Dissolved inorganic carbon, pH, temperature, salinity and other variables collected from time series and surface observations using Moored Autonomous Dissolved Inorganic Carbon (MADIC) System, Sunburst SAMI2 pH sensor, and other instruments from Kewalo Buoy near the coast of Honolulu, Hawaii from 2

To expand the number of tools available for autonomous carbonate system observations, we have developed a robust surface ocean dissolved inorganic carbon (DIC) sensor capable of extended (>year) field deployments with a laboratory determined uncertainty of plus/minus 5 umol kg-1. The prototype sensor was deployed off shore of Honolulu, Hawaii for seven months on a moored buoy equipped with a Sea-Bird Electronics CTD and SAMI pH sensor unit. The buoy was deployed ~25m from an existing CO2 buoy, which allowed us to over constrain the carbonate system and thoroughly evaluate the performance of the prototype DIC sensor. In addition, 51 discrete bottle samples were collected throughout the seven month deployment and analyzed for DIC via coulometry. Results from this field test confirm that direct measurement of DIC is ~90% more accurate than estimates of DIC calculated from contemporaneous and collocated measurements of pH and CO2. The improved accuracy from directly measuring DIC gives rise to new opportunities for quantitative, autonomous carbon cycle studies.

为扩充可用于自主式碳酸盐系统观测的工具库，我们研发了一款性能稳健的表层海水溶解无机碳（dissolved inorganic carbon, DIC）传感器，该传感器可实现超过一年的野外长期部署，实验室标定的测量不确定度为±5 μmol kg⁻¹。该原型传感器曾在夏威夷檀香山近海部署，搭载于配备海鸟电子（Sea-Bird Electronics）CTD与SAMI pH传感器组件的锚定浮标上，野外部署时长共计7个月。该浮标部署于距现有CO₂浮标约25米处，这使得我们能够对碳酸盐系统进行过度约束，从而全面评估这款原型DIC传感器的性能表现。此外，在这7个月的部署周期内，我们共采集了51份离散瓶采样样品，并通过库仑分析法对样品中的DIC含量进行了测定。本次野外测试结果证实，直接测量DIC的精度较通过同步同址获取的pH与CO₂测量值推算得到的DIC估算值高约90%。通过直接测量DIC获得的精度提升，为定量自主式碳循环研究开辟了全新机遇。