Doctoral Dissertation Research: Linking Climate and Dune Activity in the High Plains

大平原的沙地提供了对该地区过去气候变化的重要洞察。沙丘现在大多由植被稳定，但在过去10,000年里经常是活跃的。这种活动通常被归因于史前干旱时期，比历史记录中任何一次干旱都要严重。过去沙丘稳定的时期被归因于更潮湿的气候，现在沙丘沙地中埋藏的土壤的形成记录了这一时期。沙丘活动和气候之间的这种联系直观上很吸引人，但还需要更多的工作来批判性地研究这种联系。这个博士论文项目将探索沙丘活动与气候之间关系的两个假说。一些沙丘地区的活动是由沉积物供应的变化引发的，而不是由更干旱的气候变化引发的。这一假设是由许多大平原沙丘区毗邻溪流的位置提出的，这些溪流是沙丘沉积物的明显来源。一些沙丘变得活跃的气候阈值在时间和空间上都是可变的，因为在沙丘活动期间，更细的颗粒会从沉积物中去除。这一假说是由较老的风沙(风积)沙层中明显较年轻的沙丘所处的位置提出的，这些沙丘具有相对较高的粘土和粉砂含量。这些假设将通过研究堪萨斯州西南部和俄克拉荷马州狭长地带的风成沉积物的地层学来验证。将河流附近沙丘之间的活动时间与从地形上远离这些河流的沙丘之间的时间进行比较，将表明沉积物供应是否会在相对潮湿的时期导致沙丘活动。全面了解地形对干旱的反应对大平原的居民来说至关重要。越来越多的证据表明，历史上的干旱，包括沙尘暴，比过去1万年的大多数干旱都要温和。这表明，平原居民可能完全没有准备好改变为更干旱的气候制度。如果这里正在研究的假设是有效的，那么预测和准备未来严重干旱的影响将需要认识到气候和沙丘活动之间复杂的、非线性的联系。相反，如果假设得不到支持，那么这将使研究人员在将气候与沙丘活动联系起来时有更大的信心。此外，一些研究表明，过去的干旱和沙丘活动时期类似于全球变暖可能对大平原产生的潜在影响。因此，沙丘地层学不仅提供了关于过去气候的信息，而且还提供了关于未来气候的信息，但前提是过去的沙丘活动时期与过去的干旱时期能够令人满意地联系在一起。最后，该奖项为学生完成博士论文并开始在地貌学研究方面的有前途的职业生涯提供支持。

The dunefields of the Great Plains provide critical insight into past climate change in that region. The dunes are now mostly stabilized by vegetation but were often active during the past 10,000 years. Such activity is generally attributed to prehistoric dry periods that were more severe than at any drought in the historical record. Past periods of dune stability, recorded by the formation of soils now buried within the dune sand, are attributed to more humid climates. This connection between dune activity and climate is intuitively appealing, but more work is needed to critically examine this link. This doctoral dissertation project will explore two hypotheses on the relationships between dune activity and climate. Activity within some dune fields is triggered by a change in sediment supply rather than a change to a more arid climate. This hypothesis is suggested by the location of many Great Plains dune fields adjacent to streams that are the apparent source of the dune sediment. The climatic threshold at which some dunes become active is variable in both time and space because finer particles are removed from the sediment during periods of dune activity. This hypothesis is suggested by the location of apparently younger dunes within older aeolian (wind-deposited) sand sheets that have relatively high clay and silt contents. These hypotheses will be tested by studying the stratigraphy of aeolian deposits in southwest Kansas and the Oklahoma panhandle. Comparing the timing of activity among dunes near streams to the timing among dunes that are topographically removed from those streams will indicate whether sediment supply can cause dune activity during relatively humid times.Understanding the full range of landscape responses to drought is vital for residents of the Great Plains. A growing body of evidence indicates that historical droughts, including the dust bowl, were milder than most droughts of the past 10,000 years. This suggests that Plains residents may be wholly unprepared for a change to a more arid climate regime. If the hypotheses that are being investigated here are valid, then predicting and preparing for the impacts of future severe drought will require recognition of complex, nonlinear links between climate and dune activity. Conversely, if the hypotheses are not supported, then that will enable researchers to have greater confidence when connecting climate to dune activity. Furthermore, some research has suggested that past periods of aridity and dune activity are analogs for the potential impact that global warming may have on the Great Plains. Thus dune stratigraphy not only provides information about past climate, but also about future climate, but only if past periods of dune activity can be linked satisfactorily to past periods of aridity. Finally, this award provides support for a student to complete a doctoral dissertation and begin a promising career in geomorphic research.