CSIRO voyage gets up close to Antarctica’s climate challenges

The rapidly changing nature of Antarctica has been witnessed first-hand by Australia’s leading research ship on a record-breaking investigation of the icy continent.

On its 12,000km journey, RV Investigator’s complement of 39 research scientists undertook extensive studies of the Southern Ocean and Antarctic atmosphere.

There, they inspected the impact of warming waters on the massive Antarctic ice sheet as well as other chemical, physical and biological effects in the Southern Ocean.

But recently reported shifts in Antarctica’s ice systems were also observed, says the voyage’s co-chief scientist Steve Rintoul, from the CSIRO.

“It’s just as well we weren’t setting out to measure sea ice because there wasn’t much to find,” Rintoul told Cosmos.

“The ship was able to get up onto the continental shelf in Antarctica in a place we’ve never been in a non-icebreaking ship.

“It’s fair to say I think that most Antarctic scientists are pretty stunned by a number of recent changes.”

It’s not just sea ice. Rintoul says short-term weather changes have also drawn concern: “Temperature anomalies of 38 degrees – it wasn’t 38°C, it was 38°C warmer than it should have been at that time – the largest temperature anomaly ever recorded on Earth.”

Once thought to be quite resilient to the effects of climate change compared to West Antarctica, scientists are increasingly concerned the massive amounts of carbon and heat being absorbed by the world’s oceans will push East Antarctica to faster melting rates.

East Antarctica’s ice sheet and ice shells were previously considered too isolated from warm waters, to be at risk of changes in ocean systems.

But now, Rintoul says the CSIRO and Australian Antarctic Program Partnership have data to show that’s not the case anymore.

That includes the infiltration of more warm water into the region’s glaciers. Some, like the Totten Glacier, could contribute 3.5m to global sea level rise once fully melted.

“It’s about half of Greenland, it’s only one glacier, but it’s a big one,” Rintoul says.

“We’ve also, last year, found some warm water entering the Denman glacier, which holds another 1.5m of sea level rise equivalent and drains the same part of East Antarctica.

“What we find is warm waters getting there – not as much warm water as in West Antarctica – but in a sense, there’s more capacity for it to get worse.”

Melting water also contributes to shifts in ocean circulation processes responsible for transporting nutrients and shaping ocean ecosystems around the planet. Multiple reports of these systems slowing down have been reported in recent years.

As a major carbon sponge, absorbing 90% of global heat and carbon, the ocean is a vital but limited buffer against climate change. The Southern Ocean absorbs more carbon than any other region, but it’s capacity to do so may have a ceiling.

The CSIRO is hopeful the last 60 days of data collection from the RV Investigator will help flesh out the impacts of increased carbon absorption on these systems.

“Part of this voyage was motivated by tracking that evolving inventory of extra heat and extra carbon that’s piling up in the oceans,” Rintoul says.

“One of the reasons we need to do that is that there’s some evidence that that current pattern is sensitive itself to climate and so the Southern Ocean may take up less heat and carbon in the future, and that would act as a positive feedback to climate change.”