Our goal is to support the DOE’s Biological and Environmental Research (BER) mission to advance a robust predictive understanding of Earth’s climate and environmental systems by delivering a process-rich ecosystem model, extending from bedrock to the top of the vegetative canopy and atmospheric interface, in which the evolution of Arctic ecosystems in a changing climate can be modeled at the scale of a high-resolution ESM grid cell.
The Next-Generation Ecosystem Experiments (NGEE Arctic) is a 10-year project (2012 to 2022) to improve our predictive understanding of carbon (C)-rich Arctic system processes and feedbacks to climate. This is achieved through experiments, observations, and synthesis of existing datasets that strategically inform model process representation and parameterization, and that enhance the knowledge base required for model initialization, calibration, and evaluation. In Phase 1 (2012 to 2014), NGEE Arctic tested and applied a multiscale measurement and modeling framework in coastal tundra on the North Slope of Alaska. Field plots, transects, and synoptic surveys near Utqiaġvik (formerly Barrow) were chosen to represent a cold, continuous permafrost region at the northern extent of an ecological and climatic gradient. Much of our research focused on subgrid heterogeneity in thermal-hydrology, biogeochemistry, and vegetation as influenced by topography, landscape position, and drainage networks. These efforts provided datasets, derived products, and knowledge designed to meet project requirements for model initialization, parameterization, process representation, and evaluation.
Building upon research conducted in the first 3 years of the project, in Phase 2 (2015 to 2019) we maintained research at Utqiaġvik and established a set of research sites near Nome in western Alaska (i.e., Seward Peninsula). These field sites are characterized by their proximity to the transition from boreal forest to tundra, as well as by warm, discontinuous permafrost, higher annual precipitation, and well-defined watersheds with strong topographic gradients. We used variation in the structure and organization of the Seward Peninsula landscape to guide a series of process-level investigations (Questions 1 through 3) that were nested at scales ranging from soil core to plot, landscape, and watershed levels. Knowledge from those studies identified mechanisms controlling C, water, nutrient, and energy fluxes, which was used to address two integrated questions regarding the future of the Arctic in a changing climate (Questions 4 and 5). Question 6 is added in Phase 3 (2019-2022) given the strong need to understand how shrub distribution and disturbance processes in tundra ecosystems may drive future biophysical feedbacks to climate.
Q1. How does the structure and organization of the landscape control permafrost evolution and associated C and nutrient fluxes in a changing climate?
Q2. What will control rates of CO2 and CH4 fluxes across a range of permafrost conditions?
Q3. How do above- and belowground plant functional traits change across environmental gradients, and what are the consequences for Arctic ecosystem C, water, and nutrient fluxes?
Q4. What controls the current distribution of Arctic shrubs, and how will shrub distributions and associated climate feedbacks shift with warming in the 21st century?
Q5. Where, when, and why will the Arctic become wetter or drier, and what are the implications for climate forcing?
Q6. What controls the vulnerability and resilience of Arctic ecosystems to disturbance, and how do disturbances alter the physical and ecological structure and function of these ecosystems?
We focus our modeling efforts in Phase 3 on a series of process-based improvements within the E3SM Land Model (ELM, including its dynamic biogeography component ELM-FATES). These improvements to ELM use NGEE Arctic findings and syntheses from the broader Arctic science community to anchor new model development in current system understanding, and to evaluate new ELM processes and parameterizations against independent observations at spatial and temporal scales appropriate to the use of ELM and E3SM for future climate prediction.
An important challenge for Earth System Models (ESMs) is to represent land surface and subsurface processes and their complex interactions in a changing climate. This is true for all regions of the world, but it is especially important for Arctic ecosystems which are projected to warm at a rate twice that of the global average by the end of the 21st century. The Next-Generation Ecosystem Experiments (NGEE Arctic) project seeks to improve the representation of tundra ecosystems in ESMs through a coordinated series of model-inspired investigations conducted in landscapes near Utqiaġvik (formerly Barrow) and Nome, Alaska. Our goal is to support the DOE’s Biological and Environmental Research (BER) mission to advance a robust predictive understanding of Earth’s climate and environmental systems by delivering a process-rich ecosystem model, extending from bedrock to the top of the vegetative canopy and atmospheric interface, in which the evolution of Arctic ecosystems in a changing climate can be modeled at the scale of a high-resolution ESM grid cell. This goal is aligned with the High-Latitude Scientific Grand Challenge in the Climate and Environmental Sciences Division (CESD) Strategic Plan. In Phase 1 (2012 to 2014), we tested and applied a multiscale measurement and modeling framework in a coastal tundra ecosystem on the North Slope of Alaska. This region was chosen to represent a site underlain by cold, continuous permafrost at the northern extent of an ecological and climatic gradient in Alaska. In Phase 2 (2015 to 2019), three additional field sites were established on the Seward Peninsula in western Alaska, which, compared to our research site on the North Slope, are characterized by their proximity to the boreal-tundra transition zone; warmer, discontinuous permafrost; and well-defined watersheds. Integrated field, laboratory, and modeling tasks allowed our team to focus on understanding (1) the effect of landscape structure and organization on the storage and flux of C, water, and nutrients, (2) edaphic and geochemical mechanisms responsible for variable CO2 and CH4 fluxes across a range of permafrost conditions, (3) variation in plant functional traits across space and time, and in response to changing environmental conditions and resulting consequences for ecosystem processes, (4) controls on shrub distribution and associated biogeochemical and biophysical climate feedbacks, and (5) changes in snow processes and surface and groundwater hydrology expected with warming in the 21st century. A major outcome of our Phase 1 and 2 research was an integrated set of in situ and remotely sensed observations that quantify the covariation of hydro-thermal, ecosystem, vegetation dynamics, and biogeochemical function. These efforts provided unique datasets for model parameterization and benchmarking. Knowledge on topics ranging from watershed hydrology to plant physiology is now being incorporated into DOE’s Energy Exascale Earth System Model (E3SM). In Phase 3 (2020 to 2022), we propose to continue our research at sites on the North Slope and in western Alaska, while also adding a cross-cutting component on disturbance. We will use field campaigns, modeling, and data synthesis to target improvements in simulating disturbance-related processes (e.g., wildfire and abrupt permafrost thaw) and connections to dynamic vegetation (e.g., shrubs) that are missing from or poorly represented in ESMs. Our vision in Phase 3 strengthens the connection between process studies in Arctic ecosystems and high-resolution landscape modeling and scaling strategies developed in Phases 1 and 2. Safety, national and international collaboration, and a commitment to project management continue to be key underpinnings of our model-inspired research in the Arctic.