Wrapping Greenland Dummies' Guide

Reflectivity on a Planetary Scale

Earth as a whole reflects about 36 percent of incoming solar radiation.  Therefore, it has an "albedo" of 36 percent.  Fresh snow reflects 90 percent of visible light, whereas charcoal reflects 4 percent.  From space, ocean and forests have a lower albedo than snow.  Deserts have a high albedo.

On average, our ice caps reflect up to 80 percent of visible light.  The ice doesn't absorb much of the radiation, and therefore stays cold enough to stay frozen.  But as the atmosphere warms and the ice edges melt, the total ice cover is decreasing.  There is less ice around to reflect sunlight, and more dark land to absorb it.  So currently, Earth's dropping albedo is absorbing more and more solar radiation. As a result, our planet is warming even further. 

The glacier blankets will attempt to counteract this effect by trying to stop the outer edges of the glacier from melting, thereby increasing the albedo of Greenland's glacial ice and ultimately stabilizing the overall ice albedo of Earth. It's at Earth's extremes that global warming has the most devastating effects.

How the Blankets Work

Earth receives many different wavelengths of radiation from the sun.  This radiation brings light and warmth to the planet.  When this solar radiation hits anything on Earth, it is either reflected off the surface or absorbed, warming the surface.

White surfaces reflect more solar radiation than black surfaces.  Ice reflects more radiation than tarmac.

Tiny parcels of energy comprise the light and warmth within solar radiation.  Each parcel is known as a photon.   Scientists have been studying the behavior of these particles for a long time.

A photon of sunlight carries more energy than a photon of infra-red heat.  When these solar photons hit Earth’s surface, they transfer some of their energy into the material (e.g. ice) they hit.  A photon of visible sunlight can lose enough energy to become heat.

Without white snow to cover it (as is the case in the summer), Greenland's glacial ice is actually gray, because of the melt rate beyond natural control. 

The blanket must not only be able to reflect sunlight, it has to protect the ice from the warming air temperatures.  The pristine white blanket deflects most of the incoming light photons.  It still isn't 100 percent efficient, but very few light photons pass through to the ice's surface and transfer their energy into it. 

With the blankets on top, much more sunlight is reflected off the ice sheet during the summer months than would happen naturally. 

The blankets also trap a layer of very cold air between the ice and fabric – the same temperature as the frozen ice below.  This stops the ice from melting.  The fibers of the polypropylene blanket trap the warm air within themselves, and are therefore extremely good at insulating the ice.

Foil wasn't used because while it is great at reflecting heat, it is no good at insulating the object beneath it.  So, if the atmosphere above the ice is warm, foil will allow that heat to conduct straight through to the ice. The blankets absorb this heat above the blanket and stop it from reaching the ice below, because the polypropylene fibers trap the warm air above and insulate the ice.

Polypropylene Blanket Facts

 * The polypropylene blankets are incredibly strong — they will stretch to more than 55 percent of their original length prior to failing. 

* Under a static puncture test, the blankets fail at 3,800 N.  This is equivalent to placing a 380-kg weight on the blanket.

* The material is highly tear-resistant — the non-woven long fibers stop the tear from spreading.

* The chemical makeup of the blanket material makes it highly resistant to organic substances.

* The polypropylene is very heavy, weighing 340 grams per square meter.

* Like many materials used outdoors, the material is treated with UV stabilizers.  Ultimately, the sun will break down the chemical structure of the polypropylene over a matter of years, and stop it from being a great reflector and insulator.  The manufacturers have added even more UV stabilizer than usual to this blanket because of its role on the glaciers.

Hemp Blanket Facts

* The hemp blanket is much lighter than polypropylene, weighing just 150 grams per meter squared – half the weight of the polypropylene. 

* The material is made naturally from plants, so its carbon footprint is smaller.  It grows quickly and is naturally resistant to most pests.  Hemp is also environmentally friendly.  The plant requires little in the way of herbicides, pesticides and fertilizers.

* Hemp is very strong.  It is most famously used by the Navy to make ropes.  It is being increasingly used in cement mixes to make the cement stronger.  However, it is only about half the strength of polypropylene.

* Hemp is also very reflective to UV and resistant to mold.  (However, hemp ropes often rot because they trap liquid deep within the fibers.)

* Napoleon made his military uniforms from hemp – hemp linen has added strength and durability.