Late-Holocene climate and ecosystem history from Chesapeake Bay sediment cores, USA
Late-Holocene climate and ecosystem history from Chesapeake Bay sediment cores, USA
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美国切萨皮克湾沉积岩芯的全新世晚期气候和生态系统历史
DOI：
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发表时间：
2003
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通讯作者：
S. Verardo
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作者：
D. Willard;T. Cronin;S. Verardo
美国最大的河口切萨皮克湾全新世晚期沉积物中的古气候记录表明，十年至百年的气候变化和欧洲殖民对流域和河口都产生了严重影响。使用花粉和甲藻孢囊代理大西洋中部区域降水，河口盐度和溶解氧（DO）在过去的2300年，我们确定了四个干燥的间隔，集中在公元50（P1/D1），公元1000（P2/D2），公元1400（P3）和公元1600（P4）。两个百年尺度的事件，P1/D1和P2/D2，改变了森林的组成，并导致增加的盐度和溶解氧水平在河口。间隔P3和P4持续了几十年，导致松花粉产量下降。大西洋中部气候干燥的时期对应于美国东南部和中部树木年轮记录中确定的“特大干旱”。观测到的中大西洋气候变异性可以用大气环流的变化来解释，这种变化导致了长期的、也许是放大的纬向流间隔。在欧洲殖民化后，在早期的十七世纪，森林清除农业，木材和城市化改变河口水质，甲藻组合表明减少溶解氧和浊度增加。
Palaeoclimate records from late-Holocene sediments in Chesapeake Bay, the largest estuary in the USA, provide evidence that both decadal to centennial climate variability and European colonization had severe impacts on the watershed and estuary. Using pollen and dinoflagellate cysts as proxies for mid-Atlantic regional precipitation, estuarine salinity and dissolved oxygen (DO) during the last 2300 years, we identified four dry intervals, centred on ad 50 (P1/D1), ad 1000 (P2/D2), ad 1400 (P3) and ad 1600 (P4). Two centennial-scale events, P1/D1 and P2/D2, altered forest composition and led to increased salinity and DO levels in the estuary. Intervals P3 and P4 lasted several decades, leading to decreased production of pine pollen. Periods of dry mid Atlantic climate correspond to ‘megadroughts’ identified from tree-ring records in the southeastern and central USA. The observed mid-Atlantic climate variability may be explained by changes in atmospheric circulation resulting in longer-term, perhaps amplified, intervals of meridional flow. After European colonization in the early seventeenth century, forest clearance for agriculture, timber and urbanization altered estuarine water quality, with dinoflagellate assemblages indicating reduced DO and increased turbidity.