Using sediment accumulation rates in floodplain paleochannel lakes to reconstruct climate-flood relationships on the lower Ohio River
Using sediment accumulation rates in floodplain paleochannel lakes to reconstruct climate-flood relationships on the lower Ohio River
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DOI：
10.1016/j.quascirev.2022.107852
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发表时间：
2022-12
影响因子：
4
通讯作者：
Derek K. Gibson;B. Bird;H. Pollard;Cameron A. Nealy;R. Barr;J. Escobar
中科院分区：
文献类型：
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作者：
Derek K. Gibson;B. Bird;H. Pollard;Cameron A. Nealy;R. Barr;J. Escobar
利用位于伊利诺伊州（艾弗里湖）、肯塔基州（草塘）和印第安纳州（鹅塘）的三个洪泛区湖泊的14c沉积速率，研究了俄亥俄河下游晚全新世的洪水频率。沉积物堆积率的变化归因于河岸沉积物向每个地点的输送变化，这是由俄亥俄河洪水的频率控制的。在公元400年至1230年间，这三个湖泊的沉积速率达到了最低值，这表明在中世纪气候异常（MCA；约公元950-1250年）期间，俄亥俄河下游的洪水频率出现了区域性减少。沉积率在约1230 CE之后增加，并在小冰期（LIA; 1350-1820 CE）期间保持中等高水平，直到1800 CE早期开始大面积的土地清理。1820 CE以后，沉积速率进一步增加，并高于晚全新世的任何时期。区域古气候指标与上述漫滩沉积记录的对比表明，全新世晚期俄亥俄河洪水对大气环流的平均状态变化有响应。在MCA期间，当顺时针平均状态的大气环流以对流暴雨的形式将墨西哥湾向南的湿气平流到俄亥俄河流域时，俄亥俄河的洪水发生的频率最低。在低气压期间，经向平均状态大气环流增加了来自北太平洋和北极的中部大陆水分的比例，并以降雪的形式输送，因此增加了俄亥俄河的洪水。我们将LIA期间俄亥俄河洪水的增加归因于俄亥俄河流域积雪量的增加和春季融雪期间流域尺度径流的整合。随着19世纪初欧美的土地清理，洪水频率与这种关系脱钩，俄亥俄河下游变得容易受到频繁洪水的影响，尽管天气条件回到了偏南和顺时针方向。这些现代气候-洪水动态与古记录的根本不同，并表明土地利用的变化——如森林砍伐、瓦片排水和景观向集约化行作物农业的转变——已经从根本上改变了现代中西部的水文循环。
Late Holocene flood frequencies on the lower Ohio River were investigated using14C-based sedimentation rates from three floodplain lakes located in Illinois (Avery Lake), Kentucky (Grassy Pond), and Indiana (Goose Pond). Changes in sediment accumulation rates were attributed to variability in the delivery of overbank sediment to each site as controlled by the frequency of Ohio River flooding. Sedimentation rates reached their lowest values in all three lakes between 400 and 1230 CE, indicating a regional reduction in flood frequencies on the lower Ohio River during a period that included the Medieval Climate Anomaly (MCA; ca. 950–1250 CE). Sedimentation rates increased after ca. 1230 CE and remained moderately high through the Little Ice Age (LIA; 1350–1820 CE) until the onset of extensive land clearance during the early 1800s CE. After 1820 CE, sedimentation rates increased further and were higher than any other time during the late Holocene. A comparison of regional paleoclimatic proxies with the above floodplain sedimentation records shows that Ohio River flooding during the late Holocene was responsive to mean-state changes in atmospheric circulation. During the MCA, when clockwise mean-state atmospheric circulation advected southerly moisture from the Gulf of Mexico into the Ohio River Valley primarily in the form of convective rainstorms, flooding on the Ohio River was least frequent. During the LIA, meridional mean-state atmospheric circulation increased the proportion of midcontinental moisture that was sourced from the northern Pacific and Arctic and delivered as snowfall, hence increasing flooding on the Ohio River. We attribute the increase in Ohio River flooding during the LIA to an increase in snowpack volume across the Ohio River Valley and the watershed-scale integration of runoff during spring snowmelt. Following Euro-American land clearance in the early 1800s, flood frequencies decoupled from this relationship and the lower Ohio River became susceptible to frequent flooding, despite a return to southerly and clockwise synoptic atmospheric conditions. These modern climate-flood dynamics are fundamentally different than those of the paleo-record and suggest that land-use changes – such as deforestation, tile draining, and landscape conversion to intensive row crop agriculture – have fundamentally altered the modern Midwestern hydrologic cycle.