251 research outputs found
Using Multiple Sources of Knowledge to Investigate Northern Environmental Change: Regional Ecological Impacts of a Storm Surge in the Outer Mackenzie Delta, N.W.T.
Field data, remote sensing, and Inuvialuit knowledge were synthesized to document regional ecological change in the outer Mackenzie Delta and to explore the timing, causes, and implications of this phenomenon. In September 1999, a large magnitude storm surge inundated low-lying areas of the outer Mackenzie Delta. The storm was among the most intense on record and resulted in the highest water levels ever measured at the delta front. Synthesis of scientific and Inuvialuit knowledge indicates that flooding during the 1999 storm surge increased soil salinity and caused widespread vegetation death. Vegetation cover was significantly reduced in areas affected by the surge and was inversely related to soil salinity. Change detection analysis, using remotely sensed imagery bracketing the 1999 storm event, indicates severe impacts on at least 13 200 ha of terrestrial vegetation in the outer delta. Inuvialuit knowledge identifying the 1999 surge as anomalous is corroborated by geochemical profiles of permafrost and by a recently published paleo-environmental study, which indicates that storm surge impacts of this magnitude have not previously occurred during the last millennium. Almost a decade after the 1999 storm surge event, ecological recovery has been minimal. This broad-scale vegetation change is likely to have significant implications for wildlife and must be considered in regional ecosystem planning and in the assessment and monitoring of the cumulative impacts of development. Our investigations show that Inuvialuit were aware of the 1999 storm surge and the environmental impacts several years before the scientific and regulatory communities recognized their significance. This study highlights the need for multidisciplinary and locally informed approaches to identifying and understanding Arctic environmental change.La synthĂšse des donnĂ©es dâexploitation et de tĂ©lĂ©dĂ©tection de mĂȘme que des connaissances des Inuvialuit a Ă©tĂ© effectuĂ©e afin de rĂ©pertorier les changements Ă©cologiques enregistrĂ©s dans la rĂ©gion extĂ©rieure du delta du Mackenzie et dâexplorer la temporisation, les causes et les incidences de ce phĂ©nomĂšne. En septembre 1999, une onde de tempĂȘte de grande magnitude a inondĂ© les zones de faible Ă©lĂ©vation de lâextĂ©rieur du delta du Mackenzie. Il sâagit de la tempĂȘte la plus intense Ă nâavoir jamais Ă©tĂ© enregistrĂ©e, ce qui sâest traduit par les niveaux dâeau les plus Ă©levĂ©s Ă nâavoir jamais Ă©tĂ© mesurĂ©s Ă la hauteur du delta. La synthĂšse des donnĂ©es scientifiques et des connaissances des Inuvialuit nous montre que lâinondation de 1999 a eu pour effet dâaugmenter la salinitĂ© du sol et a entraĂźnĂ© la mort de la vĂ©gĂ©tation Ă grande Ă©chelle. La couverture vĂ©gĂ©tale a Ă©tĂ© rĂ©duite considĂ©rablement dans les zones visĂ©es par lâonde et Ă©tait inversement reliĂ©e Ă la salinitĂ© du sol. Lâanalyse des dĂ©tections de changement effectuĂ©e au moyen de lâimagerie tĂ©lĂ©dĂ©tectĂ©e dans le cas de la tempĂȘte de 1999 laisse entrevoir de fortes incidences sur au moins 13 200 hectares de vĂ©gĂ©tation terrestre dans lâextĂ©rieur du delta. Les connaissances des Inuvialuit, qui affirment que lâonde de 1999 Ă©tait anormale, sont corroborĂ©es par les profils gĂ©ochimiques du pergĂ©lisol ainsi que par une Ă©tude palĂ©oenvironnementale qui indique que des incidences de cette ampleur dĂ©coulant dâune onde de tempĂȘte ne se sont pas produites Ă un autre moment donnĂ© du dernier millĂ©naire. PrĂšs dâune dĂ©cennie aprĂšs lâonde de tempĂȘte de 1999, le rĂ©tablissement Ă©cologique Ă©tait minime. Ce changement de vĂ©gĂ©tation Ă grande Ă©chelle aura vraisemblablement dâimportantes incidences sur la faune et doit entrer en considĂ©ration dans la planification de lâĂ©cosystĂšme rĂ©gional ainsi que dans lâĂ©valuation et la surveillance des incidences cumulatives des travaux dâamĂ©nagement et de mise en valeur. Nos enquĂȘtes nous ont permis de constater que les Inuvialuit Ă©taient conscients des incidences environnementales de lâonde de tempĂȘte de 1999 plusieurs annĂ©es avant que les scientifiques et le personnel sâoccupant de la rĂ©glementation ne reconnaissent leur importance. Cette Ă©tude fait ressortir la nĂ©cessitĂ© dâavoir des mĂ©thodes multidisciplinaires et de faire appel aux gens de la rĂ©gion pour dĂ©terminer et comprendre les changements environnementaux dans lâArctique
Climate sensitivity of shrub growth across the tundra biome
