Oxygen Dynamics During the JGOFS Southern Ocean Process Study

本研究项目是美国联合全球海洋通量研究（JGOFS）南大洋方案的一部分，旨在：(1)更好地了解南大洋有机和无机碳通量，(2)确定调节这些通量的大小和变化的物理、生态和生物地球化学因素和过程，以及(3)将这些通量置于当代全球碳循环的背景下。JGOFS计划的主要目标之一，特别是南大洋倡议的主要目标之一，是限制碳通量，以便评估该区域是碳的净汇还是碳源。对这个项目的兴趣是为了了解影响初级生产速率的环境因素，并在广泛的空间和时间尺度上推断这些速率。研究将侧重于利用氧气在三个尺度上限制碳通量；大型，中型和局部。1)对于大规模，将采集空气样本并测量O2/N2比。由于春季和夏季的初级生产和秋季和冬季的海洋通风，大气中的氧浓度在季节时间尺度上有所不同。因此，对O2/N2信号振幅的了解将为南大洋净产生的幅度和时间提供一个衡量标准。参与JGOFS实验的船舶将每天收集空气样本，以获得南大洋上空大气氧场的纬向和时间变化的高分辨率记录。2)同样，将通过两种方式从中尺度氧场确定净初级生产力：首先通过测量从混合层收集的海水中的O2/Ar比率和O2的del 18O，其次通过沿着巡航轨道连续测量地下氧气浓度。这两种方法与空气采样程序一起，将提供净产量的时间和空间综合估计。3)碳流将通过每天测量总产氧量和净产氧量以及硝酸盐同化而受到限制。总产氧量的计算方法是将海水样品与180o标记的水一起浸泡和孵育，并测量光合作用产生的氧的del 180o。通过自动高精度温克勒滴定法比较初始样品和孵育样品之间氧浓度的相对变化来测量净氧产量。这些测量将提供每日深度综合总和净产量以及呼吸速率。此外，光合作用-辐照度实验将测量巡航期间的总产量和净产量，利用系泊点和卫星的生物光学数据推断当地的测量结果，直至中尺度和大尺度。

95-30746 BENDER This research project is part of the US Joint Global Ocean Flux Study (JGOFS) Southern Ocean Program aimed at (1) a better understanding of the fluxes of carbon, both organic and inorganic, in the Southern Ocean, (2) identifying the physical, ecological and biogeochemical factors and processes which regulate the magnitude and variability of these fluxes, and (3) placing these fluxes into the context of the contemporary global carbon cycle. One of the primary goals of the JGOFS program in general, and of the Southern Ocean initiative in particular, is to constrain the carbon flux in order to evaluate whether this region is a net sink or source of carbon. Interest in this program is directed towards gaining an understanding of the environmental factors that affect rates of primary production and the extrapolation of these rates over broad spatial and temporal scales. Research will focus on using oxygen to constrain carbon fluxes on three scales; large, meso and local. 1) For the large scale, air samples will be collected and the O2/N2 ratio will be measured. Oxygen concentrations in the atmosphere vary on seasonal time scales due to primary production in the spring and summer months and ventilation of the ocean in the fall and winter. Thus knowledge of the amplitude of the O2/N2 signal will provide a measure of the magnitude and timing of net production for the Southern Ocean. Air samples will be collected daily from ships that will participate in the JGOFS experiment to have high resolution records of zonal and temporal variations of the atmospheric oxygen field over the Southern Ocean. 2) Similarly, net primary productivity will be determined from the mesoscale oxygen field in two ways: first by measurement of O2/Ar ratios and del 18O of O2 in seawater collected from the mixed layer and second by continually measuring subsurface oxygen concentrations along the cruise track. These two approaches, together with the air sampling program, wi ll provide a temporally and spatially integrated estimate of net production. 3) Carbon flow will be constrained by undertaking daily measurements of gross and net oxygen production, and nitrate assimilation. Gross oxygen production is calculated by spiking and incubating seawater samples with 18O-labelled water and measuring the del 18O of the photosynthetically produced oxygen. Net oxygen production is measured by comparing the relative change in the oxygen concentration between initial and incubated samples by automated high precision Winkler titrations. These measurements will provide daily depth integrated gross and net production rates in addition to respiration rates. Furthermore, photosynthesis-irradiance experiments will measure gross and net production during cruises to extrapolate local measurements up to meso and large scale using bio-optical data from moorings and satellites.