The melting of Antarctica’s Pine Island Glacier has been directly linked by University of Washington researchers to El Niño. The Pine Island Glacier composes around 10 percent of the West Antarctic Ice Sheet. For the past 40 years, the floating ice shelf at the tip of the Pine Island Glacier has been thinning and melting, and causing the glacier to calve icebergs.
According to University of Washington researchers, local wind direction plays a bigger role in the melting of the Pine Island Glacier than was previously suspected. The local wind direction is directly linked to El Niño and the tropical changes it causes.
Using their combined expertise at modeling atmospheric changes, the researchers revealed new information in their study about how topography and winds are responsible for how much warm water makes it to the Pine Island Glacier and the ice shelf. The amount of warm water that reaches the ice shelf is directly related to the climate conditions in the tropical region of the Pacific Ocean.
According to the study’s coauthor, University of Washington professor of Earth and space sciences Eric Steig, the results of the study show how the melting of the Antarctic Ice Sheet depends quite a bit on the climate around the entire planet.
Because of recent El Niños, a greater amount of warm water has been reaching the Pine Island Glacier. This warm water is deeper, though under the right conditions, it can rise up and over the continental shelf and reach the outer margins of the glacier. That is exactly what has happened over the past 20 years — measurements have been taken proving the existence of a thick layer of warm water on top of the continental shelf. This layer of warm water has been in direct contact with the Pine Island Glacier.
The meltwater from the Pine Island Glacier runs off into the Amundsen Sea. The thinning of the glacier’s ice shelf has occurred at least as far back as the 1970s, when the first measurements were done by scientists. The majority of the Pine Island Glacier melting appears to be happening from below it, due to warm water lubricating the ice and driving it seaward, where huge chunks of ice calve off and from icebergs.
The researchers, however, noticed that in January 2012, the warm water layer was thinner. According to their study, about half of the melt water of 2010 came off of the Pine Island Glacier. They believe that this was due to the effects of La Niña (the cold counterpart of El Niño) causing an alteration in the winds from a westerly direction to a mostly eastern one.
Previously to the recent study which was published in the journal Science, Steig states that they “had thought that wind variability played an interesting, but relatively small role.” However, the findings of their study indicates that wind variability “has a strong effect.” Stieg added that “those changes were related to the very large 2011 La Niña event.”
While the researchers believe that the 2012 conditions were unusual, and that the shift from El Niño conditions to La Niña ones resulted less warm water moving in and less melting occurring, the edge of the Pine Island Glacier could potentially rebuild. However, the researchers don’t think that is a likely scenario. According to Steig the conditions of 2012 were “probably just a rare event.”
If Steig and his fellow researchers are correct, and the 2012 effect of La Niña was an anomaly, the melting and calving of the Pine Island Glacier will continue on into the foreseeable future.
The University of Washington researchers have shown in their study in the journal Science that climate anomalies like La Niña events and sporadic weather conditions have a much greater effect on the Pine Island Glacier and the Antarctic Ice Sheet than they were previously credited with in the past.
Written by: Douglas Cobb