20.1. Past climate recorded in the ice

We are collecting ice samples from a place where the ice is thousands of years old. These places are rare and difficult to use. Usually a deep ice core is drilled to reach ancient layers of ice, but that is very expensive and large field teams of 20 or more in large field camps take years to penetrate 3 km of ice. In contrast we are just 3 people who have recovered 2.5 km of “horizontal” ice core. The methods we use are quite novel in glaciology, but pretty familiar to people with building skills as mostly we have used circular saws, routers, electric planes, power drills and concrete grinding machines. 

First Aslak and John did a complete profile of the electrical properties of the ice _ this allowed us to get a rough idea of the age of the ice from its acidity variations. Then we made a plan to sample the ice for chemical analysis in Finland, and water isotope analysis (in the
Netherlands). These will tell us how warm and cold the seasons were, about the biological productivity of the ocean, the strength of the winds, where the dust came from, and in fact tell us some basic mechanisms of climate behaviour. We think that the oldest ice is about 15000 years old and we know that the age of ice 300 m further up the ice is 10500 years. This spans the end of the last ice age and this was, until the last 100 years, the largest and fastest change in climate that we know about.



Velocity map of the Scharffenbergbotnen valley and the line of our profile. 

So understanding what was changing in the ocean and atmospheric currents can tell us a lot of what could happen in the near future. Therefore we have sampled this part of the ice at 20 cm resolution for chemistry, meaning that we have collected and individually bagged about 1500 samples of ice. However we also need to know what happened later in time, and so we have not just sampled this very old ice, but the other 2 km of ice as well. We are very limited by how much ice we can transport home, so we have measured 1 m in every 100 m at very high resolution so we can see how thick the annual layers are, and the rest we sample very coarsely to get an idea how the 100 year average climate varied until the present. We have done about 70% of all the sampling we plan.




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