How Solar Heat Drives Rapid Melting Of Parts Of Antarctica's Largest Ice Shelf

How Solar Heat Drives Rapid Melting Of Parts Of Antarctica's Largest Ice Shelf Scientists measured the thickness and basal melt of the Ross Ice Shelf. Supplied, CC BY-ND

The ocean that surrounds Antarctica plays a crucial role in regulating the mass balance of the continent’s ice cover. We now know that the thinning of ice that affects nearly a quarter of the West Antarctic Ice Sheet is clearly linked to the ocean.

The connection between the Southern Ocean and Antarctica’s ice sheet lies in ice shelves – massive slabs of glacial ice, many hundreds of metres thick, that float on the ocean. Ice shelves grind against coastlines and islands and buttress the outflow of grounded ice. When the ocean erodes ice shelves from below, this buttressing action is reduced.

While some ice shelves are thinning rapidly, others remain stable, and the key to understanding these differences lies within the hidden oceans beneath ice shelves. Our recently published research explores the ocean processes that drive melting of the world’s largest ice shelf. It shows that a frequently overlooked process is driving rapid melting of a key part of the shelf.

Ocean fingerprints on ice sheet melt

Rapid ice loss from Antarctica is frequently linked to Circumpolar Deep Water (CDW). This relatively warm (+1C) and salty water mass, which is found at depths below 300 metres around Antarctica, can drive rapid melting. For example, in the south-east Pacific, along West Antarctica’s Amundsen Sea coast, CDW crosses the continental shelf in deep channels and enters ice shelf cavities, driving rapid melting and thinning.

Interestingly, not all ice shelves are melting quickly. The largest ice shelves, including the vast Ross and Filchner-Ronne ice shelves, appear close to equilibrium. They are largely isolated from CDW by the cold waters that surround them.

How Solar Heat Drives Rapid Melting Of Parts Of Antarctica's Largest Ice Shelf The satellite image shows that strong offshore winds drive sea ice away from the north-western Ross Ice Shelf, exposing the dark ocean surface. Solar heating warms the water enough to drive melting. Figure modified from https://www.nature.com/articles/s41561-019-0356-0. Supplied, CC BY-ND

The contrasting effects of CDW and cold shelf waters, combined with their distribution, explain much of the variability in the melting we observe around Antarctica today. But despite ongoing efforts to probe the ice shelf cavities, these hidden seas remain among the least explored parts of Earth’s oceans.

It is within this context that our research explores a new and hard-won dataset of oceanographic observations and melt rates from the world’s largest ice shelf.

Beneath the Ross Ice Shelf

In 2011, we used a 260 metre deep borehole that had been melted through the north-western corner of the Ross Ice Shelf, seven kilometres from the open ocean, to deploy instruments that monitor ocean conditions and melt rates beneath the ice. The instruments remained in place for four years.

The observations showed that far from being a quiet back water, conditions beneath the ice shelf are constantly changing. Water temperature, salinity and currents follow a strong seasonal cycle, which suggests that warm surface water from north of the ice front is drawn southward into the cavity during summer.

Melt rates at the mooring site average 1.8 metres per year. While this rate is much lower than ice shelves impacted by warm CDW, it is ten times higher than the average rate for the Ross Ice Shelf. Strong seasonal variability in the melt rate suggests that this melting hotspot is linked to the summer inflow.

How Solar Heat Drives Rapid Melting Of Parts Of Antarctica's Largest Ice Shelf Summer sea surface temperature surrounding Antarctica (a) and in the Ross Sea (b) showing the strong seasonal warming within the Ross Sea polynya. Figure modified from https://www.nature.com/articles/s41561-019-0356-0. Supplied, CC BY-ND

To assess the scale of this effect, we used a high-precision radar to map basal melt rates across a region of about 8,000 square kilometres around the mooring site. Careful observations at around 80 sites allowed us to measure the vertical movement of the ice base and internal layers within the ice shelf over a one-year interval. We could then determine how much of the thinning was caused by basal melting.

Melting was fastest near the ice front where we observed short-term melt rates of up to 15 centimetres per day – several orders of magnitude higher than the ice shelf average rate. Melt rates reduced with distance from the ice front, but rapid melting extended far beyond the mooring site. Melting from the survey region accounted for some 20% of the total from the entire ice shelf.

The bigger picture

Why is this region of the shelf melting so much more quickly than elsewhere? As is so often the case in the ocean, it appears that winds play a key role.

During winter and spring, strong katabatic winds sweep across the western Ross Ice Shelf and drive sea ice from the coast. This leads to the formation of an area that is free of sea ice, a polynya, where the ocean is exposed to the atmosphere. During winter, this area of open ocean cools rapidly and sea ice grows. But during spring and summer, the dark ocean surface absorbs heat from the sun and warms, forming a warm surface pool with enough heat to drive the observed melting.

Although the melt rates we observe are far lower than those seen on ice shelves influenced by CDW, the observations suggest that for the Ross Ice Shelf, surface heat is important.

