It was fantastic to catch up with Alumnus Ben Stoker recently, when he presented a Careers lecture to our Sixth Form students on his work in Polar Science.

Since leaving Bury Grammar School in the Class of 2013, Ben completed a Bachelors in Physical Geography and a Masters in Polar and Alpine Change at the University of Sheffield, before continuing his studies at Charles University, Prague with a PhD in Physical Geography and Geoecology. Later this year Ben will begin a Postdoctoral research fellowship at Lamont-Doherty Earth Observatory at Columbia University, New York. 

‘Geography students hold the key to the world’s problems’ – Michael Palin

When I studied Geography at Bury Grammar School, my teacher used this quote a lot and I think it still holds true. Geography effectively works to bridge between all the physical sciences and the humanities and uses our knowledge from these subjects to try to understand the modern world and address the greatest problems we face.

My masters work was split into two different themes; I looked at historical glaciations, mostly focusing on the Ice Age history of Northern Ireland and the United Kingdom and at contemporary glaciations,particularly how modern glaciers in Arctic Norway were responding to modern climate change.

I spent a month-long visit in Svalbard, a Norwegian Island in the Arctic Circle where I stayed at the University Centre in Svalbard in Longyearbyen, which is named after the glacier Longyearbreen. During this time, we were looking at how arctic glaciers affect the environment and how they are responding to climate change, by monitoring how these glaciers change through time.

Gaining an understanding of the size of these glaciers is easy using satellite images from different years to map and assess the changes in area. ​But if you want to know the change in volume of ice it gets more tricky, and that’s where we use radar surveys. This works by having two antennas, a transmitter and a receiver. The transmitter emits a signal, similar to a radio wave. When these waves hit a surface or a material with a different density, then some waves are reflected and transmitted back. We use the amount of time it takes for a wave to be reflected back to estimate the thickness of different materials. Ice is a reasonably simple material, with a similar density throughout, so when these waves reach the bottom of the ice and hit bedrock at the base of a glacier it causes a lot of waves to be reflected back.

Above you can see an example of a radar system in real life (upper left image) that we used to investigate a glacier called Rieperbreen in Svalbard (upper right image). Here you can see the survey we collected and how thick the ice was. At its thickest around 60m. We can then combine measurements of the ice thickness with knowledge of the ice extent to calculate the volume of ice there is. This allowed us to create a map showing the change in ice thickness (lower image).

In 2018 I moved to Prague and started a PhD on long term ice age histories, with a focus on North America. The last 2.6 million years is called the Quaternary period. During this time, climate went through cycles of cooling and warming driven by changes in the earths orbital pattern around the sun. If we can understand the reasons and processes for ice sheet growth during these climate cycles then it can help us understand the potential implications of future ice sheet retreat under modern climate change.​​

A key thing to understand is the timing of ice sheet retreat and how fast ice sheet retreat was and this was a main theme in my PhD. ​We did this through a method called ‘cosmogenic nuclide dating’ that merges physics, chemistry and geography. As cosmic rays from the sun or supernova explosions reach the earth’s surface and hit rocks there, it causes reactions in the earth’s surface. This creates rare cosmogenic nuclides that are not ‘naturally’ present on the earth’s surface except when created by this process. Chemistry allows us to process and analyse rock samples from the earth’s surface to measure the amount of cosmogenic nuclides in a sample. Physics then provides us with the knowledge of the rate these nuclides are produced at and allows us to estimate the amount of time a surface has been exposed to the atmosphere based on the amount of these nuclides in a sample. This then allows us to calculate the amount of time since an area was last covered by ice. 

We wanted to go to an understudied part of Canada to use this method and look at how quickly the ice retreated 15,000 years ago and what caused it to retreat. The reason this area is understudied is because it is remote, and we could only access our sites by either float plane or helicopter. Whilst we were there, we searched for boulders that had been transported by the ice so that we could take samples for cosmogenic nuclide dating. This involves taking a sample from the upper 2 cm, using a saw and then hammer and chisel. These samples were then later sent to a lab for processing which then told us about a period of rapid ice sheet retreat that occurred around 14,000 years ago and resulted in ~3.4 metres of sea level rise in just over 300 years.

As we were flying around in 2018, we saw that the landscape was undergoing dramatic changes, we began to see huge landslides. These landslides we noticed caused hazards as they blocked rivers in some places causing a flood risk and, leaked contaminants into these rivers which have often been associated with mercury contaminating the water in these areas. So, we landed in some of these locations and wanted to investigate them. One of the key things to note when we came up close to these things is that they are super wet, debris rich slumps, and that’s because of the large amounts of ice buried within them. This is effectively a result of ice from the ice sheet being buried 15,000 years ago when the ice sheet retreat. The cold temperatures in arctic Canada have preserved this ice though, but now with modern climate change we are beginning to thaw this 15,000 years old ice and create an unexpected hazard.

These landslides can also be very useful for biologists. The frozen material means you can find incredibly well-preserved animals that can be up to 20,000 years old and we can use these to reconstruct how the environment must have looked 20,000 years ago! Here you can see a CT scan of this preserved arctic ground squirrel.

Thank you to Ben Stoker for sharing this brilliant insight into your research and we wish you the best in your Postdoctoral research fellowship later this year. Our current BGS Geographers were certainly inspired by your achievements, and we look forward to following your future work!