Scientists have long known that the melting of the Greenland ice sheet has been a big contributor to the rise of sea levels around the world in recent years -- and now, an international team of scientists has identified a surprising factor that could be driving the melting.
It turns out that clouds may be playing a bigger role in the melting process than previously thought by acting like a blanket that traps heat above the ice sheet at night, increasing meltwater runoff.
Clouds are responsible for about 25 percent of the Greenland ice sheet meltwater runoff that we see today, Kristof Van Tricht, a Ph.D. student of earth and environmental sciences at the University of Leuven in Belgium and lead author of the research, told The Huffington Post.
"The nighttime warming is something that we all know, but we were really surprised that it is in fact the dominant driver of the enhanced runoff that we see in our results," he said.
The researchers used two satellites, CloudSat and CALIPSO, to take images of clouds above the Greenland ice sheet from 2007 to 2010. The images allowed the researchers to analyze the structure, height, thickness and composition of the clouds.
Then, the researchers used their analyses to help build snow and climate model simulations to see how the ice sheet may respond to an environment with clouds and without clouds.
This is something we have to get right if we want to predict the future." Dr. Tristan L’Ecuyer, professor of atmospheric and oceanic sciences
The researchers discovered that cloud coverage prevents the ice that melts in the sunlight during the day from refreezing at night, and keeps heat from the daytime trapped on the Earth's surface.
"It turns out that we really need to include the warming effect of clouds to get realistic estimates of current and future ice sheet melt and subsequent global sea level rise," Van Tricht said. "This global sea level rise is happening as we speak and it is not to be considered an issue in the far future. Several of the larger cities in the world are only a few feet above sea level."
And the world could face another foot of sea level rise over the next 80 years, Dr. Tristan L’Ecuyer, professor of atmospheric and oceanic sciences at the University of Wisconsin-Madison and a co-author of the research, said in a statement.
"Parts of Miami and New York City are less than two feet above sea level; another foot of sea level rise and suddenly you have water in the city," he said, adding, "Many of the countries most susceptible to sea level rise tend to be the poorest; they don’t have the money to deal with it... This is something we have to get right if we want to predict the future."
Dr. Ralf Bennartz, a professor of earth and environmental sciences at Vanderbilt University who was not involved in the study, praised the new research.
"This study shows very clearly for the case of the Greenland ice sheet that if we are able to better understand how clouds change as climate changes, we will be able to get much tighter constraints on Greenland surface melt and ultimately sea-level rise," he told The Washington Post.
The research was published in the journal Nature Communications on Jan. 12.
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