The School of Earth and Atmospheric Sciences Presents Dr. Nathan Paldor, Hebrew University of Jerusalem

A Lagrangian Formulation of Knudsen (1900)’s Relations and its Applications to Surface Currents

The conservation of water mass (or volume if the density is uniform) and the mass of salt are the basis of the relations developed by Knudsen in 1900 for estimating the flows into, and out of, fixed volumes in space e.g. fixed depth ranges in fjords or semi-enclosed ocean basins. For over a century the relations were applied as a very basic tool of descriptive Physical Oceanography that explains phenomena such as the high salinity in the Mediterranean Sea and the Red Sea. Recently, a simple version of the relation was adapted to oceanic currents by formulating it in Lagrangian coordinates. The Lagrangian counterpart of Knudsen relations can be combined with reanalysis sea surface salinity data such as that archived in Simple Ocean Data Assimilation (SODA) to elucidate general features of ocean currents.

In my talk I will present the central features of the new theory and apply it to two ocean currents: The Irminger Current (IC) that flows around Greenland and the westward surface currents in the equatorial ocean. In the case of the salty IC the theory yields quantitative estimates of the difference between the entrainment rates of surrounding fresher water east and west of Greenland. In the case of the westward equatorial surface flows the theory provides indicators of the flows that are much more robust and reliable than direct velocity or wind data.