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.

The ocean surface mixed layer depth (MLD) is an important parameter within several research disciplines, as variations in the MLD influence air-sea CO₂ exchange and ocean primary production. A new method is presented in which acoustic mapping of the MLD is done remotely by means of echo sounders. This method allows for observations of high-frequency variability in the MLD, as horizontal and temporal resolutions can be increased by orders of magnitude compared to traditional in situ measurements.