Disturbing new research shows warm waters rushing towards world’s largest ice cap in Antarctica

by Laura Herraiz Borreguero, Alberto Naveira Doodle and Jess Melbourne-Thomas, The Conversation

Credit: Shutterstock

Warmer waters are heading towards the East Antarctic Ice Sheet, according to our alarming new research that reveals a potential new driver of global sea level rise.

The research, published today in Natural climate change, shows that changing water circulation in the Southern Ocean could compromise the stability of the East Antarctic Ice Sheet. The ice cap, the size of the United States, is the largest in the world.

Changes in water circulation are caused by changes in wind patterns and related to factors such as climate change. The resulting warming waters and sea level rise can damage marine life and threaten coastal human settlements.

Our findings underscore the urgency of limiting global warming to less than 1.5℃, to avoid the most catastrophic climate damage.

Ice sheets and climate change

Ice sheets include glacial ice that has accumulated from precipitation on land. Where the sheets extend from the land and float on the ocean, they are called ice shelves.

The West Antarctic Ice Sheet is well known to be melting and contributing to sea level rise. But until now, much less was known about its eastern counterpart.

Our research has focused off a region known as the Aurora subglacial basin in the Indian Ocean. This area of ​​frozen sea ice is part of the East Antarctic Ice Sheet.

How this basin will respond to climate change is one of the greatest uncertainties in sea level rise projections this century. If the basin were to melt completely, global sea level would rise by 5.1 meters.

Much of the basin lies below sea level, making it particularly susceptible to melting oceans. This is because deep sea water requires lower temperatures to freeze than shallower sea water.

What we found

We reviewed 90 years of oceanographic observations off the Aurora subglacial basin. We have seen unequivocal ocean warming at a rate of up to 2℃ to 3℃ since the first half of the 20th century. This is equivalent to 0.1℃ to 0.4℃ per decade.

The warming trend has tripled since the 1990s, reaching a rate of 0.3℃ to 0.9℃ every decade.

So how is this warming related to climate change? The answer relates to a belt of strong westerly winds over the Southern Ocean. Since the 1960s, these winds have moved south towards Antarctica during years when the southern annular mode, a climatic factor, is in a positive phase.

The phenomenon has been partly attributed to the increase in greenhouse gases in the atmosphere. As a result, westerly winds approach Antarctica in summer, bringing warm water with them.

Disturbing new research shows warm waters rushing towards world's largest ice cap in Antarctica

Where ice caps extend from land and float on the ocean, they are called ice shelves. Pictured: Iceberg Alley in East Antarctica. Credit: Dr Joel B Pedro, author provided

The East Antarctic Ice Sheet was once thought to be relatively stable and immune to warming oceans. This is partly because it is surrounded by very cold water known as “dense plateau water”.

Part of our research has focused on the Vanderford Glacier in East Antarctica. There, we observed warm water replacing the colder, denser water on the shelf.

The movement of warm waters towards East Antarctica is expected to worsen throughout the 21st century, further threatening the stability of the ice sheet.

Why it’s important for marine life

Previous work on the effects of climate change in East Antarctica has generally assumed that warming occurs first in the surface layers of the ocean. Our findings – that deep waters warm first – suggest that there is a need to rethink the potential impacts on marine life.

Robust assessment work is needed, including investments in monitoring and modeling that can link physical changes to complex ecosystem responses. This should include the possible effects of very rapid changes, known as tipping points, which can mean the ocean is changing much faster than marine life can adapt.

East Antarctic marine ecosystems are likely to be highly vulnerable to warming waters. Antarctic krill, for example, reproduce by sinking eggs in the ocean depths. Warming deeper waters can affect the development of eggs and larvae. This would in turn affect krill populations and dependent predators such as penguins, seals and whales.

Disturbing new research shows warm waters rushing towards world's largest ice cap in Antarctica

Minke whale surfacing through the ice in Antarctica, where warming water will impact marine ecosystems. Credit: Jess Melourne-Thomas

Limit global warming below 1.5℃

We hope our findings will inspire global efforts to limit global warming to below 1.5℃. To achieve this, global greenhouse gas emissions must fall by around 43% by 2030 and be close to zero by 2050.

Warming above 1.5℃. greatly increases the risk of destabilization of the Antarctic ice sheet, leading to substantial sea level rise.

But staying below 1.5℃ would keep sea level rise to no more than an additional 0.5 meters by 2100. This would provide greater opportunities for people and ecosystems to adapt.

Investigating the drivers of Antarctic ice retreat

Provided by The Conversation

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Quote: Disturbing new research shows warm waters rushing towards world’s largest ice cap in Antarctica (2022, August 3) Retrieved August 4, 2022 from https://phys.org/news/2022-08-world- biggest-ice-sheet-antarctica .html

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