Please select your home edition
Edition
Naiad/Oracle Supplier

Research shows massive reduction in Antarctic Bottom Water volume

by CSIRO on 20 Jun 2012
Deploying a mooring carrying a suite of monitoring sensors into the sea ice Steve Rintoul
New research by teams of Australian and US scientists has found there has been a massive reduction in the amount of Antarctic Bottom Water, the cold dense water that drives global ocean currents, found off the coast of Antarctica.

Comparing detailed measurements taken during the Australian Antarctic program's 2012 Southern Ocean marine science voyage to historical data dating back to 1970, scientists estimate there has been as much as a 60 per cent reduction in the volume of Antarctic Bottom Water.

In an intensive and arduous 25-day observing program, temperature and salinity samples were collected at 77 sites between Antarctica and Fremantle. Such ship transects provide the only means to detect changes in the deep ocean.

The new measurements, which have not yet been published, suggest the densest waters in the world ocean are gradually disappearing and being replaced by less dense waters.

'The amount of dense Antarctic Bottom Water has contracted each time we've measured it since the 1970s,' said Dr Steve Rintoul, of CSIRO and the Antarctic Climate and Ecosystems CRC. 'There is now only about 40 per cent as much dense water present as observed in 1970.'

The ocean profiles also show that the dense water formed around Antarctica has become less saline since 1970.
'It's a clear signal to us that the oceans are responding rapidly to variations in climate in polar regions. The sinking of dense water around Antarctica is part of a global pattern of ocean currents that has a strong influence on climate, so evidence that these waters are changing is important,' Dr Rintoul said.

The research was carried out by more than 50 scientists on the Australian Antarctic Division's research and resupply vessel Aurora Australis, which sailed to Commonwealth Bay, west along the Antarctic coast, and returned into Fremantle.

The Australian Antarctic Division's Chief Scientist, Dr Nick Gales, said the findings of the oceanographic study are profoundly important.

'Not only will this research improve our understanding of ocean currents, but will also feed into our knowledge of how the Southern Ocean and the Antarctic continent drives the world's climate processes,' Dr Gales said.

Dr Rintoul was Chief Scientist on the recent voyage and has made a dozen voyages to the Southern Ocean. 'When we speak of global warming, we really mean ocean warming: more than 90 per cent of the extra heat energy stored by the earth over the last 50 years has gone into warming up the ocean.

The Southern Ocean is particularly important because it stores more heat and carbon dioxide released by human activities than any other region, and so helps to slow the rate of climate change' Dr Rintoul said. 'A key goal of our work is to determine if the Southern Ocean will continue to play this role in the future.'

The causes of the observed changes in the Southern Ocean are not yet fully understood. Changes in winds, sea ice, precipitation, or melt of floating glacial ice around the edge of Antarctica may be responsible. Data collected on the latest voyage will help unravel this mystery.

A major challenge is the lack of observations at high latitude, where much of the ocean is covered by sea ice in winter. During the voyage scientists deployed nine drifting profilers, called Argo floats, which will transmit profiles of temperature and salinity every 10 days for the next five years. These ice-capable floats in the seasonal ice zone in the Australian sector of the Southern Ocean are funded through Australia's Integrated Marine Observing System.

'The Argo floats have revolutionised our ability to measure the ocean, particularly in winter when ship observations are very rare,' said Dr Rintoul. 'On this voyage, we deployed a new kind of float designed to survive encounters with the sea ice. These floats will allow us to see how dense water forms in winter for the first time.'

The Aurora Australis visited Commonwealth Bay as part of a celebration of the centenary of Sir Douglas Mawson's Australian Antarctic Expedition. Dr Rintoul's team had the opportunity to repeat oceanographic measurements made by Mawson's team 100 years ago, obtaining one of the few century-long records obtained anywhere in the ocean.

'Our measurements collected in 2012 are quite different to those collected by Mawson in 1912,' Dr Rintoul said. 'This is an indication of a change in the ocean currents that may be related to a reduction in the amount of dense water formed near Antarctica.'

