The Times Australia
The Times World News

.
The Times Real Estate

.

West Antarctica’s ice sheet was smaller thousands of years ago – here’s why this matters today

  • Written by Dan Lowry, Ice Sheet & Climate Modeller, GNS Science
West Antarctica’s ice sheet was smaller thousands of years ago – here’s why this matters today

As the climate warms and Antarctica’s glaciers and ice sheets melt, the resulting rise in sea level has the potential to displace hundreds of millions of people[1] around the world by the end of this century.

A key uncertainty in how much and how fast the seas will rise lies in whether currently “stable” parts of the West Antarctic Ice Sheet can become “unstable”.

One such region is West Antarctica’s Siple Coast, where rivers of ice flow off the continent and drain into the ocean.

This map shows the Siple Coast and its ice streams.
The Ross Ice Shelf holds back the flow of ice streams from West Antarctica’s Siple Coast. Journal of Geophysical Research, CC BY-SA[2][3]

This ice flow is slowed down by the Ross Ice Shelf, a floating mass of ice nearly the size of Spain, which holds back the land-based ice. Compared to other ice shelves in West Antarctica, the Ross Ice Shelf has little melting at its base because the ocean below it is very cold.

Although this region has been stable during the past few decades, recent research suggest this was not always the case. Radiocarbon dating of sediments[4] from beneath the ice sheet tells us that it retreated hundreds of kilometres some 7,000 years ago, and then advanced again to its present position within the last 2,000 years.

Figuring out why this happened can help us better predict how the ice sheet will change in the future. In our new research[5], we test two main hypotheses.

Read more: What an ocean hidden under Antarctic ice reveals about our planet's future climate[6]

Testing scenarios

Scientists have considered two possible explanations for this past ice sheet retreat and advance. The first is related to Earth’s crust below the ice sheet.

As an ice sheet shrinks, the change in ice mass causes the Earth’s crust to slowly uplift in response. At the same time, and counterintuitively, the sea level drops near the ice because of a weakening of the gravitational attraction between the ice sheet and the ocean water.

As the ice sheet thinned and retreated since the last ice age, crustal uplift and the fall in sea level in the region may have re-grounded floating ice[7], causing ice sheet advance.

A graphic showing how Earth's crust uplifts and sea level drops near the ice sheet as it loses mass.
Earth’s crust uplifts and sea level drops near the ice sheet as it loses mass. AGU, CC BY-SA[8][9]

The other hypothesis is that the ice sheet behaviour may be due to changes in the ocean. When the surface of the ocean freezes, forming sea ice, it expels salt into the water layers below. This cold briny water is heavier and mixes deep into the ocean, including under the Ross Ice Shelf. This blocks warm ocean currents from melting the ice.

A graphic showing the interaction between cold dense waters and warmer deep flows under the Ross Ice Shelf.
Top: Cold dense shelf water blocks warm circumpolar deep water from melting the ice. Bottom: Warm circumpolar deep water flows under the ice shelf, causing ice melting and retreat. AGU, CC BY-SA[10][11]

Seafloor sediments and ice cores[12] tell us that this deep mixing was weaker in the past when the ice sheet was retreating. This means that warm ocean currents may have flowed underneath the ice shelf and melted the ice. Mixing increased when the ice sheet was advancing.

We test these two ideas with computer model simulations of ice sheet flow and Earth’s crustal and sea surface responses to changes in the ice sheet with varying ocean temperature.

Because the rate of crustal uplift depends on the viscosity (stickiness) of the underlying mantle, we ran simulations within ranges estimated for West Antarctica. A stickier mantle means slower crustal uplift as the ice sheet thins.

The simulations that best matched geological records had a stickier mantle and a warmer ocean as the ice sheet retreated. In these simulations, the ice sheet retreats more quickly as the ocean warms.

When the ocean cools, the simulated ice sheet readvances to its present-day position. This means that changes in ocean temperature best explain the past ice sheet behaviour, but the rate of crustal uplift also affects how sensitive the ice sheet is to the ocean.

Three polar tents set up on the Ross Ice Shelf.
Changes in ocean temperature best explain the retreat of West Antarctica’s ice sheet in the past. Veronika Meduna, CC BY-SA[13]

What this means for climate policy today

Much attention has been paid to recent studies[14] that show glacial melting may be irreversible in some parts of West Antarctica, such as the Amundsen Sea embayment.

In the context of such studies, policy debates hinge on whether we should focus on adapting to rising seas rather than cutting greenhouse gas emissions. If the ice sheet is already melting, are we too late for mitigation?

