Variability of USA East Coast surface total alkalinity distributions revealed by automated instrument measurements
Variability of USA East Coast surface total alkalinity distributions revealed by automated instrument measurements
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DOI：
10.1016/j.marchem.2021.103960
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发表时间：
2021-03
期刊：
影响因子：
3
通讯作者：
C. W. Hunt;J. Salisbury;D. Vandemark;Steffen Aßmann;P. Fietzek;C. Melrose;R. Wanninkhof;K. Azetsu-Scott
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文献类型：
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作者：
C. W. Hunt;J. Salisbury;D. Vandemark;Steffen Aßmann;P. Fietzek;C. Melrose;R. Wanninkhof;K. Azetsu-Scott
海水总碱度(TA)是用于监测海洋碳循环的一个重要决定因素，其空间分布以前是通过离散的瓶装样品在美国东海岸表征的。利用这些数据，建立了几个基于实际盐度的区域TA反演模型(S)。然而，大范围的季节或年际变化在这些模型中没有得到很好的解决，现有数据具有高度的季节性偏见。这项研究报告了首次在科考船上长时间部署新的商用TA滴定仪的结果，以及产生的持续的水面TA测量结果。该仪器在2017年6个月和2018年两个月的夏季东海岸海洋酸化调查(ECOA-2)期间在美国东海岸的七个邮轮上运行，总共收集了近11,000个表面TA测量数据。这些工作的数据，以及一组新合成的11,000多个区域地表TA观测，被分析以重新检查TA和S在美国东海岸的分布。总体而言，S和TA的区域分布与前人的研究结果基本一致，但线性TA：S的回归随时间的变化明显不同，并偏离了先前建立的模型。这种可变性可能是由于生物、季节性和阶段性影响的组合，并表明由于这些因素，S估计的TA估计可能会有±10-20μ摩尔/公斤−1的重大误差。这一发现可能会对数值生态系统建模和无机碳系统计算产生影响。本文的新结果提供了更精细的地表TA：S关系，在空间和时间上提供了更多的数据，并改善了TA建模的不确定性。
Seawater total alkalinity (TA) is one important determinant used to monitor the ocean carbon cycle, whose spatial distributions have previously been characterized along the United States East Coast via discrete bottle samples. Using these data, several regional models for TA retrievals based on practical salinity (S) have been developed. Broad-scale seasonal or interannual variations, however, are not well resolved in these models and existing data are highly seasonally biased. This study reports findings from the first long duration deployment of a new, commercially available TA titrator aboard a research vessel and the continuous underway surface TA measurements produced. The instrument, operated on seven East Coast USA cruises during six months in 2017 and for two months in 2018 on the summertime East Coast Ocean Acidification survey (ECOA-2), collected a total of nearly 11,000 surface TA measurements. Data from these efforts, along with a newly synthesized set of more than 11,000 regional surface TA observations, are analyzed to re-examine distributions of TA and S along the United States East Coast. Overall, regional distributions of S and TA generally agreed with prior findings, but linear TA:S regressions varied markedly over time and deviated from previously developed models. This variability is likely due to a combination of biological, seasonal, and episodic influences and indicates that substantial errors of ±10–20 μmol kg−1in TA estimation from S can be expected due to these factors. This finding has likely implications for numerical ecosystem modeling and inorganic carbon system calculations. New results presented in this paper provide refined surface TA:S relationships, present more data in space and time, and improve TA modeling uncertainty.