Some excellent news for far-future sea level rise

Much better than a sharp stick in the eye–.

Brand-new design discovers processes that might help slow loss at some glaciers.

Velocity of recent ice flow around Antarctica. Thwaites Glacier is one of the smaller purple regions on the left side of this image.

Enlarge/ Velocity of recent ice flow around Antarctica. Thwaites Glacier is among the smaller purple regions on the left side of this image.


Glaciers are moody things with myriad characters. Some are pretty persistent, declining to melt excessive as Earth’s environment warms. However others are rather sensitive, with the prospective to diminish more than you might expect if you press them too far.

Much of this relates to the shape of the bedrock underneath. Some glaciers that touch the ocean have bedrock bases that slope downward as you head inland. If the glacier starts pulling away downhill, seawater can flow in and float the ice more and more easily, destabilizing it so it retreats quicker.

Each marine glacier has a “grounding line”– the point where ice stops resting on strong ground and starts floating, rather, like a canoe pushing off from coast. When you hear about an “ice shelf,” that’s the drifting portion of the glacier. The position of the grounding line along the bedrock is where topography plays such a huge role. But a new study from a group led by NASA’s Eric Larour reveals how the bedrock can move, too, making these sensitive glaciers a little less sensitive.

The concept isn’t new. The retreat of these glaciers can be sped up or slowed by a variety of processes, consisting of altering water level out front. As sea level rises, the floating effect undoubtedly increases, speeding up ice loss. And there are weirder factors: glaciers in fact apply a gravitational destination on the seawater around them, pulling a mound of water in close. If the glacier diminishes, that gravitational pull likewise diminishes, which actually lets water slosh away– lowering sea level at the coast.

Bedrock likewise reacts to changes in the mass of ice on top. Increasing ice acts to slowly depress the land surface area (which is why the land below Greenland’s ice sheet is roughly bowl-shaped). Losing ice enables the bedrock to rebound up. And in this case, that suggests that the bedrock at the grounding line below a delicate glacier can spring upward to fulfill the ice, helping to preserve the friction that slows retreat.

The concern is, how much of an effect does this have? Numerous models that are utilized to simulate altering glaciers try to consist of these procedures however are limited to coarser resolutions. In this brand-new research study, the researchers designed Antarctica to a resolution of 1 kilometer. It turns out, that makes a quite huge difference.

The study is concentrated on Antarctica’s Thwaites Glacier, which is among the continent’s most delicate and susceptible– and for that reason a significant wildcard when it comes to how rapidly future sea level increase will accumulate. Numerous versions of the design were run to simulate the next 500 years, each time including another process to see what effect it had.

The two largest effects were rebounding bedrock followed by the gravitational attraction, both of which slowed Thwaites Glacier’s shrinking. The greater model resolution showed that these processes were more powerful in the instant vicinity of the glacier than you would see in coarser models that balance over bigger areas. Together, they decreased the motion of the glacier’s grounding line by almost 40 percent in the year 2350, decreasing its contribution to water level increase by 25 percent.

While that result suggests that these processes might be crucial and useful in the long run for glaciers like Thwaites, there was sadly really little difference this century. Around 2100, there was just a 1-percent change in sea level rise contribution. Larger changes in mass were required prior to rebounding bedrock or weaker gravitational attraction might end up being substantial aspects.

Among the more sobering truths about water level increase is that it will continue long into the future, even if we effectively stop global warming. Ice sheets merely take a very long time to totally react to a warmer world. This study reveals that complicated elements like moving bedrock might not have a huge impact on delicate glaciers over the coming decades, but they have to be properly accounted for if you wish to forecast those changes out a couple of centuries– where they can offer some unusual great news.

Science,2019 DOI: 101126/ science.aav7908( About DOIs).

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Angie Ronson

Angie Ronson is Editor-in-Chief at THRS. She covers the transformative impact of new technology on all sectors.