Read more: We can still prevent the collapse of the West Antarctic ice sheet – if we act fast to keep future warming in check[15]

Our study suggests it is premature to give up on mitigation.

Global climate models run under high-emissions scenarios show less sea ice formation and deep ocean mixing[16]. This could lead to the same cold-to-warm ocean switch that caused extensive ice sheet retreat thousands of years ago.

For West Antarctica’s Siple Coast, it is better if we prevent this ocean warming from occurring in the first place, which is still possible if we choose a low-emissions future.

References

  1. ^ hundreds of millions of people (www.ipcc.ch)
  2. ^ Journal of Geophysical Research (www.researchgate.net)
  3. ^ CC BY-SA (creativecommons.org)
  4. ^ Radiocarbon dating of sediments (agupubs.onlinelibrary.wiley.com)
  5. ^ new research (www.nature.com)
  6. ^ What an ocean hidden under Antarctic ice reveals about our planet's future climate (theconversation.com)
  7. ^ re-grounded floating ice (www.nature.com)
  8. ^ AGU (agupubs.onlinelibrary.wiley.com)
  9. ^ CC BY-SA (creativecommons.org)
  10. ^ AGU (agupubs.onlinelibrary.wiley.com)
  11. ^ CC BY-SA (creativecommons.org)
  12. ^ sediments and ice cores (www.nature.com)
  13. ^ CC BY-SA (creativecommons.org)
  14. ^ recent studies (www.nature.com)
  15. ^ We can still prevent the collapse of the West Antarctic ice sheet – if we act fast to keep future warming in check (theconversation.com)
  16. ^ deep ocean mixing (www.nature.com)

Read more https://theconversation.com/west-antarcticas-ice-sheet-was-smaller-thousands-of-years-ago-heres-why-this-matters-today-225670

The Times Features

How weight stigma in maternity care harms larger-bodied women and their babies

According to a study from the United States[1], women experience weight stigma in maternity care at almost every visit. We expect this experience to be similar in Australia, ...

10 Ways to Make Money Online and Provide Financial Stability

The possibility of earning money online has reached unprecedented heights. The proper strategy enables anyone to begin earning money. You don't need fancy degrees or special skil...

The Power of Exterior Design: How Facades Influence Property Value

First impressions count when it comes to real estate, and nothing quite sets the tone for a property like its exterior design. A building's facade is more than just an aesthetic ...

The Best Adjustable Bed and Mattress Packages for Comfort

The appropriate bed and mattress are essential for establishing the perfect sleep environment. If you seek a way to upgrade your sleep experience, adjustable bed and mattress pac...

Designing a Modern Home: Features That Will Make Your Dream House Stand Out

Designing your dream home is an exciting journey, and for many, it’s an opportunity to create a space that reflects their personal style, functionality needs, and modern trends. ...

Client Dinners Done Right: Tips for Meaningful Engagement

Client dinners offer more than just a meal—they’re an opportunity to build lasting business relationships in a more personal and relaxed setting. Done well, these dinners can str...

Times Magazine

Top Benefits of Hiring Commercial Electricians for Your Business

When it comes to business success, there are no two ways about it: qualified professionals are critical. While many specialists are needed, commercial electricians are among the most important to have on hand. They are directly involved in upholdin...

The Essential Guide to Transforming Office Spaces for Maximum Efficiency

Why Office Fitouts MatterA well-designed office can make all the difference in productivity, employee satisfaction, and client impressions. Businesses of all sizes are investing in updated office spaces to create environments that foster collaborat...

The A/B Testing Revolution: How AI Optimized Landing Pages Without Human Input

A/B testing was always integral to the web-based marketing world. Was there a button that converted better? Marketing could pit one against the other and see which option worked better. This was always through human observation, and over time, as d...

Using Countdown Timers in Email: Do They Really Increase Conversions?

In a world that's always on, where marketers are attempting to entice a subscriber and get them to convert on the same screen with one email, the power of urgency is sometimes the essential element needed. One of the most popular ways to create urg...

Types of Software Consultants

In today's technology-driven world, businesses often seek the expertise of software consultants to navigate complex software needs. There are several types of software consultants, including solution architects, project managers, and user experienc...

CWU Assistive Tech Hub is Changing Lives: Win a Free Rollator Walker This Easter!

🌟 Mobility. Independence. Community. All in One. This Easter, the CWU Assistive Tech Hub is pleased to support the Banyule community by giving away a rollator walker. The giveaway will take place during the Macleod Village Easter Egg Hunt & Ma...

LayBy Shopping