Water columns properties measured by CTD sensors during seasonal cruises in the Gulf of Alaska for the Northern Gulf of Alaska LTER project, 2018 and 2019

This data set contains measurements of water properties such as temperature, conductivity, chlorophyll fluorescence, PAR, oxygen, beam attenuation, and beam transmission. These measurements were collected by a Seabird 9 CTD and associated sensors on a CTD rosette lowered from a ship at discrete stations during cruises for the Northern Gulf of Alaska Long Term Ecological Research (NGA LTER) project. Three cruises occurred in both 2018 and 2019 - spring, summer, and fall - for 6 cruises total. Ships conducting the cruises include R/V Tiglax (TGX), R/V Sikuliaq (SKQ), and R/V Wolstad (WSD). R/V Sikuliaq provides her own CTD instrument, but for the other, smaller, ships, the instrument is provided by the NGA LTER program. The CTDs have dual temperature and conductivity sensors; from these measurements, salinity and density (as sigma-t) were calculated. CTDs are also outfitted with dual SBE 43 oxygen sensors, a WET Labs C-Star to measure light transmission and attenuation, a WET Labs ECO-AFL/FL to measure chlorophyll fluorescence, and a photosynthetically active radiation (PAR) sensor. Additional instruments include a Deep-SUNA to optically measure nitrate and a LISST to measure particle size and concentration. Another instrument on the rosette (an underwater Vision Profiler UVP whose data is not included here) required a long soak at 30 m that may have impacted depiction of the near-surface stratification. Data from each cruise are presented in 3 formats: vertical profiles of 1 dbar averages in netCDF and CSV formats, and data corresponding to the times of Niskin water bottle sampling in CSV format. Raw sensor voltages are included. Although preliminary data for the SUNA and LISST are included in these files, more complete, internally recorded versions of these data will be made available via the NGA LTER program. These data are part of the Northern Gulf of Alaska Long Term Ecological Research (NGA LTER) program. The LTER program is a National Science Foundation–funded network of 28 sites nationwide that focus on the influence of long-term and large-scale phenomenon on ecosystems. Additional funding for sampling is provided by the North Pacific Research Board (NPRB), the Alaska Ocean Observing System (AOOS), and the Exxon Valdez Oil Spill Trustee Council (EVOS) via the Gulf Watch Alaska program.