Please select your home edition
Edition
Absolute Marine

Ice-sheet retreat can halt due to long phases of climate warming

by British Antarctic Survey on 20 Oct 2012
Edge of the Brunt Ice Shelf, Weddell Sea Pete Bucktrout
Ice-sheet retreat can halt temporarily during long phases of climate warming, according to scientists. A UK team led by Durham University has found that the geometry of channels underneath the ice can be a strong control on ice behaviour, temporarily masking the signals of retreat.

The findings, which provide the first simulation of past ice-sheet retreat and collapse over a ten thousand year period in Antarctica, shed new light on what makes ice stable or unstable and will help refine predictions of future ice extent and global sea-level rise, the researchers say.

The International Panel on Climate Change (IPCC) has stated that one of the main challenges in predicting future sea-level rise is to quantify and model the interactions between evolving ice sheets, oceans, sea level and climate. Significant efforts have been made over the last decade to develop computer models and collect data in order to reduce uncertainties and understand the potential impacts under scenarios of future climate change.

The results of the new research from Durham University, the University of Sheffield, the University of Cambridge, and British Antarctic Survey are published this week in the journal Nature Geoscience.

Lead author, Dr. Stewart Jamieson, a glaciologist at the Department of Geography, Durham University, said: 'Our research shows that the physical shape of the channels is a more important factor in controlling ice stability than was previously realised. Channel width can have a major effect on ice flow, and determines how fast retreat, and therefore sea-level rise, can happen.'

Although climatic and oceanic changes are crucial drivers of ice loss, the research shows that the landscape below the ice strongly controls the speed of any retreat.

Dr. Jamieson added: 'Our results suggest that during an overall phase of retreat an ice stream can appear almost stable when in fact, in the longer-term, the opposite may be the case.

'Getting a clearer picture of the landscape beneath the ice is crucial if future predictions of change in the ice-sheets and sea level are to be improved.'

Marine-based ice streams are the fast flowing arteries of ice sheets, draining approximately 90 per cent of the ice that reaches the sea. They flow through large channels where the ice can move thousands of metres in a year. According to the scientists, the unpredictable nature of ice streams makes forecasting ice-sheet retreat extremely difficult. If ice streams speed up they can cause sea level to rise.


Durham University co-author Dr. Chris Stokes said: 'Ice streams are like taps filling a bath, but the problem here is that we do not know if something is suddenly going to turn them up or even turn them off.'

Satellite imagery from the last 20 years has led to advances in our knowledge of ice sheet stability and has shown that many ice streams are getting thinner and retreating because the ocean and climate are warming. The new research shows that ice behaviour can successfully be simulated in places where ice streams meet the sea.

The researchers looked at the landscape of the seafloor in Marguerite Bay, in the Antarctic Peninsula, and saw that during a rapid phase of recession 13,000 years ago, retreat paused many times. Using a computer model designed to work in situations of rapid change, they found they could reproduce the same pattern in a series of simulations. These showed that ice dragged on the sides of the channel more where it was narrow, causing retreat to slow and in places temporarily stop for decades to centuries before retreat continued.

Many ice streams are found in channels with beds that are below sea level and that deepen inland. Current theory suggests that ice loss can increase rapidly in deeper water, but the new findings show that channel width plays a crucial role and that narrow bottlenecks in the landscape beneath the ice can cause retreat to slow down.

Dr. Andreas Vieli, Department of Geography, Durham University, said: 'We can see from our simulations and from new maps of the ocean floor that these bottlenecks occur in the same place as pauses or slowdowns in past ice retreat. This means we should look more closely at the shape of the bed underneath Greenland and Antarctica to better understand how ice might retreat in the future.'

Dr. Claus-Dieter Hillenbrand from British Antarctic Survey added: 'Knowledge of the factors influencing stability and retreat of ice streams is of particular concern because significant portions of the West Antarctic and Greenland ice sheets are currently losing mass that contributes significantly to sea-level rise. Our model results help to explain the apparently time-transgressive retreat of ice streams around Antarctica following the last ice age.'

