Going Under

By Bill McGuire

If your children or grand children live within sight of the sea, then be afraid. Very afraid. Sea-level rise is set to be one of the most devastating and disruptive consequences of climate breakdown and the prospect of the oceans drowning coastal communities by the end of the century is growing by the day. The prevailing view sees perhaps a metre or so of sea-level rise by the century’s end – enough in its own right to doom low-lying islands and coastlines – but the true picture may be far worse. A number of studies suggest that sea levels by 2100 could be two or three metres up on today; perhaps as much as five metres. A truly terrifying scenario.

uk_sealevel_rise

How the UK would look on an ice-free Earth

Global sea levels rose by around 20cm during the 20th century and are climbing now at close to half a centimetre a year. Much of this is due to the expansion of the oceans as they warm, but melting ice is playing an ever more important role in hiking the rate of the rise. The problem is that the Earth is not heating up uniformly, and the bad news for us is that temperatures across the polar regions are climbing far more rapidly than anywhere else. Of course, this is where the vast majority of our world’s ice resides; in total, a staggering 24 billion cubic kilometres of it – close to seventy per cent of all the fresh water on Earth. The great ice sheets of Greenland and Antarctica have been bastions of stability since the end of the last Ice Age around 10,000 years ago. During the second half of the 20th century, however, and especially in the last few decades, they have started to crumble, shedding vast quantities of freshwater into the oceans.

Until recently, attention has been focused on accelerating melting of the Greenland and West Antarctic ice sheets, which are the most sensitive to rising temperatures. The last 20 years or so has seen a huge increase in the melting rate of the Greenland Ice Sheet, which is now shedding close to 400 billion tonnes of ice every year. Even more worryingly, the melting rate is increasing exponentially, which means it will continue to accelerate rapidly.

The news from West Antarctica is not good either. In the five years from 2012 to 2017, ice loss from the West Antarctic Ice Sheet shot up threefold, from 76 billion tonnes annually, to a colossal 219 billion tonnes. In total, more than 2.7 trillion tonnes of Antarctic ice has melted in the last quarter century, adding three-quarters of a centimetre to global sea level. At the new rate, the contribution over the next 25 years would be 1.5cm. Not really too much to worry about. If, however, the rate of increase is maintained over this period, then the annual rise by the mid-2040s – barely more than 20 years away – would be close toa catastrophic five centimetres a year. And this is without the growing contribution from Greenland and from the increasing expansion of sea water as the oceans continue to warm. It is not known how the melt rate will change in coming decades, but it is a sobering thought that even if the rate of increase stays as it is, low-lying lands and all coastal population centres would be threatened with permanent inundation by the century’s end.

As if this wasn’t bad enough, new research from East Antarctica paints an even more disturbing picture. The East Antarctic Ice Sheet dwarfs those of both Greenland and West Antarctica. Complete melting of the Greenland Ice Sheet would raise global sea levels by around seven metres, while melting of all the ice in West Antarctica would add another five or so. If East Antarctica lost its ice, however, it would push up sea levels by a staggering fifty metres or more. Until recently, the East Antarctic Ice Sheet was regarded as largely stable, and some studies even suggested that it might have been growing. The new study (1) reveals, however, that this is now changing, and changing with a vengeance. What was a sleeping giant is now beginning to wake up.

Satellite data reveals that a cluster of colossal glaciers, which together make up about an eighth of the coastline of East Antarctica, are starting to melt as the surrounding ocean gets progressively warmer. The loss of the giant (It’s about the size of Spain!) Totten Glacier – just one of the cluster – would, on its own, raise global sea levels by more than three metres. The new data show that it and its companions are now moving increasingly rapidly seawards and thinning as they do so, meaning that even the worst predictions for rising sea levels may be optimistic. As with the many other indicators that flag the remorseless breakdown of the stable climate that fostered the growth of our civilisation, the collapse of the polar ice sheets sends us the message that time has run out. Prevarication is no longer an option. Only serious and determined action now will give us any chance of avoiding a climate calamity that will swamp the world’s coastlines and displace hundreds of millions – if not billions – of people.

(1) https://www.nasa.gov/feature/goddard/2018/more-glaciers-in-antarctica-are-waking-up

 

Bill   McGuire   is  Professor   Emeritus   of  Geophysical   &   Climate Hazards   at  UCL   and   author  of   Waking   the  Giant:   How   a  Changing Climate Triggers Earthquakes, Tsunamis and Volcanic Eruptions. He was   a   contributor  to   the   IPCC  2012   report   on  Climate   Change   &Extreme Events and Disasters.

 

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The truth behind Antarctica’s fast-melting ice

By Kate Goldstone

Resources:

 

Introduction

Antarctica, which has long been thought to be relatively safe from vast ice melts, has proved us wrong. It’s actually in just as much trouble as the Arctic.

Plenty of people believed the ice on Antarctica wouldn’t melt as fast as the Arctic. Then, in April 2017, scientists claimed Antarctica’s ice might actually be melting a lot faster than anyone predicted. It matters because Antarctica is home to 90% of the world’s ice. If it keeps melting this quickly, and the continent’s massive ice sheets go, we’re looking at profound worldwide effects including mass flooding.

