Two cruises, one in May 1999 and the second in January 2000 will sample upper ocean and atmospheric boundary layer variability in the Japan/East Sea. The spring cruise will focus on studying frontal dynamics, characterizing bio-optical variability associated with the spring phytoplankton bloom and documenting the location, range and properties of water masses formed at the subpolar front during the preceding winter. The wintertime cruise will focus on documenting the upper ocean response to cold air outbreaks with particular attention to processes associated with water mass formation and subduction at the subpolar front. Both cruises will employ a towed, undulating profiler (SeaSoar) to make highly-resolved observations of the upper ocean. We will use real-time remotely sensed sea surface temperature and ocean color images (R. Arnone, NRL and scientists from the Korean Ocean Research and Development Institute, KORDI) to determine the location of the subpolar front and to select intensive survey locations. Real-time access to remotely sensed imagery will allow us to modify our sampling in response to changes in the front. Repeated intensive grid surveys will provide approximately synoptic, three-dimensional coverage while a sequence of longer sections will document oceanic and atmospheric boundary layer variability away from the front. In addition to the suite of physical and bio-optical sensors carried by SeaSoar, we will use a shipboard Acoustic Doppler Current Profiler (ADCP) and GPS navigation to measure upper ocean currents. We will also perform a limited number of hydrographic and bio-optical stations off the Korean coast and across the subpolar front. Professor S. Yang (Kwangju University) will perform additional biological and bio-optical sampling (e.g. nutrient analysis, primary production, pigments).
SeaSoar
• Continuous vertical profiles from the surface to 350 m towing at 8 knots.
• Along-track horizontal resolution of 3 km.
• Dual Seabird temperature and conductivity sensors
• Chlorophyll fluorescence
• Light transmission
• Fast-response oxygen sensor
• Photosynthetically available radiation (PAR)
• Bioluminescence
• Spectral absorption and attenuation (Wetlabs HiStar, 100 bands at 3.3 nm resolution)
• Backscatter (Hobilabs HiStar, 6 wavelength bands)
Hydrographic Casts
• Temperature, salinity, chlorophyll fluorescence, light transmission, PAR, dissolved oxygen, nutrients, pigment concentrations, primary production (N15 method).
Optical Casts
• Spectral absorption and attenuation (Wetlabs HiStar and AC-9), upwelling and downwelling irradiance (Satlantic), PAR.
Shipboard Sensors
• 150 khz narrowband ADCP (velocity to 350 m)
• Pulse-coded doppler sonar system (January 2000 only, velocity to 1500 m)
• P-code GPS
• GPS heading (Ashtech)
• Flow-through system with near-surface temperature, conductivity and spectral absorption and attenuation (Wetlabs AC-9).
Meteorological Measurements
• Shipboard Improved Meteorology Sensors (IMET) 15 m above the sea surface measuring wind velocity, air temperature, sea surface temperature, relative humidity, air pressure, short- and long-wave radiation and rainfall.
• Additional wind velocity, air temperature, relative humidity and air pressure sensors at 10.8 m, 8.4 m and 22.7 m above the sea surface.
• Sonic anemometers for boundary layer turbulence.
• Atmospheric soundings using GPS sondes. Vertical profiles of temperature, humidity, pressure and wind velocity.
Satellite Characterization
• Real-time thermal and ocean color imagery.
• Underway absorption, scattering and attenuation measurements.
• Remote sensing reflectance.