北极地区热融湖塘甲烷排放特征及影响因素

Characteristics of methane emission of thermokarst lakes and ponds and its influencing factors in the Arctic region

北极地区显著升温导致多年冻土快速退化,进而发育形成大量热融湖塘,是温室气体排放热点。通过对1992—2023年2月北极热融湖塘甲烷(CH_(4))研究结果的整合梳理,本研究系统揭示了北极地区热融湖塘CH_(4)排放特征、热融湖塘的CH_(4)循环过程以及微生物机制。结果显示:北极地区CH_(4)年平均排放通量约为(7.78±19.60)g CH_(4)·m^(-2)·a^(-1),不同区域存在显著差异,高排放区出现在东西伯利亚和阿拉斯加地区[(23.40±26.50)g CH_(4)·m^(-2)·a^(-1);(11.00±26.40)g CH_(4)·m^(-2)·a^(-1)]。冒泡排放是北极热融湖塘CH_(4)排放的主导途径,年排放通量约为(13.80±28.60)g CH_(4)·m^(-2)·a^(-1),占比可达52.02%。湖塘沉积物类型对热融湖塘CH_(4)排放具有重要影响,叶叨码冻土区的排放为(17.90±32.90)g CH_(4)·m^(-2)·a^(-1),是非叶叨码冻土区的3.24倍。同时,泥炭地热融湖塘CH_(4)的主要排放途径及变化存在一定的不确定性,其对气温升高的响应可能略不同于其他湖泊,对气候变化具有高度敏感性。热融湖塘扩张与排水的变化趋势以及CH_(4)产生过程与氧化过程对热融湖塘的CH_(4)排放潜力同样具有重要影响。目前,北极地区热融湖塘CH_(4)排放的系观测仍然存在诸多空白,尤其缺乏多种排放途径的联合观测,对CH_(4)微生物过程认识不足。该研究能够进一步加深对北极地区热融湖塘排放特征及具体排放机制的认识,为评估该地区热融湖塘CH_(4)排放潜力及其对气候变化的影响提供科学参考。

Significant warming in the Arctic has led to the rapid degradation of permafrost,resulting in the development of a large number of thermokarst lakes and ponds,which are hotspots for greenhouse gas emissions.Based on the published results of methane(CH_(4))in Arctic thermokarst lakes and ponds from 1992 to March 2022,this paper systematically investigated the CH_(4) emission characteristics,carbon dynamics process,and the microbial mechanism of thermokarst lakes and ponds in the Arctic.The results showed that the annual CH_(4) emission flux in the Arctic was about(7.78±19.60)g CH_(4)·m^(-2)·a^(-1),with significant differences among sub-regions.High CH_(4) emission[(23.40±26.50)g CH_(4)·m^(-2)·a^(-1) to(11.00±26.40)g CH_(4)·m^(-2)·a^(-1)]were recorded in Eastern Siberia and Alaska.Bubble emission was the main pathway of CH_(4) emission from Arctic thermokarst lakes and ponds,with an annual emission flux of about(13.80±27.80)g CH_(4)·m^(-2)·a^(-1),accounting for 52.02% of the total CH_(4) emissions.The type of lake sediment significantly influences CH_(4) emissions from thermokarst lakes and ponds.Emissions from yedoma-type permafrost areas are(17.90±32.90)g CH_(4)·m^(-2)·a^(-1),which is 3.24 times that of non-yedoma permafrost areas.However,the main pathways and changes of CH_(4) emissions from peatland thermokarst lakes and ponds remain highly uncertain.The expansion and drainage trends of thermokarst lakes and ponds and the production and oxidation processes of CH_(4) also have important impacts on the potential CH_(4) emissions.There is still a lack of systematic observation for multiple CH_(4) emissions pathways from thermokarst lakes and ponds in the Arctic,especially in understanding the microbial process of CH_(4) production and oxidation.This study improved our understanding of the emission characteristics and mechanisms of CH_(4) from thermokarst lakes and ponds in the Arctic,providing valuable insights into the potential impact of CH_(4) emissions from this region and its impacts on climate change.