Tag Archives: antarctic

Antarctic warmth brings more snow, reducing sea level rise Updated for 2026

Evidence is mounting that the more the Antarctic warms under the impact of climate change, the more snow will fall on it, causing a build-up of ice.

The research, published in Nature Climate Change, builds on high-quality ice-core data and fundamental laws of physics captured in global and regional climate model simulations.

The team of authors, led by scientists from Germany’s Potsdam Institute for Climate Impact Research (PIK), says each degree Celsius of warming in the region could increase Antarctic snowfall by about 5%.

The suggestion that Antarctic snowfall is increasing is not itself new. But what the Potsdam scientists have done is important: they both provide new evidence to support the contention, and explore its potential consequences.

Katja Frieler, climate impacts and vulnerabilities researcher at PIK, and lead author of the report, says: “Warmer air transports more moisture, and hence produces more precipitation. In cold Antarctica, this takes the form of snowfall.

“We have now pulled a number of various lines of evidence together and find a very consistent result: temperature increase means more snowfall on Antarctica.”

The answers are in the ice-cores

To reach a robust estimate, the PIK scientists collaborated with colleagues in the Netherlands and the US including co-author Peter U. Clark, professor of geology and geophysics at Oregon State University.

“Ice-cores drilled in different parts of Antarctica provide data that can help us understand the future”, he says. “Information about the snowfall spanning the large temperature change during the last deglaciation, 21,000 to 10,000 years ago, tells us what we can expect during the next century.”

The researchers combined the ice-core data with simulations of the Earth’s climate history and comprehensive future projections by different climate models, and were able to pin down temperature and accumulation changes in warming Antarctica.

The ‘good news’ is that the increasing snowfall on the continent will add to the mass of the ice sheet and increase its height, offsetting sea level rise from other causes.

But on balance, Antarctica will still lose ice to the ocean

But the ‘bad news’, say the researchers, is that most of the snow won’t stay there. “Snow piling up on the ice is heavy and presses down – the higher the ice, the more pressure”, co-author Ricarda Winkelmann explains.

On the basis of another previous PIK study, the extra snow will increase the amount of ice flowing to the ocean. “Because additional snowfall elevates the grounded ice-sheet on the Antarctic continent but less so the floating ice shelves at its shore, the ice flows more rapidly into the ocean and contributes to sea level”, says Dr Winkelmann.

So on balance, the sea level-lowering effect from the extra snow is a relatively small one: the 5% increase in Antarctic snowfall that they expect for every 1°C rise in temperature would mean an estimated drop in sea-level of only about three centimetres after a century. By contrast melting ice in Greenland threatens metres of sea level rise.

Adding to Antarctica’s contribution to sea level rise, rising sea levels in the Southern Ocean – mainly caused by the thermal expansion of oceans and melting glaciers around the world, most importantly on Greenland – will allow coastal ice shelves to flow more rapidly into the ocean.

Furthermore even slight warming of the waters lapping Antarctica will make it easier for coastal ice to break off, allowing more of the continental ice mass to discharge into the ocean.

So the frozen continent will still be a net source of sea level rise in a warming world, says co-author Anders Levermann – PIK professor of dynamics of the climate system, and lead author of the sea-level rise chapter in the latest report by Intergovernmental Panel on Climate Change.

“If we look at the big picture, these new findings don’t change the fact that Antarctica will lose more ice than it will gain, and that it will contribute to future sea-level change”, he says.

Dr Frieler agrees: “Under global warming, the Antarctic ice sheet, with its huge volume, could become a major contributor to future sea-level rise, potentially affecting millions of people living in coastal areas.”

Alex Kirby writes for Climate News Network.

Oliver Tickell edits The Ecologist.

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Carbon stored deep in Antarctic waters ended the last ice age Updated for 2026

It’s well known that carbon in the atmosphere is causing global warming. What is less well known, outside of scientific circles at least, is the role oceans have to play in this.

