Assessing ocean-forced, marine-terminating glacier change in Greenland during climatic warm periods and its impact on marine productivity (Kang-Glac)

评估气候温暖时期格陵兰岛受海洋驱动、海洋终止的冰川变化及其对海洋生产力的影响 (Kang-Glac)

• 批准号: NE/V007289/1
• 负责人: Colm O'Cofaigh
• 金额: $ 80.2万
• 依托单位: Durham University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2024
• 资助国家: 英国
• 起止时间: 2024 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FV007289%2F1
• 关键词: Assessing; ocean; forced; marine; terminating

The receding Greenland Ice Sheet (GrIS) is now the largest contributor to global sea-level rise. A major driving force behind this recession is the encroachment of warm ocean water through fjords to the faces of marine-terminating outlet glaciers (MTOGs) that drain the ice sheet. Satellite data confirm that these glaciers have thinned, accelerated and retreated over the past few decades, but with significant temporal and spatial variability. Despite this information, our ability to predict how, and at what rate, the ice sheet will respond to future warming is made difficult by a lack of direct observations from these remote and often ice-infested areas and by the limited time-series of existing datasets. Constraining Greenland's likely decay trajectory is necessary to evaluate policy options with regard to its contribution to sea level rise. However, the wider effects of this decay also encompass the marine environments bordering the landmass. Increasing the supply of freshwater to these areas (as meltwater and icebergs) alters circulation patterns and impacts North Atlantic weather systems, including those affecting the UK. It also brings nutrients to offshore areas that promote marine productivity, which in turn has the potential to draw down more atmospheric CO2 and bury organic carbon in fjord and shelf sediments. To date, these processes have not been quantified and we need to improve our understanding of this negative feedback to climate change before it can be incorporated into predictive models.One way to determine which ice-ocean-marine ecosystem scenarios are analogues for future warming scenarios is to extend the record of modern observations back over the last 11,700 years of the Holocene using proxies from marine sediment cores. A few records of 20th Century iceberg calving and warm water encroachment exist around Greenland but there are no comprehensive, coupled records of past glacier change, ocean warming and marine productivity for earlier periods. Here, we propose to generate these long-term records for the Holocene era for a key location in SE Greenland (Kangerlussuaq Fjord) calibrated by observations of the present-day system over three annual cycles. We will then use numerical modelling constrained by our new data to test how the Greenland Ice Sheet responded to climatic warming during the Holocene, particularly during the Holocene Thermal Maximum when summer temperatures were analogous to those predicted for 2100.We will acquire a full suite of oceanographic, biological and geological observations during a 6-week multidisciplinary cruise to SE Greenland on the UK's new polar research vessel, the RRS Sir David Attenborough, making full use of its state-of-the-art capabilities as a logistical platform. We will use cruise datasets to determine modern interactions between warm water inflows and glacial meltwater outflows, and to quantify marine productivity, sedimentation and nutrient cycling. At the same time, we will collect long and short marine-sediment cores and terrestrial rock samples to constrain past changes in glacier dynamics and derive coupled proxy records of ocean temperatures and carbon burial/storage. To do this, we will calibrate the sediment-core signals with our modern observations using an anchored mooring and repeat observations.

正在消退的格陵兰冰盖（GrIS）现在是全球海平面上升的最大贡献者。这次衰退背后的一个主要驱动力是温暖的海水通过峡湾侵蚀到海洋终端出口冰川（MTOG）的表面，这些冰川将冰盖排干。卫星数据证实，这些冰川在过去几十年中变薄、加速和退缩，但在时间和空间上有很大的变化。尽管有这些信息，但由于缺乏对这些偏远且经常有冰出没的地区的直接观测，以及现有数据集的时间序列有限，我们难以预测冰盖将如何以及以何种速度对未来变暖做出反应。限制格陵兰可能的衰退轨迹对于评估其对海平面上升的贡献方面的政策选择是必要的。然而，这种衰减的更广泛影响也包括与陆地接壤的海洋环境。增加这些地区的淡水供应（如融水和冰山）改变了环流模式，影响了北大西洋的天气系统，包括影响英国的天气系统。它还将营养物质带到近海地区，促进海洋生产力，这反过来又有可能吸收更多的大气二氧化碳，并将有机碳埋在峡湾和陆架沉积物中。到目前为止，这些过程还没有被量化，我们需要更好地理解这种对气候变化的负反馈，然后才能将其纳入预测模型。确定哪些冰-海洋-海洋生态系统情景与未来变暖情景类似的一种方法是使用海洋沉积物岩心的代理物将现代观测记录追溯到全新世的过去11，700年。格陵兰周围存在一些世纪冰山崩解和温水入侵的记录，但没有过去冰川变化、海洋变暖和早期海洋生产力的综合、耦合记录。在这里，我们建议生成这些长期记录全新世时代的一个关键位置在格陵兰岛东南部（Kangerlussuaq峡湾）校准的观测现今的系统在三个年度周期。然后，我们将使用受我们新数据约束的数值模拟来测试格陵兰冰盖如何对全新世气候变暖做出反应，特别是在全新世最热时期，夏季温度与2100年预测的温度相似。在英国新的极地研究船RRS大卫阿滕伯勒爵士号上对格陵兰岛东南部进行为期6周的多学科巡航期间进行生物和地质观测，充分利用其作为后勤平台的最先进能力。我们将使用巡航数据集来确定温暖的水流入和冰川融水流出之间的现代相互作用，并量化海洋生产力，沉积和营养循环。与此同时，我们将收集长和短的海洋沉积物岩心和陆地岩石样本，以限制冰川动力学过去的变化，并得出海洋温度和碳埋藏/储存的耦合代理记录。为此，我们将使用锚定系泊和重复观测，用我们的现代观测校准沉积物岩心信号。