The researchers say that understanding ice-stream behaviour and the rate of mass loss from ice sheets and glaciers is British Antarctic Survey website

Gold Coast Marine Expo 2017 660x82NaiadBakewell-White Yacht Design

Related Articles

Vibrant Life in Northern sector of the Great Barrier Reef
If you're curious about state of Great Barrier Reef north of Cairns, dive into world of Cairns local, Jemma Craig. If you're curious about the state of the Great Barrier Reef north of Cairns, take a minute to dive into the world of Cairns local, Jemma Craig.The 24-year old took the chance to document her first scuba dive on the reefs surrounding Raine Island, an area reported last year as being severely affected by coral bleaching.
Posted on 20 Jan
The Deepwater Horizon aftermath
Researchers analyze 125 compounds from oil spilled in Gulf of Mexico to determine their longevity at different levels. Researchers analyze 125 compounds from oil spilled in the Gulf of Mexico to determine their longevity at different contamination levels. The oil discharged into the Gulf of Mexico following the explosion and sinking of the Deepwater Horizon (DWH) rig in 2010 contaminated more than 1,000 square miles of seafloor.
Posted on 1 Jan
What happened to Deepwater Horizon Oil?
What happened to the 160 million gallons of oil that gushed for 87 days into the Gulf of Mexico in 2010? Six years after the Deepwater Horizon oil spill, we are continually asked two questions. What happened to the 160 million gallons of oil that gushed for 87 days into the Gulf of Mexico in 2010? Was discharging 1.67 million gallons of chemicals into the ocean to disperse the oil a good or bad idea?
Posted on 24 Dec 2016
Great Barrier Reef managers and industry prepare for summer
Marine park managers, scientists and experts recently met for the annual pre-summer workshop Marine park managers, scientists and experts recently met for the annual pre-summer workshop to assess climate-related risks to the Great Barrier Reef over the coming months. Current predictions by the Bureau of Meteorology and National Oceanic and Atmospheric Administration are for a summer of average sea temperatures across the Great Barrier Reef.
Posted on 7 Dec 2016
Introducing the Airbnb of the mooring and marina world
Have you ever struggled to find an available mooring, or do you have a mooring that is sitting vacant? Have you ever struggled to find an available mooring, or do you have a mooring that is sitting vacant? makefastmooring.com is aiming to solve this problem by connecting boat owners with those with vacant moorings or berths. With a growing number of moorings and marinas in New Zealand, Australia and around the world, makefastmooring.com allows people to find, rent and share moorings and berths.
Posted on 7 Dec 2016
Princess to pay largest ever criminal penalty for vessel pollution
Princess Cruise Lines has agreed to plead guilty to seven felony charges stemming from deliberate pollution of the seas Princess Cruise Lines Ltd. (Princess) has agreed to plead guilty to seven felony charges stemming from its deliberate pollution of the seas and intentional acts to cover it up. Princess will pay a $40 million penalty– the largest-ever criminal penalty involving deliberate vessel pollution – and plead guilty to charges related to illegal dumping of oil contaminated waste from the cruise ship.
Posted on 2 Dec 2016
Race for Water catamaran to be equipped with new hydrogen system
Race for Water will make it possible for the crew to free themselves of the need for fossil fuels during new mission. Race for Water will make it possible for the crew to completely free themselves of the need for fossil fuels during the new mission against the pollution of the oceans.
Posted on 26 Nov 2016
Radio spectrum changes have been put into place in New Zealand
New Zealand, along with a number of other countries, has been required to change some maritime VHF repeater channels New Zealand, along with a number of other countries, has been required to change some maritime VHF repeater channels to make space for newly allocated international services for ship tracking and data services. On the October 1st, New Zealand moved a few private VHF repeater services, most Coastguard VHF repeater services, and all NowCasting weather services. An updated radio handbook and freq
Posted on 2 Nov 2016
Operation Retune underway in remote corners of New Zealand
Radio technicians have been working at sites for the Maritime VHF channel changes Radio technicians have been working at sites for the Maritime VHF channel changes The scenery is spectacular but getting to transmitters sites in New Zealand can be a challenge for radio technicians working on the Maritime VHF change over.
Posted on 4 Oct 2016
Skies clear for final day of the Auckland On the Water Boat Show
Heavy rain which hit the Auckland On the Water Boat Show has cleared and it is business as usual The heavy rain which hit the Auckland On the Water Boat Show and the rest of the province has cleared and it is business as usual for the final day. The crowds were at the Viaduct Events Centre gat at 10.00am this morning - a little surprising given the heavy rain which has plagued Auckland over night and at Show opening time, plus the All Blacks Test match which started at 11.00am.
Posted on 1 Oct 2016