delta13C DIC measurements in the Arctic Ocean

Stable carbon isotopes of Dissolved Inorganic Carbon (d13CDIC) in the ocean are generally not well understood as they are governed by a complex interplay of biological processes and air-sea exchange. In the Arctic Ocean d13CDIC values are prone to change in the near future with rapidly changing climate conditions. This study provides a baseline to assess the d13CDIC of the Arctic Ocean with a focus on upper to intermediate waters (to ~500 m). Measured d13CDIC values in the Arctic Ocean range from ~ -1 to +2 per mill. In the Eurasian Basin the d13CDIC values lie between ~1 to 1.5 per mill and exhibit little variation within the upper layers. In the Canada Basin d13CDIC values reach 2 per mill in the surface layer, with lowest values of ~ 1 per mill found at ~200 m water depth. At greater depth d13CDIC values range from ~1 to 1.5 per mill within both basins. In the Canada Basin nutrient levels are higher than in the Eurasian Basin and associated variations in d13CDIC are clearly related to biological processes. However, low d13CDIC values in the Canada Basin are also strongly influenced by air-sea exchange processes. The different d13CDIC patterns between the Canada Basin and the Eurasian Basin appear to be linked to differences in transport processes within the Arctic Ocean halocline. The upper layers in the Canadian Basin have direct contributions of waters from the Laptev, East Siberian and Chukchi shelves, which contain elevated fractions of river waters and sea-ice related brines; whereas their counterparts, in the Eurasian Basin, are mostly formed by halocline waters from the Barents and Kara seas. River waters have low d13CDIC of ~ 8 per mill on average, but in the Arctic basins this signal is lost and low d13CDIC values show no correlation to river water fractions contained in the water mass. Also no relation between d13CDIC and sea-ice related brine contribution is apparent.海洋中溶解无机碳（Dissolved Inorganic Carbon，d13CDIC）的稳定碳同位素组成因受生物过程与海-气交换的复杂交互作用调控，其分布特征长期以来尚未得到充分阐释。北冰洋的d13CDIC值随气候条件快速变化，在近期易发生显著改变。本研究以北冰洋上层至中层水体（约500米以浅）为研究重点，构建了评估该海域d13CDIC分布的基准基线。 实测北冰洋d13CDIC值范围约为-1‰至+2‰。其中欧亚海盆的d13CDIC值介于~1‰至1.5‰之间，且上层水体的变化幅度极小。加拿大海盆表层水体的d13CDIC值可达2‰，而在约200米水深处则出现约1‰的最低值；在两个海盆的更深层水体中，d13CDIC值均维持在~1‰至1.5‰的区间内。 加拿大海盆的营养盐水平高于欧亚海盆，与之相关的d13CDIC变化显著受生物过程调控。不过加拿大海盆内的低d13CDIC值同时也受到海-气交换过程的强烈影响。加拿大海盆与欧亚海盆之间的d13CDIC分布差异，似乎与北冰洋盐跃层内的输运过程差异有关。加拿大海盆的上层水体直接源自拉普捷夫海、东西伯利亚海及楚科奇陆架的水体，这些水体富含河流水与海冰相关卤水；而欧亚海盆的上层水体则主要由巴伦支海与喀拉海来源的盐跃层水体形成。 河流水的平均d13CDIC值约为-8‰，但在北冰洋海盆中该特征信号已消失，低d13CDIC值与水体团中的河流水占比无明显相关性；同时，d13CDIC与海冰相关卤水贡献量之间也未呈现显著关联。