Our seas contain 60 times more carbon than the atmosphere, and they can release it at sufficiently rapid rates to cause dramatic changes in the climate. In fact, as we describe in research published in Nature, CO₂ released by the oceans brought about the end of the last ice age.

More than 50 million cubic kilometres of ice once covered North America and Scandinavia. It melted away between approximately 19,000 and 10,000 years ago, releasing enough water to raise the sea level by about 130 metres.

This came after CO₂ concentrations increased by approximately 50%, from 180 to 280 parts per million between the last ice age and the current interglacial period. To explain such a pronounced increase, we have to look at the ocean.

Scientists have thought for a long time that the southern sectors of the Atlantic, Indian and Pacific Oceans, a region known as the Southern Ocean, may be key to explaining the increase in atmospheric CO₂.

Large volumes of deep water loaded with carbon come to the surface in this area. However, the low concentration of certain nutrients (for example iron) in surface waters limits the metabolism of planktonic organisms, which cannot fully consume all the carbon brought to the surface ocean, resulting in CO₂ being ‘outgassed’ to the atmosphere.

We wanted to assess if the ocean contributed to the atmospheric CO₂ increase during the last deglaciation, so it made sense to look at areas that are important today for the ocean-atmosphere exchange of carbon: the Atlantic Sector of the Southern Ocean and the Eastern Equatorial Pacific, another area where deep, cold water rises to the surface.

But how can we then go back in time and check if these areas were a source of CO₂ in the atmosphere? The answer is buried a few thousand meters below the surface of the oceans.

The well-kept secrets secrets of long dead plankton

Research vessels such as the Joides Resolution are capable of drilling the sea floor to recover long sequences of sediments in which the history of the oceans is recorded. The sediments contain, among other things, fossils of tiny organisms that once lived in the upper ocean, called foraminifera. These creatures build chalky shells, and the waters they live in influence their chemical composition.

After death, the shells sink to the bottom of the oceans, where they accumulate. We analysed the sediment cores and looked for the isotopic composition of the element boron present in shells that lived during particular times of interest.

Boron tells us pH levels of the waters, which in turn tells us about carbon levels: a high concentration of CO₂ in the waters will make them more acidic (lower pH), and vice versa.

We found a link. When the glaciers of the last ice age were melting, and the atmospheric CO₂ was increasing, the surface waters of the Southern Ocean and the Eastern Equatorial Pacific were also more acidic. This signalled an increased concentration of CO₂ – much higher than those in the atmosphere.

This is the key finding of our research: the deep ocean was a source of CO₂ to the atmosphere during key intervals of the last deglaciation, which explains the large increase in CO₂ concentrations.

Where did this carbon come from?

It’s the next obvious question. Previous research has found that the last ice age saw much less carbon exchanged between ocean and atmosphere than we see today, mostly because the Southern Ocean was intensely stratified at the time and deep waters rarely made it to the surface.

Nutrients and CO₂ were accumulating in the deep Southern Ocean, due to the decay of the organic matter that was being produced in the surface ocean and transported to the abyss.

During the deglaciation, the effective communication between deep and upper ocean was re-established, and this carbon ‘reservoir’ was leaked to the atmosphere.

Since the beginning of the industrial revolution the oceans have absorbed an estimated 155 billion tonnes of carbon, about 30% of the total human emissions.

The present atmospheric CO₂ concentrations, approximately 400 parts per million, have not been seen on Earth since the Pliocene, around 3 million years ago, and the rate of increase is unprecedented in the period of on-off glaciers we have had since.

Humanity is performing a large scale experiment with the Earth, and the consequences are already being seen in the form of increased atmospheric and oceanic temperatures, raising sea levels and ocean acidification, to name a few.

How the oceanic uptake of CO₂ is going to operate in the future remains unknown, but studies like ours advance our understanding of how the ocean works to store and release carbon on timescales of millennia and that therefore are way beyond the reach of the instrumental record.

The paper: ‘Boron isotope evidence for oceanic carbon dioxide leakage during the last deglaciation‘ by M. A. Martínez-Botí et al is published in Nature.

