Please select your home edition
Edition
Zhik Isotak Ocean

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

Southern Spars - 100Mariners Museum 660x82Insun - AC Program

Related Articles

Int Moth Worlds - Zhik returns to its spiritual home at 2017 Worlds
Zhik is returning to its roots as the official clothing sponsor of the 2017 McDougall McConaghy Moth World Championships Zhik, the innovative sailing apparel specialist, is returning to its roots as the official clothing sponsor of the 2017 McDougall McConaghy Moth World Championships. And, ten years on, the Moths are returning to their spiritual home on Lake Garda. Zhik and the International Moth class are virtually synonymous with each other.
Posted on 20 Jul
A Few Rays – Moisturising, Anti-Aging Action …
Consistent moisturising sun protection has an anti-aging action Consistent moisturising sun protection has an anti-aging action Out on a boat, sailors are exposed to extreme conditions for their skin. There are UV rays from the sun, hopefully some wind if you are a sailor, and the drying effects from wet and dry cycles during the course of your day
Posted on 23 Jun
BoatUS looks at accuracy of 22 Years of hurricane season predictions
BoatUS Seaworthy Program, which helps BoatUS members avoid injuries and boat damage by analyzing insurance claims data With most 2017 storm forecasts now predicting average to above-average storm activity for the 2017 Atlantic Hurricane Season (June 1 – November 30), just how accurate are these predictions, and do boaters need to adjust their hurricane prep plans this year?
Posted on 13 Jun
Caffari to lead a team with sustainability message in Volvo Ocean Race
Sixth confirmed team out of a possible eight for the upcoming edition will amplify United Nations Environment’s campaign Caffari’s ambition is to build a multi-national, 50-50 male/female squad, with the majority under 30 years of age. As part of the sustainability focus, the messages around diversity in age and gender will be strong themes of a campaign that in sporting terms may not start as a favourite, but could easily surprise on the water.
Posted on 13 Jun
A Few Rays - What is Broad Spectrum Protection?
What is Broad Spectrum sunscreen? Ultraviolet rays only make up a small proportion of all of the sun’s rays. What is Broad Spectrum sunscreen? Ultraviolet rays (UVA, UVB and UVC) only make up a small proportion of all of the sun’s rays. UVA and UVB sun-rays are however the biggest contributors to skin damage from sun.
Posted on 19 Apr
Frigid flying – Coast Guard aircrews take on New England Winter
Freezing rain? Teeth-chattering temperatures? Limited visibility? Coast Guard aircrews are still ready to fly. Freezing rain? Teeth-chattering temperatures? Limited visibility? Coast Guard aircrews are still ready to fly. At Air Station Cape Cod, aviation maintenance and electronic technicians work around the clock to ensure the MH-60 Jayhawk helicopters are prepared and ready to launch. There is one thing the maintenance crews and pilots cannot control: winter weather.
Posted on 9 Feb
When whales meet sails
CAMPER helmsman Roberto ‘Chuny’ Bermudez found himself nearly face to face with whale in middle of North Atlantic Ocean. Currently the database for marine mammal strikes is very sparse. We are requesting sailors and boaters help to submit information on current and past incidents, however long ago that may be. By giving a location, date, identification if possible, and any other relevant information you can help scientists better understand where marine mammals are at risk for strikes
Posted on 8 Jan
Vendée Globe – Uncertainty about weather condition in North Atlantic
Alex Thomson and Armel le Cléac'h are probably looking closely at the wind models for the North Atlantic. Alex Thomson and Armel le Cléac'h are probably looking closely at the wind models for the North Atlantic. It does not seem to be easy.
Posted on 4 Jan
10,000 metric tons of plastic enter Great Lakes every year
A new study inventories and tracks high concentrations of plastic in Great Lakes could help inform cleanup efforts A new study by Rochester Institute of Technology that inventories and tracks high concentrations of plastic in the Great Lakes could help inform cleanup efforts and target pollution prevention.Researchers found that nearly 10,000 metric tons—or 22 million pounds—of plastic debris enter the Great Lakes every year from the United States and Canada.
Posted on 2 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