Neglected fluxes: Understanding the evolution of weathering as continental ice sheets retreat

被忽视的通量：了解大陆冰盖退缩时风化的演变

• 批准号: 1603452
• 负责人: Ellen Martin
• 金额: $ 82.03万
• 依托单位: University of Florida
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2021-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1603452&HistoricalAwards=false
• 关键词: Neglected; fluxes; Understanding; evolution; weathering

The Greenland Ice Sheet is the largest ice sheet in the northern hemisphere. However, as the arctic warms the ice sheet has been retreating, and as a result, altering the fundamental nature of weathering and the delivery of nutrients and elements to the ocean. The proposed work is focused on the hydrological, biological, biogeochemical, and the isotopic signatures of proglacial watersheds, which are watershed that convey dilute but high volume glacial meltwater from the top and underneath the ice sheet to the ocean, and deglacial watersheds, which are watersheds that are no longer physically connected to the ice sheet and sourced only by annual precipitation and permafrost melt. The PIs contend that while deglacial watersheds have received less attention, preliminary work suggests they may be equally or more important than proglacial watersheds for oceanic and atmospheric fluxes. Moreover, as the ice sheet melts, the area contributing to meltwater and constituent fluxes will increasingly be from deglacial watersheds. The understanding gained from this work will provide a context for the prediction of future land-ocean and land-atmosphere fluxes in response to continued ice sheet retreat. Results of the project have the potential to change our understanding of global CO2, nutrient, and isotope cycling in response to ice sheet collapse and permit predictions of the future responses to global warming and ice sheet retreat. Results will also provide a context to interpret past high latitude ice sheet retreat and climate change based on marine isotope records. The project includes training for undergraduate, graduate, and postdoctoral researchers, as well as a collaboration with students and faculty at a Greenlandic academic institution.The proposed study will test the hypotheses that (1) deglacial and proglacial watersheds contribute distinct elemental, isotopic, and nutrient fluxes to the ocean and atmosphere as a result of evolving weathering patterns, and (2) these reactions and associated fluxes will change within and between watersheds as the Greenland Ice Sheet retreats. The project focuses on three field areas: deglacial and proglacial watersheds near Kangerlussuaq and Narsasuaq and a deglacial watershed near Sisimiut. Each area has a distinct water balance, exposure age, and weathering characteristics, and will be sampled three times over two melt seasons to evaluate intra-seasonal and inter-annual variations. Mass balance models and PHREEQc modeling of solute data will be used to identify and assess extents of weathering reactions. Weathering extents will also be estimated based on trends in proportional contributions of minerals and offsets between dissolved and bedload strontium and lead isotope ratios, and will be linked to phosphorous fluxes and organic carbon lability and degradation. This holistic approach will provide a broad view of the relative elemental, nutrient and isotopic fluxes in proglacial and deglacial environments. These results will provide magnitudes, time scales, and drivers of weathering reactions, with a goal of linking fluxes to past records and future predictions of global climate change associated with continental ice sheet collapse.

格陵兰冰盖是北半球最大的冰盖。 但是，随着北极的温暖，冰盖已经撤退，因此，改变了风化的基本性质以及将营养物质和元素传递到海洋中。 所提出的工作集中于前进分水岭的水文，生物，生物地球化学和同位素特征，这些分水岭是流域，这些分水岭从顶部和冰层下方和不再是冰层的冰层下方，冰层下方和冰期散发出来的冰层，并在物理上散发出来的冰层，并在冰层下面进行了冰淇淋，这些冰层的冰层和冰期又是冰川，并且在冰上散发出冰层，并且在冰上散发出冰层，并且在冰上散发出冰层，并且在冰层中有所不同，并且在冰层下进行了灌输，并且在冰层中有所不同。多年冻土融化。 PIS认为，尽管冰川流域受到了较少的关注，但初步工作表明，它们可能比海洋和大气通量的前冰流域同样重要或更重要。 此外，随着冰盖的融化，造成融化和成分通量的区域将越来越多地来自冰川流域。 从这项工作中获得的理解将为未来的土地海洋和土地大气通量预测，以响应持续的冰盖撤退。该项目的结果有可能改变我们对全球二氧化碳，营养素和同位素循环的理解，以响应冰盖崩溃，并允许预测未来对全球变暖和冰盖撤退的反应。 结果还将提供一个背景，以根据海洋同位素记录来解释过去的高纬度冰盖静修和气候变化。 The project includes training for undergraduate, graduate, and postdoctoral researchers, as well as a collaboration with students and faculty at a Greenlandic academic institution.The proposed study will test the hypotheses that (1) deglacial and proglacial watersheds contribute distinct elemental, isotopic, and nutrient fluxes to the ocean and atmosphere as a result of evolving weathering patterns, and (2) these reactions and associated随着格陵兰冰盖撤退，流域内部和之间的通量会发生变化。该项目侧重于三个田间区域：Kangerlussuaq和Narsasuaq附近的冰期和冰期流域，以及西西米特附近的冰川流域。 每个区域都有不同的水平衡，暴露年龄和风化特征，并将在两个熔体季节进行三次取样，以评估季节内和年际变化。 质量平衡模型和溶质数据的Phreeqc模型将用于识别和评估风化反应的扩展。还将根据矿物质和溶解层和铅同位素比率之间的比例贡献的趋势进行估计，并将与磷酸通量以及有机碳的衰减和降解有关。这种整体方法将为冰期和冰纹环境中的相对元素，营养和同位素通量提供广泛的看法。 这些结果将提供风化反应的大小，时间尺度和驱动因素，其目的是将通量与过去的记录以及与大陆冰盖倒塌相关的全球气候变化的未来预测联系起来。