Given this heat is closely linked to surface climate, it is likely that the predicted reductions in sea ice within the coming century will increase basal melt rates. While the rapid melting we observed is currently balanced by ice inflow, glacier models show that this is a structurally critical region where the ice shelf is pinned against Ross Island. Any increase in melt rates could reduce buttressing from Ross Island, increasing the discharge of land-based ice, and ultimately add to sea levels.

While there is still much to learn about these processes, and further surprises are certain, one thing is clear. The ocean plays a key role in the dynamics of Antarctica’s ice sheet and to understand the stability of the ice sheet we must look to the ocean.The Conversation

About The Author

Craig Stewart, Marine Physicist, National Institute of Water and Atmospheric Research

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Related Books

Climate Change: What Everyone Needs to Know

by Joseph Romm
0190866101The essential primer on what will be the defining issue of our time, Climate Change: What Everyone Needs to Know® is a clear-eyed overview of the science, conflicts, and implications of our warming planet. From Joseph Romm, Chief Science Advisor for National Geographic's Years of Living Dangerously series and one of Rolling Stone's "100 people who are changing America," Climate Change offers user-friendly, scientifically rigorous answers to the most difficult (and commonly politicized) questions surrounding what climatologist Lonnie Thompson has deemed "a clear and present danger to civilization.". Available On Amazon

Climate Change: The Science of Global Warming and Our Energy Future second edition Edition

by Jason Smerdon
0231172834This second edition of Climate Change is an accessible and comprehensive guide to the science behind global warming. Exquisitely illustrated, the text is geared toward students at a variety of levels. Edmond A. Mathez and Jason E. Smerdon provide a broad, informative introduction to the science that underlies our understanding of the climate system and the effects of human activity on the warming of our planet.Mathez and Smerdon describe the roles that the atmosphere and ocean play in our climate, introduce the concept of radiation balance, and explain climate changes that occurred in the past. They also detail the human activities that influence the climate, such as greenhouse gas and aerosol emissions and deforestation, as well as the effects of natural phenomena.  Available On Amazon

The Science of Climate Change: A Hands-On Course

by Blair Lee, Alina Bachmann
194747300XThe Science of Climate Change: A Hands-On Course uses text and eighteen hands-on activities to explain and teach the science of global warming and climate change, how humans are responsible, and what can be done to slow or stop the rate of global warming and climate change. This book is a complete, comprehensive guide to an essential environmental topic. Subjects covered in this book include: how molecules transfer energy from the sun to warm the atmosphere, greenhouse gases, the greenhouse effect, global warming, the Industrial Revolution, the combustion reaction, feedback loops, the relationship between weather and climate, climate change, carbon sinks, extinction, carbon footprint, recycling, and alternative energy. Available On Amazon

From The Publisher:
Purchases on Amazon go to defray the cost of bringing you InnerSelf.comelf.com, MightyNatural.com, and ClimateImpactNews.com at no cost and without advertisers that track your browsing habits. Even if you click on a link but don't buy these selected products, anything else you buy in that same visit on Amazon pays us a small commission. There is no additional cost to you, so please contribute to the effort. You can also use this link to use to Amazon at any time so you can help support our efforts.

 

enafarzh-CNzh-TWdanltlfifrdeiwhihuiditjakomsnofaplptruesswsvthtrukurvi

follow InnerSelf on

facebook-icontwitter-iconrss-icon

 Get The Latest By Email

{emailcloak=off}

EVIDENCE

Antarctic Ice Shelves Reveals A Missing Piece Of The Climate Puzzle
Antarctic Ice Shelves Reveals A Missing Piece Of The Climate Puzzle
by Katherine Hutchinson
Ice shelves, massive floating bodies of ice, are well-known for their buffering effect on land-based ice sheets as they…
Why We Won't Be Heading Into An Ice Age Any Time Soon
Why We Won't Be Heading Into An Ice Age Any Time Soon
by James Renwick
When I studied climate in my university geography course in the 1960s, I am sure we were told that the Earth was…
How Volcanoes Influence Climate And How Their Emissions Compare To What We Produce
How Volcanoes Influence Climate And How Their Emissions Compare To What We Produce
by Michael Petterson
Everyone is going on about reducing our carbon footprint, zero emissions, planting sustainable crops for biodiesel etc.
What Is Climate Sensitivity?
What Is Climate Sensitivity?
by Robert Colman and Karl Braganza
Humans are emitting CO2 and other greenhouse gases into the atmosphere. As these gases build up they trap extra heat…
There Are No Time-travelling Climatologists: Why We Use Climate Models
There Are No Time-travelling Climatologists: Why We Use Climate Models
by Sophie Lewis and Sarah Perkins-Kirkpatrick
The first climate models were built on fundamental laws of physics and chemistry and designed to study the climate…
What Caused Major Climate Change In The Past?
This Is What Caused Major Climate Change In The Past
by James Renwick
Earth had several periods of high carbon dioxide levels in the atmosphere and high temperatures over the last several…
Will Three Billion People Really Live In Temperatures As Hot As The Sahara By 2070?
Will Three Billion People Really Live In Temperatures As Hot As The Sahara By 2070?
by Mark Maslin
Humans are amazing creatures, in that they have show they can live in almost any climate.
Tree Rings And Weather Data Warn Of Megadrought
Tree Rings And Weather Data Warn Of Megadrought
by Tim Radford
Farmers in the US West know they have a drought, but may not yet realise these arid years could become a megadrought.