The tundra biome is experiencing rapid temperature increases that have been linked to a shift in tundra vegetation composition towards greater shrub dominance. Shrub expansion can amplify warming by altering the surface albedo, energy and water balance, and permafrost temperatures. To account for these feedbacks, global climate models must include realistic projections of vegetation dynamics, and in particular tundra shrub expansion, yet the mechanisms driving shrub expansion remain poorly understood. Dendroecological data consisting of multi-decadal time series of annual growth of shrub species provide a previously untapped resource to explore climate-growth relationships across the tundra biome. We analysed a dataset of approximately 42,000 annual growth records from 1821 individuals, comprising 25 species from eight genera, from 37 arctic and alpine sites. Our analyses demonstrate that the sensitivity of shrub growth to climate was (1) heterogeneous across the tundra biome, (2) greater at sites with higher soil moisture and (3) strongest for taller shrub species growing at the northern or upper elevational edge of their range. Across latitudinal gradients in the Arctic, climate sensitivity of growth was greatest at the boundary between low- and high-arctic vegetation zones, where permafrost conditions are changing and the majority of the global permafrost soil carbon pool is stored. Thus, in order to more accurately estimate feedbacks among shrub change, albedo, permafrost thaw, carbon storage and climate, the observed variation in climate-growth relationships of shrub species across the tundra biome will need to be incorporated into earth system models.JRC.H.3-Forest Resources and Climat
Connecting LandâAtmosphere Interactions to Surface Heterogeneity in CHEESEHEAD19
The Chequamegon Heterogeneous Ecosystem Energy-Balance Study Enabled by a High-Density Extensive Array of Detectors 2019 (CHEESEHEAD19) is an ongoing National Science Foundation project based on an intensive field campaign that occurred from June to October 2019. The purpose of the study is to examine how the atmospheric boundary layer (ABL) responds to spatial heterogeneity in surface energy fluxes. One of the main objectives is to test whether lack of energy balance closure measured by eddy covariance (EC) towers is related to mesoscale atmospheric processes. Finally, the project evaluates data-driven methods for scaling surface energy fluxes, with the aim to improve modelâdata comparison and integration. To address these questions, an extensive suite of ground, tower, profiling, and airborne instrumentation was deployed over a 10 km Ă 10 km domain of a heterogeneous forest ecosystem in the ChequamegonâNicolet National Forest in northern Wisconsin, United States, centered on an existing 447-m tower that anchors an AmeriFlux/NOAA supersite (US-PFa/WLEF). The project deployed one of the worldâs highest-density networks of above-canopy EC measurements of surface energy fluxes. This tower EC network was coupled with spatial measurements of EC fluxes from aircraft; maps of leaf and canopy properties derived from airborne spectroscopy, ground-based measurements of plant productivity, phenology, and physiology; and atmospheric profiles of wind, water vapor, and temperature using radar, sodar, lidar, microwave radiometers, infrared interferometers, and radiosondes. These observations are being used with large-eddy simulation and scaling experiments to better understand submesoscale processes and improve formulations of subgrid-scale processes in numerical weather and climate models
Recommended from our members
Managing the whole landscape: historical, hybrid, and novel ecosystems
The reality confronting ecosystem managers today is one of heterogeneous, rapidly transforming landscapes,
particularly in the areas more affected by urban and agricultural development. A landscape management
framework that incorporates all systems, across the spectrum of degrees of alteration, provides a fuller set of
options for how and when to intervene, uses limited resources more effectively, and increases the chances of
achieving management goals. That many ecosystems have departed so substantially from their historical trajectory
that they defy conventional restoration is not in dispute. Acknowledging novel ecosystems need not
constitute a threat to existing policy and management approaches. Rather, the development of an integrated
approach to management interventions can provide options that are in tune with the current reality of rapid
ecosystem change
Constraints on the cosmic expansion history from GWTC-3
We use 47 gravitational-wave sources from the Third LIGO-Virgo-KAGRA Gravitational-Wave Transient Catalog (GWTC-3) to estimate the Hubble parameter , including its current value, the Hubble constant . Each gravitational-wave (GW) signal provides the luminosity distance to the source and we estimate the corresponding redshift using two methods: the redshifted masses and a galaxy catalog. Using the binary black hole (BBH) redshifted masses, we simultaneously infer the source mass distribution and . The source mass distribution displays a peak around , followed by a drop-off. Assuming this mass scale does not evolve with redshift results in a measurement, yielding ( credible interval) when combined with the measurement from GW170817 and its electromagnetic counterpart. This represents an improvement of 17% with respect to the estimate from GWTC-1. The second method associates each GW event with its probable host galaxy in the catalog GLADE+, statistically marginalizing over the redshifts of each event's potential hosts. Assuming a fixed BBH population, we estimate a value of with the galaxy catalog method, an improvement of 42% with respect to our GWTC-1 result and 20% with respect to recent studies using GWTC-2 events. However, we show that this result is strongly impacted by assumptions about the BBH source mass distribution; the only event which is not strongly impacted by such assumptions (and is thus informative about ) is the well-localized event GW190814
- âŠ