EAR-PF: Morphodynamics of giant dunes in wind and water

Julia Cisneros博士获得了美国国家科学基金会EAR博士后奖学金，与Jeff Nittrouer博士和Ryan Ewing博士分别在德克萨斯州休斯敦莱斯大学和大学站德克萨斯农工大学进行风或水形成的巨大沙丘研究。该项目旨在了解巨大的沙丘如何在沙漠和河流中移动和运输沉积物。在沙漠中，巨大的沙丘在数千年的时间里迁移和变化，记录了全球气候的变化。在河流中，巨大的沙丘会在几天到几个月的时间内迁移，并对重大的景观改变事件做出反应，比如极端的洪水。巨大的沙丘也存在于其他星球上（例如，在土星的卫星土卫六上），而在地球上，它们的沉积物被保存在沉积岩记录中，为难以到达的古代环境提供了关键记录。然而，人们对它们的地形结构知之甚少，也不知道多种尺度的沙丘是如何共存的。这些信息对于提高我们对不同环境下形成的巨大沙丘的理解至关重要。该项目旨在利用西斯内罗斯博士博士在河流沙丘研究期间获得的专业知识，使她能够比较和对比河流和沙漠环境中的沙丘操作。作为一个土生土长的德克萨斯人，她计划利用她在德克萨斯州休斯顿的博士后研究平台，鼓励代表性不足和少数族裔的学生设想自己从事类似的职业。外展工作建立在Cisneros现有的外展工作的基础上，旨在了解有色人种年轻女孩对地球科学职业的障碍和看法。为了理解这一点，她将举办为期两天的夏季地球科学夏令营，以继续学习如何吸引有色人种的年轻女孩，以支持在地球科学领域获得进一步的多样性。本研究的主要目标是通过研究地球上沙漠和河流中最大、最复杂的河床形态动力学，为跨越环境和尺度的河床形态动力学建立一个统一的框架。巨型沙丘通常由较小的沙丘组成，这些沙丘叠加在大沙丘上。然而，对于它们的地形结构和平移，沉积物如何在它们的结构中运输，以及多种尺度的河床如何共存，人们知之甚少。为了提高我们对巨型沙丘形态动力学的理解，西斯内罗斯博士将分析沙丘形态，并通过对河流和沙漠沙丘区进行重复调查，确定巨型沙丘、复合沙丘和简单沙丘的形态动力学。这些调查将在洛杉矶的密西西比河最下游进行，那里有简单的和巨大的复合沙丘，以及在加利福尼亚州的阿尔戈多内斯沙丘场进行，那里有巨大的复合沙丘。NM白沙沙丘场的现有数据将用于简单沙丘的调查。本研究结果为两个研究领域提供了新的表征床型分析技术和泥沙通量量化方法，从而建立了沙丘形态动力学的研究框架。此外，通过将叠加沙丘对河流中复合沙丘动力学的影响联系起来，并将这些方法外推到沙漠中，本研究将解开地球和其他行星上巨型沙丘缓慢移动的形态动力学。这项工作的结果将有助于行星科学、地貌学、沉积学和工程学等学科的发展。该项目获得了地球科学部地貌学和土地利用动力学项目的共同资助。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。

Dr. Julia Cisneros has been granted an NSF EAR Postdoctoral Fellowship to conduct research on giant sand dunes formed by wind or water at Rice University, Houston, TX and Texas A&M University, College Station, TX with Dr. Jeff Nittrouer and Dr. Ryan Ewing, respectively. This project seeks to understand how giant sand dunes move and transport sediment in deserts and rivers. In deserts, giant dunes migrate and change over thousands of years, recording the variability in global climate. In rivers, giant dunes migrate over days to months and respond to significant landscape-altering events, such as extreme floods. Giant dunes exist also on other worlds (e.g., on Titan, a moon of Saturn), and here on Earth, their deposits are preserved in the sedimentary rock record providing key records of inaccessible and ancient environments. Still, little is known about their topographic structure or how multiple scales of dunes may co-exist. This information is vital to improve our understanding of giant dunes formed in various environments. This project seeks to use the expertise gained by Dr. Cisneros during her PhD investigation of dunes in rivers, allowing her to compare and contrast dune operations across both rivers and desert environments. As a native Texan, she plans to use her postdoctoral researcher platform in Houston, TX to encourage underrepresented and minoritized students to envision themselves in similar careers. The outreach work builds on Cisneros’ existing outreach efforts that seek to understand the barriers and perceptions young girls of color feel towards careers in the Geosciences. To understand this, she will run a two-day summer Geoscience Camp in order to continue learning how to engage young girls of color in support of gaining further diversity in the Geosciences.This study’s primary objective is to develop a unifying framework for bedform morphodynamics that spans environments and scales through studying the morphodynamics of Earth’s largest and most complex bedforms in deserts and rivers. Giant dunes commonly comprise smaller, superimposed dunes climbing up the large dunes stoss. Still, little is known of their topographic structure and translation, how sediment is transported across their structure, and how multiple scales of bedforms can coexist. To improve our understanding of giant dune morphodynamics, Dr. Cisneros will analyze dune morphology and identify the morphodynamics of giant, compound and simple dunes through deploying repeat surveys of river and desert dune areas. These surveys will be conducted on the lowermost Mississippi River, LA, where simple and giant, compound dunes exist, and in the Algodones Dune Field, CA, which comprises giant, compound dunes. Existing data of the White Sands Dune Field, NM will be used for investigation of simple desert dunes. Results of this study provide both research fields with new characterization bedform analysis techniques and methods for quantifying sediment flux, thereby creating an investigative framework of dune morphodynamics. Further, through relating the influence of superimposed dunes to compound dune dynamics in rivers and extrapolating those methods to deserts, this study will unlock the slow-moving morphodynamics of giant dunes on Earth and other planets. The results of this work will contribute to disciplines ranging from planetary sciences, geomorphology, sedimentology, and engineering. This project received co-funding from the Geomorphology and Land-use Dynamics program in the Earth Science division.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.