Ocean Circulation and Climate Dynamics

Physical Key Processes

Ocean mixing

Average distribution of the dissipation rate of turbulent kinetic energy at the sill within the rift valley determined from several AUV missions. From Tippenhauer et al. (2015).

Small-scale mixing processes are an essential component of the ocean circulation and the ocean‘s climate. Mixing processes transport heat, salt and other dissolved substances between layers of different densities. The associated diapycnal heat flux is an important driver of the meridional overturning circulation and impacts heat ... more

 

 

Convection and Transformation of Watermasses

Time series of the thermal development in the top 1800 m in the main convection zone of the North Atlantic, the Labrador Sea. The convection of colder and heavier surface waters is clearly present during the winter months. However, a general warming trend and absence of deep-reaching convection during the later years of this time series are also evident.

The ocean is a stratified medium, which means that certain characteristic properties, such as temperature, salinity, dissolved oxygen or the greenhouse gas carbon dioxide, change with depth and geographic position. One of the objectives of physical oceanography is to develop an exact understanding of the physical processes which cause the observed distributions of those key properties in the ocean. Such an understanding is necessary to ... more

Physical processes in upwelling regions

The sea surface temperature (SST) in the Peruvian upwelling regime observed by MODIS Aqua with 1 km horizontal resolution is shown on the left. A zoom into the near-surface temperature field associated with a submesoscale filament observed by a glider is shown on the right.

Meso- and submesoscale variability in tropical upwelling regimes

Tropical upwelling regimes are characterized by pronounced meso- and submesoscale variability such as eddies and filaments. Understanding these phenomena is crucial as they cause horizontal and ... more

 

 

Ventilation of oxygen minimum zones

Mean zonal velocity (top, a) and oxygen content (bottom, b) as obtained from meridional ship sections taken between 28.5° and 23°W during 1999-2008. Eastward current bands, marked by reddish colors, are generally associated with elevated oxygen content (bottom). Grey lines mark neutral densities (Brandt et al. 2010).

Regions with low dissolved oxygen content in the ocean exist in the eastern tropical Pacific and Atlantic as well as in the northern Indian Ocean. Models proposed and observations showed changes in the expansion of oxygen-poor regions, especially a vertical expansion concurrently with decreasing oxygen content. The future ocean may experience major biogeochemical shifts triggered by oxygen changes leading to positive ... more