Freshwater budget and salinity variability in the subpolar and subtropical gyres of the North Atlantic

直到最近几年，盐度和淡水分布变化的研究由于缺乏观测的时间和空间分辨率而受到阻碍，因此只能通过平均5年以上的时间来研究盐度异常。随着ARGO方案的启动，盐度剖面的数量急剧增加，从1999年该方案开始到2014年4月，在全球海洋中收集了190万条ARGO剖面。整个ARGO阵列在2005-2007年左右在北大西洋就位。尽管作出了这一努力，但空间和时间覆盖范围不足以详细确定北大西洋次极地的盐度变化。我们利用Argo剖面研究了盐度剖面与动态高度之间的关系。动态高度也是通过高度计测量的，自1992年以来一直有高质量的数据可用。因此，结合ARGO浮标和高度计数据，我们可以将高采样的时间段(大约从2005-2007年开始)延长到过去，直到1992年高度计测量的开始。在第一阶段，利用ARGO资料和测高技术建立了高空间分辨率(0.25×0.25格点)和时间(日)分辨率的盐度时间序列(1992-2012)。为了计算当地淡水通量对盐度变化的影响，更新后的HOAPS 3气候学HOAPS 3.3于2015年5月面世并得到应用。继续提案的目标以第一阶段的结果为基础，包括：(1)利用观测(ARGO、CTD、高度计)、高分辨率(1/24)模式、GECCO2合成结果(TP 3.1)和更新的HOAPS气候学结果(TP 2.1)，分析区域含盐量的月至多年变化，以及淡水通量和涉及的过程。分别计算了700m以上和混合层表层淡水通量的变化和影响。(Ii)研究锋面、曲流和涡旋的表层和次表层结构的演变和变异性，计算涡旋中的盐度异常，跟踪盐度异常沿其路径并评估所涉及过程的作用；(Iii)计算700m高空，特别是进入亚极地西大西洋和穿过MAR进入东大西洋的涡旋盐度输送的时间序列，以及(Iv)检查盐度重建在东北大西洋浅于1900m深度区域是否有效，并检验通过增加卫星对表层盐度的观测，盐度剖面重建的质量是否有所改善。

Up to recent years, the study of salinity and freshwater distribution changes was hampered by the lack of temporal and spatial resolution of the observations, so that salinity anomalies could only be studied by averaging over 5 years. With the onset of the Argo programme, the number of salinity profiles dramatically increased, and 1.9 million Argo profiles were collected in the global ocean between the onset of the program in 1999 and April 2014. The full Argo array was in place in the North Atlantic around 2005 - 2007. Despite this effort, the spatial and temporal coverage is not sufficient to identify salinity variations in detail in the subpolar North Atlantic. We used the Argo profiles to exploit the relation between the salinity profiles and dynamic height. Dynamic height is also measured by altimetry, and high quality data are available since 1992. A combination of Argo floats and altimeter data thus allowed us to extend the time period with high sampling (starting about 2005-2007) into the past till 1992, the onset of the altimeter measurements. In the first phase, high spatial (0.25 x 0.25 grid) and temporal (daily) resolution salinity time series (1992-2012) in the upper 700m were constructed using Argo data and altimetry. To calculate the influence of local freshwater fluxes on the salinity changes, the updated HOAPS 3 climatology HOAPS 3.3 became available in May 2015 and was applied. The objectives of the continuation proposal are based on the results of the first phase, and are (i) Analyse the monthly to multiannual variability in the regional salinity contents, together with freshwater fluxes and involved processes using observations (Argo, CTD, altimeter), a high resolution (1/24) model, results from the GECCO2 synthesis (TP 3.1) and from the updated HOAPS climatology (TP 2.1). Calculate content changes and influence of surface freshwater fluxes for upper 700m and separately for the mixed layer. (ii) Study the evolution and variability of surface and subsurface structures of fronts, meanders, and eddies, calculate salinity content anomalies in eddies, follow salinity anomalies along their pathways and assess the role of the involved processes (iii) Calculate time series of eddy salinity transports in the upper 700m, especially into the subpolar western Atlantic and across the MAR into the eastern Atlantic, and (iv) check whether the salinity reconstructions are valid in regions shallower than 1900m depth in the Northeast Atlantic, and test whether the quality of the reconstructions of the salinity profile improve by adding satellite observations of surface salinity.