A UCC team travelled to a frozen Hudson Bay last winter to study how natural chemical activity in the sea causes ozone loss in the upper atmosphere, writes Dick Ahlstrom.
THE HUDSON BAY in Canada gets pretty nippy in late winter, with temperatures hovering around minus 25 degrees. So you need a really compelling reason to be there, particularly as wind-chill can take things down to minus 55 degrees.
An atmospheric physics expedition dispatched earlier this year by University College Cork felt it had just such a reason, to better understand how natural processes at the poles cause large scale depletion of atmospheric ozone.
This loss occurs separately to the ozone destruction caused by human activity, says Dr Stewart Vaughan who travelled into the blizzards and onto the Hudson Bay ice last February. The UCC-based Marie Curie research fellow and second-year PhD student Jun Chen went to Canada on an expedition to study this ozone loss.
"The main goal was to try and clarify the exact nature of the interaction between the ice, the sea water and the atmosphere and these annual ozone depletion events," explains Vaughan, who is based until next September in the department of physics. "In the spring in the polar regions, there is a massive decrease in ozone and that has been linked to bromine species coming out of the brine in the sea ice."
Ice-loss feeds bromine oxide, iodine oxide and other halogen oxides into the atmosphere and he and Chen wanted a closer look at the nature of this release.
Funding from the EU, Science Foundation Ireland and the Environmental Protection Agency helped support a trip to the eastern fringes of the Hudson Bay and so Vaughan and Chen found themselves on the ice, carrying with them a novel spectrometer developed by UCC's Laser Spectroscopy group.
The idea is to detect what chemical species are found above the ice using spectroscopy. This is typically done by sending a light beam over some distance and then bouncing it off a mirror back into the spectrograph, Vaughan explains. The returning light spectrum identifies the chemicals in the intervening body of air.
A group from Leeds University had used a device where the light beam travelled about 5km between source and spectrograph, but the new UCC device uses a different approach.
"We have a similar system but we have two highly reflective mirrors," explains Vaughan. These are placed no more than 10m apart, with the light beam bouncing back and forth many times before being read by the spectrograph.
The key advantage of the new approach is the resolution of the reading. The data comes from a much smaller space, only metres compared to many km, he says.
"We wanted to pinpoint exactly where these chemicals were being emitted from. We wanted to be able to locate the bursts coming out of the ice." The processes are not well understood but the assumption is it may be possible to see what is going on in the ice where bromine levels are highest.
That was the plan, but the bitterly cold conditions and happenstance conspired to spoil the party. They set up the device and it began to deliver useful data, but then its light source inexplicably failed. This was replaced, but then the main electricity generator that provided power for the research centre at the Inuit town of Kuujjuarapik blew up. The resultant power surge burnt out their second light source, and put the research expedition out of business. A serious blizzard quickly followed, which forced a halt to everyone's research.
"In the end, we didn't get the data we wanted," Vaughan acknowledged. There were gains, however. They confirmed that the novel spectrograph worked and could deliver the data. The trip has also integrated UCC into the international research network studying naturally driven atmospheric change.
"One of the main reasons we joined up is this is the first time to go on a field campaign," he says. It also allowed UCC to join the network of laboratories doing this science. "It was good to make contact with them."
He won't miss the weather. "It was seriously cold," he says. They could work outdoors for just five or 10 minutes before having to retreat inside to thaw out.
"One day it got up to only minus four degrees and it felt like we were on the beach," Vaughan says.