Kuroshio Extension System Study (KESS)
|The Kuroshio Extension System Study (KESS) consisted of a high-resolution in situ instrument array comprised of a line of moorings across the Kuroshio jet to measure the time-varying velocity, temperature and salinity at various levels in the vertical, profiling floats (not shown), and an array of bottom-sitting echo sounders to map the structure of the dynamic density and velocity fields above. (E. Paul Oberlander)|
|Recovering the KESS moorings aboard the R/V Melvile in May 2006.|
The Kuroshio Extension System Study (KESS) is a large multi-institutional, international investigation of the Kuroshio Extension supported by the National Science Foundation that was undertaken in the spring of 2004. It involved an ambitious deployment of state-of-the-art instruments for a period of two years with the goal of identifying and quantifying the dynamic and thermodynamic processes governing the intense meandering and eddy variability of the KE and the interaction between the KE and its recirculation gyre.
The Kuroshio, like the Gulf Stream its North Atlantic equivalent, is one of the most energetic current systems in the world and is a dominant feature of the North Pacific circulation. A key branch of the oceanic transport of heat from the equator to the pole, it plays a fundamental role in the global climate system. The position of the current defines the location of one of the most intense air sea heat exchange regions on the globe, where the warm Kuroshio waters encounter the cold dry air masses coming from the Asian continent, and as such, its variations play an important role in steering storm tracks across the North Pacific. In this way, it strongly affects North American climate.
In order to better understand the processes that govern the intense meandering of the Kuroshio jet and the net effect of that variability on the time-mean system, a large-scale, two-year sea-going observational program was performed at the downstream location of the jet's highest variability. The Kuroshio Extension System Study (KESS) consisted of a high-resolution in situ instrument array comprised of a line of moorings across the jet to measure the time-varying velocity, temperature and salinity at various levels in the vertical, profiling floats, and an array of bottom-sitting echo sounders to map the structure of the dynamic density and velocity fields above. By combining these measurements with satellite data, the study provided a unique opportunity to observe the relation between surface fields and motions below the surface. The measurements obtained allow the examination of the dynamical balances of heat, salt, momentum and other physical properties throughout the water column both in an instantaneous and a longer time-mean picture.
My particular interest in the Kuroshio system is how the jet and its variability interact. The hypothesis is that these eddy-mean flow interactions are of first order importance in 1. altering the strength, structure and stability of the mean jet; 2. forcing the jet's flanking recirculations; 3. driving deep abyssal motions and 4. modulating the low-frequency variability observed in the system. As such, understanding the relationship between the time-varying and time-mean components of the circulation is a necessary part of our overall picture of the Kuroshio, and western boundary current jet systems in general. I work towards this understanding through a combined approach of the analysis of the observational data together with both the study of a general circulation model in the Kuroshio region and numerical experiments with a highly-simplified dynamical model.
Learn more about the KESS experiment and some of its early results at uskess.org.
Read a general discussion about the theoretical aspect of KESS, with which I am involved.
See a non-technical poster describing KESS and my work on eddy-mean flow interactions in the Kuroshio Extension presented at the WHOI Board of Trustees meeting in 2007.
See slides from a more technical presentation describing how KESS observations relate to theoretical studies of eddy-mean flow interactions in unstable jets presented at the European Geosciences Union General Assembly