Miguel Martinez-Boti is Visiting Researcher, National Oceanography Centre at the University of Southampton.

Gianluca Marino is Researcher in Oceans & Climate Change at the Australian National University.

This article was originally published on The Conversation. Read the original article.

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Antarctica: warming ocean trebles glacial melt Updated for 2026

The Antarctic ice shelf is under threat from a silent, invisible agency – and the rate of melting of glaciers has trebled in the last two decades.

The ocean waters of the deep circumpolar current that swirl around the continent have been getting measurably warmer and nearer the ocean surface over the last 40 years, and now they could be accelerating glacier flow by melting the ice from underneath, according to new research.

And a separate study reports that the melting of the West Antarctic glaciers has accelerated threefold in the last 21 years.

West Antarctic ice sheet – a potential 4.8m of sea level rise

If the West Antarctic ice sheet were to melt altogether – something that is not likely to happen this century – the world’s sea levels would rise by 4.8 metres, with calamitous consequences for seaboard cities and communities everywhere.

Researchers from Germany, Britain, Japan and the US report in Science journal that they base their research on long-term studies of seawater temperature and salinity sampled from the Antarctic continental shelf.

This continued intrusion of warmer waters has accelerated the melting of glaciers in West Antarctica, and there is no indication that the trend is likely to reverse.

Other parts of the continent so far are stable – but they could start melting for the first time. “The Antarctic ice sheet is a giant water reservoir”, said Karen Heywood, professor of environmental sciences at the University of East Anglia, UK.

“The ice cap on the southern continent is on average 2,100 metres thick and contains 70% of the world’s fresh water. If this ice mass were to melt completely, it could raise global sea level by 60 metres. That is not going to happen, but it gives you an idea of how much water is stored there.”

Temperatures in the warmest waters in the Bellinghausen Sea in West Antarctica have risen from 0.8°C in the 1970s to about 1.2°C in the last few years.

“This might not sound much, but it is a large amount of extra heat available to melt the ice“, said Sunke Schmidtko, an oceanographer at the Geomar Helmholtz Centre for Ocean Researchin Kiel, Germany, who led the study. “These waters have warmed in West Antarctica over 50 years. And they are significantly shallower than 50 years ago.”

Unpredictable consequences on ice and ecology

The apparent rise of warm water, and the observed melting of the West Antarctic ice shelf, could be linked to long-term changes in wind patterns in the Southern Ocean. Although melting has not yet been observed in other parts of the continent, there could be serious consequences for other ice shelves.

The shelf areas are also important for Antarctic krill – the little shrimp that plays a vital role in the Antarctic ocean food chain – as they serve as protective ‘nurseries’ for the young crustaceans. Warming ice shelves may have unpredictable consequences for spawning cycles, krill abundance, and wider ocean biodiversity.

Meanwhile, according to US scientists writing in Geophysical Research Letters, the glaciers of the Amundsen Sea in West Antarctica are shedding ice faster than any other part of the region.

Tyler Sutterley, a climate researcher at the University of California Irvine, and NASA space agency colleagues used four sets of observations to confirm the threefold acceleration.

They took their data from NASA’s Gravity Recovery and Climate Experiment (GRACE) satellites, from a NASA airborne project called Operation IceBridge, from an earlier satellite called ICESat, and from readings by the European Space Agency’s Envisat satellite.

Glaciers losing 16 billion tonnes of ice a year

The observations spanned the period 1992 to 2013 and enabled the researchers to calculate the total loss of ice, and also the rate of change of that loss. In all, during that period the continent lost 83 billion tonnes of ice per year on average.

After 1992, the rate of loss accelerated by 6.1 billion tonnes a year, and between 2003 and 2009 the melt rate increased by 16.3 gigatonnes a year on average. So the increasing rate of loss is now nearly three times the original figure.

“The mass loss of these glaciers is increasing at an amazing rate”, said Isabella Velicogna, Earth system scientist at both UC Irvine and the NASA Jet Propulsion Laboratory.

Tim Radford writes for Climate News Network.

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