Los Alamos National Laboratory

Model Mixes Ice, Heat, Water and Salt to View the Ocean’s Future

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Glacial Decline

A recent report notes that the decline of glaciers and mountain ice caps in both hemispheres has already led to sea-level increases — and that doesn’t include melting from Greenland and the Antarctic.  That conclusion is based on the increased flow speed of ice draining from the interior of the ice sheets, with a corresponding increase in ice loss.

Because “Current climate models don’t represent ice-sheet changes very well, we are in the process of putting together some new ice-sheet models to look at the sea-level rise issue,” Jones says.  The goal is “to figure out how rapidly that ice is going to melt, because if Greenland melts you get about six meters of sea level rise, and that is pretty significant.”

Though not a cause for complacency, the time frame for such occurrences is on a geologic scale.  Because Greenland’s ice sheet, for example, is several kilometers thick, “The question is whether a complete melting will take a thousand years or a few hundred years,” Jones says.

The Cause Is Us

Analyses of ice core samples dating back eons, combined with modern-day computer simulations, have firmly established the cause of global warming — and it is us.

The power of the Cray high-performance computers the COSIM researchers use allows them to turn on or off various factors that may or may not contribute to global warming.  That’s let them confirm that greenhouse gases generated by burning fossil fuels cause climate changes.  “We can turn off the industrial, human-caused carbon dioxide emissions and artificially pretend that humans didn’t exist, and see what the natural forcing is,” Jones says.

“When you do that, in the early part of the century you can explain some of what we see via natural warming, but anything from about 1975 onward can’t be explained by any kind of natural forcing — either solar variability or any other natural process.  Unless you include the human contribution to greenhouse gases you can’t match the observations,” he says.  Based on that data, current climate change scenarios show a 1 to 2 percent increase in carbon dioxide per year, or a doubling over the next 100 years.

No Ice Age

Improved ocean and ice models have let climate scientists put to rest at least one of the more ominous global warming scenarios, in which changes in the Atlantic Ocean’s currents have a dramatic cooling effect on Northern Europe.  Such cooling brought on a cataclysmic ice age in the popular 2004 movie, The Day After Tomorrow, which was replete with scientists rushing to model climate changes on supercomputers.

Real-life scientist Jones, however, says this scenario will not take place, at least not due to the driving force, known as thermohaline circulation, depicted in the movie.

This circulation pattern acts like a heat pump, transporting heat from the equator to the North Atlantic.  It is primed by water cooling as it moves northward.  As it does, water evaporates and ice forms.  Each of those actions rejects salt, leaving a higher salt content in the ocean as it flows northeast.  As it approaches Northern Europe the cold, heavier, salt-laden water sinks, completing the circulation and drawing more warm water northward, warming the nearby land mass.

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