Closing the Isotope Hydrology at Summit: Measurements of Source Regions, Precipitation and Post-deposition Processes

格陵兰冰盖的稳定同位素记录是了解北极气候变化在十年到千年尺度上的黄金标准。虽然同位素信息解释的基本原则在一般意义上似乎是可靠的，但气象和冰川学过程可能会混淆简单的解释。关注的过程是湿度来源的变化、云过程、表面消融、吹雪和大气中的蒸汽扩散。该项目的目标是通过在首脑会议、尤里卡和雷克雅未克进行为期三年的测量活动，解决控制冰盖同位素组成方面的根本不确定性。该项目将使用测量和建模来评估：1)在湿度源与云微物理条件下，雪捕获的氧同位素组成和氘过量的变化程度；2)吹雪和雪内蒸汽扩散在多大程度上干扰了对同位素记录变异性的准确解释。将在首脑会议、尤里卡和雷克雅未克对水蒸气的同位素组成进行连续测量，并对新落雪和吹雪的同位素组成进行每日测量。这些将结合对降雪和吹雪的数量、大小分布和大致习惯的测量，评估降雪的湍流测量，地表潜热通量（消融和结霜）和能量平衡，以及极地云和大气结构的遥感。将钻取高分辨率的铁芯，以使详细的同位素测量和模型与冰川学记录相协调。新的同位素测量将启动一个新兴的国际泛北极同位素测量合作网络，补充现有北极观测网络活动下的北极观测。首脑会议的先进测量增强了该地点作为监测和了解北极变化的综合观测站的地位。

The stable isotopic records from the Greenland Ice Sheet are the gold standard for understanding climate variations in the Arctic on decadal to millennial scales. While the basic tenets that underlie interpretation of isotopic information appear robust in a mean sense, meteorological and glaciological processes can confound simple interpretations. Processes of concern are variations in moisture sources, cloud processes, surface ablation, blowing snow and vapor diffusion in the firn. The project objectives are to resolve fundamental uncertainties in the controls on the isotopic composition of the ice sheet through a 3-year measurement campaign at Summit, Eureka and Reykjavik. The project will use measurements and modeling to evaluate 1) the degree to which oxygen isotopic composition and deuterium excess of snow capture variations in moisture sources versus cloud microphysical conditions, and 2) the degree to which blowing snow and vapor diffusion within the firn confound accurate interpretation of variability in the isotopic record. Continuous measurements of the isotopic composition of water vapor and daily measurements of the isotopic composition of freshly-fallen and blowing snow will be made at Summit, Eureka and Reykjavik. These will be combined with measurements of the amount, size distribution, and approximate habit of falling and blowing snow, turbulence measurements to evaluate snow lofting, surface latent heat flux (ablation and frost) and energy balance, and remote sensing of polar clouds and atmospheric structure. High-resolution firn cores will be drilled to reconcile the detailed isotopic measurements and modeling with glaciological records. The new isotope measurements will jump start an emerging international pan-Arctic cooperative network of isotope measurements, which complements Arctic observations under existing Arctic Observing Network activities. The advanced measurements at Summit enhance the site as a comprehensive observatory for monitoring and understanding Arctic change.