Since 1992 scientists from Australia, France, and the United States have collaborated to maintain a regular, long-term oceanographic time-series between Hobart, Tasmania, and the French Antarctic base at Dumont d’Urville as part of the SURVOSTRAL program. Hitching a ride on the regular resupply voyages conducted by the French Institut Polaire (generally 5 per year, between October and March) aboard the vessel l’Astrolabe, scientists have been able to collect thousands of valuable XBT temperature profiles to ~800m depth along the line IX28, as well as using the ship’s thermosalinigraph to take high resolution measurements of the sea surface temperature. This effort has yielded a unique, long-term climate-quality dataset in a traditionally data-sparse region, allowing scientists to monitor the pace of climate change in an area that is otherwise difficult to access. 

All this changed in 2020, when almost 30 years of continuous observations were nearly brought to a screeching halt thanks to the complications of the coronavirus pandemic. International and state border closures in Australia, uncertainty over the timing and extent of resupply voyages to Dumont d’Urville, together with strict and ever-changing quarantine requirements before visits to both Australia and Antarctica made 2020 a season like no other. Indeed, it was not clear in mid-2020 if the program would proceed at all, which would have marked the first missed season in the program’s history! 

Working together with the program’s institutional partners, the respective national and Australian state governments (including the Tasmanian State Controller and the Tasmanian Department of State Growth, who also fund SOOS), and the French navy (who operate l’Astrolabe) a way forward was found, and the season was saved! However, those observations have come at a price, with ship riders were required to quarantine both prior to departure (to ensure that the virus does not make it aboard the vessel and eventually to Antarctica) and upon return to Hobart (to ensure that Tasmania remains COVID-19 free). Voyages that in pre-COVID days were of 2-3 weeks duration were extended for well over a month! But in order to maintain a dataset vital to science, it’s a small, and hopefully temporary price to pay. With the current system in place, the Australian/French IX28 line is the only global XBT Ship of Opportunity program able to maintain normal operation with ship riders on board.

By Chris Chapman and Rebecca Cowley (CSIRO Oceans and Atmosphere)