Sea surface fugacity of carbon dioxide (fCO2ssw) was measured across the Weddell gyre and the eastern sector in the Atlantic Southern Ocean in autumn. During the occupation between February and April 2019, the region of the study transect was a potential ocean CO2 sink. A net CO2 flux (FCO2) of −6.2 (± 8; sink) mmol m–2 d–1 was estimated for the entire study region, with the largest average CO2 sink of −10.0 (± 8) mmol m–2 d–1 in the partly ice-covered Astrid Ridge (AR) region near the coast at 68°S and −6.1 (± 8) mmol m–2d–1 was observed in the Maud Rise (MR) region. A CO2 sink was also observed south of 66°S in the Weddell Sea (WS). To assess the main drivers describing the variability of fCO2ssw, a correlation model using fCO2 and oxygen saturation was considered. Spatial distributions of the fCO2 saturation/O2 saturation correlations, described relative to the surface water properties of the controlling variables (chlorophyll a, apparent oxygen utilization (AOU), sea surface temperature, and sea surface salinity) further constrained the interplay of the processes driving the fCO2ssw distributions. Photosynthetic CO2 drawdown significantly offsets the influence of the upwelling of CO2-rich waters in the central Weddell gyre and enhanced the CO2 sink in the region. FCO2 of −6.9 mmol m–2 d–1 estimated for the Weddell gyre in this study was different from FCO2 of −2.5 mmol m–2 d–1 in autumn estimated in a previous study. Due to low CO2 data coverage during autumn, limited sea-air CO2 flux estimates from direct sea-surface CO2 observations particularly for the Weddell gyre region are available with which to compare the values estimated in this study. This highlights the importance of increasing seasonal CO2 observations especially during autumn/winter to improving the seasonal coverage of flux estimates in the seasonal sea ice-covered regions of the Southern Ocean.

中文翻译：

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南大洋威德尔环流和近海莫德陆上秋季海气二氧化碳通量的变化

秋季在威德尔环流和大西洋南大洋东部地区测量了海面二氧化碳逸度 (fCO2ssw)。在 2019 年 2 月至 2019 年 4 月的占领期间，研究断面所在的区域是一个潜在的海洋 CO2 汇。整个研究区域的净 CO2 通量 (FCO2) 估计为 -6.2 (± 8; sink) mmol m–2 d–1，最大平均 CO2 汇为 -10.0 (± 8) mmol m–2 d–在 68°S 的海岸附近部分被冰覆盖的 Astrid Ridge (AR) 地区出现了 1，在 Maud Rise (MR) 地区观察到了 -6.1 (± 8) mmol m-2d-1。在威德尔海 (WS) 的 66°S 以南也观察到了一个 CO2 汇。为了评估描述 fCO2ssw 变异性的主要驱动因素，考虑了使用 fCO2 和氧饱和度的相关模型。fCO2 饱和度/O2 饱和度相关性的空间分布，相对于控制变量（叶绿素 a、表观氧利用率 (AOU)、海面温度和海面盐度）的地表水特性的描述进一步限制了驱动 fCO2ssw 分布的过程的相互作用。光合二氧化碳下降显着抵消了威德尔环流中部富含二氧化碳的水域上涌的影响，并增强了该地区的二氧化碳汇。本研究中为威德尔环流估计的 -6.9 mmol m-2 d-1 的 FCO2 与先前研究中估计的秋季 -2.5 mmol m-2 d-1 的 FCO2 不同。由于秋季 CO2 数据覆盖率较低，因此可利用直接海面 CO2 观测的有限海气 CO2 通量估计值，特别是针对威德尔环流区域，可用于比较本研究中估计的值。