Sea level rise from the melting ice sheet could soon be off

Where we talk in detail today about climate change and its various effects, the conversation was once easy. We call it “global warming” and were annoyed with the cooking outside in the summer and the high altitude demands of many of our favorite cities.

Scientists are now concerned that sea level rise could be locked, as ice sheets and glaciers cross “tipping points” that cannot stop their damage. Research is underway to determine how we can avoid these points of return.

The threat of sea level rise due to melting ice is often discounted by climate change skeptics. The general quote is that a floating ice cube does not change water level as it melts due to the displacement principle. However, this is not responsible for the fact that most of the Antarctic ice actually sits on land. When this ice melts, it leads directly to an increase in sea level.

Although the loss of floating ice will not directly cause sea level rise, the concern is that the loss of ice sheets will increase the melting rate of the thawed glaciers. Credit: NASA, Public Domain

The main concern is the danger caused by the Twitts Glacier, which scientists have dubbed the “Doomsday Glacier.” The glacier is trapped, especially in the east, by a large floating ice shelf. This slows down the flow of the glacier and helps keep it stable. The floating ice shelf further aids in this task as it sits opposite a large underwater mountain, acting as a bracket.

Recently, scientists have noticed that floating ice shelves are showing alarming signs of deterioration. Large cracks have spider webs all over the ice, which raises concerns for the long-term stability of the shelf. The effect is similar to a crack in a window; Once they reach a certain point, the whole glass breaks. Complicating the problem further, the ice shelf seems to be losing its grip on the mountain under the water as it retains it because the warm water is melting the sheet from the bottom.

When ground ice sits on the ground below sea level, it can allow seawater to move downwards if the ice sheet is not heavier than dense sea water otherwise it will be displaced. This water then melts the ice from the bottom at an increasing rate as the grounding line moves further inland. Credit: NASA, Public Domain

The Twitts Glacier is already responsible for about 4% of the global sea level rise each year. The concern is that with the loss of floating ice sheets, the glacier can increase its flow towards the ocean, only increasing the sea level rise by up to 5% in the short term. Scientists are currently hoping that the ice shelf will break within the next 5 years.

The long-term effects are profound if uncertain at this stage. If the vast Thoites glacier breaks up and melts, scientists hope the process could happen in a few centuries, contributing to a 65-centimeter rise in global sea levels. If the vast West Antarctic ice sheet is lost, it will add 3.3 meters to the global sea level, which will completely change the map of the world.

We like Greenland ice, not green

Many glaciers, such as the Jacobusvan Isbrai Glacier, are retreating from the industrial age. The concern is that soon, their losses could be locked regardless of future reductions in greenhouse gas emissions. Credit: NASA, Public Domain

This is not just a problem in the Southern Hemisphere. Scientists believe that 1-2 meters of sea level rise from the glaciers of Greenland may be stuck which is melting regardless of what we do now. The 140-year record of glacier melting rates in the ice-sheet elevation and the Jacobshavan Basin indicates that there may be a reaction effect that causes rapid ice loss. As the ice sheet thins, it comes in contact with warm air at lower altitudes, accelerating the effect.

The melting ice is also playing havoc with the movement of the sea. Greenland’s icy cold water is slowing down the currents responsible for transporting heat through the world’s oceans. The fear is that it could disrupt rainfall in key areas, create more droughts and warm the southern oceans, accelerating the melting of West Antarctic ice sheets.

There is some comfort in the scale of time that has been prophesied, at least for the present living people. It is expected that the progress of 1-2 m growth from Jakobshavn melting will take a few centuries, even if we can’t stop it now. It is also not certain that a tipping point has been passed, however, with global temperatures and the concentration of greenhouse gases still increasing, that point may be incomplete. Regardless of the lack of return to pre-industrial temperatures, the researchers believe that significant ice loss, and corresponding sea level rise, is almost certain.

The most painful predictions suggest that damage to Greenland’s ice sheets could be locked in at 1.5 degrees Celsius, which could be reached by 2030. If the models are correct, once this point is reached, emissions will decrease and global temperatures will stabilize. The ice sheet will not be enough to rescue, which will continue to melt slowly for a long time and the sea level will rise.

Future thoughts

Taken apart, both glaciers do not pose an immediate threat to our coastal cities over the next decade. However, if multiple climate systems continue to be pushed beyond the no-return point, as we have explored before, we may be able to reduce emissions and stop significant negative changes before we are able to stabilize the climate.

[Banner image: “Surprise Glacier” by USGS. Thumbnail: Calving at Perito Moreno by NASA Goddard.]

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