Three Dimensional Pseudovorticity Field in the West Spitsbergen Current

摘要

Dynamical features of polar oceans, captured by traditional treatment of hydrographic data sets, are only two fields: dynamical height of sea surface relative to certain depth, and geostrophic currents by assuming a certain level of no motion. Much information about the polar water is lost by such a treatment. In fact, the ocean flow is not purely geostrophically balanced. It contains two parts: geostrophic currents and ageostrophic circulations. The geostrophic currents are obtained from the hydrographic data sets (traditional physical oceanographic treatment), and the ageostrophic circulation is forced the geostrophic flow (called the geostrophic forcing) and surface wind field. Therefore, the three-dimensional circulation (both geostrophic and ageostrophic) can also be calculated by the hydrographic and surface wind data sets. There are potentially significant errors with the traditional treatment of the hydrographic data (e.g., only computing geostrophic currents), particularly in regions having strong temperature and salinity gradient, such as in the west Spitsbergen current. Neither geostrophic current nor dynamical height can provide detail information about the three- dimensional flow field near the west Spitsbergen current. In order to diagnose the three dimensional flow field, a new theory should be adapted.