Temperature–salinity distribution in the northeastern Atlantic from ship and Argo vertical casts

摘要

The present study defines new interpolation functions for hydrological data.These functions are applied to generate climatological maps oftemperature–salinity distribution with a 25 m depth interval and a 30 kmspace interval (MEDTRANS data set). The data undergo rigorous initialdata quality control, having passed several filtering procedures. Thegridding is done on neutral density surfaces, which allows betterrepresentation of thermohaline fronts for the same gridding radius. Themulti-pass Barnes optimum interpolation procedure with spatially variablesize of the gridding window is used. The shape of the window accounts for thedominant along-isobath direction of water mass transport over steeply slopingtopography. A local ratio of topographic to planetary β-effects isused to define the shape of the window as a function of the relativeimportance of the topographic influence. The N/f ratio is applied toaccount for the baroclinic compensation decay of the topographic influence onwater mass transport with the distance from the bottom. The gridded fieldsare available at the website of the Centre of Oceanography of the Universityof Lisbon (href="http://co.fc.ul.pt/en/data"target="_blank">http://co.fc.ul.pt/en/data).The MEDTRANS climatology gives more details of the distribution ofwater characteristics in the subtropical northeastern Atlantic than otheralternative climatologies and is able to reproduce a number of dynamicfeatures described in the literature: the acceleration in the meanders of theAzores current; the cyclonic gyre in the Gulf of Cadiz; and the splitting andseparation of the Mediterranean Water (MW) outflow in two veins near theGorringe and Galicia banks. Seasonal climatologies, computed for the warm(May–October) and cold (November–April) seasons, reveal stronger zonalextension of the upper ocean patterns during the warm season, as compared tothe cold one.