Glacial‐Holocene δ15N record from the Gulf of Tehuantepec, Mexico: Implications for denitrification in the eastern equatorial Pacific and changes in atmospheric N2O
Glacial‐Holocene δ15N record from the Gulf of Tehuantepec, Mexico: Implications for denitrification in the eastern equatorial Pacific and changes in atmospheric N2O
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DOI：
10.1029/2002gb002028
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发表时间：
2004-03
影响因子：
5.2
通讯作者：
R. Thunell;A. B. Kepple
中科院分区：
文献类型：
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作者：
R. Thunell;A. B. Kepple
过去23,000年来，利用沉积物有机质的氮同位素组成(δ15Norg)和其他水柱生产力的地球化学示踪剂，重建了沿热带北太平洋东部墨西哥边缘的特万特佩克湾的反硝化强度。末次冰期δ15Norg变化范围为6.5~8.6‰，增大幅度为2 3~17ka。冰川消融的标志是δ15Norg的急剧增加，最大值(9.9Norg)出现在博林/阿勒德时期和最早的全新世。δ15Norg值在过去10,000年间出现下降，晚全新世的值与冰川时期的值相似。我们的数据表明，在最后一次冰期，该地区的反硝化作用很小，这与研究地点生物扰动沉积物的沉积是一致的。在冰川消融和全新世早期，反硝化作用的强度急剧增加，表明存在一个强烈的氧气极小区。这一时期还以该地区层状沉积物的沉积为标志。δ15Norg记录显示出与格陵兰冰芯大气N2O浓度记录相似的时间趋势。目前，热带东太平洋和阿拉伯海的反硝化作用占全球海洋固定氮损失的很大一部分，而海洋-大气N2O通量的很大一部分来自这些地区。过去这些地区N2O排放量的大幅变化将直接影响全球温室气体浓度。
The intensity of denitrification in the Gulf of Tehuantepec, along the Mexican margin of the eastern tropical North Pacific (ETNP), was reconstructed for the last 23,000 years using the nitrogen isotopic composition of sediment organic matter (δ15Norg) in conjunction with other geochemical tracers of water column productivity. During the last glacial period, δ15Norg values ranged from 6.5 to 8.6‰ with values increasing between 23 and 17 ka. Deglaciation was marked by an abrupt increase in δ15Norg with maximum values (9.9‰) occurring during the Bølling/Allerød period and the earliest Holocene. A decline in δ15Norg values occurred over the last 10,000 years, with late Holocene values being similar to those of the glacial period. Our data suggest that denitrification in this region was minimal during the last glacial and is consistent with the deposition of bioturbated sediments at the study site. The intensity of denitrification increased dramatically during deglaciation and the early Holocene, signaling the presence of a strong oxygen minimum zone. This period is also marked by the deposition of laminated sediments in the region. The δ15Norg records display similar temporal trends to those seen in the Greenland ice core record of atmospheric N2O concentrations. At present, denitrification within the eastern tropical Pacific and Arabian Sea accounts for a major portion of the global marine loss of fixed nitrogen, and a significant fraction of the ocean‐atmosphere N2O flux originates from these areas. Large changes in N2O emissions from these regions in the past would have directly impacted global greenhouse gas concentrations.