DSpace Collection:

Responses of surface SOC to longterm experimental warming vary between different heath types in the high Arctic tundra

2022-03-24T07:15:14Z

Title: Responses of surface SOC to longterm experimental warming vary between different heath types in the high Arctic tundra Authors: Jung, Ji Young; Michelsen, Anders; Kim, Mincheol; Nam, Sungjin; Schmidt, Niels M.; Jeong, Sujeong; Choe, Yong-Hoe; Lee, Bang Yong; Yoon, Ho Il; Lee, Yoo Kyung Abstract: Over the past few decades the Arctic has warmed up more than the lower latitudes. Soil organic carbon (SOC) in the Arctic is vulnerable to climate change, and carbon dioxide (CO2) produced via SOC decomposition can amplify atmospheric temperature increase. Although SOC composition is relevant to decomposability, studies on its compositional changes with warming are scarce, particularly in the Arctic. Therefore, we investigated the responses of SOC and the bacterial community to climate manipulation under Cassiope and Salix heath vegetation communities in permafrost-affected soil in Zackenberg, Greenland. After 8-9 years of experimental warming, we evaluated changes in SOC quantity and quality of three density fractions of soil: free light fraction (FLF), occluded light fraction (OLF) and heavy fraction (HF). The SOC content at 0-5-cm depth was significantly reduced with warming under Cassiope, and it was accompanied by decreased FLF content, attributed to accelerated decomposition of the FLF by warming. However, SOC molecular composition and bacterial community composition were not affected by warming. By contrast, there was no warming effect on SOC under Salix, which could be partially due to smaller temperature increases caused by higher moisture levels associated with larger silt and clay contents, or to different responses of the dominant plant species to temperature. In both soils, more than 55% of SOC was associated with minerals, and its molecular composition indicated microbial decomposition. Our results suggested that long-term warming in the high Arctic could induce the loss of SOC, particularly in the FLF; however, the response could vary with vegetation type and/or soil properties, that is, soil texture.

Approximation of most penetrating particle size for fibrous filters considering Cunningham slip correction factor

2022-03-24T07:15:03Z

Title: Approximation of most penetrating particle size for fibrous filters considering Cunningham slip correction factor Authors: Jung, Chang Hoon; Yoon, Young Jun; Um, Junshik; Lee, Seoung Soo; Lee, Ji Yi; Chiao, Sen; Kim, Yong Pyo Abstract: In the estimation of the aerosol collection efficiency using fibrous filters, there exist a size range where particles in fibrous collectors penetrate most effectively, and a corresponding minimum collection efficiency. For small particles, for which the diffusion mechanism is dominant, the Cunningham slip correction factor affects the collection efficiency and the most penetrating particle size. Therefore, for the accurate estimation, the Cunningham slip correction factor should be considered. However, many previous studies have ignored the Cunningham slip correction factor because of its complexity and the associated difficulty in deriving appropriate parameterization, especially for the most penetrating particle size. In this study, the analytic expression for the most penetrating particle size and the corresponding expression for the minimum collection efficiency were analytically derived; furthermore, the effects of the Cunningham slip correction factor were determined. To accommodate the slip factor for all particle size ranges, the Cunningham slip correction factor was simplified and modified. The obtained analytic expression for the most penetrating particle size showed a good agreement with the exact solution.

Arctic ship-based evidence of new particle formation events in the Chukchi and East Siberian Seas

2022-03-24T07:14:48Z

Title: Arctic ship-based evidence of new particle formation events in the Chukchi and East Siberian Seas Authors: Dall'Osto, M.; Park, J.; Kim, Joo-Hong; Kang, Sung-Ho; Park, Kihong; Beddows, D.C.S.; Harrison, Roy M.; Yoon, Young Jun Abstract: Arctic aerosol-climate interactions are controlled by multiple factors including sources, processes and removal mechanisms of particles. The Arctic is mostly ocean, surrounded by mostly land, and our understanding of Arctic aerosol processes is incomplete due to scarce measurements carried out in sea ice regions. In particular, it is currently not known if these particular regions are sources of aerosols of primary or secondary origin. We present new results from ship-based measurements illustrating that marine new particle production and growth events occur in open ocean and melting sea ice regions in the Chukchi and East Siberian Seas. We report two new particle formation events during which a recently formed nucleation mode (<15 nm diameter) is detected and is observed to slowly grow into an Aitken mode (0.1-3.8 nm/h). Our results suggest that new particle formation occurs in the marine boundary layer contributing to the Arctic aerosol population in the study region for the first time studied and herein reported.

