A high-resolution study of Thorium isotopes in relation to the cycling of other trace elements in the Southern Ocean

天然放射性核素是海洋运输过程的强大示踪剂。在国际极地年活动广泛的世界海洋中微量元素和同位素循环的大型国际研究机构GEOTRACES的框架下，我们建议确定Th同位素231Pa227Ac沿零子午线和德雷克海峡的高分辨率分布。这次采样是与与RV Polarstein一起考察的一个国际地球化学家团队对其他微量元素的采样协调进行的。这种联合采样使我们能够直接将我们将从钍同位素和231PA的分布中获得的关于颗粒动力学(聚集、解聚和颗粒沉降率)和陆源输入的信息应用于其他示踪剂的运输。同样，我们将能够面对关于水团通风和上升流的结果，因为我们将从230th/231pa和227Ac分布、水文数据以及从平行提案中描述的其他示踪剂(Nd/Hf同位素；氟利昂和氦同位素)得出的结论得出结论。这些数据将与(反向)GCM模型中的其他示踪剂数据一起解释。我们预计，这种方法将提高我们使用一套示踪剂作为过去海洋气候更可靠指标的能力。

Natural radionuclides are powerful tracers for the rate of transport processes in the ocean. In the framework of GEOTRACES, a large international study on the cycling of trace elements and isotopes in the world ocean with extensive activities in the International Polar Year, we propose to determine the high-resolution distribution of Th isotopes, 231Pa and 227Ac along the Zero meridian and in the Drake Passage. The sampling has taken place in coordination with sampling of other trace elements by an international team of geochemists on an expedition with RV Polarstern. This joint sampling allows us to directly apply the information on particle dynamics (aggregation, disaggregation and particle sinking rates) and terrigenous input that we will obtain from the distribution of thorium isotopes and 231Pa, to the transport of other tracers. Similarly, we will be able to confront the results on water mass ventilation and upwelling, as we will derive from 230Th/231Pa and 227Ac distributions, with hydrographic data and the conclusions drawn from other tracers described in parallel proposals (Nd/Hf isotopes; freons and He isotopes). The data will be interpreted along with other tracer data in (inverse) GCM models. We expect that this approach will improve our ability to use a set of tracers as more reliable proxies for past ocean climate.