Energy does not "vanish"

The TRR 181 Vorstand (left to right): Speaker Prof. Carsten Eden, Prof. erich Becker, Deputy speaker Prof. Monika Rhein, Prof. Hans Burchard, Prof. Jin-Song von Storch, PhD/Postdoc representative Dr. Brenda Quinn and Prof. Marcel Oliver. Missing is Prof. Valerio Lucarini. (UHH/CEN/M. Ruhnau)

The energy of a closed system is steady. It is not lost but rather converted into other forms, such as when kinetic energy is transferred into thermal energy or vice versa heat results in a force.

However, this fundamental principle of natural science is often still a problem for climate research.  For example, in case of the calculation of ocean currents, where small-scale vortices as well as mixing processes they induce need to be considered, without fully understanding where the energy for their creation originates from. This is similar in the atmosphere, the only difference being that air is moving instead of water. Again, local turbulences can drive larger movements or vice versa waves on a larger scale can disintegrate into small structures. All these processes are important for the Earth’s climate and determine how temperatures will rise in the future.

How exactly the energy transfer between waves, eddies and local turbulences in the ocean and the atmosphere works, often remains unclear. The interdisciplinary project „Energy Transfers in Ocean and Atmosphere“ wants to change this: oceanographers, meteorologists and mathematicians from Hamburg, Bremen and Rostock work closely together to achieve this goal (see participating institutions). The aim is to develop energetically consistent mathematical models and thus enhance climate analyzes and forecast accuracy. The project is funded by the German Research Foundation.

Three types of structures, called dynamical regimes, exist:

  • small scale turbulence (from the smallest scales up to a few meters),
  • internal gravity waves (a few meters up to hundreds of kilometers),
  • and geostrophically balanced currents (a few kilometers up to thousands).

For the latter, the Earth's rotation and the resulting geostrophic balance plays a crucial role. Each of these three are very similar in the ocean and atmosphere, but follow different laws of physics – they originate and vanish through different ways – and are connected by a variety of complex processes. The transfer of energy between the regimes is fundamental for the global energy cycle in atmosphere and ocean.