New paper: Soil mineral depletion drives early Holocene lake acidification

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By Richard Chiverrell

Every year, about May, student examination season begins, teaching winds down and the thoughts of Physical Geographers turn to fieldwork, travel, seeing the world, all preferably with sediment corer in hand. In 2007 an intrepid team of John Boyle, Rich Chiverrell, Andy Plater and Oliver Boyle (John’s brother) set sail, more or less literally for Norway, on the Newcastle to Bergen ferry. Our travels were to test a numerical model developed by John Boyle that suggested that changes in lake and terrestrial ecosystems, the acidification of surface waters during the early postglacial period, could be explained by the weathering and depletion of the mineral apatite from soils. The modelling was published in a brilliantly titled paper ‘Loss of apatite caused irreversible early-Holocene lake acidification’ in the journal Holocene. We docked in Bergen around 6pm and then drove for 12 hours to north of Nordfjord to the island of Vågsøy, avoiding reindeer, sleep, horrendous sheeting rain and sadly all the Nordfjord ferries (closed for the night), to sample the sediments of Kråkenes Lake. We arrived around 6am and grabbed 4-5 hours sleep in a delightful sea front cottage, before sampling a 8.96-m-long core from the terrestrialized peat bog that forms the southwestern arm of the lake using a 1-m-long, 70-mmdiameter Russian corer in 10 overlapping drives. The coring was completed in 4 hours, a pretty remarkable 2 days. After surviving on meagre rations of vacuum packed gammon and Uncle Ben’s stir fry sauce (note other brands exist) prompted by the lack of fishing prowess displayed by members of the team (they did catch seaweed) and Sunday shopping hours in Norway (i.e. closed), we had two days to explore the catchment and the seaboard of western Norway on our journey south. Thankfully the shops opened Monday and more fitting food stocks were procured.

Twelve months later we won a Natural Environment Research Council Grant to carry out the first validation of John’s numerical model, principally testing whether the changes in soil primary mineral concentrations after the end of the last Ice Age deplete at the same rate and extent as the acidification observed in many postglacial and formerly glaciated lakes. Easily weathered minerals in this case apatite (source of mineral phosphorus) appear to be quickly released to soils and water courses producing a base-rich phase seen in lake sediment records with an associated higher ecological productivity early after deglaciation, and this phase ends as the supply of base declines. The acidification that follows had previously been attributed to climate change and plant-soil community succession. The findings of this research, with the laboratory work completed by research assistant Dr Ian Thrasher, have just been published in the journal Geology in a paper called ‘Soil mineral depletion drives early Holocene lake acidification’. Hopefully you will be convinced by our case! The explanation in this paper has some wide ranging implications, mainly arising from that this acidification process is difficult to reverse, unless you completely refresh land surfaces e.g. a new glaciation, producing new terrain by volcanic eruption or really really large-scale turn-over of soils by erosion. We will be following these implications up with further papers on phosphorus dynamics and other implications in the coming months.

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Summer 2012: GPGs researching glacial environments in Iceland

Hi, I’m Kerrell and in my third year of the Geology & Physical Geography BSc degree. Over the summer, myself and 3 friends Mike, Lewis and Alex spent 6 weeks conducting our 3rd year dissertation project in South East Iceland.

Lewis, Alex, Mike and me on Falljokull glacier

Lewis, Alex, Mike and me on Falljokull glacier

Our projects varied but all were linked to the changing environments within a temperate glacier region. Lewis and myself conducted a study on the landforms within an ice marginal zone around 2 glaciers. I focussed on the Virkisjökull & Falljökull twinned glacier system and Lewis on the Svínafellsjökull glacier margin. Mike and Alex also worked within the Virkisjökull & Falljökull system, with Mike focussing on dating Late Holocene behaviour of the glaciers using lichenometry and Alex centring his project on the evolution of the sandur system over 5-6 weeks within the ice contact zone.

Mike and the huge boulder that we used to mark the edge of Virkisjokull on our first day. It retreated 8m in total!

Mike and the huge boulder that we used to mark the edge of Virkisjökull on our first day. It retreated 8m in total!

Me on the ice the day we walked up the glacier!

Me on the ice the day we walked up the glacier!

Conducting out dissertation in Iceland was a once in a lifetime experience and to work within such close proximity to such an active glacier margin was a fantastic opportunity. On our first day we visited both glaciers that we’d be working on and were in complete awe of the huge glacier bodies that flowed over the mountainous regions. The boys were actually speechless for a few peaceful moments!

An amazing day in South East Iceland

An amazing day in South East Iceland

Having the chance to work in such a dynamic region was very exciting. The landscape, particularly within the ice marginal zone was constantly changing and you could notice subtle differences in the landforms on a daily basis. We were very lucky in that when the UK was experiencing the torrential downpours over summer, we had pretty great weather…we even came back with a tan! Although there was a few days of awful conditions were we just couldn’t do any work in the field due to the drenching rain with water droplets the size of sponges and gale force winds. We even had to prop up the boy’s tent as the wind was so strong.

Lewis & Alex being brave in shorts looking out over Virkisjokull & Falljokull

Lewis & Alex being brave in shorts looking out over Virkisjökull & Falljökull

Conducting our own research projects was an experience that all of us really enjoyed. On our hour walk to the glacier every day, we’d talk about how working in the field on our own was teaching us so many vital skills and has particularly encouraged myself and Mike to further our education with a postgraduate degree. The work was very tough, the terrain was strenuous and being so far away from home at time took its toll on all of us. But being given the opportunity to work in a temperate glacial zone, that will never be the same again due to constant retreat, was the greatest reward for all our hard work. As well as working hard in the field we also took the time to enjoy Iceland as a beautiful country and visited sites such as Jökulsárlón (where James Bond was filmed!) and also attempted to make friends with the lethal seagull with claws….the Icelandic Skua.

On return to the UK, we had to present a 15 minute talk to staff and fellow students to summarise our findings in the field and we’re all currently working on a 10,000 word report and our final maps to hand in for our overall dissertation mark. The experience was amazing and the fact that we conducted our dissertation in Iceland had the rest of our department a bit jealous. Combining both geological and geomorphological concepts has really allowed us to pursue our dissertation with lots of enthusiasm which will hopefully keep us going to the final deadline.

Alex, Me, Lewis, Mike and our supervisor Richard at Jökulsárlón

Alex, Me, Lewis, Mike and our supervisor Richard at Jökulsárlón