Collaborative Research: Understanding Change in the Climate and Hydrology of the Arctic Land Region: Synthesizing the Results of the ARCSS Fresh Water Initiative Projects

北极的气候正在发生变化。根据北极气候影响评估（ACIA），“北极气候正在迅速变暖，预计会发生更大的变化”。这些变化令人担忧，因为它们可能对全球海洋环流产生影响。ARCSS淡水综合研究（FWI）旨在解决与北极淡水循环有关的许多更广泛问题的科学基础，特别是在陆地上。特别是，FWI的目标是解决“……关键，未解决的问题……本质上是跨学科和综合的”。其中三个问题直接涉及北极气候与该地区水和能源平衡的耦合影响。2002年，NSF资助了一组18个FWI项目，这些项目与随后的ARCSS项目一起旨在解决上述FWI问题。但是，需要进行综合活动，以便更充分地利用FWI项目的成果。这项工作将利用具有大量陆地表面活动的FWI项目的研究成果，并将结果纳入一个综合活动，该活动将记录和归因观测到的北极水文循环变化，包括该地区的气候和全球气候系统。主要的综合机制将是一个耦合的区域陆地-大气模式（极地WRF或MM5），以及一个中等复杂程度的海洋-陆地-大气系统全球模式（使用更有限）。要解决的首要科学问题是：北极陆地过程的变化如何影响该地区的气候，这些变化对北极水文循环（包括与大气的耦合和反馈）的影响是什么，以及北极淡水系统的变化对全球气候的影响是什么？该研究将解决两个支持性的科学问题：1)如何使用FWI研究的结果来更好地理解影响观测到的泛北极陆地系统淡水平衡变化的水文过程？2)观测到的北极陆地水文循环变化在多大程度上是由于其他地区（通过大气过程）输入的变化，以及观测到的陆地水文变化在多大程度上输出到大气和全球海洋系统？第一个问题是关于哪些水文过程促成了观测到的变化的归因问题，并将在泛北极尺度上使用非耦合、部分耦合和完全耦合的陆地-大气模拟策略来解决。解决第二个问题需要记录水文变化对全球气候的影响（通过海洋变化）。它将通过使用中等复杂程度的全球陆地-海洋-大气耦合模式（维多利亚大学ESCM气候模式）来解决。迄今为止，我们对北极地区的变化及其在全球气候中更广泛的作用的了解有限。本研究旨在提供北极系统内关键水文过程的全面视图，以及它们如何通过海洋和大气途径与区域和全球系统相互作用。预计这将使人们更好地了解水文过程如何促成观测到的变化以及北极外过程的贡献。对这些相互作用和反馈的详细分析将为气候界了解北极在气候变率和变化中的作用提供有价值的信息。

The climate of the Arctic is changing. According to the Arctic Climate Impact Assessment (ACIA), "Arctic climate is now warming rapidly, and much larger changes are projected". These changes are of concern because of their possible implications for global ocean circulation. The ARCSS Freshwater Integration Study (FWI) was designed to address the scientific basis of many of these broader issues that are related to the arctic freshwater cycle, especially over land. In particular, FWI has the objective of addressing "... key, unresolved issues ... [that are] fundamentally cross-disciplinary and synthetic in nature". Three of these issues deal directly with the coupled implications of arctic climate and the water and energy balances of the region. NSF funded a group of 18 FWI projects in 2002, which together with subsequent ARCSS projects were intended to address the FWI questions outlined above. However there is a need for synthesis activities to exploit more fully results of the FWI projects. This work will utilize research results from the FWI projects that have a substantial land surface activity, and will incorporate the results in a synthesis activity that will document and attribute observed change in the arctic hydrologic cycle, both for the climate of the region, and the global climate system. The primary synthesis mechanism will be a coupled regional land-atmosphere model (either polar WRF or MM5), and (more limited use) of a global model of medium complexity of the ocean-land-atmosphere system. The overarching science question to be addressed is: How do changes in arctic land processes affect the climate of the region, what are the implications of these changes for the arctic hydrologic cycle (including coupling and feedbacks with the atmosphere), and what are the impacts of changes in the arctic freshwater system on global climate?The research will address two supporting science questions: 1) How can the results from the FWI studies be used to better understand the hydrologic processes affecting observed change in the freshwater balance of the pan arctic land system? and 2) To what extent are the observed changes in Arctic terrestrial hydrologic cycle due to imported change from other regions (via atmospheric processes), and to what extent are the observed terrestrial hydrologic changes exported to the atmosphere and to the global ocean system? The first question leads to attribution questions regarding which hydrologic processes have contributed to observed change, and will be addressed using a strategy of uncoupled, partially coupled, and fully coupled land-atmosphere modeling at the pan-arctic scale. Addressing the second question will require documenting the effect of hydrologic change on global climate (via changes in the oceans). It will be addressed through use of a coupled GLOBAL land-ocean-atmosphere model of medium complexity (University of Victoria ESCM climate model).To date our understanding of change in the Arctic region and its broader role in global climate has been limited. This research seeks to provide a comprehensive view of key hydrological processes within the Arctic system and how they interact regionally and with the global system via oceanic and atmospheric pathways. It is expected that this will result in a better understanding of how hydrologic processes have contributed to observed change and the contribution from extra-Arctic processes. Detailed analysis of these interactions and feedbacks will provide valuable information to the climate community for understanding the role of the Arctic in climate variability and change.