David Olefeldt
A5002062365- Climate change and permafrost
- Peatlands and Wetlands Ecology
- Cryospheric studies and observations
- Atmospheric and Environmental Gas Dynamics
- Methane Hydrates and Related Phenomena
- Geology and Paleoclimatology Research
- Fire effects on ecosystems
- Geological Studies and Exploration
- Mercury impact and mitigation studies
- Coastal wetland ecosystem dynamics
- Arctic and Antarctic ice dynamics
- Marine and coastal ecosystems
- Hydrocarbon exploration and reservoir analysis
- Botany and Plant Ecology Studies
- Hydrology and Watershed Management Studies
- Soil and Water Nutrient Dynamics
- Landslides and related hazards
- Climate variability and models
- Marine animal studies overview
- Flood Risk Assessment and Management
- Indigenous Studies and Ecology
- Plant Water Relations and Carbon Dynamics
- Smart Materials for Construction
- Coal Properties and Utilization
- Soil Moisture and Remote Sensing
University of Alberta
2015-2024
University of Guelph
2011-2023
University of British Columbia
2020
McGill University
2011-2014
Lund University
2012
Significance Over many millennia, northern peatlands have accumulated large amounts of carbon and nitrogen, thus cooling the global climate. shorter timescales, peatland disturbances can trigger losses peat release greenhouses gases. Despite their importance to climate, remain poorly mapped, vulnerability permafrost warming is uncertain. This study compiles over 7,000 field observations present a data-driven map nitrogen stocks. We use these maps model impact thaw on find that will likely...
Abstract Wetlands are the largest natural source of atmospheric methane. Here, we assess controls on methane flux using a database approximately 19 000 instantaneous measurements from 71 wetland sites located across subtropical, temperate, and northern high latitude regions. Our analyses confirm general emissions soil temperature, water table, vegetation, but also show that these relationships modified depending type (bog, fen, or swamp), region (subarctic to temperate), disturbance. Fen was...
Abstract Thermokarst is the process whereby thawing of ice-rich permafrost ground causes land subsidence, resulting in development distinctive landforms. Accelerated thermokarst due to climate change will damage infrastructure, but also impact hydrology, ecology and biogeochemistry. Here, we present a circumpolar assessment distribution landscapes, defined as landscapes comprised current landforms areas susceptible future development. At 3.6 × 10 6 km 2 , are estimated cover ∼20% northern...
Methane (CH4 ) emissions from the northern high-latitude region represent potentially significant biogeochemical feedbacks to climate system. We compiled a database of growing-season CH4 terrestrial ecosystems located across permafrost zones, including 303 sites described in 65 studies. Data on environmental and physical variables, conditions, were used assess controls emissions. Water table position, soil temperature, vegetation composition strongly influenced had interacting effects. Sites...
Permafrost vulnerability to climate change may be underestimated unless effects of wildfire are considered. Here we assess impacts on soil thermal regime and rate thermokarst bog expansion resulting from complete permafrost thaw in western Canadian peatlands. Effects peatlands last for 30 years include a warmer deeper active layer, spatial continuously thawed layers (taliks). These the associated with tripled along edges. Our results suggest that is directly responsible 2200 ± 1500 km
As the permafrost region warms, its large organic carbon pool will be increasingly vulnerable to decomposition, combustion, and hydrologic export. Models predict that some portion of this release offset by increased production Arctic boreal biomass; however, lack robust estimates net balance increases risk further overshooting international emissions targets. Precise empirical or model-based assessments critical factors driving are unlikely in near future, so address gap, we present from 98...
Rapid Arctic environmental change affects the entire Earth system as thawing permafrost ecosystems release greenhouse gases to atmosphere. Understanding how much carbon will be released, over what time frame, and relative emissions of dioxide methane is key for understanding impact on global climate. In addition, response vegetation in a warming climate has potential offset at least some accelerating feedback from carbon. Temperature, organic carbon, ground ice are regulators determining...
We present an approach to estimate the feedback from large-scale thawing of permafrost soils using a simplified, data-constrained model that combines three elements: soil carbon (C) maps and profiles identify distribution type C in soils; incubation experiments quantify rates lost after thaw; models thermal dynamics response climate warming. call Permafrost Carbon Network Incubation-Panarctic Thermal scaling (PInc-PanTher). The assumes stocks do not decompose at all when frozen, but once...