Large loss of CO2 in winter observed across the northern permafrost region (vol 9, pg 852, 2019)

2022-03-24T07:14:12Z

Title: Large loss of CO2 in winter observed across the northern permafrost region (vol 9, pg 852, 2019) Authors: Natali, Susan M.; Watts, Jennifer D.; Rogers, Brendan M.; Potter, Stefano; Ludwig, Sarah M.; Selbmann, Anne-Katrin; Sullivan, Patrick F.; Abbott, Benjamin W.; Arndt, Kyle A.; Birch, Leah; Bjorkman, Mats P.; Bloom, A. Anthony; Celis, Gerardo; Christensen, Torben R.; Christiansen, Casper T.; Commane, Roisin; Cooper, Elisabeth J.; Crill, Patrick; Czimczik, Claudia; Davydov, Sergey; Du, Jinyang; Egan, Jocelyn E.; Elberling, Bo; Euskirchen, Eugenie S.; Friborg, Thomas; Genet, Helene; Gockede, Mathias; Goodrich, Jordan P.; Grogan, Paul; Helbig, Manuel; Jafarov, Elchin E.; Jastrow, Julie D.; Kalhori, Aram A. M.; Kim, Yongwon; Kimball, John S.; Kutzbach, Lars; Lara, Mark J.; Larsen, Klaus S.; Lee, Bang-Yong; Liu, Zhihua; Loranty, Michael M.; Lund, Magnus; Lupascu, Massimo; Madani, Nima; Malhotra, Avni; Matamala, Roser; McFarland, Jack; McGuire, A. David; Michelsen, Anders; Minions, Christina; Oechel, Walter C.; Olefeldt, David; Parmentier, Frans-Jan W.; Pirk, Norbert; Poulter, Ben; Quinton, William; Rezanezhad, Fereidoun; Risk, David; Sachs, Torsten; Schaefer, Kevin; Schmidt, Niels M.; Schuur, Edward A. G.; Semenchuk, Philipp R.; Shaver, Gaius; Sonnentag, Oliver; Starr, Gregory; Treat, Claire C.; Waldrop, Mark P.; Wang, Yihui; Welker, Jeffrey; Wille, Christian; Xu, Xiaofeng; Zhang, Zhen; Zhuang, Qianlai; Zona, Donatella Abstract: Recent warming in the Arctic, which has been amplified during the winter1,2,3, greatly enhances microbial decomposition of soil organic matter and subsequent release of carbon dioxide (CO2)4. However, the amount of CO2 released in winter is not known and has not been well represented by ecosystem models or empirically based estimates5,6. Here we synthesize regional in situ observations of CO2 flux from Arctic and boreal soils to assess current and future winter carbon losses from the northern permafrost domain. We estimate a contemporary loss of 1,662？TgC per year from the permafrost region during the winter season (October？April). This loss is greater than the average growing season carbon uptake for this region estimated from process models (？1,032？TgC per year). Extending model predictions to warmer conditions up to 2100 indicates that winter CO2 emissions will increase 17% under a moderate mitigation scenario―Representative Concentration Pathway 4.5―and 41% under business-as-usual emissions scenario―Representative Concentration Pathway 8.5. Our results provide a baseline for winter CO2 emissions from northern terrestrial regions and indicate that enhanced soil CO2 loss due to winter warming may offset growing season carbon uptake under future climatic conditions.

DSpace Collection:

Responses of surface SOC to long­term experimental warming vary between different heath types in the high Arctic tundra

Approximation of most penetrating particle size for fibrous filters considering Cunningham slip correction factor

Arctic ship-based evidence of new particle formation events in the Chukchi and East Siberian Seas

Large loss of CO2 in winter observed across the northern permafrost region (vol 9, pg 852, 2019)

Responses of surface SOC to longterm experimental warming vary between different heath types in the high Arctic tundra