Surface-to-bottom total alkalinity, inorganic carbon and CTD data in coastal areas leeward of the Macaronesia archipelagos during POS533

Surface-to-bottom seawater sampling for total alkalinity (AT), total inorganic carbon (TIC) and dissolved oxygen determination were performed in archipelagic coastal waters of the Macaronesia region during the POS533 cruise (from February 28 to March 19, 2019) on board the RV Poseidon. The Macaronesia region show a high variability due to its location in a coupling area between the Canary Upwelling System along the Northwest African coast and the oligotrophic open-ocean waters of the Northeast Atlantic subtropical gyre and the influence of the island interaction with the Canary Current. Thus is a key zone in terms of CO2 distribution, natural and anthropogenic carbon inventory and air-sea exchange and requires the develop of regional-scale field studies. The water-column sampling was carried out in leeward coastal stations located in the archipelagos of Cape Verde, Canary and Madeira, as well as in the Cape Verde Ocean Observatory (CVOO) and the European Station for Time-Series in the Ocean of the Canary Islands (ESTOC). A bottle rosette sampler containing twelve 10 L Niskin bottles was used for depth water sampling. The obtained dataset includes temperature, salinity, AT, TIC and dissolved oxygen. The temperature and salinity were monitored by using a CTD placed in the rosette. The AT and TIC was determined on board from the depth water samples using a VINDTA 3C and following Mintrop et al., (2000). Samples were potentiometrically titrated with HCl for AT determination, while TIC was coulometrically determined. Both AT and TIC values were corrected using certified reference material (CRM) bottles (batch 177, provided by A. Dickson at Scripps Institution of Oceanography), giving values with an accuracy of ±1.5 and ±1.0 µmol kg-1, respectively. The dissolved oxygen was determined from the seawater samples collected in pre-calibrated glass wide neck bottles by using the WINKLER method, introduced by Winkler (1888) and optimized by Carpenter (1965) and Carrit and Carpenter (1966). A Metrohm 888 Titrando operated with the software Tiamo and an amperometric electrode to determine the end point was used for the titration (Culberson and Huang, 1987). These in-situ collected data improve the knowledge about the biogeochemistry in eastern boundary transitional areas and allows a better understanding of the role in the climate change of archipelagic waters, coastal regions and island/continental shelves. The provided datasets can be used in further biogeochemical studies in the Macaronesia region and in the entire Northeast Atlantic. The monitoring and data collection received fundings from the Atmosphere-Ocean-Islands-Biogeochemical interactions in the Macaronesian Archipelagos of Cabo Verde, the Canaries and Madeira project (AIMAC project) and the European Union's Horizon 2020 research and innovation program under grant agreement Nº 820989 (COMFORT project). In this case, the measurements complemented those done for iron study (Santana-Casiano and Quack, 2021).

本数据集基于2019年2月28日至3月19日POS533航次的野外调查数据，调查团队搭乘RV Poseidon号研究船，在马卡罗尼西亚（Macaronesia）群岛沿岸海域开展了从表层至海底的海水采样工作，用于测定总碱度（total alkalinity, AT）、总无机碳（total inorganic carbon, TIC）与溶解氧（dissolved oxygen）。
马卡罗尼西亚海域地处西北非洲沿岸加那利上升流系统与东北大西洋亚热带环流寡营养开阔大洋水域的交汇耦合区，同时受岛屿与加那利海流相互作用的影响，因此其环境变量具有高度变异性。该海域是研究二氧化碳分布、自然与人为碳储量以及海-气交换过程的关键区域，亟需开展区域尺度的野外调查研究。
本次水柱采样工作覆盖了佛得角、加那利与马德拉群岛的背风沿岸站位，同时包含佛得角海洋观测站（Cape Verde Ocean Observatory, CVOO）以及加那利群岛海洋长期观测欧洲站（European Station for Time-Series in the Ocean of the Canary Islands, ESTOC）。
采样过程采用搭载12个10升尼斯金（Niskin）采水器的采水器架（bottle rosette sampler）完成分层海水采样。本次获取的数据集包含水温、盐度、总碱度（AT）、总无机碳（TIC）与溶解氧（dissolved oxygen）数据。
水温与盐度通过安装在采水器架上的CTD（温盐深仪）进行原位监测。总碱度（AT）与总无机碳（TIC）的现场测定基于分层海水样品，使用VINDTA 3C分析仪完成，实验方法参照Mintrop等人（2000）的研究。其中总碱度（AT）采用盐酸（HCl）电位滴定法测定，总无机碳（TIC）则采用库仑法测定。
总碱度与总无机碳的测定值均通过标准参考物质（certified reference material, CRM）瓶（批次177，由斯克里普斯海洋研究所的A. Dickson提供）进行校准，最终测定的准确度分别为±1.5 µmol kg⁻¹与±1.0 µmol kg⁻¹。
溶解氧的测定采用温克勒法（WINKLER method），基于预先校准的广口玻璃采水瓶采集的海水样品完成，该方法由Winkler于1888年提出，并经Carpenter（1965）以及Carrit与Carpenter（1966）优化。本次滴定采用搭载Tiamo软件的Metrohm 888 Titrando滴定仪以及安培电极判定滴定终点，实验方法参照Culberson与Huang（1987）的研究。
本次原位采集的数据提升了我们对东部边界过渡海域生物地球化学过程的认知，有助于进一步理解群岛水域、沿岸区域以及岛屿/大陆架在气候变化中发挥的作用。本数据集可应用于马卡罗尼西亚海域乃至整个东北大西洋区域的后续生物地球化学研究。
本次监测与数据采集工作得到了"佛得角、加那利与马德拉马卡罗尼西亚群岛大气-海洋-岛屿生物地球化学相互作用"项目（AIMAC项目）以及欧盟地平线2020研究与创新计划（资助协议编号Nº 820989，COMFORT项目）的资助。本次测定数据补充了Santana-Casiano与Quack（2021）针对铁元素研究的相关观测结果。