Local and Remote Forcing of Denitrification in the Northeast Pacific for the Last 2,000 Years
Local and Remote Forcing of Denitrification in the Northeast Pacific for the Last 2,000 Years
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DOI：
10.1029/2019pa003577
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发表时间：
2019-08
影响因子：
3.5
通讯作者：
Yi Wang;I. Hendy;R. Thunell
中科院分区：
文献类型：
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作者：
Yi Wang;I. Hendy;R. Thunell
沉积物δ 15 N（δ 15 Nsed）已被广泛用作水体反硝化作用的指标。当与其他生产力代理相结合时，它可以深入了解水柱氧合长期变化背后的驱动力。加州圣巴巴拉盆地的高分辨率（~2年）δ 15 Nsed和生产率代用记录（总有机碳[TOC]、Si/Ti和Ca/Ti）由年代确定的卡斯滕岩心（SPR 0901 - 03 KC）生成。这些记录揭示了过去2,000年来南加州上升流和氧合之间的关系。Si/Ti（海岸上升流代理）和TOC（总输出生产力代理）之间的相关性表明，风旋上升流影响南加州初级生产力，特别是在海岸上升流较弱的时段。δ 15 Nsed、TOC和干旱指标之间的一致性支持大气环流对δ 15 Nsed的局部控制，因为与增强的北太平洋高压单体相关的持续偏北风导致增强的沿海上升流。在东北太平洋，δ 15 Nsed被用作从热带北太平洋东部（ETNP）经加州暗流向北输送的反硝化信号的水团示踪剂。来自加州湾佩斯卡德罗斜坡的1,200年δ 15 Nsed记录位于ETNP和南加州的地下沃茨之间。在中世纪气候异常期间，佩斯卡德罗和圣巴巴拉盆地δ 15 Nsed之间的一致性表明了ETNP和南加州之间在百年时间尺度上的联系。然而，当阿留申低压在小冰河时期异常强大时，出现了一种异相关系。我们认为，当加州暗流和ETNP反硝化作用减弱时，富含营养物的亚北极水平流可能将高15 N硝酸盐输送到南加州。
Sedimentary δ15N (δ15Nsed) has been widely applied as a proxy for water column denitrification. When combined with additional productivity proxies, it provides insights into the driving forces behind long‐term changes in water column oxygenation. High‐resolution (~2 years) δ15Nsed and productivity proxy records (total organic carbon [TOC], Si/Ti, and Ca/Ti) from Santa Barbara Basin, California, were generated from a well‐dated Kasten core (SPR0901‐03KC). These records reveal the relationship between Southern California upwelling and oxygenation over the past 2,000 years. Inconsistencies between Si/Ti (coastal upwelling proxy) and TOC (total export productivity proxy) suggest wind curl upwelling influenced Southern California primary productivity, especially during intervals of weak coastal upwelling. Coherence between δ15Nsed, TOC, and drought indicators supports a local control of δ15Nsed by atmospheric circulation, as persistent northerly winds associated with an intensified North Pacific High pressure cell lead to enhanced coastal upwelling. In the northeast Pacific, δ15Nsed is used as a water mass tracer of denitrification signals transported north from the eastern tropical North Pacific (ETNP) via the California Undercurrent. A 1,200‐year δ15Nsed record from the Pescadero slope, Gulf of California, lies between denitrifying subsurface waters in the ETNP and Southern California. During the Medieval Climate Anomaly, coherence between Pescadero and Santa Barbara Basin δ15Nsed indicates connections between ETNP and Southern California on centennial timescales. Yet an out‐of‐phase relationship occurred when the Aleutian Low was anomalously strong during the Little Ice Age. We suggest intensified nutrient‐rich subarctic water advection might have transported high‐15N nitrate into Southern California when the California Undercurrent and ETNP denitrification weakened.