How Massive Glaciers Melt

Summer 2021

New research by a team that included a Johns Hopkins engineer promises to enable more accurate ice flow predictions, helping scientists better forecast how melting glaciers will contribute to rising sea levels, which have been linked to coastal and wetland flooding and destructive erosion around the world.

In a recent issue of Journal of Geophysical Research: Earth SurfaceHarihar Rajaram and team offer a new method of estimating how heat flows upward from the Earth to beds of ice sheets in Greenland and Antarctica, affecting their viscosity and rates of movement.

“Mass ice loss from Greenland is the single largest contributor to sea level rise today, and Antarctica is projected to contribute significantly to sea level rise in the decades to come,” says Rajaram, a professor of environmental health and engineering. “The temperature of ice near the bed determines how fast it can flow. It is important that ice sheet models incorporate accurate bed conditions so that we make correct projections out to 2050 and 2100. Our method is a big step in the right direction.”

Rajaram worked on the study with experts from the Geological Survey of Denmark and Greenland, NASA, the University of Maryland, the University of California, and the University of Alaska.

The team’s method is groundbreaking, Rajaram says, because it provides high-resolution estimates of variations in heat flow across a scale of hundreds of meters, accounting for the complex bed topography and geological features—such as valleys and ridges—underneath the massive ice sheets. Though it has long been understood that heat flow is greater in valleys and lesser on ridges, this was the first time a model has taken these factors into account.

The researchers created a simple statistical model to estimate influence of glacier bed topography on geothermal heat flow and applied it to digital elevation models of the subglacial topography beneath the Greenland and Antarctic ice sheets. The result? A far more detailed geothermal heat flow map than what has been offered before.

“We discovered that heat flow in central East Greenland and the Antarctic Peninsula is halved along ridges and doubled within glacier valleys,” Rajaram says.

The researchers hope their method and results will be not only adopted into present-day ice flow models to improve ice flow predictions but also used to estimate the influence of topography on geothermal heat flux in non-ice-covered areas.

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