NSFGEO-NERC: Collaborative Research: Accelerating Thwaites Ecosystem Impacts for the Southern Ocean (ARTEMIS)

阿蒙森海拥有南极洲沿海最具生产力的冰间湖，从太空中可以看到充满活力的绿色沃茨，大气中的二氧化碳吸收通量密度比南大洋的平均水平高出10倍。该区域易受气候变化的影响，海冰迅速减少，沿海冰逸发生阶段性变化，邻近的西南极冰盖（WAIS）冰川融化最快。在一个生态系统经历如此巨大的变化，这是至关重要的，以解决气候敏感的驱动程序和反馈的融水相关的铁（Fe）的交付，这支撑生产力在这个否则高营养，低叶绿素区域。我们以前的实地研究（ASPIRE）确定了融化WAIS和微量营养元素Fe的输送到冰间湖生态系统之间的明确联系，以及其在快速CO2下降中的作用。我们最近的数值模拟工作（INSPIRE）提出了几种途径，铁的交付，优化现场工作的方法，并指导提高机制的理解铁的供应和循环。一个正在进行的物理海洋学领域的计划（TARSAN，国际思韦茨冰川合作，ITGC的一部分）提供了一个理想的物理框架，为我们的下一个研究工作。我们在这里建议与Tarsan支持的英国科学家合作，为两个团队提供重要的附加值。Tarsan于2019年2月至3月乘船探索了阿蒙森海东部，预计将于2021年2月至3月再次在Thwaites地区运营。他们将使用一整套物理海洋学技术，包括2个冰架下的AUV，滑翔机，水面车辆，微观结构剖面仪，船上CTD，密封标签，惰性气体和正在进行的传感器，以表征负责快速冰川融化的冰-海洋相互作用。在2019年期间，Tarsan和THOR（也是ITGC）收集了详细的测深，沉积和冰架空洞信息（2019年9月可用），这些信息将立即改进和更新INSPIRE模型以适应当今的边界条件。我们的NSFGEO-NERC联合项目（ARTEMIS）将促进ASPIRE/INSPIRE团队成员与TARSAN/ITGC之间的合作，为2021年资助的探险增加地球化学测量，并以适度的额外物流成本建立现有的滑翔机基础设施和密封标签专业知识（为自动驾驶车辆增加地球化学传感器）。ARTEMIS更新模型的数值运行将为TARZAN 2021年的实地工作提供信息。所做的观察将改善我们的理解和我们的模型，允许更复杂的评估铁在当前和未来的情况下的作用。我们的团队（ARTEMIS）将增加船上地球化学观测（痕量金属，碳酸盐系统，营养物质，有机物质，微生物）和自主车辆地球化学观测（硝酸盐，叶绿素a，光学后向散射），以收集对了解WAIS融化对冰间湖生态系统和区域碳（C）循环的影响至关重要的知识。ARTEMIS结合了美国组成部分的专业知识，包括碳酸盐系统和微生物生态学家（Yager），痕量金属地球化学家（谢雷尔），微量金属同位素地球化学家（菲茨西蒙斯），有机地球化学家（Medeiros），冰-海洋-大气相互作用专家（Stammerjohn）和一个数值海洋建模师（St-Laurent），英国部分由3名物理海洋学家组成：TARSAN首席PI（Heywood），精通地球化学的自动驾驶车辆专家（Queste）和海洋学家，其车辆是海洋哺乳动物（Boehme）。这个国际小组将在海上和岸上进行分析，以解决ASPIRE/ INSPIRE调查结果所产生的一系列相互关联的问题。

The Amundsen Sea hosts the most productive polynya in coastal Antarctica, with its vibrant green waters visible from space, and an atmospheric CO2 uptake flux density 10x higher than average for the Southern Ocean. The region is vulnerable to climate change, with rapid losses in sea ice, episodic shifts in the coastal icescape, and the fastest melting glaciers in the adjacent West Antarctic Ice Sheet (WAIS). In an ecosystem experiencing such dramatic change, it is critical to resolve the climate-sensitive drivers and feedbacks of the meltwater-associated iron (Fe) delivery, which underpins productivity in this otherwise high-nutrient, low chlorophyll region. Our previous field research (ASPIRE) identified a clear link between the melting WAIS and the delivery of micronutrient Fe to the polynya ecosystem, and its role in rapid CO2 drawdown. Our recent numerical modeling effort (INSPIRE) suggests several pathways for Fe delivery, ways to optimize fieldwork, and guidance for improving mechanistic understanding of Fe supply and cycling. An ongoing physical oceanographic field program (TARSAN, part of the International Thwaites Glacier Collaboration, ITGC) offers an ideal physical framework for our next research effort. We propose here to collaborate with TARSAN-supported UK scientists, providing significant value added to both teams. TARSAN explored the eastern Amundsen Sea by ship in Feb-Mar 2019 and expects to operate in the Thwaites region again in Feb-Mar 2021. They will use a full suite of physical oceanographic techniques, including 2 under-ice-shelf AUVs, gliders, surface vehicles, a microstructure profiler, shipboard CTD, seal tags, noble gases, and underway sensors to characterize the ice-ocean interactions responsible for rapid glacial melting. During 2019, TARSAN and THOR (also ITGC) collected detailed bathymetric, sedimentary, and ice-shelf cavity information (available Sept 2019) that will immediately improve and update the INSPIRE model to present-day boundary conditions. Our combined NSFGEO-NERC project (ARTEMIS) will facilitate collaboration between ASPIRE/INSPIRE team members and TARSAN/ITGC, add biogeochemical measurements to the funded 2021 expedition, and build on existing glider infrastructure and seal tag expertise (adding biogeochemical sensors to autonomous vehicles) at modest additional logistical cost. Numerical runs with ARTEMIS's updated model will inform TARZAN's 2021 field effort. Observations made will improve our understanding and our model, allowing a more sophisticated assessment of the role of Fe in present and future scenarios. Our team (ARTEMIS) would add shipboard biogeochemical observations (trace metals, carbonate system, nutrients, organic matter, microorganisms) and autonomous vehicle biogeochemical observations (nitrate, Chl a, optical backscatter) to gather knowledge critical to understanding the impact of WAIS melting on both the polynya ecosystem and the regional carbon (C) cycle. ARTEMIS combines the expertise of a US component comprising a carbonate system and microbial ecologist (Yager), a trace metal biogeochemist (Sherrell), a trace metal isotope geochemist (Fitzsimmons), an organic geochemist (Medeiros), an ice-ocean-atmosphere interactions expert (Stammerjohn), and a numerical ocean modeler (St-Laurent), with a UK component comprising 3 physical oceanographers: TARSAN lead PI (Heywood), a biogeochemically savvy autonomous vehicle expert (Queste), and an oceanographer whose vehicles are marine mammals (Boehme). This international team will work together at sea and with shore-based analyses to address a set of interconnected questions arising from the findings of ASPIRE/ INSPIRE.