Collaborative Research: US GEOTRACES GP17-ANT: Nitrogen isotope dynamics on the Amundsen Sea continental margin

南极洲大陆架是一个动态的、往往具有生物生产力的极地环境，对海洋环流、养分和碳循环具有全球重要性。由于其高纬度位置和南极近端冰盖的影响，在持续的全球变暖下，南极大陆架将迅速变化。然而，人们对南极大陆架的自然状态知之甚少，先前的研究表明，这种环境随着时间的推移而改变，这也预示着它未来可能会发生怎样的变化。本研究将利用天然氮同位素研究南极大陆架氮循环的运作。氮是生命的关键营养物质，在许多环境中限制生物生产力，并提供了海洋水域生物生长和分解之间平衡的整体观点。氮同位素测量与美国GEOTRACES GP17-ANT考察队的其他测量相结合，将确定南极大陆架（阿蒙森海大陆架）的主要生物生产力来源和汇，该大陆架可能特别容易受到南极冰盖融化加速的影响。这些测量还将提供关键的基线信息，以支持利用沉积物岩心和其他档案重建过去的变化。该项目将培养研究生和本科生，并支持一名早期职业博士后研究员。美国GEOTRACES GP17-ANT探险队将提供机会，在阿蒙森海陆架上生成微量元素和同位素的补充数据集。阿蒙森海陆架是南极边缘环境，其特征是丰富的海冰、融化的冰架和高产的冰陆。对于GP17-ANT的所有站点，将测量硝酸盐氮和氧同位素比值的全深度剖面，以及几个代表性站点的总溶解氮氮同位素比值，以深入了解氮源和水柱中的循环。此外，将从比标准方法允许的更深深度的GEOTRACES大容量泵样品中测量悬浮颗粒氮同位素比率，以研究深海珊瑚氮同位素比率作为古代用物的再生和地面真实性。最后，将从地表沉积物样品中测量大块沉积物和硅藻结合的氮同位素比率，为正在进行的使用更长沉积物岩心的古海洋学重建提供地面真实性。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The continental shelf of Antarctica is a dynamic and often biologically productive polar environment, with global importance for ocean circulation, nutrient and carbon cycling. Due to its high latitude location and the impacts of the proximal Antarctic ice sheet, the Antarctic continental shelf stands to change quickly under ongoing global warming. Yet the natural state of the Antarctic continental shelf is poorly known, and previous research suggests that this environment has changed through time, which would also signal how it may change in the future. This study will investigate the operation of the nitrogen cycle on the Antarctic continental shelf, using the natural isotopes of nitrogen. Nitrogen is a critical nutrient for life, limits biological productivity in many environments, and provides a holistic view of the balance between biological growth and decomposition in ocean waters. The nitrogen isotope measurements, combined with the other measurements of the U.S. GEOTRACES GP17-ANT expedition, will determine the major sources and sinks of biological productivity on a segment of the Antarctic continental shelf – the Amundsen Sea shelf – that may be particularly susceptible to change as Antarctic ice sheet melting accelerates. The measurements will also provide key baseline information to support the reconstruction of past changes using sediment cores and other archives. The project will train graduate and undergraduate students and support one early career postdoctoral researcher.The U.S. GEOTRACES GP17-ANT expedition will provide the opportunity to generate complementary data sets of trace elements and isotopes on the Amundsen Sea shelf, an Antarctic margin environment characterized by abundant sea ice, melting ice shelves, and highly productive polynyas. For all stations of GP17-ANT, full depth profiles of the nitrogen and oxygen isotope ratios of nitrate will be measured, along with nitrogen isotope ratios of total dissolved nitrogen at a few representative stations to provide insight into nitrogen sources and cycling in the water column. Moreover, suspended particle nitrogen isotope ratios will be measured from the GEOTRACES high-volume pump samples from deeper depths than standard methods allow, to investigate regeneration and ground-truth the application of deep-sea coral nitrogen isotope ratios as a paleo-proxy. Lastly, from surface sediment samples, bulk sediment and diatom-bound nitrogen isotope ratios will be measured, providing ground-truthing for ongoing paleo-oceanographic reconstructions using longer sediment cores.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.