Ice Age Geology of the Great Barrier Reef

20,000 Years Ago

Twenty thousand years ago, during the last ice age, most of earth’s water was locked in ice and glaciers. The sea level around Australia’s coastline was approximately 100 to 120 meters lower. As a result, Australia’s continental shelf was exposed during the last glacial period. In the present-day, many areas where coral grows used to be exposed land. Back then, a narrower band of coral reef thrived in the location of what is now the edge of the continental shelf of east Australia. As sea level rose, this coral reef drowned and the ocean covered a number of landscapes unique to the Australian continent. 

In order to uncover some of these drowned landscapes, the expedition will systematically survey the Fraser and Capricorn-Bunker shelf, the Capricorn Channel, and southern Swain Reef edges and slopes. The Capricorn-Bunker and Swain Reefs make up the southern extent of the present-day Great Barrier Reef, and mark the transition from tropical to temperate ocean conditions to the south. The goal of the science team is to determine whether the drowned reef system that has been extensively mapped in the northern and central GBR resembles the drowned reefs in the southern GBR, or whether such drowned reefs extend this far south at all. Understanding the southern extent of the drowned reefs and examining these lost landscapes is a vital piece of the puzzle in the examination of the history and formation of the Great Barrier Reef as we know it today. 

Mapping the Ice Age Submerged Landscapes 

The primary exploration tool for this expedition is R/V Falkor’s advanced mapping technology. Multibeam sonar will create detailed maps of the seafloor, illuminating ancient submerged reef terraces, pinnacles, rivers and shorelines. Falkor’s mapping system is highly effective in capturing high-resolution imagery of Australia’s seafloor features, as demonstrated through previous expeditions like Northern Depths of the Great Barrier Reef and Seamounts, Canyons, and Reefs of the Coral Sea.

The multibeam bathymetry datasets created from this expedition will be added to Geoscience Australia’s public AusSeabed data portal. They will also be added to the GEBCO Seabed 2030 project, which seeks to map the world’s entire seafloor by 2030. These detailed undersea maps are critical for Australia’s future management decisions within the Great Barrier Reef Marine Park and coinciding UNESCO World Heritage Area. As the Great Barrier Reef is a designated World Heritage Area, Australia is committed to protecting the it’s rich environmental and cultural significance for future generations. 

Corals Make Clouds 

To complement the Ice Age GBR mapping campaign,  this expedition will also measure atmospheric aerosol particles produced by coral reefs. Aerosols produced by corals are a natural process that can create cloud cover, protecting coral from harsh sunlight. An aerosol sampler will be used during the expedition to take constant measurements. The aerosol data will be used by the Reef Restoration and Adaptation Program to investigate technologies to reduce coral bleaching by creating cooling cloud cover. The data will help create more robust atmospheric models to be added to the CSIRO eReefs hydrodynamic models.