'Mawson's expedition really marked the transition from the 'Heroic Age' of Antarctic exploration to a period where science was the primary motivation for Antarctic expeditions. I think he would have gotten a real kick out of the idea that measurements made by his team a century ago are still useful and that Australian scientists are continuing his legacy by studying Antarctica and its connection to the rest of the CSIRO website
Schaefer 2016 Ratchet Block 660x82InSunSport - NZBakewell-White Yacht Design

Related Articles

WHO statement on Zika virus
The third meeting of the EC convened by the Director-General under IHR 2005 regarding microcephaly and Zika virus The third meeting of the Emergency Committee (EC) convened by the Director-General under the International Health Regulations (2005) (IHR 2005) regarding microcephaly, other neurological disorders and Zika virus was held by teleconference on 14 June 2016, from 13:00 to 17:15 Central European Time.
Posted on 16 Jun
Atlantic Cup 2016 - a race with an environmental commitment
The Atlantic Cup continues to further its mission for the 2016 race by examining the global economic impact of the ocean The Atlantic Cup continues to further its mission for the 2016 race by examining the global economic impact of the ocean and how an unhealthy ocean can affect the economy.
Posted on 7 Apr
Zika virus situation report
From 1 January 2007 to 16 March 2016, Zika virus transmission was documented in a total of 59 countries and territories. From 1 January 2007 to 16 March 2016, Zika virus transmission was documented in a total of 59 countries and territories. Cuba and Dominica are the latest to report autochthonous (local) transmission of Zika virus on 14 and 15 March, respectively. Five of these countries and territories reported a Zika virus outbreak that is now over.
Posted on 2 Apr
Have Norway scientists solved the Bermuda Triangle mystery?
The Bermuda Triangle has been said to have claimed numerous ships and aircraft over the years The Bermuda Triangle has been said to have claimed numerous ships and aircraft over the years, and everything from aliens to remnants from the lost island of Atlantis have been fingered as the culprits.
Posted on 15 Mar
Cyclone Winston Relief Fund – Help the people of Fiji
Sea Mercy is sending volunteer fleet of small and large vessels, loaded with shelter, food and medical supplies to Fiji. Sea Mercy is once again sending our volunteer fleet of small and large vessels, loaded with shelter, food, water and medical supplies and teams to Fiji.
Posted on 27 Feb
Flying Scot Atlantic Coast Champs - Hanson Medals awarded for rescues
US Sailing Safety at Sea Committee awarded the Arthur B. Hanson Rescue Medals to eight boats for their heroic efforts The US Sailing Safety at Sea Committee awarded the Arthur B. Hanson Rescue Medals to eight boats for their heroic efforts when a microburst storm hit the 2015 Flying Scot Atlantic Coast Championship, hosted by the Blackbeard Sailing Club, in New Bern, NC on September 12.
Posted on 2 Feb
Eco-warriors Sea-Bin crowd sharing critical stage with nine days to go
The automated marina cleaning SeaBin project has raised 86% of their target with 9 days left. The automated marina cleaning SeaBin project has raised $198,020 of $230,000.00 with nine days left on their Indiegogo crowdfunding platform, but they need more help now.
Posted on 29 Dec 2015
Higher levels of Fukushima Cesium detected offshore
Scientists monitoring the spread of radiation in the ocean from the Fukushima nuclear accident report Scientists monitoring the spread of radiation in the ocean from the Fukushima nuclear accident report finding an increased number of sites off the US West Coast showing signs of contamination from Fukushima. This includes the highest detected level to date from a sample collected about 1,600 miles west of San Francisco.
Posted on 6 Dec 2015
Don’t be a Tosser – Not your usual environmental article!!
The word ‘Tosser’ in the Oxford English dictionary means – ‘a person or thing that throws something’. The word ‘Tosser’ in the Oxford English dictionary means – ‘a person or thing that throws something’. There is no need for me to tell you the other meaning that is commonly used around the world. However in this article it will refer to both at the same time as someone who tosses trash into the ocean, truly is a tosser.
Posted on 3 Dec 2015
Warming ocean worsened Australia’s fatal 2010/2011 floods
Researchers shows that warming of Indian and Pacific oceans played a role in increasing the risk of floods in 2010/2011 A study by a team of U.S. and Australian researchers shows that long-term warming of the Indian and Pacific oceans played an important role in increasing the risk of the kind of devastating floods that struck Australia in 2010/2011.
Posted on 21 Nov 2015