Saturday, March 14, 2009

Brrrrr ....

It's another cold day here in Barrow. Today the temp was -24F as I walked to the lab building at 9 am. Luckily the winds are fairly calm today ... but even so, with an 8 mph wind, the wind chill dropped to -42F.

So for those of you who might be interested, here is a chart that allows you to determine the wind chill based on air temperature and wind speed. So you can see, at very cold temperatures, just a small breeze can make a big difference in how cold it feels (and how quickly frostbite will set in).


So here's the "WHY" behind wind chill: Because of a phenomenon knows as "evaporative cooling", your skin can feel colder than the actual outside temperature. It takes heat to evaporate a liquid ... so let's say the liquid in question is the moisture on your skin. As it evaporates, it is taking heat from the surroundings, which will cool those surroundings. So as the moisture from your skin evaporates it takes with it some heat and hence cools your skin surface. Also at play is a phenomenon known as "convection", a major mode of heat transfer. There is "natural" and "forced" convection ... natural convection is just due to the diffusion of heat away from a body. Forced convection means something else is helping along that heat transfer. In the case of wind chills, the wind is helping to force the convection process. In both cases, the rate of heat loss depends on the real air temperature and the wind speed above the surface (in this case, your skin).

So, since we're talking science ... today we started a photochemistry experiment. (Photochemistry = light induced chemistry). We have samples that contain a pollutant that has recently been identified in the Arctic: tetrabromobisphenol A (TBBPA), a brominated flame retardant. Brominated flame retardants are added to many consumer products like electronics, fabrics, upholstery, etc ... in order to slow down or minimize the extent of fire. These flame retardants do great things in terms of keeping people safe from potential fire hazards, but we're now finding out that some of them aren't so good for your health ... and that they are getting transported all over the planet. We want to know if this particular pollutant is reactive in snow and ice and if it is, what might it turn into. So today I put out on the snowpack a set of sealed vials (pictured below) that contain a known amount of TBBPA in clean water and in refrozen Barrow snowmelt water ... we'll see if the TBBPA goes away and if it is more or less reactive in the snow samples. This might give us an idea of how it will react in the snow and ice in the Arctic.


In other news ... today the OASIS team presented a talk to the Barrow community about the work we are doing here. Remember, OASIS means Ocean Air Sea Ice Snow interactions. Sandy Steffen (of Environment Canada) and Paul Shepson (of Purdue University) did a great job - mainly determined by the fact that as I looked around during the seminar no one was sleeping! Below are some shots before and during the talk ...



Stay tuned for more exciting happenings from Barrow!

3 comments:

cammyeg said...

Very interesting! How do you prevent frostbite when your face is exposed to the wind and temp?

cammyeg said...

OH, and what is a brominated flame retardant doing in the arctic? Was it in the snow? the ice? where? and more importantly, what is it doing there? That cant be good.

Dr G said...

To prevent frostbite you pretty much have to cover up exposed skin. In really cold conditions, skin can freeze in just a few minutes.

As for the pollutants ... there are a lot of different kinds of pollutants that get transported to the Arctic from far away. Pesticides, industrial chemicals, etc can get into the atmosphere, and then the wind transports them to the poles. Once a pollutant gets to a cold climate it pretty much stays there and has no propensity to move elsewhere. Brominated flame retardants are just now starting to be found in the Arctic in air and in wildlife. We're going to try to measure them in snow and ice while we are here to see what concentrations we find. It isn't good, because eventually these pollutants can get into wildlife ... and people in the Arctic still rely on hunting and subsistence lifestyles for their food ... so eventually the pollutants can find their way into humans as well. Not so good ...