This dataset contains a variety of oceanographic and atmospheric measurements including time series of temperature, salinity, current speed and direction and discrete samples of salinity, dissolved oxygen, oxygen isotope and trace gas concentrations of the water column. It also includes atmospheric measurements including temperature, humidity and wind speed and direction. The data were collected in the Amundsen Sea region of the Antarctic between 2012 and 2017. The majority of the data were collected during RRS James Clark Ross cruise JR20140126 from January to March 2014. Moorings were deployed in 2012 and redeployed in 2014, most collected data until 2016. Measurements were taken using a variety of instrumentation, including conductivity-temperature-depth (CTD) profilers with attached auxiliary sensors, acoustic Doppler current profilers (ADCPs), Radiosondes and Microstructure profilers (MVP). Discrete water samples were also taken and analysed for salinity, dissolved oxygen and oxygen isotope concentration and trace gas concentrations. Measurements were also taken by CTD profilers, current meters and ADCPs deployed on moorings and by CTDs deployed on tags on seals. The project was designed to discover how and why warm ocean water gets close to the ice shelf in Antarctica (and in particular the Amundsen Sea) and is part of the wider iSTAR programme. The principal investigator for this project is Professor Karen Heywood, University of East Anglia and the project was funded by the Natural Environment Research Council. Data from the project are held at the British Oceanographic Data Centre. BODC do not expect to receive data from the Moving Vessel Profiler (MVP) deployed by the project. The originator has identified data quality issues with these datasets and has indicated that they won't be supplied. We expect to receive all other data collected by the project. The Korean Polar Research Institute (KOPRI) collected CTD and Lowered Acoustic Doppler Current Profiles (LADCP) data in 2012 (cruise ANA02C- report accessible via http://repository.kopri.re.kr/handle/201206/4603 ) and 2016 (cruise ANA06B- report not yet available).