"Hair Dryer" Winds Could Strain Vulnerable Antarctic Ice Shelf
Warm, dry winds sweeping across Antarctica can temporarily cause extraordinary melting events. Known as "foehn" winds — from a German word often translated as "hair dryer" — they pack a major punch, even during the frigid fall and winter months.
It's a natural phenomenon, periodically occurring in various regions of the ice sheet. But some researchers say continued climate change could alter some of the atmospheric circulation patterns driving the winds, potentially causing them to occur more frequently in the future.
That could put a major strain on places like the vulnerable Larsen C ice shelf, located on the northeast Antarctic Peninsula.
Research increasingly suggests that foehn winds have a major effect on the ice shelf's melt rates in ways that could make it more prone to fracturing and potentially collapsing.
A new study this week in Geophysical Research Letters is the latest to highlight the issue. Led by Tri Datta of the University of Maryland's Earth System Science Interdisciplinary Center, the researchers found that foehn events at Larsen C cause a substantial increase in surface melting, even after the regular summer melt season has ended.
"Even if you don't have large-scale melting occurring during the summer, the ice shelf is still vulnerable to foehn winds occurring during other parts of the season," Datta said. In fact, foehn events tend to be strongest during the colder seasons, she added.
The extra meltwater trickles down into the porous snow on top of the ice sheet and refreezes there once temperatures go back down, the researchers note. This causes the ice shelf to become denser, which scientists believe can make it more vulnerable to breaking and collapsing down the road.
The region has already seen some major changes in the past two decades. In 2002, the nearby Larsen B ice shelf abruptly collapsed, likely weakened by a series of unusually warm summers that caused large amounts of meltwater to accumulate on its surface.
And in 2017, Larsen C made headlines when it calved one of the largest icebergs ever recorded. Since then, experts have been keeping a close eye on the ice shelf, monitoring any processes that could affect its future stability.
Datta cautioned that there's no proven link between the influence of foehn winds and the 2017 calving. But the wind events could make the ice shelf susceptible to more breakage in the future — especially if they start to happen more frequently.
The research highlights a series of intense foehn events at Larsen C that occurred between 2015 and 2017 during the fall and winter. In March of 2015, 2016 and 2017, for instance — autumn for Antarctica — melting associated with foehn events ranged from 190% to 300% higher than the melting otherwise typically observed during this time of the year.
Datta also noted that there's no increasing trend so far in foehn events at Larsen C. In fact, there's some evidence to suggest they may have slightly declined since 2009, possibly in response to a shift in a natural climate variation that affects atmospheric circulation patterns in the Southern Hemisphere.
But some researchers have warned that future warming could have an effect on these winds in the coming decades.
Glaciologist Peter Munneke of Utrecht University in the Netherlands is one of those scientists who suggest that foehn winds may happen more frequently in a warming world. The conditions that lead to foehn events are often characterized by strong westerly winds around Antarctica. And some research indicates that "westerly winds in the southern hemisphere will increase under increased greenhouse gas concentrations," he noted in an email to E&E News.
Munneke led a 2018 study, also published in Geophysical Research Letters, that pointed to a significant increase in winter melting on the Larsen C ice shelf when foehn winds sweep through. The researchers noted that although no trends have been observed in these kinds of events so far, they "anticipate an increase in winter melt as a response to increasing greenhouse gas concentration" in the future.
And that would mean a one-two punch from climate change on the Antarctic Peninsula.
Datta noted that continued climate warming will likely cause additional melting in the region either way, particularly during the warmer months of the year. But she agreed that while the impact of climate change on atmospheric circulation in the Southern Hemisphere still needs more investigation, it's an important consideration, as well.
"It's certainly something to worry about," she said.
Reprinted from Climatewire with permission from E&E News. E&E provides daily coverage of essential energy and environmental news at www.eenews.net.