Transient tracer distributions in the Fram Strait in 2012 and inferred anthropogenic carbon content and transport
Transient tracer distributions in the Fram Strait in 2012 and inferred anthropogenic carbon content and transport
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DOI：
10.5194/os-12-319-2016
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发表时间：
2016-02
期刊：
影响因子：
3.2
通讯作者：
T. Stöven;T. Tanhua;M. Hoppema;Wilken‐Jon Appen
中科院分区：
文献类型：
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作者：
T. Stöven;T. Tanhua;M. Hoppema;Wilken‐Jon Appen
人为碳在海洋内部的储存是调节大气中二氧化碳浓度增加的一个重要过程。极地地区预计将成为人为碳的净汇。因此，对溶解无机碳的运移估计和人为补偿可以提供有关相应储存过程规模的信息。本文介绍了2012年在弗拉姆海峡78°50‘N采集的瞬时示踪剂、溶解无机碳(DIC)和总碱度(TA)数据。介绍了一种示踪关系理论，该理论允许在高纬度地区应用逆高斯渡越时间分布(IG-TTD)和估计人为碳浓度。利用2002-2010年同一断面的平均流速测量值，估算了通过弗拉姆海峡840m以上的边界流对DIC和人为碳的净通量。新理论解释了理论(基于IG-TTD)示踪年龄关系和现场数据的特定示踪年龄关系之间的差异，是通过水团形成过程中的饱和效应和/或1996年格陵兰海SF6的故意释放实验，而不是通过不同的混合或通风过程。根据这一假设，在弗拉姆海峡的中等深度(500-1600m)，确定了SF6的最大超出量为0.5fmoL kg−1。人为碳浓度在大西洋水/循环大西洋水中为50-55微克−-1，在极地表层水/暖极表层水中为40-45微克克−-1，在较深水层中为10-35微克克−-1，最低浓度在底层。通过弗拉姆海峡的净通量表明，∼0.4PGC DIC和∼0.01PGC yr−1人为碳从北冰洋净流出到北大西洋，尽管存在很高的不确定性。
The storage of anthropogenic carbon in the ocean's interior is an important process which modulates the increasing carbon dioxide concentrations in the atmosphere. The polar regions are expected to be net sinks for anthropogenic carbon. Transport estimates of dissolved inorganic carbon and the anthropogenic offset can thus provide information about the magnitude of the corresponding storage processes. Here we present a transient tracer, dissolved inorganic carbon (DIC) and total alkalinity (TA) data set along 78°50′ N sampled in the Fram Strait in 2012. A theory on tracer relationships is introduced, which allows for an application of the inverse-Gaussian–transit-time distribution (IG-TTD) at high latitudes and the estimation of anthropogenic carbon concentrations. Mean current velocity measurements along the same section from 2002–2010 were used to estimate the net flux of DIC and anthropogenic carbon by the boundary currents above 840 m through the Fram Strait. The new theory explains the differences between the theoretical (IG-TTD-based) tracer age relationship and the specific tracer age relationship of the field data, by saturation effects during water mass formation and/or the deliberate release experiment of SF6 in the Greenland Sea in 1996, rather than by different mixing or ventilation processes. Based on this assumption, a maximum SF6 excess of 0.5–0.8 fmol kg−1 was determined in the Fram Strait at intermediate depths (500–1600 m). The anthropogenic carbon concentrations are 50–55 µmol kg−1 in the Atlantic Water/Recirculating Atlantic Water, 40–45 µmol kg−1 in the Polar Surface Water/warm Polar Surface Water and between 10 and 35 µmol kg−1 in the deeper water layers, with lowest concentrations in the bottom layer. The net fluxes through the Fram Strait indicate a net outflow of ∼ 0.4 DIC and ∼ 0.01 PgC yr−1 anthropogenic carbon from the Arctic Ocean into the North Atlantic, albeit with high uncertainties.