Computer model shows breakup of iceberg logjams

March 2, 2017 by Robert Perkins, California Institute of Technology
Computer model shows breakup of iceberg logjams
Credit: B. Minchew/Caltech

Projections of how much the melting of ice sheets will contribute to sea-level rise can vary by several meters based on the rate of iceberg calving at the edges of those ice sheets. To provide climate scientists with models that make more accurate forecasts, a postdoctoral researcher at Caltech has created a computer simulation of one of the key processes controlling glacial calving.

Glaciers are moving slabs of ice that slowly grind downhill. Where they end in the sea, chunks break off, forming icebergs in a process known as calving. When temperatures plummet in the winter, those icebergs can freeze together and create a traffic jam that prevents further icebergs from breaking off from the glacier.

During the winter, the glacier loses much less ice to the sea. The eventual spring breakup of what is known as the mélange—that frozen iceberg logjam—occurs suddenly, and is the focus of research by Caltech's Alexander Robel.

"I developed a computer model that simulates how the first iceberg calving of the warm season creates a shock wave that travels through the jammed mélange, breaking it up," says Robel, a National Oceanic and Atmospheric Administration (NOAA) Postdoctoral Scholar and a Stanback Postdoctoral Scholar at Caltech. His new model was featured in Nature Communications on February 28.

The mélange is a frozen granular material, so Robel adapted an open-source computer simulation called the Discrete-Element Bonded-Particle Sea Ice Model to show how icebergs freeze together in the winter and then transmit the shock of the first iceberg calving in the summer.

Computer model shows breakup of iceberg logjams
This animation shows how a single calving event sends out a shockwave that triggers a breakup of the frozen mélange. Credit: Alexander Robel

That first calving is made possible by the thinning of sea ice in warmer water, which reduces the ability of the mélange to act a bulwark against the glacier.

Robel tailored his modeled glaciers to resemble fjords in Greenland. Those fjords are narrow channels of water that are prone to trapping mélange. Robel was able show that the threshold at which spring sea-ice breakup is likely to occur is based in part on the thickness of sea ice within the mélange, but also on the shape of the channel within which the mélange is trapped.

Robel, who is a researcher in Caltech's Division of Geological and Planetary Sciences, home to the Seismological Laboratory, says his work was inspired in part by seismological studies of the way fractures propagate through elastic materials—drawing a connection between earthquakes and .

Computer model shows breakup of iceberg logjams
This animation shows how mélange responds to pressure applied by the movement of a glacier. Credit: Alexander Robel

Robel's paper is titled "Thinning Sea Ice Weakens Buttressing Force of Iceberg Mélange and Promotes Calving."

Explore further: Ice loss accelerating in Greenland's coastal glaciers, study finds

More information: Alexander A. Robel. Thinning sea ice weakens buttressing force of iceberg mélange and promotes calving, Nature Communications (2017). DOI: 10.1038/ncomms14596

Related Stories

Image: Glacial 'aftershock' spawns Antarctic iceberg

February 16, 2017

Pine Island Glacier has shed another block of ice into Antarctic waters. The loss was tiny compared to the icebergs that broke off in 2014 and 2015, but the event is further evidence of the ice shelf's fragility.

Climate change and the physics of falling icebergs

September 4, 2014

For thousands of years, the massive glaciers of Earth's polar regions have remained relatively stable, the ice locked into mountainous shapes that ebbed in warmer months but gained back their bulk in winter. In recent decades, ...

Recommended for you

A decade on, smartphone-like software finally heads to space

March 20, 2019

Once a traditional satellite is launched into space, its physical hardware and computer software stay mostly immutable for the rest of its existence as it orbits the Earth, even as the technology it serves on the ground continues ...

Tiny 'water bears' can teach us about survival

March 20, 2019

Earth's ultimate survivors can weather extreme heat, cold, radiation and even the vacuum of space. Now the U.S. military hopes these tiny critters called tardigrades can teach us about true toughness.

Researchers find hidden proteins in bacteria

March 20, 2019

Scientists at the University of Illinois at Chicago have developed a way to identify the beginning of every gene—known as a translation start site or a start codon—in bacterial cell DNA with a single experiment and, through ...

Turn off a light, save a life, says new study

March 20, 2019

We all know that turning off lights and buying energy-efficient appliances affects our financial bottom line. Now, according to a new study by University of Wisconsin-Madison researchers, we know that saving energy also saves ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.