What’s going on, and is the trend continuing? Here’s what you need to know.

 

How Arctic and Antarctic sea ice differ

Because the Arctic and Antarctics’ geography is different, so is their ice. The Arctic ocean is partly enclosed, mostly surrounded by land. Its ice is less mobile and floes tend to clump together into thick ridges. Ridge ice has a longer life cycle and stays frozen for longer. The region is home to 5.8 million square miles of sea ice in winter, reducing to roughly 2.7 million square miles by the end of the summer.

The Antarctic is totally different. Made up of land surrounded by ocean, the sea ice there moves freely and drifts faster. There are fewer ice ridges as a result, and the lack of a land boundary to the north means the ice naturally floats northwards into warmer waters before melting. Winter sees about 6.9 million square miles of Antarctic ocean covered in sea ice, but by the end of the summer there are only around 1.1 million square miles of it left.

 

Clear warnings in 2017

April 2017 saw the first reports of Antarctica’s ice melting faster than previously predicted, thanks to the discovery of a network of lakes and streams under the continent’s ice shelves which created a destabilising influence on the ice above. The study was published in the journal Nature and revealed the process is taking place in areas where scientists didn’t think there was any liquid water. As global temperatures keep rising, the speed of the damage can only increase. The team examined satellite images dating as far back as 1973 as well as aerial images snapped by military aircraft way back in the 1940s. And the results were a shocker – some of the streams flowed for 75 miles, and some of the lakes were several miles across.

A few months later in November 2017 a study examined the east Antarctic Totten ice shelf, finding it unexpectedly vulnerable to warming waters. And still governments failed to react, never mind act. March 2018 saw scientists announce more of the Totten Ice Shelf was floating than they’d predicted. Multiple different types of supporting evidence proved the point. Now it looks a lot like a certainty. If Larsen C and Totten melt, the world’s sea levels will rise as much as 5 metres. Totten could easily contribute a 3m sea level rise all on its own.

 

Another equally clear warning in 2018

In August 2018, more headline news surfaced about Antarctica’s ice. It appeared a couple of enormous glaciers to the east of the region had lost ice mass disturbingly quickly in the years since the millennium. The results hinted that forecasts for sea level rise this century will have to be revised upwards, but nobody knows exactly how much. While it’s obvious the ice in Antarctica is melting frighteningly quickly, the complex dependencies and inter-dependencies that make it happen aren’t at all clear.

So far most molten Antarctic ice has come from the west of the continent. The Antarctic Peninsula is under particular threat, reaching out into the ocean and exposed to warmer waters, and the Larsen C ice sheet, which famously cracked in 2017, is also to the west. East Antarctica has long been thought to be more stable, cut off from the planet’s weather systems by powerful spinning gales that stop the warmth getting anywhere near. On the other hand it’s so remote that scientists have spent decades guestimating what might happen instead of actually measuring. But they keep getting it wrong. In 2015 one piece of research hinted the region was putting on extra ice, not losing it, but closer examination revealed it was simply not true.

Even if Totten disappears, we probably won’t see a 5m rise by 2100. There’s such a lot we don’t know about the behaviour of Antarctic ice and the many factors a big melt depends on. It apparently takes hundreds of gigatonnes of ice to raise sea levels by just one millimetre, and Totten isn’t anywhere near that level… yet. But it might speed up, and we have no idea how fast the melting could ultimately become once we pass a tipping point, also unknown.

There are more unknowns around the effect of the geology underneath the continent, the shape of the bedrock itself. And the channels running from underneath the Totten link it to the ocean give warmer water the access it needs to potentially kick off a runaway melt.

Only one thing is clear. The original consensus was far too cautious. Now we know for sure Antarctica is losing ice mass hand over fist. It has been losing ice for years. And nobody knows where the tipping point is.

 

The effects of runaway sea level rises

The cities under the most threat from rising sea levels also happen to be amongst the biggest on the planet, the most financially, socially and culturally important. Alexandria in Africa, The Hague in Europe, Miami in North America and Rio de janiero in South America are all at risk, home to a total of 10 million people, almost all of whom would be displaced. Ten million migrants from just four cities… that’s hard to deal with. And it’s only the tip of the iceberg, if you’ll forgive the pun. On every continent, in every sea-facing country, we’d have to build vast amounts of new housing stock for migrants.

Cities don’t operate in isolation, either. Every drowned city means drowned transport networks, communications networks, power, utilities and food networks, all left under water permanently. Wildlife will suffer just as badly, forced out of natural habitats. It actually doesn’t bear thinking about… but it’s happening all the same. As UN environment chief Erik Solheim said before last year’s Bon conference, “[We] still find ourselves in a situation where we are not doing nearly enough to save hundreds of millions of people from a miserable future.”

 

What are governments doing about Antarctic ice loss?

Antarctic ice melt is driven by climate change. Governments are not doing enough about climate change. All over the world those in power are still prevaricating, delaying, discussing and disagreeing while Rome burns. It’s our job to force them to act. Will you join us?