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

正在消退的格陵兰冰盖（GrIS）现在是全球海平面上升的最大原因。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，这些冰川排出了冰盖。卫星数据证实，这些冰川在过去几十年里变薄、加速和退缩，但具有显著的时空变异性。尽管有这些信息，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，由于缺乏从这些偏远且经常被冰覆盖的地区进行的直接观测，以及现有数据集的有限时间序列，而变得困难。限制格陵兰岛可能的衰变轨迹对于评估其对海平面上升的贡献的政策选择是必要的。然而，这种衰退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）会改变环流模式，影响北大西洋天气系统，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大陆架沉积物中。迄今为止，这些过程还没有被量化，我们需要提高对气候变化负反馈的理解，然后才能将其纳入预测模型。确定冰-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，利用海洋沉积物岩心的代用物，将现代观测记录延伸至全新世过去11700年。格陵兰岛周围有一些20世纪冰山崩解和暖水侵蚀的记录，但没有关于过去冰川变化、海洋变暖和早期海洋生产力的综合、耦合记录。在这里，我们建议在格陵兰岛东南部（Kangerlussuaq Fjord）的一个关键位置生成这些全新世时期的长期记录，这些记录是通过对现今系统的三个年周期的观测来校准的。然后，我们将使用受新数据约束的数值模拟来测试格陵兰冰盖在全新世期间对气候变暖的反应，特别是在全新世热最大值期间，夏季温度与预测的2100年相似。我们将在为期6周的多学科巡航中获得全套海洋学，生物学和地质观测，在英国新的极地研究船上，大卫·阿滕伯勒爵士，充分利用其最先进的能力作为后勤平台。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、沉积和营养循环。同时，我们将收集长、短海洋沉积物岩心和陆相岩石样本，以约束冰川动力学的过去变化，并获得海洋温度和碳埋藏/储存的耦合代理记录。为了做到这一点，我们将使用锚系泊和重复观测，用我们的现代观测校准沉积物岩心信号。

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.