Vertical Profiles of Trapped Greenhouse Gases in Alaskan Permafrost Active Layers Before the Spring Thaw Eunji Byun 1, Ji-woong Yang 1, Yongwon Kim 2 and Jinho Ahn 1 1 School of Earth and Environmental Science, Seoul National University (SNU), Seoul, Korea 2 International Arctic Research Center (IARC), University of Alaska Fairbanks, Alaska, U.S.A.

CO 2 CH 4 Modified from French (2007) Increase of active part and decomposable carbons Amount and timing? Atmospheric GHGs

Soil GHGs can be transported by diffusion, ebullition and plant-mediated ways. Can these processes always push GHGs out from subsurface to the atmosphere? Active layer freezes and thaws repetitively. What if the active layer forms temporal barriers to escape of GHGs?

The fate of GHGs under the active layer? Trapped or Released Depending on the permeability of surrounding soils Instantly or More longer Trapped  Released Accumulated  Emitted at once e.g. CH 4 burst during transitional seasons Mastepanov et al. (2008); Song et al. (2012); Chang et al. (2014)

TS: tundra vegetation NY, SY and CR*: black spruce forests *fire burned in 2010 PF: peat mosses Temperature logger Drilling a frozen soil core 29 April 2013 – 10 May 2013 by Ji-woong Yang, Jinho Ahn and Yongwon Kim Latitudinal variation along Alaskan highway

Visual description on samples

Cut! Drilling soil cores before spring thaw Trapped gas extraction from frozen soil samples (Headspace method) NaCl saturated 10 mL Left at 65 ℃ for 30 min Shaken over 2 min (Kim et al., 2012; RESTEK, 2000) Frozen Thawed

CH 4 CO 2 CO 2 and CH 4 concentration measurements 7890A GC system with FID and TCD Agilent Technologies

Vertical profiles of measured values: (1) two peak CH 4 results (PF and TS) (Byun et al. in preparation)

Vertical profiles of measured values: (2) results of three non-peak CH 4 cases (NY, SY and CR) (Byun et al. in preparation)

δ 13 C CH 4 δ D CH 4

SiteDepth (cm)C 1 /C 2 CH 4 (ppmv*) PF n.a. TS n.a. TS *methane parts per million by volume (ppmv) of headspace (HS) gas n.a.: not available due to low concentration and/or limited sample volume “CD-diagram for classification of bacterial and thermogenic natural gas by the combination of δ 13 C CH4 and δ D CH4 information.” (Figure 4: Whiticar, 1999) “Natural gas interpretative (“Bernard”) diagram combining the molecular and isotope compositional information.” (Figure 12: Whiticar, 1999) Bacterial Carbonate Reduction Microbial oxidation

The trapped CH 4 ? All those three peak CH 4 can be told to be generated microbially in soils by its isotopic information. The measured amounts are not likely from instant production for just a few days. (  winter production or residuals from last summer) (Elberling et al., 2011; Lee et al., 2012) Those were only extracted when the surrounding soils physically collapsed.

Temperature logger installed Permafrost (perennially cryotic) Active layer (seasonally frozen) The fate of trapped CH 4 ? Downward thawing Downward freezing

* * * * * * * * * * * * * * * * * * * * * CH 4 CO 2

* * * * * * * * * * * * * * * * * * * * * CH 4

CO 2 CH 4 * * * * * * * * * The fate of trapped CH 4 under frozen active layer? Inter-annually varied active layer thicknesses! Shallower A.L. Deeper A.L. A.L. this year

Physical, chemical and biological factors of active layer soils can affect its formation and transportation. Production can be influenced by nutritional levels, microbial communities and temperatures. Transportation can be inhibited by physical barriers seasonally or even permanently depending on thaw range. Whether this phenomenon can be broad to some other permafrost soils needs to be more investigated. High levels of trapped CH4 were found from only 2 out of 5 soil cores in this study. It can be improved by such a detailed subsurface profiles accompanied by relevant efflux measurements at surface. (Summary) Trapped CH 4 under frozen active layer?

Any Questions and Comments: Thank you all for being here and especially Dona to bring me here 2015 EGU BG2.3 “Vertical profiles of trapped greenhouse gases in Alaskan permafrost active layers before the spring thaw”