Carbon Emissions under Arctic Snow (CEAS)

直到最近，人们对北极土壤冬季二氧化碳排放的重要性的认识还非常有限，这是因为人们错误地假设，与其他来源相比，雪下冻土的排放量微不足道。因此，北极冬季月份的二氧化碳排放经常被全球碳循环预算省略，我们测量控制二氧化碳排放的大气-雪地过程并在气候模型中模拟它们的能力也不发达。这限制了我们预测未来气候的能力，特别是在北极冻土带和森林地区，这些地区约占地球陆地表面的27%，自20世纪末以来变暖的速度是全球平均速度的两倍多。二氧化碳是一种气体，它导致地球大气中的热量被困住，导致地球变暖，它是由分解土壤中有机物质的微生物排放的。当土壤冻结时会发生分解，但随着土壤温度的降低，二氧化碳排放的速度会下降，当二氧化碳排放变得微不足道时，二氧化碳排放会下降到零下20摄氏度。冬季积雪对北极土壤温度有重要影响，就像盖在床上的羽绒被一样。羽毛之间有一层厚厚的羽绒被，中间夹着大量的空气，可以起到绝缘作用。被困在积雪中的雪晶之间的空气也有类似的作用，限制了夏季变暖的土壤到漫长的北极冬季寒冷大气中的热量损失。由于北极地区一年中至少有半年的地面通常是积雪覆盖的，因此我们必须了解控制积雪对土壤温度和二氧化碳排放的影响的过程，并在气候模型中准确地表示这些过程。在这里，我们要问的是，北极积雪中测量的二氧化碳浓度对积雪物理性质(例如雪晶的大小)的变化有多敏感？在气候模型中对积雪密度和导热系数进行更真实的模拟，能减少北极积雪对二氧化碳排放量的低估吗？而且，未来冬季土壤温度和积雪的变化可能会对未来的二氧化碳排放产生怎样的影响？为了回答这些问题，我们将创建一个新的北极气象、土壤和雪特性以及二氧化碳浓度的野外测量数据库。我们将利用这个数据库在气候模型中更真实地表示控制冬季二氧化碳排放的过程，这将导致对更广泛的北极地区未来冬季二氧化碳排放的模型预测充满信心。通过将实地测量和实验室测量与气候模型相结合，加拿大、芬兰和英国科学家之间的这种合作将增加我们对北极环境变化的预测性理解，这些变化是由我们的地球变暖引起的，并促成了这一变化。

Until recently, awareness of the importance of winter carbon dioxide emissions from arctic soils was highly limited, resulting from incorrect assumptions that emissions from frozen soils beneath snow were insignificant compared to other sources. Consequently, carbon dioxide emissions during arctic winter months are frequently omitted from global carbon cycling budgets and our capacity to measure atmosphere-snow-soil processes controlling carbon dioxide emission and simulate them in climate models are under-developed. This limits our ability to make future climate projections, especially in arctic tundra and forested regions, which characterise about 27% of the Earth's land surface and are warming more than twice as fast as the global average since the late twentieth century.Carbon dioxide, a gas which causes the Earth's atmosphere to trap heat causing the planet to warm, is emitted by microbes decomposing organic material in soil. Decomposition can occur when the soil is frozen, but rates of carbon dioxide emission decrease as soil temperatures decrease, down to -20 degrees Celsius when carbon dioxide emissions become negligible. Winter snow cover has an important impact on arctic soil temperatures, acting like a duvet covering a bed. A thick duvet with lots of air trapped between the feathers provides insulation. Air trapped between the snow crystals within a snowpack acts in a similar manner, limiting the loss of heat from soils warmed in the summer to the cold atmosphere during long arctic winters. As the ground is often snow covered for at least half of the year in Arctic regions, it is vital that we understand processes that control the impact of snow cover on soil temperatures and carbon dioxide emissions, and accurately represent these processes in climate models. Here we ask, how sensitive are measured carbon dioxide concentrations within arctic snowpacks to the variability of snowpack physical properties (e.g. size of the snow crystals)? Can more realistic simulations of snowpack density and thermal conductivity in climate models reduce the underprediction in carbon dioxide emissions from arctic snowpacks? And, how may future changes in winter soil temperatures and snow cover affect future carbon dioxide emissions? In order to answer these questions, we will create a new field measurement database of arctic meteorology, soil and snow properties, and carbon dioxide concentrations. We will use this database to develop more realistic representations of processes controlling winter carbon dioxide emissions in climate models, which will lead to confident model projections of future winter carbon dioxide emissions from the wider Arctic region. By combining field and laboratory measurements with climate modelling, this partnership between Canadian, Finnish and UK scientists will increase our predictive understanding of Arctic environmental change resulting from, and contributing to, our warming planet.