Collaborative Research: An Interdisciplinary Investigation of Groundwater-Carbon Coupling in Large Peat Basins and its Relation to Climate Change

学术价值：全新世期间北部泥炭地的增长创造了一个全球重要的温室气体源和汇。然而，这些大型碳库对全球变暖的反应仍然不确定。不同的数学模型预测，未来的变暖可能会通过增加碳固存的速度或加速温室气体的排放来改变泥炭地的碳平衡。然而，这些稳态分析模型对自然泥炭地做出了不切实际的假设，泥炭地是空间和时间可变的生态系统，仍在积累碳。因此，这项研究将开发一个瞬态三维数值模型，将多相地下水流动与溶质运移、有机质反应性和泥炭积累耦合起来。我们在过去25年中对大型泥炭盆地的调查证明了气候、地下水、景观和泥炭地碳通量之间的密切联系，这支持了建立这样一个模型的必要性。这种新的瞬态地下水-泥炭积累模型将通过在不同尺度上收集的多组野外、实验室和遥感数据进行校准。然后，对这一校准模型的敏感性分析应该为大型泥炭盆地在区域一级对气候变化的响应提供可靠的预测。这种方法可以在明尼苏达州北部的冰川湖阿加西泥炭地（GLAP）得到最好的测试，尽管气候相对干燥和周期性干旱，但该地区还是发展了一个区域性泥炭盆地。遥感、野外仪器、地球物理勘探和计算建模的最新进展将用于开发和校准GLAP地区的瞬态耦合地下水-泥炭堆积模型。这项跨学科的研究将集中在几个重要的问题上，包括深层泥炭中的碳循环和可变形介质的水力学。这项研究还将确定来自大型泥炭地的甲烷通量是否由来自深层超压气体穴的沸腾（即冒泡）所主导，这些气体穴是全球重要的、以前未被解释的大气甲烷来源。此外，本研究将评估区域河流系统的配置是否会放大气候变化对泥炭地生态系统的影响。更广泛的影响：本研究的更广泛影响将通过以下方面得到扩展：1)在大型跨学科调查中培训研究生和本科生；2)向K-12学校和公众提供推广服务；3)为州立公园和其他解说中心开发3D计算机可视化展览；4)将我们的研究成果与Morin组织的地区和国家教育计划联系起来。可视化展览将专门为耗资160万美元的讲解中心设计，该中心位于大沼泽休闲区，最近由明尼苏达州建立，毗邻我们的田野区域。这次展览将把我们的实地测量结果与泥炭地在全球碳循环中的作用联系起来，向公众展示。它将延续GLAP研究小组与管理明尼苏达州北部和其他地方公共土地的官员之间密切合作的悠久传统。

Intellectual Merit: The growth of northern peatlands during the Holocene created a globally important source and sink for greenhouse gases. The response of these large carbon reservoirs to Global Warming, however, remains uncertain. Different mathematical models predict that future warming could alter the carbon balance of peatlands by either increasing the rate of carbon sequestration or accelerating the emissions of greenhouse gases. However, these steady-state analytical models make unrealistic assumptions about natural peatlands, which are spatially and temporally variable ecosystems that are still accumulating carbon. This investigation will therefore develop a transient 3D numerical model that couples multiphase groundwater flow to solute transport, organic matter reactivity, and peat accumulation. The need for such a model is supported by our investigations in large peat basins over the past 25 years that demonstrate the close linkages among climate, groundwater, landscape, and peatland carbon fluxes. This new transient groundwater-peat accumulation model will be calibrated by multiple sets of field, lab, and remote sensing data collected at a range of scales. A sensitivity analysis of this calibrated model should then provide reliable predictions for the response of large peat basins to climate change at the regional level.This approach can best be tested in the Glacial Lake Agassiz Peatlands (GLAP) of northern Minnesota where a regional peat basin developed despite the relatively dry climate and periodic droughts. Recent advances in remote sensing, field instrumentation, geophysical exploration, and computational modeling will be used to develop and calibrate a transient coupled groundwater-peat accumulation model for the GLAP region. This interdisciplinary investigation will focus on several important problems including carbon cycling in the deeper peat and the hydraulics of a deformable media. This study will also determine if methane fluxes from large peatlands are dominated by ebullition (i.e., bubbling) from deep overpressured gas pockets representing a globally important and previously unaccounted for source of atmospheric methane. In addition, this investigation will evaluate whether the configuration of the regional river system amplifies the effects of climate change on peatland ecosystems.Broader Impacts: The broader impacts of this study will be extended by 1) training graduate and undergraduate students in a large interdisciplinary investigation, 2) providing outreach to K-12 schools and the general public, 3) developing 3D computer visualization exhibits for state parks and other interpretive centers, and 4) linking our research results to regional and national educational programs organized by Morin. The visualization exhibits will be specifically designed for a new $1.6 million interpretive center at the Big Bog Recreational Area, which was recently established by the State of Minnesota adjacent to our field area. This exhibit will link results from our field measurements to the role of peatlands in the global carbon cycle for the general public. It will continue the long tradition of close cooperation between the GLAP research group and the officials that manage public land in northern Minnesota and elsewhere.