IMOS OceanCurrent is going to sea on the upcoming CAPSTAN 06 voyage, where we’ll use the information available on the website to contextualise the observations taken during the voyage. We are boarding CSIRO research vessel (RV) Investigator today!

Following departure from Brisbane and initial activities in coastal waters, the first open ocean part of the CAPSTAN 06 voyage to Fiji onboard the RV Investigator will depart from waters near Bundaberg and head towards the Fraser Seamount, a seamount located ~200 km east of Australia. There, we plan to take targeted measurements of the circulation and water properties around the seamount.
 
As we depart from waters near Bundaberg (Figure 1a, orange star), we’ll find Sea Surface Temperatures (SST) of ~20degC (~1degC warmer than climatological values; Figure 1a, b) before meeting the East Australian Current (EAC) at the continental shelf break. At the moment, the EAC is narrow and coherent, flowing southward at 0.7 m/s, with 23.5degC SST surface-signature, contrasting with the 22degC surrounding waters.  Two weeks ago, the SWOT satellite altimeter measured a 0.2 m SSH slope just off K’gari (former Fraser Island; Figure 1c), with low values to the west, balancing the EAC southward geostrophic flow at that location. 

We’ll then proceed to the Fraser Seamount (155.5E, 24.5S, Figure 1, clear star), rising from 4000 m to 400 m depths, and being part of the Coral Sea Marine Park. The interaction between deep ocean seamounts and surrounding flow may result in the  upwelling of cold, nutrient-rich waters to the euphotic zone. This upwelling, often seen downstream of the dominant flow, may induce a biological response, observed by high values phyto- and zooplankton. We plan to adapt our sampling strategy to the direction of the currents interacting with the Fraser Seamount as we approach the region.
 
Currently, the circulation around this seamount is dominated by a weak cyclonic eddy that has moved westwards since seen in SWOT and Gridded SSH (Figure 1d). The latest SST 4h composite shows 21oC filaments and associated submesoscale eddies near the seamount (Figure 1a).  
 
As we move to the southward part of the Coral Sea, we shift scales to focus on the sea-wide circulation. Now, we have a very quiet Coral Sea, with no strong eddies and no extreme SST anomalies (Figure 2). According to the Bureau of Meteorology’s ocean temperature long-range forecast, there are no marine heatwaves forecasted for the Coral Sea for September to November. The monthly mean SSTA maps show us that the mild SST conditions we are seeing have been present in the Coral Sea for the past months. 

Currently, the surface waves reaching the southern part of the Coral Sea have 1-2 m significant wave height (SWH, Figure 3), coming from the south, with northeasterly waves of ~0.6 m SWH arriving in Bundaberg. Surface waves are forecasted by the BOM to keep same direction and increase in intensity to 3 m in the next days in the southern part of the Coral Sea.
 
You can follow the RV Investigator and see the voyage livestream here.
 
The CAPSTAN program is a maritime education and training initiative of Australia’s national science agency, CSIRO, the University of Tasmania’s Institute for Marine and Antarctic Studies (IMAS), and the Australian and New Zealand International Scientific Drilling Consortium (ANZIC). CAPSTAN is supported by grants of sea time on RV Investigator from the CSIRO Marine National Facility (MNF). IMOS, MNF, and ANZIC receive funding from the National Collaborative Research Infrastructure Strategy (NCRIS).