LATEST VIDEOS

Tiny Plankton Drive Processes In The Ocean That Capture Twice As Much Carbon As Scientists Thought
Tiny Plankton Drive Processes In The Ocean That Capture Twice As Much Carbon As Scientists Thought
by Ken Buesseler
The ocean plays a major role in the global carbon cycle. The driving force comes from tiny plankton that produce…
Climate Change Threatens Drinking Water Quality Across The Great Lakes
Climate Change Threatens Drinking Water Quality Across The Great Lakes
by Gabriel Filippelli and Joseph D. Ortiz
“Do Not Drink/Do Not Boil” is not what anyone wants to hear about their city’s tap water. But the combined effects of…
Talking About Energy Change Could Break The Climate impasse
Talking About Energy Change Could Break The Climate Impasse
by InnerSelf Staff
Everyone has energy stories, whether they’re about a relative working on an oil rig, a parent teaching a child to turn…
Crops Could Face Double Trouble From Insects And A Warming Climate
Crops Could Face Double Trouble From Insects And A Warming Climate
by Gregg Howe and Nathan Havko
For millennia, insects and the plants they feed on have been engaged in a co-evolutionary battle: to eat or not be…
To Reach Zero Emissions Government Must Address Hurdles Putting People Off Electric Cars
To Reach Zero Emissions Government Must Address Hurdles Putting People Off Electric Cars
by Swapnesh Masrani
Ambitious targets have been set by the UK and Scottish governments to become net-zero carbon economies by 2050 and 2045…
Spring Is Arriving Earlier Across The US, And That's Not Always Good News
Spring Is Arriving Earlier Across The US, And That's Not Always Good News
by Theresa Crimmins
Across much of the United States, a warming climate has advanced the arrival of spring. This year is no exception.
The Last Ice Age Tells Us Why We Need To Care About A 2℃ Change In Temperature
The Last Ice Age Tells Us Why We Need To Care About A 2℃ Change In Temperature
by Alan N Williams, et al
The latest report from the Intergovernmental Panel on Climate Change (IPCC) states that without a substantial decrease…
A Georgia Town Gets Half Of Its Electricity From President Jimmy Carter's Solar Farm
A Georgia Town Gets Half Of Its Electricity From President Jimmy Carter's Solar Farm
by Johnna Crider
Plains, Georgia, is a small town that is just south of Columbus, Macon, and Atlanta and north of Albany. It is the…

LATEST ARTICLES

Hurricanes And Other Extreme Weather Disasters Prompt Some People To Move And Trap Others In Place
Hurricanes And Other Extreme Weather Disasters Prompt Some People To Move And Trap Others In Place
by Jack DeWaard
If it seems like extreme weather disasters such as hurricanes and wildfires are becoming more frequent, severe and…
If All Cars Were Electric, UK Carbon Emissions Would Drop By 12%
If All Cars Were Electric, UK Carbon Emissions Would Drop By 12%
by George Milev and Amin Al-Habaibeh
The COVID-19 lockdown has led to reduced pollution and emissions in the UK and around the world, providing a clear…
Brazil’s Jair Bolsonaro Is Devastating Indigenous Lands, With The World Distracted
Brazil’s Jair Bolsonaro Is Devastating Indigenous Lands, With The World Distracted
by Brian Garvey, and Mauricio Torres
The Amazon fires of 2019 drove the greatest single year loss of Brazilian forest in a decade. But with the world in the…
Why Countries Don't Count Emissions From Goods They Import
Why Countries Don't Count Emissions From Goods They Import
by Sarah McLaren
I would like to know if New Zealand’s carbon emissions of 0.17% include emissions produced from products manufactured…
Green Bailouts: Relying On Carbon Offsetting Will Let Polluting Airlines Off The Hook
Green Bailouts: Relying On Carbon Offsetting Will Let Polluting Airlines Off The Hook
by Ben Christopher Howard
The coronavirus pandemic has grounded thousands of aircraft, contributing to the largest-ever annual fall in CO₂…
Longer Growing Seasons Have A Limited Effect On Combating Climate Change
Longer Growing Seasons Have A Limited Effect On Combating Climate Change
by Alemu Gonsamo
Climate warming is leading to early springs and delayed autumns in colder environments, allowing plants to grow for a…
Both Conservatives And Liberals Want A Green Energy Future, But For Different Reasons
Both Conservatives And Liberals Want A Green Energy Future, But For Different Reasons
by Deidra Miniard et al
Political divisions are a growing fixture in the United States today, whether the topic is marriage across party lines,…
How The Climate Impact Of Beef Compares With Plant-based Alternatives
How The Climate Impact Of Beef Compares With Plant-based Alternatives
by Alexandra Macmillan and Jono Drew
I am wondering about the climate impact of vegan meat versus beef. How does a highly processed patty compare to…