Biological and physical controls on N2, O2, and CO2 distributions in contrasting Southern Ocean surface waters
Biological and physical controls on N2, O2, and CO2 distributions in contrasting Southern Ocean surface waters
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DOI：
10.1002/2014gb004975
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发表时间：
2015-07
影响因子：
5.2
通讯作者：
P. Tortell;H. Bittig;A. Körtzinger;E. M. Jones;M. Hoppema
中科院分区：
文献类型：
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作者：
P. Tortell;H. Bittig;A. Körtzinger;E. M. Jones;M. Hoppema
本文介绍了2010-2011年南方夏季南大洋表层水的二氧化碳分压、氧气浓度、生物氧饱和度（ΔO2/Ar）和N2饱和度（ΔN2）的测量结果。浮游植物生物量在不同的水文带之间变化强烈，在锋面混合区和海冰融化区叶绿素a （Chl a）浓度较高。pCO2和ΔO2/Ar表现出较大的空间梯度（范围分别为90 ~ 450 μ atm和- 10 ~ 60%），并与Chl a呈强共变。然而，生物O2积累与溶解无机碳（DIC）减少的比例显著低于光合化学计量学的预期，反映了O2和CO2气海平衡的不同时间尺度。我们测量了显著的海洋CO2吸收，平均海气通量（~−10 mmol m−2 d−1）显著超过区域气候值。表层水体中N2以过饱和为主（平均ΔN2为+2.5%），物理过程导致混合层O2过饱和和欠饱和（平均ΔO2phys = 2.1%）。箱形模式计算能够重现ΔN2和ΔO2phys沿巡航轨迹的大部分空间变化率，证明了海气交换过程（例如，大气压力变化和气泡注入）和混合层夹带对地面气体不平衡的显著影响。净群落产量（NCP）由夹带校正的地表ΔO2/Ar数据得出，范围从~−40到bbb300 mmol O2 m−2 d−1，与基于季节性混合层DIC赤字的独立NCP估计具有良好的一致性。在水文锋面区和海冰融化分层区观察到NCP升高，反映了对地表水光场和养分有效性的物理控制。
We present measurements of pCO2, O2 concentration, biological oxygen saturation (ΔO2/Ar), and N2 saturation (ΔN2) in Southern Ocean surface waters during austral summer, 2010–2011. Phytoplankton biomass varied strongly across distinct hydrographic zones, with high chlorophyll a (Chl a) concentrations in regions of frontal mixing and sea ice melt. pCO2 and ΔO2/Ar exhibited large spatial gradients (range 90 to 450 µatm and −10 to 60%, respectively) and covaried strongly with Chl a. However, the ratio of biological O2 accumulation to dissolved inorganic carbon (DIC) drawdown was significantly lower than expected from photosynthetic stoichiometry, reflecting the differential time scales of O2 and CO2 air‐sea equilibration. We measured significant oceanic CO2 uptake, with a mean air‐sea flux (~ −10 mmol m−2 d−1) that significantly exceeded regional climatological values. N2 was mostly supersaturated in surface waters (mean ΔN2 of +2.5%), while physical processes resulted in both supersaturation and undersaturation of mixed layer O2 (mean ΔO2phys = 2.1%). Box model calculations were able to reproduce much of the spatial variability of ΔN2 and ΔO2phys along the cruise track, demonstrating significant effects of air‐sea exchange processes (e.g., atmospheric pressure changes and bubble injection) and mixed layer entrainment on surface gas disequilibria. Net community production (NCP) derived from entrainment‐corrected surface ΔO2/Ar data, ranged from ~ −40 to > 300 mmol O2 m−2 d−1 and showed good coherence with independent NCP estimates based on seasonal mixed layer DIC deficits. Elevated NCP was observed in hydrographic frontal zones and stratified regions of sea ice melt, reflecting physical controls on surface water light fields and nutrient availability.