The Arctic is undergoing a shift toward a warmer and wetter climate. Recent experiments indicate that the carbon balance of subarctic wet tundra is sensitive to both summer warming and deeper snow. However, few studies have combined experimental data with process-oriented models to predict how the terrestrial carbon cycle will respond to future climate change. Here, we use CoupModel, a process-oriented model, to investigate CO₂ and CH₄ dynamics in a subarctic wet tundra ecosystem under two contrasting climate change scenarios over the 21^st century. Our findings show that the model successfully reproduced the treatment effects of warming on CO₂ and CH₄ fluxes comparing to measurements from control, open top chambers and snow addition plots. For 2014–2020, the studied ecosystem functioned as a minor source of CH₄ and a neutral balance of CO₂, resulting in the overall greenhouse gas emissions of 10.5 ± 79.1 g CO₂-eq m^-2 yr^-1. The calibrated model was used to predict CO₂ and CH₄ fluxes and their seasonal variations under future climate scenarios. By 2100, a warmer climate could enhance the mean annual sink strength of CO₂ to 10.7 g C-CO₂ m^-2 yr^-1 under SSP126 (Shared Socioeconomic Pathway 1 and the radiative forcing level of 2.6 W m^-2) and 26.2 g C-CO₂ m^-2 yr^-1 under SSP585 (Shared Socioeconomic Pathway 5 and the radiative forcing level of 8.5 W/m²). However, increasing trends in the CH₄ budget were marginally small. The negligible response of CH₄ emission can be mainly explained by insignificantly wetter climate and limited soil C stock. For the radiative balance of the ecosystem, CO₂-equivalent flux of methane offset 78% of CO₂ sink in SSP126, and 31% in SSP585. Overall, the subarctic wet tundra transitions from being a source to a sink for greenhouse gases, excluding N₂O.

中文翻译：

---

在两种共享的社会经济途径气候情景下预测亚北极湿地的 CO2 和 CH4 通量及其季节性变化


北极正在经历向更温暖、更潮湿的气候转变。最近的实验表明，亚北极湿苔原的碳平衡对夏季变暖和更深的积雪都很敏感。然而，很少有研究将实验数据与面向过程的模型相结合来预测陆地碳循环将如何响应未来的气候变化。在这里，我们使用 CoupModel（一种面向过程的模型）来研究 21^世纪两种截然不同的气候变化情景下亚北极湿润苔原生态系统中的 CO₂ 和 CH₄ 动态。我们的研究结果表明，与对照、开顶室和加雪图的测量值相比，该模型成功地再现了变暖对 CO₂ 和 CH₄ 通量的处理效果。在 2014-2020 年，所研究的生态系统作为 CH₄ 的次要来源和 CO₂ 的中性平衡发挥作用，导致总温室气体排放量为 10.5 ± 79.1 g CO_2-eq ^{m-2 yr-1}。校准模型用于预测未来气候情景下 CO₂ 和 CH₄ 通量及其季节性变化。到 2100 年，气候变暖可以提高 CO₂ 的年平均汇强度，达到 SSP126（共享社会经济途径 1 和辐射强迫水平 2.6 W ^m-2）和 SSP585（共享社会经济途径 5 和辐射强迫水平 8.5 W/m²）下 26.2 g C-CO ₂ ^{m-2 yr-1}。然而，CH₄ 预算的增长趋势略小。 CH₄ 排放的响应可以忽略不计，主要是由于气候不太潮湿和土壤 C 储量有限。对于生态系统的辐射平衡，甲烷的 CO₂ 等效通量抵消了 SSP126 中 78% 的 CO₂ 汇，在 SSP585 中抵消了 31%。总体而言，亚北极湿润苔原从温室气体（不包括 N₂O）的源转变为汇。