Estuarine dynamics
Estuaries comprise of the region within coastal water bodies where terrestrial fresh water interacts with oceanic salt water. Classically, the turbulent mixing between these water masses results in an inflow of saline water and an outflow of fresh water – the estuarine circulation or exchange flow. This basic circulation is a wide-spread phenomenon of the coastal ocean, occurring in river mouths, underneath floating glaciers and even in the Baltic Sea as a whole. Under certain conditions, such as in regions with intense evaporation, with a strong wind-driven circulation or ice cover, the classical circulation pattern may be altered or even inverted.
In our group, we investigate and quantify the underlying hydrodynamic processes and their interactions, using analytical theory, numerical modeling, and observational methods. Our numerical simulations cover a wide range of estuaries from highly idealized to complex and realistic, and we actively partake in the development of new analysis methods.
A core topic is the study of the exchange flow and its link to turbulent salt mixing via water mass transformation. To this end, we often make use of the Total Exchange Flow (TEF) analysis framework which allows to consistently quantify the estuarine circulation and the related estuarine mixing in terms of Knudsen bulk values. We also apply water mass transformation theory to understand exchange and mixing in isohaline coordinates, which supports the interpretation of estuaries and river plumes as one continuous functional unit.
In addition to the estuarine circulation and mixing, we further investigate estuarine sediment transport, river plume dynamics including plume-plume interaction, physical drivers of oxygen deficiency in estuaries, and, as a topic of high economic and ecological relevance, the salt intrusion into river estuaries. To support the international collaboration and research on this topic, we actively participate in the SCOR Working Group 172 on salt intrusion bringing together experts around the world.
Selected publications
Burchard, H., A universal law of estuarine mixing. J. Phys. Oceanogr., 50, 81-93, 2020.
Muche, Y., K. Klingbeil, M. Lorenz, A.E. Yankovsky, H. Burchard, Numerical investigation of the influence of wind and tides on salt mixing and cross-shore transport in river plumes, J. Geophys. Res.: Oceans, accepted for publication.