In-situ observations were conducted onboard the Korean icebreaker Araon in the Chukchi borderlands during two summer cruises: from August 2 to 16, 2011 at 18 stations, and from August 5 to 20, 2015 at 27 stations. Vertical profiles of temperature, salinity, fluorescence, and irradiance were obtained using the CTD and profiling radiometer.A profiling Reflectance Radiometer (PRR) system (Biospherical Instruments, USA) was used for optical sampling, which consists of an underwater profiler PRR-800 and a surface reference radiometer PRR-810. The sampling frequency of the PRR is 5 Hz, and the lower limit of irradiance detection reaches 10−5 μW/(cm2·nm). The PRR measures 18 bands from 305–875 nm, and the bandwidth is 10 nm. A compact CTD (Alec Electronics, Japan) was deployed together with PRR-800 and is equipped with temperature, salinity, pressure and fluorescence sensors.