Search for: All records

Abstract Arctic permafrost soils store vast amounts of carbon (C)‐rich organic matter that has accumulated due to low temperatures that suppress microbial decomposition. As Arctic warming intensifies, soil microbes become increasingly active, even while plant growth remains dormant. Seasonal decoupling between plant and microbial decomposer growth can accelerate carbon dioxide (CO₂) release from soils, however, most Earth system models underestimate cold‐season C emissions and do not accurately represent the freeze–thaw transitions that govern microbial access to substrates during these critical periods. These model–data mismatches often stem from empirical formulations, such as using a fixed Q₁₀functions to represent microbial respiration, an oversimplification of a complex interplay of temperature, moisture, and substrate diffusion. To address this, we incorporated explicit, temperature‐dependent diffusional constraints on microbial activity, (the Dual Arrhenius Michaelis–Menten (DAMM) model), into the Stoichiometrically Coupled Acclimating Microbe–Plant–Soil (SCAMPS) model which uses the Q₁₀function to represent microbial respiration. We used this enhanced model (SCAMPS_DAMM) to simulate Arctic ecosystem responses to a 50‐year winter warming scenario and compared outcomes to the original SCAMPS framework. While both models predicted overall soil C losses under warming, SCAMPS_DAMM produced more constrained increases in microbial respiration and plant productivity. These differences led to similar total ecosystem C declines but divergent patterns of C and N allocation between plant and soil pools. Thus, incorporating mechanistic constraints on microbial access to substrates through explicit representation of temperature and moisture controls altered model projections of Arctic biogeochemical responses to climate change. 

Abstract. Tundra environments are experiencing elevated levels of wildfire, and thefrequency is expected to keep increasing due to rapid climate change in theArctic. Tundra wildfires can release globally significant amounts ofgreenhouse gasses that influence the Earth's radiative balance. Here wedevelop a novel method for estimating carbon loss and the resultingradiative forcings of gaseous and aerosol emissions from the 2015 tundrawildfires in the Yukon–Kuskokwim Delta (YKD), Alaska. We paired burn depthmeasurements using two vegetative reference points that survived the fireevent – Sphagnum fuscum and Dicranum spp. – with measurements of local organic matter and soil carbonproperties to estimate total ecosystem organic matter and carbon loss. Weused remotely sensed data on fire severity from Landsat 8 to scale ourmeasured losses to the entire fire-affected area, with an estimated totalloss of 2.04 Tg of organic matter and 0.91 Tg of carbon and an average lossof 3.76 kg m−2 of organic matter and 1.68 kg m−2 of carbon in the2015 YKD wildfires. To demonstrate the impact of these fires on the Earth'sradiation budget, we developed a simple but comprehensive framework toestimate the radiative forcing from Arctic wildfires. We synthesizedexisting research on the lifetime and radiative forcings of gaseous andaerosol emissions of CO2, N2O, CH4, O3 and itsprecursors, and fire aerosols. The model shows a net positive cumulativemean radiative forcing of 3.67 W m−2 using representative concentration pathway (RCP) 4.5 and 3.37 W m−2using RCP 8.5 at 80 years post-fire, which was dominated by CO2emissions. Our results highlight the climate impact of tundra wildfires,which positively reinforce climate warming and increased fire frequencythrough the radiative forcings of their gaseous emissions. 

{"Abstract":["This project is integrating scientific research in the Arctic with education and outreach, with a strong central focus on engaging undergraduate students and visiting faculty from groups that have had little involvement in Arctic science to date. The central element of the project is a month-long research expedition to the Yukon River Delta in Alaska. The expedition provides a deep intellectual and cultural immersion in the context of an authentic research experience that is paramount for "hooking" students and keeping them moving along the pipeline to careers as Arctic scientists. The overarching scientific issue that drives the research is the vulnerability and fate of ancient carbon stored in Arctic permafrost (permanently frozen ground). Widespread permafrost thaw is expected to occur this century, but large uncertainties remain in estimating the timing, magnitude, and form of carbon that will be released when thawed. Project participants are working in collaborative research groups to make fundamental scientific discoveries related to the vulnerability of permafrost carbon in the Yukon River Delta and the potential implications of permafrost thaw in this region for the global climate system.\n This data set includes vegetation biomass and elemental analysis, thaw depth, and point intercept results from the 2018 expedition."]} 

{"Abstract":["This project is integrating scientific research in the Arctic with education and outreach, with a strong central focus on engaging undergraduate students and visiting faculty from groups that have had little involvement in Arctic science to date. The central element of the project is a month-long research expedition to the Yukon River Delta in Alaska. The expedition provides a deep intellectual and cultural immersion in the context of an authentic research experience that is paramount for "hooking" students and keeping them moving along the pipeline to careers as Arctic scientists. The overarching scientific issue that drives the research is the vulnerability and fate of ancient carbon stored in Arctic permafrost (permanently frozen ground). Widespread permafrost thaw is expected to occur this century, but large uncertainties remain in estimating the timing, magnitude, and form of carbon that will be released when thawed. Project participants are working in collaborative research groups to make fundamental scientific discoveries related to the vulnerability of permafrost carbon in the Yukon River Delta and the potential implications of permafrost thaw in this region for the global climate system.\n This data set includes vegetation biomass and elemental analysis, thaw depth, and point intercept results from the 2019 expedition."]}