The statistics are grim. Collectively, the Antarctic and Greenland ice caps are losing about 427 billion tonnes of ice one year on average. That’s over 1.1 billion tonnes per day. The water from these liquefying ice caps flows into the oceans, causing sea levels to rise higher and higher.
There are few signs that the melting of the ice caps will slow down anytime soon. If anything, it’s going to get exponentially faster, scientists say. Like the glaciers themselves, it’s a slow start but comes with terrifying momentum.
Ice caps store 99% of all fresh water on Earth. That’s a staggering amount of water, and the importance is obvious if you’ve ever stood on the shore of one of North America’s Great Lakes and gazed at the aquatic horizon. All this water, enough to make it look like an inland sea, is only a fraction of what is carried in the solid mass of Antarctica.
Together, the ice of Antarctica and Greenland would raise sea level by about 230 feet if everything melted. The seas would eat up a significant portion of the earth’s present land, drowning coastal cities like New York, Los Angeles, and Houston. Low-lying Florida would simply disappear. And Antarctica, once a snow-covered wasteland, would become a rocky archipelago, free of the overlying ice and partially submerged by rising seas.
But a completely ice-free Earth is not going to happen in our lifetimes, not possibly even in the next few thousand years. Most projections estimate sea level rise to be around a foot by 2100, far less than is possible. Until the next century, Earth’s ice caps will still be firmly in place, if they shrink.
However, the last thing we should take away from this fact is a feeling of complacency. Even small changes in sea level have dire consequences. That single foot of sea level rise could devastate low-lying coastal towns and force massive inland migrations. And melting glaciers have the potential to alter ocean currents, which could alter global weather patterns in unpredictable ways.
The ice caps that adorn the Earth’s North and South Poles are so ingrained in our mental geography that their presence is often just an afterthought. Even elementary school students know how to splash white on the top and bottom of a drawing of the Earth. But go back in time about 40 million years, and those icy promontories are disappearing. Indeed, for most of Earth’s existence, the poles have been ice-free.
Prior to our current Ice Age (which simply refers to the fact that there is permanent ice on the surface), dinosaurs roamed Antarctica and alligators swam in Alaska. Even in more recent times, the planet has been much hotter and wetter than it is now.
In the mid-Pliocene, about 3 million years ago, temperatures were 5 to 9 degrees Fahrenheit warmer than they are today, and the seas were as much as 50 feet, over 75 feet, higher.
It is not unusual for the ice caps to be smaller and for the sea level to be significantly higher than it is today. But, as with global temperatures, rapid changes in our natural world are having dire consequences for ecosystems and the organisms that depend on them.
Less ice means more ocean
The majority of sea level rise today comes from two things: melting ice and expanding water. As the water warms it becomes less dense, and some estimates suggest that as much as half of the sea level rise this decade is due to the warming of the water of the oceans which occupies more space. But as melt rates are only expected to increase, the disappearance of the ice caps will become the most important factor in sea level rise in the future.
The meltwater that causes the oceans to rise comes from the ice caps of Greenland and Antarctica. Although the Arctic ice cap is also shrinking, it does not contribute to sea level rise because this ice is already floating in the ocean – it takes up all the space possible.
Estimates of the contribution of melting Greenland and Antarctic ice to sea level rise vary, although scientists have constantly improved their models. A study estimates that, since the start of satellite recording in the 1990s, the two ice caps have contributed a total of 17.8 millimeters at sea level rise. Another recent paper says that Antarctica alone has contributed 0.36 millimeters per year to the rise in sea level, and a total of 14 millimeters since 1979. During this period, the ice sheet has lost mass to increasing rates – from 44 billion tonnes per year between 1979 and 1990 to as many as 277 billion tonnes per year by 2017.
Read more: How much will climate change heat the Earth up by the year 2100?
Although sea level rise is currently measured in millimeters, that may soon change. Most studies point out that ice loss and sea level rise will continue to increase over time. A study finds a noticeable inflection point in 2030, where in the worst-case scenario, ice caps begin to add tens of millimeters to sea level each decade, ending with more than a foot of sea level rise. sea. This is about as much sea level rise per decade as we have seen in the past 30 years.
One of the reasons for this could be that the ice caps are flowing into the ocean at an increasingly rapid rate. As the warmer ocean water eats away at their base, the massive glaciers that stretch from the mountains of Antarctica and Greenland and stretch far out into the ocean hold them back less.
The result is ice falling into the ocean, where it can melt even faster. A glacier in Greenland, for example, recently doubled its speed in just five years. In Antarctica, several ice caps, scientists say, are at high risk of completely collapsing, including Thwaites Glacier, sometimes called the “Doomsday Glacier”. If it collapsed and melted, it could raise sea level up to 3 feet.
Once started, it is probably difficult to stop the disintegration process of the ice sheet. It even means controlling our emissions and putting an end to global warming. might not stop the ice caps from melting.
And, while some evidence has indicated that Antarctica may gain more ice than it loses as wetter conditions increase snowfall, more recent studies say that is not true. Although parts of the continent have seen more precipitation, Antarctica has lost ice, on average, since we started monitoring it.
So while the ice caps aren’t going to go away, it’s largely irrelevant. There is so much water trapped in ice on Earth that releasing even a small part can cause big changes. We only have to look back in time to see what lies ahead. During the last interglacial period, just over 100,000 years ago, global temperatures were about 3 degrees warmer than today. It’s about as hot as the the planet should be in 2100, if we’re lucky. Despite this relatively small temperature change, sea level may have been 10 feet higher than they are today. Is this a glimpse of our future? Only time will tell.