Biophysics of submesoscale features in a Central New Zealand shelf sea from glider observations

Greater Cook Strait (GCS) is a shallow shelf sea between the North and South Islands of New Zealand. This relatively shallow continental shelf is influenced by strong winds and tides, as well as freshwater inflows from large South Island rivers. River plumes that travel up to 100km offshore, create a hot spot of low salinity submesoscale feature (LSMF) in Central NZ. Submesoscale features are persistent through all seasons as observed from previous glider missions in GCS. An experiment during Austral Spring 2018 was undertaken to characterise LSMFs using two ocean gliders. One glider traversed the established transect line while the second glider was used as a virtual mooring within a submesoscale feature. Preliminary results of this experiment will be presented in this poster. The two glider sampling strategy of a LSMF enabled us to evaluate energy and salinity budgets of one LSMF over time and space as the feature propagated through GCS. The ‘on station’ mode of sampling provides observational records of the vertical structure of the water column in a small confined shelf region (35 km²). The data will be used to investigate the evolution in water column stability, stratification and subsequent implication on primary production in the presence of an LSMF.