The new gridded WOCE-Argo Global Hydrographic Climatology (WAGHC) is described and compared with the NOAA WOA13 atlas. The monthly fields of temperature and salinity for 65 depth levels have a 1/4° spatial resolution. Two versions of the climatology were produced and differ with respect to the spatial interpolation performed on isobaric or isopycnal surfaces, respectively. The climatology characterizes the thermohaline state of the world ocean for the time period from 2008 to 2012.

Two types of marine geoid exist with the first type being the average level of sea surface height if the water is at rest (classical definition), and the second type being satellite-determined with the condition that the water is usually not at rest. The associated absolute dynamic ocean topography (DOT) also has two types. Horizontal gradients of the two DOTs are different with the 1st (2nd) type representing the absolute (relative) surface geostrophic currents.

The Western Valley is one of the passages across the Iceland–Scotland Ridge through which a strong overflow of cold, dense water has been thought to feed the deep limb of the Atlantic Meridional Overturning Circulation (AMOC), but its strength has not been known. Based on a field experiment with instruments moored across the valley, we show that this overflow branch is much weaker than previously thought and that this is because it is suppressed by the warm countercurrent in the upper layers.

Results from a high-resolution ocean model show that during the strong El Niños of 1983 and 1998, transport of warm water in the equatorial Pacific was dominated by the North Equatorial Counter Current and not by equatorial Kelvin waves. The results show why the NECC fails to do this in most years and how stronger than normal annual Rossby waves near the Equator can both trigger the El Niño in the western Pacific and help to ensure that the warm water arrives off South America around Christmas.

The study finds that changes in seawater temperature due to El Niño and La Niña, anomalous warm and cold events, are in principle detectable by means of the oceanic tidally induced magnetic field. Furthermore, subsurface processes in the onset of those anomalous events lead the surface processes by several months. This causes a lead in the oceanic tidally induced magnetic field signals over sea-surface temperature signals.