Oceanography, seafloor mapping and satellites combine to map the world’s strongest current

Oceanography, seafloor mapping and satellites combine to map the world’s strongest current

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CTD rose emerging from the depths with image of water samples. Credit: Mark Horstmann

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CTD rose emerging from the depths with image of water samples. Credit: Mark Horstmann

From space to the seabed, an Australian and international research expedition has mapped a highly active ‘hotspot’ in the world’s strongest current simultaneously by ship and satellite, and discovered an underwater mountain range.

Halfway between Tasmania and Antarctica, the Southern Ocean massif surveyed in high resolution and 3D detail spans 20,000 square kilometers through layers of eddy currents to the seafloor 4,000 meters below.

The FOCUS expedition aboard the CSIRO Research Vessel (RV) has been operating in the Antarctic Circumpolar Current for the past five weeks to understand how heat leakage through this natural barrier contributes to the melting of Antarctic ice shelves and potential sea level rise.

The flight is designed to work with the new Surface Water and Ocean Topography (SWOT) satellite, jointly developed by NASA and the French space agency Center National d’Etudes Spatiales (CNES), enabling simultaneous mapping of precise ocean features from the satellite. And the ship.

CSIRO, Australia’s national science agency, and the Australian Antarctic Program Partnership worked with collaborators and equipment from the US and France to address important climate questions, Voyage’s chief scientist, Dr Benoit LeGracey, said.

“The oceans have absorbed more than 90 percent of the heat from global warming and about 25 percent of the carbon dioxide generated by human activity.”2 “Emissions,” Dr. LeGrisi said, “provide a tremendous service as a ‘climate shock absorber’.”

“Knowing how to deal with human-induced climate change brings urgency to tracking the pathways of heat and carbon in the global climate system. We have been working at a gateway where heat is being funneled towards Antarctica, contributing to melting ice and sea levels.” We need to “Understanding how this gate works, how much heat passes through it, and how this might change in the future.”

While mapping ocean currents, the accompanying bathymetric map revealed ancient, dormant underwater volcanoes.


The crew brings a CTD rose to the RV investigator’s photo. Credit: Mark Horstmann

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The crew brings a CTD rose to the RV investigator’s photo. Credit: Mark Horstmann

CSIRO geophysicist Dr Chris Yule said the team carried out high-resolution mapping using RV Investigator’s global multibeam echo system. The survey included a seabed area of ​​20,000 square kilometers2most of which have not been assigned before.

“To our delight, we have discovered a stunning chain of ancient seamounts, which includes eight long-dormant volcanoes with peaks up to 1,500 meters high and one with a double vent,” Dr Yule said.

“Four of them are new finds, and we’ve filled in details on two seamounts and a ridge that had been partially mapped on a previous trip. We now know that the ridge, just west of the survey area, descends into a valley more than 1,600 meters high. -High Escarpment.”

The survey area is located 200 nautical miles (370 km) west of Macquarie Island and the tectonically active Macquarie Ridge area. Seamounts were formed by volcanoes emerging from hot magma over the past 20 million years.

Voyage lead scientist Dr Helen Phillips, from the University of Tasmania’s Australian Antarctic Program Partnership, said new discoveries about the shape of the seafloor are vitally important for understanding ocean dynamics.

The Antarctic Circumpolar Current “feels” the seafloor and mountains in its path, and when it encounters barriers such as ridges or seamounts, “oscillations” are created in the water flow that form eddies. Valleys and cliffs can also accelerate deep currents on the ocean floor, Dr. Phillips said.

“Gyres are like weather systems in the ocean, playing a key role in transporting heat and carbon from the top of the ocean to the deeper layers – a crucial buffer against global warming. Knowing the depth and shape of the sea floor is crucial for us.” Determining the influence of existing mountains, ridges and valleys Under the sea on the Antarctic Circumpolar Current and heat leakage towards Antarctica.”

Dr Phillips said that although integrating all the ship and satellite data would take some time, a successful voyage was key to building knowledge about ocean circulation that informs climate policy.

“Eventually, we want to convert daily maps of ocean sea surface rise from satellites into daily maps of heat movement in the Southern Ocean toward Antarctica. This will help governments and communities plan how to adapt to rising sea levels and how quickly they need to act.” “, She said.

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