Abstract The northern permafrost region has been projected to shift from a net sink source of carbon under global warming. However, estimates the contemporary greenhouse gas (GHG) balance and budgets remain highly uncertain. Here, we construct first comprehensive bottom‐up CO 2 , CH 4 N O across terrestrial using databases more than 1000 in situ flux measurements land cover‐based ecosystem upscaling approach for period 2000–2020. Estimates indicate that emitted mean annual 12 (−606, 661) Tg...
Abstract Tundra and boreal ecosystems encompass the northern circumpolar permafrost region are experiencing rapid environmental change with important implications for global carbon (C) budget. We analysed multi-decadal time series containing 302 annual estimates of dioxide (CO 2 ) flux across 70 non-permafrost ecosystems, 672 summer CO 181 ecosystems. find an increase in sink but not despite similar increases uptake. Thus, recent non-growing-season losses have substantially impacted balance...
Loss of permafrost can modify the export and composition dissolved organic carbon (DOC) from subarctic peatlands by changing hydrological regime altering ecosystem structure function. In Stordalen peatland complex (68.20°N, 19.03°E) recent thaw has caused a conversion palsa parts (an ombrotrophic, affected type) into both bog flow‐through fen types. Within we estimated DOC mass balance assessed for one catchment, catchment two fens in order to assess possible impacts on export. The were...
Palsa mires, nutrient poor permafrost peatlands common in subarctic regions, store a significant amount of carbon (C) and it has been hypothesized their net ecosystem C balance (NECB) is sensitive to climate change. Over two years we measured the NECB for Stordalen palsa mire found accumulate 46 g m −2 yr −1 . While comparable without permafrost, component fluxes differ considerably magnitude. Specifically, had both lower growing season CO 2 uptake wintertime losses, but importantly also low...
Rich fens are common boreal ecosystems with distinct hydrology, biogeochemistry and ecology that influence their carbon (C) balance. We present growing season soil chamber methane emission (FCH4 ), ecosystem respiration (ER), net exchange (NEE) gross primary production (GPP) fluxes from a 9-years water table manipulation experiment in an Alaskan rich fen. The study included major flood drought years, where wetting drying treatments further modified the severity of droughts. Results support...
Abstract. Methane emissions from boreal and arctic wetlands, lakes, rivers are expected to increase in response warming associated permafrost thaw. However, the lack of appropriate land cover datasets for scaling field-measured methane circumpolar scales has contributed a large uncertainty our understanding present-day future emissions. Here we present Boreal–Arctic Wetland Lake Dataset (BAWLD), dataset based on an expert assessment, extrapolated using random forest modelling available...
Abstract. Methane (CH4) emissions from the boreal and arctic region are globally significant highly sensitive to climate change. There is currently a wide range in estimates of high-latitude annual CH4 fluxes, where based on land cover inventories empirical flux data or process models (bottom-up approaches) generally greater than atmospheric inversions (top-down approaches). A limitation bottom-up approaches has been lack harmonization between site-level classes present spatial datasets....
Abstract The magnitude of future emissions greenhouse gases from the northern permafrost region depends crucially on mineralization soil organic carbon (SOC) that has accumulated over millennia in these perennially frozen soils. Many recent studies have used radiocarbon ( 14 C) to quantify release this “old” SOC as CO 2 or CH 4 atmosphere dissolved and particulate (DOC POC) surface waters. We compiled ~1,900 C measurements 51 sites assess vulnerability thawing tundra, forest, peatland, lake,...
Abstract Soils are warming as air temperatures rise across the Arctic and Boreal region concurrent with expansion of tall-statured shrubs trees in tundra. Changes vegetation structure function expected to alter soil thermal regimes, thereby modifying climate feedbacks related permafrost thaw carbon cycling. However, current understanding impacts on temperature is limited local or regional scales lacks generality necessary predict stability a pan-Arctic scale. Here we synthesize shallow...
Understanding methane (CH4) emission from thermokarst lakes is crucial for predicting the impacts of abrupt thaw on permafrost carbon-climate feedback. However, observational evidence, especially high-altitude regions, still scarce. Here, by combining field surveys, radio- and stable-carbon isotopic analyses, metagenomic sequencing, we present multiple characteristics CH4 emissions 120 in 30 clusters along a 1100 km transect Tibetan Plateau. We find that have high during ice-free period...