Methane (CH4) fluxes from Alaska and other arctic regions may be sensitive to thawing permafrost and future climate change, but estimates of both current and future fluxes from the region are uncertain. This study estimates CH4 fluxes across Alaska for 2012-2014 using aircraft observations from the Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE) and a geostatistical inverse model (GIM). We find that a simple flux model based on a daily soil temperature map and a static map of wetland extent reproduces the atmospheric CH4 observations at the state-wide, multi-year scale more effectively than global-scale, state-of-the-art process-based models. This result points to a simple and effective way of representing CH4 flux patterns across Alaska. It further suggests that contemporary process-based models can improve their representation of key processes that control fluxes at regional scales, and that more complex processes included in these models cannot be evaluated given the information content of available atmospheric CH4 observations. In addition, we find that CH4 emissions from the North Slope of Alaska account for 24% of the total statewide flux of 1.74 ± 0.44 Tg CH4 (for May-Oct.). Contemporary global-scale process models only attribute an average of 3% of the total flux to this region. This mismatch occurs for two reasons: process models likely underestimate wetland area in regions without visible surface water, and these models prematurely shut down CH4 fluxes at soil temperatures near 0°C. As a consequence, wetlands covered by vegetation and wetlands with persistently cold soils could be larger contributors to natural CH4 fluxes than in process estimates. Lastly, we find that the seasonality of CH4 fluxes varied during 2012-2014, but that total emissions did not differ significantly among years, despite substantial differences in soil temperature and precipitation; year-to-year variability in these environmental conditions did not affect obvious changes in total CH4 fluxes from the state.

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CARVE 大气观测对阿拉斯加甲烷通量的多年估计

来自阿拉斯加和其他北极地区的甲烷 (CH4) 通量可能对永久冻土融化和未来气候变化敏感，但对该地区当前和未来通量的估计尚不确定。本研究使用来自北极水库碳脆弱性实验 (CARVE) 和地质统计反演模型 (GIM) 的飞机观测结果估计了 2012-2014 年阿拉斯加的 CH4 通量。我们发现，基于每日土壤温度图和湿地范围静态图的简单通量模型比全球范围的最先进技术更有效地再现了全州多年尺度的大气 CH4 观测基于过程的模型。这一结果指出了一种简单而有效的方式来表示整个阿拉斯加的 CH4 通量模式。它还进一步表明，当代基于过程的模型可以改进它们对控制区域尺度通量的关键过程的表示，并且鉴于可用大气 CH4 观测的信息内容，无法评估这些模型中包含的更复杂的过程。此外，我们发现阿拉斯加北坡的 CH4 排放量占全州总通量 1.74 ± 0.44 Tg CH4（5 月至 10 月）的 24%。当代全球规模的过程模型仅将总通量的平均 3% 归因于该区域。这种不匹配的发生有两个原因：过程模型可能低估了没有可见地表水的区域的湿地面积，并且这些模型在土壤温度接近 0°C 时过早地关闭了 CH4 通量。作为结果，植被覆盖的湿地和土壤持续寒冷的湿地对自然 CH4 通量的贡献可能比过程估计中的更大。最后，我们发现 2012-2014 年 CH4 通量的季节性变化，但尽管土壤温度和降水量存在显着差异，但总排放量在各年之间没有显着差异；这些环境条件的逐年变化并未影响来自该州的 CH4 总通量的明显变化。