Monitoring the melting ice
Climate change has been a hot (pun unintended) topic in the news recently. The latest UN climate talk opened on Friday, with the hope of reaching the global treaty that the Copenhagen talks in December failed to produce.
I’m not going to get into the seemingly never-ending debate on whether climate change is a natural or man-made phenomenon, but there is irrefutable evidence that global temperatures are steadily rising and one consequence of this is the melting ice-caps, as seen in this news story.
What I do want to discuss, however, is one way that this is being monitored. Cryosat-2, a satellite built by the European Space Agency, was launched last Thursday. Its job is to measure not only the area of ice, but the depth too, in order to produce an accurate measurement of the volume of ice at both the Arctic and Antarctic. It is hoped that the satellite will stay in orbit for up to 10 years and be the first way of monitoring changes in the ice-caps in this much detail.
The satellite will use radar to make the depth measurements, and it was reported yesterday that the equipment had been switched on and is in working order. Microwaves will be sent down to both the surface of the ice and the surface of the water below the ice through cracks in its surface. By calculating the distance of these two locations, the depth of the ice can be calculated.
This is explained in this PowerPoint presentation which contains a problem-solving activity that can be used with GCSE classes during a lesson on the uses of the waves of the electromagnetic spectrum. They will need to use the speed= distance/time equation and assume that the speed of the microwaves is 300 000 000 m/s (as it is an EM wave, it has the same speed as light). How much of this information you give them would be dependent on their ability.
Distance = speed x time
Distance = 300 000 000 x 0.0048
Distance = 1 440 000
This distance is the distance to the ice and back again so…
1 440 000 / 2 = 720 000
Height of satellite = 720 000m (770km)
Distance = speed x time
Distance = 300 000 000 x 0.00480012
Distance = 1 440 036m
1 440 036/2 = 720 018m
Take this away from the height of the satellite gives you 18m. This is a little of the thick side for most ice (average thickness in the arctic is 2.5m) but I figured there might be some bits nearing this thickness and it makes the calculations a little easier to do.
This story could also be used when teaching the application of satellites. If this is the case, then this bbc news story includes some useful videos on how the satellite will work.