We left early again today to install two more stakes, this time in locations we have previously installed stakes. The glacier is always in motion, and in these locations it moves about 15 meters per year. This means the stake we installed last year is now 15 meters down-glacier. We keep installing poles at the same initial location so that we can track how the glacier’s speed is changing with time. We cant just keep measuring the same pole because the glacier’s speed varies with location, and as the pole moves into a new location its speed will change. In this case the fastest moving part of the glacier is about 2/3s of the way towards the terminus, above and below this it moves slower. By installing poles each year in the same initial location, we can then tell whether that part of the glacier is slowing down, speeding up, or staying constant. We call this measuring an “index velocity”. In general, the glacier is slowing down, largely because the deformation of ice is strongly dependent on its thickness, and the glacier is getting thinner with time.


The steam drill in action.


I like this panorama because it shows several things. The long pole laying in front of Jason is the one we are about to drop in the hole that Jason is drilling. It is 6 meters long, and if we sink it so that the top is flush with the surface, it will melt out completely within 3 summers. A little downglacier you can see the pole we installed at this same point in space last year. It now has a GPS antenna on it and we are measuring its position every 15 seconds. A little further downglacier, you can see the pole we installed 2 years ago. It will likely melt out completely this summer. (Click on the panorama and drag to look around, press Shift to zoom in, Command (Mac) or Control (PC) to zoom out.) Enlarge this panorama