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。这次经济衰退背后的一个主要驱动力是温暖的海水通过峡湾侵入海洋终止出口冰川（MTOG）表面，从而排干冰盖。卫星数据证实，这些冰川在过去几十年里已经变薄、加速和消退，但具有显着的时间和空间变化。尽管有这些信息，但由于缺乏对这些偏远且经常冰雪覆盖的地区的直接观测以及现有数据集的时间序列有限，我们预测冰盖如何以及以何种速度对未来变暖做出反应的能力变得困难。限制格陵兰岛可能的衰退轨迹对于评估其对海平面上升的影响的政策选择是必要的。然而，这种衰退的更广泛影响还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）会改变环流模式并影响北大西洋的天气系统，包括影响英国的天气系统。它还为近海地区带来了营养物质，促进了海洋生产力，进而有可能吸收更多大气中的二氧化碳，并将有机碳埋藏在峡湾和陆架沉积物中。迄今为止，这些过程尚未被量化，我们需要提高对这种对气候变化的负反馈的理解，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相似的一种方法是使用海洋沉积物岩心的代理将现代观测记录追溯到全新世的最后11,700年。格陵兰岛周围存在一些关于 20 世纪冰山崩解和温水侵蚀的记录，但没有关于过去冰川变化、海洋变暖和早期海洋生产力的全面、耦合记录。在这里，我们建议为格陵兰岛东南部（康克鲁斯瓦克峡湾）的一个关键地点生成全新世的长期记录，并通过对当今系统在三个年度周期的观测进行校准。然后，我们将使用受新数据约束的数值模型来测试格陵兰冰盖如何应对全新世期间的气候变暖，特别是在全新世最热期间，夏季气温与 2100 年的预测类似。我们将乘坐英国新型极地研究船 RRS Sir David 前往格陵兰岛东南部进行为期 6 周的多学科巡航，获得全套海洋学、生物和地质观测数据 艾登堡充分利用其最先进的能力作为物流平台。我们将使用巡航数据集来确定暖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、沉积和养分循环。同时，我们将收集长和短的海洋沉积物核心和陆地岩石样本，以约束过去冰川动力学的变化，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，通过现代观测来校准沉积物岩心信号。