Yokohata Tokuta, Saito Kazuyuki, Ito Akihiko, Ohno Hiroshi, Tanaka Katsumasa, Hajima Tomohiro, Iwahana Go
Center for Global Environmental Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, 305-8506 Japan.
Research Center for Environmental Modeling and Application, Japan Agency for Marine-Earth Science and Technology, 3173-25 Showamachi, Kanazawaku, Yokohama, 236-0001 Japan.
Prog Earth Planet Sci. 2020;7(1):56. doi: 10.1186/s40645-020-00366-8. Epub 2020 Oct 2.
The Yedoma layer, a permafrost layer containing a massive amount of underground ice in the Arctic regions, is reported to be rapidly thawing. In this study, we develop the Permafrost Degradation and Greenhouse gasses Emission Model (PDGEM), which describes the thawing of the Arctic permafrost including the Yedoma layer due to climate change and the greenhouse gas (GHG) emissions. The PDGEM includes the processes by which high-concentration GHGs (CO and CH) contained in the pores of the Yedoma layer are released directly by dynamic degradation, as well as the processes by which GHGs are released by the decomposition of organic matter in the Yedoma layer and other permafrost. Our model simulations show that the total GHG emissions from permafrost degradation in the RCP8.5 scenario was estimated to be 31-63 PgC for CO and 1261-2821 TgCH for CH (68 percentile of the perturbed model simulations, corresponding to a global average surface air temperature change of 0.05-0.11 °C), and 14-28 PgC for CO and 618-1341 TgCH for CH (0.03-0.07 °C) in the RCP2.6 scenario. GHG emissions resulting from the dynamic degradation of the Yedoma layer were estimated to be less than 1% of the total emissions from the permafrost in both scenarios, possibly because of the small area ratio of the Yedoma layer. An advantage of PDGEM is that geographical distributions of GHG emissions can be estimated by combining a state-of-the-art land surface model featuring detailed physical processes with a GHG release model using a simple scheme, enabling us to consider a broad range of uncertainty regarding model parameters. In regions with large GHG emissions due to permafrost thawing, it may be possible to help reduce GHG emissions by taking measures such as restraining land development.
叶德马层是北极地区含有大量地下冰的永久冻土层，据报道正在迅速融化。在本研究中，我们开发了永久冻土退化与温室气体排放模型（PDGEM），该模型描述了由于气候变化导致的包括叶德马层在内的北极永久冻土解冻以及温室气体（GHG）排放情况。PDGEM包括叶德马层孔隙中所含高浓度温室气体（CO和CH）通过动态退化直接释放的过程，以及叶德马层和其他永久冻土中有机物分解释放温室气体的过程。我们的模型模拟表明，在RCP8.5情景下，永久冻土退化产生的温室气体总排放量估计为CO 31 - 63PgC，CH 1261 - 2821TgCH（扰动模型模拟的第68百分位数，对应全球平均地表气温变化0.05 - 0.11°C）；在RCP2.6情景下，CO为14 - 28PgC，CH为618 - 1341TgCH（0.03 - 0.07°C）。在两种情景下，叶德马层动态退化产生的温室气体排放量估计均不到永久冻土总排放量的1%，这可能是因为叶德马层的面积占比小。PDGEM的一个优点是，通过将具有详细物理过程的先进陆面模型与使用简单方案的温室气体释放模型相结合，可以估计温室气体排放的地理分布，使我们能够考虑模型参数方面的广泛不确定性。在因永久冻土融化导致温室气体排放量大的地区，采取限制土地开发等措施可能有助于减少温室气体排放。
