Allison Chinchar
CNN
Allison Chinchar wrote this article in CNN:
In an ever-warming climate, ripple effects or chain reactions could lead to altered weather patterns across the globe thanks to a melting Antarctic ice sheet, a new study says.
The study, published in the journal Nature Geoscience, found that as Earth continues to heat up, the land underneath the Antarctic ice sheet will become more exposed. As a result of that process, wind patterns will shift, and rainfall will increase over Antarctica, which could trigger processes that speed up ice loss.
"We found that ice sheet retreat exposing previously ice-covered land led to big increases in rainfall, which through a feedback mechanism dramatically warms the ocean," Catherine Bradshaw, senior scientist at the UK Met Office and lecturer at the University of Exeter told CNN.
"This feedback mechanism could potentially trigger additional processes that accelerate ice loss."
The joint study is based on combining climate modeling and data comparisons from the Middle Miocene epoch (13-17 million years ago).
Why do we care about something that happened more than 13 million years ago? Because carbon dioxide levels and global temperatures during the Middle Miocene were similar to those Earth is forecast to reach by the end of this century.
- When it rains it pours
"With the big ice sheet on Antarctica like we have today, the predominant winds are known as katabatic winds, and these go from the land to the sea," Bradshaw told CNN. "They originate from the ice sheet where it is very high, very cold and very dry -- in fact Antarctica receives only a few inches of snowfall a year and is so dry it is classified as a desert."
Bradshaw cautions that those winds could actually reverse -- blowing instead from the cooler sea to the warmer, drier land -- if Antarctica continues to warm. Generating the same results we see from daily sea breezes as well as seasonal monsoon winds that occur around the world.
A monsoon is simply a seasonal reversal of wind direction which results in changes in precipitation for a specific region of the globe. For Antarctica, this means an increase in rain.
"The surface of the Antarctic ice sheet is very bright, and it reflects some 50-80% of the sunlight that hits it. Where the ice sheet retreats and exposes the darker land surface underneath, this ground is much less reflective and so absorbs more sunlight, which warms it up," Bradshaw told CNN.
Bradshaw explained that ice-free ground at the coast warms up more than the surrounding sea surface which in turn causes the change in wind direction. Similar to the seas breezes Florida experiences, these winds can bring in moisture from the surrounding ocean that can dramatically increase rainfall.
"What happens to an ice sheet when rainfall increases depends on where the rain falls and whether it is cold enough to fall as snow instead of rain." said Bradshaw.
"If the temperatures are warm enough for the moisture to fall as rain over the ice-free area, this could trigger processes that can accelerate ice loss. Conversely, if the temperatures are cold enough for the moisture to fall as snow over the ice sheet, this can cause ice growth."
As the Earth continues to warm, scientists may be able to learn from monsoonal regions of the world about how to prevent a collapse of the Antarctic ice sheet. While that may sound a little far-fetched, this new research shows it may have actually happened in the past when the Antarctic ice sheet was even more unstable.
"Essentially, if more land is exposed in Antarctica, it becomes harder for a large ice sheet to reform, and without (favorable) orbital positions in the Middle Miocene playing a role, perhaps the ice sheet would have collapsed at that time," Bradshaw said in a news release.
While the study suggests that the Antarctic ice sheet was capable of major advance and retreat across the continent during the Middle Miocene, Dr Bradshaw emphasizes that conditions now are not identical to those millions of years ago.
"It is important to stress that there were many important processes not included in our study, which, considering our findings, require additional research to establish exactly what the implications are for the future," Bradshaw told CNN. "This is the work that I intend to do next, but have not yet started."
In an ever-warming climate, ripple effects or chain reactions could lead to altered weather patterns across the globe thanks to a melting Antarctic ice sheet, a new study says.
The study, published in the journal Nature Geoscience, found that as Earth continues to heat up, the land underneath the Antarctic ice sheet will become more exposed. As a result of that process, wind patterns will shift, and rainfall will increase over Antarctica, which could trigger processes that speed up ice loss.
"We found that ice sheet retreat exposing previously ice-covered land led to big increases in rainfall, which through a feedback mechanism dramatically warms the ocean," Catherine Bradshaw, senior scientist at the UK Met Office and lecturer at the University of Exeter told CNN.
"This feedback mechanism could potentially trigger additional processes that accelerate ice loss."
The joint study is based on combining climate modeling and data comparisons from the Middle Miocene epoch (13-17 million years ago).
Why do we care about something that happened more than 13 million years ago? Because carbon dioxide levels and global temperatures during the Middle Miocene were similar to those Earth is forecast to reach by the end of this century.
- When it rains it pours
"With the big ice sheet on Antarctica like we have today, the predominant winds are known as katabatic winds, and these go from the land to the sea," Bradshaw told CNN. "They originate from the ice sheet where it is very high, very cold and very dry -- in fact Antarctica receives only a few inches of snowfall a year and is so dry it is classified as a desert."
Bradshaw cautions that those winds could actually reverse -- blowing instead from the cooler sea to the warmer, drier land -- if Antarctica continues to warm. Generating the same results we see from daily sea breezes as well as seasonal monsoon winds that occur around the world.
A monsoon is simply a seasonal reversal of wind direction which results in changes in precipitation for a specific region of the globe. For Antarctica, this means an increase in rain.
"The surface of the Antarctic ice sheet is very bright, and it reflects some 50-80% of the sunlight that hits it. Where the ice sheet retreats and exposes the darker land surface underneath, this ground is much less reflective and so absorbs more sunlight, which warms it up," Bradshaw told CNN.
Bradshaw explained that ice-free ground at the coast warms up more than the surrounding sea surface which in turn causes the change in wind direction. Similar to the seas breezes Florida experiences, these winds can bring in moisture from the surrounding ocean that can dramatically increase rainfall.
"What happens to an ice sheet when rainfall increases depends on where the rain falls and whether it is cold enough to fall as snow instead of rain." said Bradshaw.
"If the temperatures are warm enough for the moisture to fall as rain over the ice-free area, this could trigger processes that can accelerate ice loss. Conversely, if the temperatures are cold enough for the moisture to fall as snow over the ice sheet, this can cause ice growth."
As the Earth continues to warm, scientists may be able to learn from monsoonal regions of the world about how to prevent a collapse of the Antarctic ice sheet. While that may sound a little far-fetched, this new research shows it may have actually happened in the past when the Antarctic ice sheet was even more unstable.
"Essentially, if more land is exposed in Antarctica, it becomes harder for a large ice sheet to reform, and without (favorable) orbital positions in the Middle Miocene playing a role, perhaps the ice sheet would have collapsed at that time," Bradshaw said in a news release.
While the study suggests that the Antarctic ice sheet was capable of major advance and retreat across the continent during the Middle Miocene, Dr Bradshaw emphasizes that conditions now are not identical to those millions of years ago.
"It is important to stress that there were many important processes not included in our study, which, considering our findings, require additional research to establish exactly what the implications are for the future," Bradshaw told CNN. "This is the work that I intend to do next, but have not yet started."
