Persistently declining oxygen levels in the interior waters of the eastern subarctic Pacific
Persistently declining oxygen levels in the interior waters of the eastern subarctic Pacific
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DOI：
10.1016/j.pocean.2007.08.007
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发表时间：
2007-01-01
影响因子：
4.1
通讯作者：
Robert, Marie
中科院分区：
文献类型：
--
作者：
Whitney, Frank A.;Freeland, Howard J.;Robert, Marie
帕帕海洋站(OSP，北纬50度，西经145度)50年的测量表明，亚北极太平洋内陆水域的趋势既受到短期(几年到二十年)大气或海洋环流振荡的影响，也受到持续气候趋势的影响。在1956至2006年间，海洋混合层以下至少1000米深的水域一直在变暖并失去氧气。在100m-400m(sigma(0)=26.3-27.0)的密度面上，海洋在0.005-0.012摄氏度(-1)范围内变暖，而氧气在0.39-0.70mmolkg(-1)y(-1)i或以123mmolm(-2)y(-1)的积分速率下降(50年减少22%)。在此期间，低氧边界(定义为60微克分子氧-2千克(-1))已从400米至300米变浅。在阿拉斯加环流，26.2等压线偶尔通风，而在OSP 26.0西格玛(0)，自1971年以来，随着上层海洋的继续分层，再也没有出现在海洋表面。为了解释OSP的50年记录，利用略微修改的“NO”参数评估了亚北极太平洋内部含氧水的等温输送[Broecker，W.，1974]。“不”是一个保守的水团示踪剂。地球和行星科学通讯23,100-107]。北太平洋内水中硝酸盐-氧特征最高的是白令海环流、西亚北冰洋环流和东堪察加洋流区，这是冬季混合的结果，与26.6等温线相似。通过与亚热带和鄂霍次克海中没有发现的低水位混合，这一特征随着水流向东横跨太平洋而被冲淡。沿着不列颠哥伦比亚省和阿拉斯加东南部的海岸可以看到从加利福尼亚州向北流动的低水位的证据。在WOCE调查期间，阿拉斯加环流次表层水中的氧气供应类似于亚北极水域的60%和亚热带水域的40%，而OSP的这种估计值周期性地变化了20%。OSP资料中可辨别的其他特征包括较深等压线以类似18年的周期增加通风的周期，以及由经过的中尺度涡旋引起的强烈的短期(几个月)变率。讨论了氧气减少对沿海生态系统的潜在影响。皇冠版权所有(C)2007由爱思唯尔有限公司出版。保留所有权利。
Fifty years of measurements at Ocean Station Papa (OSP, 50 degrees N, 145 degrees W) show trends in the interior waters of the subarctic Pacific that are both impacted by short term (few years to bi-decadal) atmospheric or ocean circulation oscillations and by persistent climate trends. Between 1956 and 2006, waters below the ocean mixed layer to a depth of at least 1000 m have been warming and losing oxygen. On density surfaces found in the depth range 100-400 m (sigma(0) = 26.3-27.0), the ocean is warming at 0.005-0.012 degrees C y(-1), whereas oxygen is declining at 0.39-0.70 mu mol kg(-1) y(-1) I or at an integrated rate of 123 mmol m(-2) y(-1) (decrease of 22% over 50 years). During this time, the hypoxic boundary (defined as 60 mu mol O-2 kg(-1)) has shoaled from similar to 400 to 300 m. In the Alaska Gyre, the 26.2 isopycnal occasionally ventilates, whereas at OSP 26.0 sigma(0) has not been seen at the ocean surface since 1971 as the upper ocean continues to stratify. To interpret the 50 year record at OSP, the isopycnal transport of oxygenated waters within the interior of the subarctic Pacific is assessed by using a slightly modified "NO" parameter [Broecker, W., 1974. "NO" a conservative water-mass tracer. Earth and Planetary Science Letters 23, 100-107]. The highest nitrate-oxygen signature in interior waters of the North Pacific is found in the Bering Sea Gyre, Western Subarctic Gyre and East Kamchatka Current region as a consequence of winter mixing to the similar to 26.6 isopycnal. By mixing with low NO waters found in the subtropics and Okhotsk Sea, this signature is diluted as waters flow eastward across the Pacific. Evidence of low NO waters flowing north from California is seen along the coasts of British Columbia and SE Alaska. Oxygen in the subsurface waters of the Alaskan Gyre was supplied similar to 60% by subarctic and 40% by subtropical waters during WOCE surveys, whereas such estimates are shown to periodically vary by 20% at OSP. Other features discernable in the OSP data include periods of increased ventilation of deeper isopycnals on an similar to 18 year cycle and strong, short term (few month) variability caused by passing mesoscale eddies. The potential impacts of declining oxygen on coastal ecosystems are discussed. Crown Copyright (c) 2007 Published by Elsevier Ltd. All rights reserved.