Subglacial Chemical Weathering under East Antarctica

非技术描述化学风化是岩石和矿物转变为粘土、氧化物和化学养料的过程。大多数这些风化反应会消耗大气气体，如氧气和二氧化碳，因此化学风化可以推动大气化学发生自然的、长期的变化。岩石通过化学风化释放出的营养物质被输送到海洋，对维持地球上的生命是必要的。该项目的主要目的是评估南极洲最大的冰盖下发生了多少化学风化。在世界其他地方，通过分析河流的流出来评估化学风化，但这种直接测量化学流出的方法是不可能的，因为几乎整个南极洲都被冰覆盖。在南极洲，研究人员使用了横跨北极山脉的样本，在那里，流动的冰与山峰的相互作用导致岩石和矿物物质从冰川底部涌出。该项目将评估这种新兴矿物材料相对于下伏岩石的化学风化程度，以及这种风化发生的时间尺度。技术描述来自横贯北极山脉遗址的初步数据有力地表明，化学风化的矿物产物(粘土和氧化物)在新兴物质中比在下伏岩石中更丰富。然而，这种物质的化学变化可能发生在南极洲冰川形成之前或最近。为了限制风化的时间线，从而评估南极洲现代的风化速度，这个项目将分析风化矿物中的两个稀有的放射性同位素。由于这些同位素在放射性衰变过程中会丢失，它们可以作为时钟，对化学风化过程中形成的粘土和氧化物进行计时。冰层形成之前的矿物会有这些同位素附着在它们的表面，但不会出现在它们的晶体结构中。通过首先通过化学方法去除粘土和氧化物表面的元素，然后分析矿物本身，项目调查人员将确定这些矿物是最近在冰下形成的，还是在无冰环境中预先形成的。通过计算这些矿物形成的时间，并分析冰将它们运离大陆的速度，他们将能够计算出横贯北极山脉上下的化学风化速率。其结果将是对南极东部冰盖下风化对地球海洋营养物质化学影响的估计。这项研究将为下一代极地科学家提供宝贵的培训。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Nontechnical DescriptionChemical weathering is the process by which rocks and minerals are turned to clay, oxides, and chemical nutrients. Most of these weathering reactions consume atmospheric gases, such as oxygen and carbon dioxide, and therefore chemical weathering can drive natural, long-term changes in atmosphere chemistry. The nutrients released from rocks by chemical weathering are transported to the oceans and are necessary for the maintenance of life on Earth. The principal aim of this project is to assess how much chemical weathering occurs beneath Antarctica's largest ice sheet. Elsewhere in the world, chemical weathering is assessed by analyzing the outflow of rivers, but such direct measurements of chemical outflow are not possible because nearly all of Antarctica is covered by ice. In Antarctica investigators use samples from the Transantarctic Mountains where the interaction of flowing ice with mountain peaks causes rock and mineral material to emerge from the glacier base. This project will assess the degree to which this emerging mineral material has been chemically weathered compared to the underlying rock and the time scale at which such weathering occurs. Technical DescriptionPreliminary data from a Transantarctic Mountain site strongly suggests that the mineral products of chemical weathering (clays and oxides) are more abundant in the emerging material than in the underlying rocks. However, the chemical alteration of this material could have occurred recently or prior to glaciers forming in Antarctica. To constrain the timeline of weathering and thereby assess modern rates of weathering in Antarctica, this p[project will analyze two rare, radioactive isotopes within the weathered minerals. Because these isotopes are lost through radioactive decay, they act as clocks that can time the formation of the clays and oxides that form during chemical weathering. Minerals that pre-date the ice will have these isotopes clinging to their surface but not in their crystal structure. By first chemically removing the elements on the surface on the clays and oxides and then analyzing the minerals themselves, the project investigators will determine whether the minerals formed recently under the ice or beforehand in an ice-free environment. By calculating how recently these minerals formed and by analyzing the rate at which ice transports them off the continent, they will be able to calculate chemical weathering rates at locations up and down the Transantarctic Mountains. The result will be an estimate the impact of weathering under the East Antarctic ice sheet on the chemistry of the Earth's ocean nutrients. This research will provide valuable training for the next generation of polar scientists.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.