain with the MODIS-IGBP 20-class land use database and select Noah as the LSM.

Case, Jonathan L.↗
NASA NTRS1990

Satellite measurements of large-scale air pollution - Measurements of forest fire smoke

The transport, optical properties, total mass, and removal of smoke produced by forest fires in western Canada during late July and early August 1982 are studied using NOAA 7 AVHRR data. Color composite imagery is produced to track the movement of the smoke over Canada and the U.S. as the smoke traveled thousands of km from the source region. Smoke optical thickness, particle size, and single scattering albedo are computed using radiances measured by AVHRR bands 1 and 2. Results show that smoke optical thickness ranged from less that 0.1 to greater than 3.7 and the geometric mean mass radii ranged from 300 to 900 nm. The smoke single scattering albedo ranged from 0.9 to nearly 1.0. The total smoke mass over the eastern U.S. ranged from 0.1 to 0.5 Tg, which is close to the 0.5 Tg estimated from the forest fuel content. The smoke lifetime is estimated to be between 15 and 20 days.

Ferrare, Richard A.↗
DOE OSTI2025

Microbial Ecology of Permafrost Soils: Populations, Processes, and Perspectives

Permafrost microbial research has flourished in the past decades, due in part to improvements in sampling and molecular techniques, but also the increased focus on the permafrost greenhouse gas feedback to climate change and other ecological processes in high latitude and alpine permafrost soils. Permafrost microorganisms are adapted to these extreme environments and remain active at low temperatures and when resources are limited. They are also an important component of global elemental cycles as they regulate organic matter turnover and greenhouse gas production, particularly as permafrost thaws. Here we review the permafrost microbiology literature coupled with an exploration of its historical aspects, with a particular focus on a new understanding advanced by molecular biology techniques. We further identify knowledge gaps and ways forward to improve our understanding of microbial contributions to ecosystem biogeochemistry of permafrost-affected systems.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Next generation Arctic vegetation maps: Aboveground plant biomass and woody dominance mapped at 30 m resolution across the tundra biome

The Arctic is warming faster than anywhere else on Earth, placing tundra ecosystems at the forefront of global climate change. Plant biomass is a fundamental ecosystem attribute that is sensitive to changes in climate, closely tied to ecological function, and crucial for constraining ecosystem carbon dynamics. However, the amount, functional composition, and distribution of plant biomass are only coarsely quantified across the Arctic. Therefore, we developed the first moderate resolution (30 m) maps of live aboveground plant biomass (g m −2 ) and woody plant dominance (%) for the Arctic tundra biome, including the mountainous Oro Arctic. We modeled biomass for the year 2020 using a new synthesis dataset of field biomass harvest measurements, Landsat satellite seasonal synthetic composites, ancillary geospatial data, and machine learning models. Additionally, we quantified pixel-wise uncertainty in biomass predictions using Monte Carlo simulations and validated the models using a robust, spatially blocked and nested cross-validation procedure. Observed plant and woody plant biomass values ranged from 0 to ∼6000 g m −2 (mean ≈ 350 g m −2 ), while predicted values ranged from 0 to ∼4000 g m −2 (mean ≈ 275 g m −2 ), resulting in model validation root-mean-squared-error (RMSE) ≈ 400 g m −2 and R 2 ≈ 0.6. Our maps not only capture large-scale patterns of plant biomass and woody plant dominance across the Arctic that are linked to climatic variation (e.g., thawing degree days), but also illustrate how fine-scale patterns are shaped by local surface hydrology, topography, and past disturbance. By providing data on plant biomass across Arctic tundra ecosystems at the highest resolution to date, our maps can significantly advance research and inform decision-making on topics ranging from Arctic vegetation monitoring and wildlife conservation to carbon accounting and land surface modeling.

Climate change↗
NASA NTRS1986

Basement-cover relations and internal structure of the Cape Smith klippe: A 1.9 Ga greenstone belt in northern Quebec, Canada

The Cape Smith Belt is a 380x60 km tectonic klippe composed of greenschistto amphibolite-grade mafic and komatiitic lava flows and fine-grained quartzose sediment, intruded by minor syn- to post-tectonic granitoids. Previously studied transects in areas of relatively high structural level show that the belt is constructed of seven or more north-dipping thrust sheets which verge toward the Superior Province (Archean) foreland in the south and away from an Archean basement massif (Kovik Antiform) external to the Trans-Hudson Orogen (Early Proterozoic) in the north. A field project (mapping and structural-stratigraphic-metamorphic studies) directed by MRS was begun in 1985 aimed at the structurally deeper levels of the belt and underlying basement, which are superby exposed in oblique cross-section (12 km minimum structural relief) at the west-plunging eastern end of the belt. Mapping now complete of the eastern end of the belt confirms that all of the metavolcanic and most of the metasedimentary rocks are allochthonous with respect to the Archean basement, and that the thrusts must have been rooted north of Kovik Antiform. The main findings follow.

St-Onge, M. R.↗
DOE OSTI2022

The collapse of the Cordilleran–Laurentide ice saddle and early opening of the Mackenzie Valley, Northwest Territories, Canada, constrained by 10 Be exposure dating

Deglaciation of the northwestern Laurentide Ice Sheet in the central Mackenzie Valley opened the northern portion of the deglacial Ice-Free Corridor between the Laurentide and Cordilleran ice sheets and a drainage route to the Arctic Ocean. In addition, ice sheet saddle collapse in this section of the Laurentide Ice Sheet has been implicated as a mechanism for delivering substantial freshwater influx into the Arctic Ocean on centennial timescales. However, there is little empirical data to constrain the deglaciation chronology in the central Mackenzie Valley where the northern slopes of the ice saddle were located. Here, we present 30 new 10Be cosmogenic nuclide exposure dates across six sites, including two elevation transects, which constrain the timing and rate of thinning and retreat of the Laurentide Ice Sheet in the area. Our new 10Be dates indicate that the initial deglaciation of the eastern summits of the central Mackenzie Mountains began at ~15.8 ka (17.1–14.6 ka), ~1000 years earlier than in previous reconstructions. The main phase of ice saddle collapse occurred between ~14.9 and 13.6 ka, consistent with numerical modelling simulations, placing this event within the Bølling–Allerød interval (14.6–12.9 ka). Our new dates require a revision of ice margin retreat dynamics, with ice retreating more easterly rather than southward along the Mackenzie Valley. In addition, we quantify a total sea level rise contribution from the Cordilleran–Laurentide ice saddle region of ~11.2 m between 16 and 13 ka.

58 GEOSCIENCES↗