Why all this sudden activity on the British-Irish Ice Sheet?
Archibald Geikie’s map of 1886
Ever since the discovery of ice ages there has been a quest to work out the extent, thickness and geometry of the ice sheet that once covered most of the British Isles. Archibald Geikie’s map in 1894 was an inspired start and steady progress since then has added much detail.
There was a concerted effort to finish the job, completing many decades work in just five years with over 40 researchers on the BRITICE-CHRONO project, investigating the far corners of the ice sheet. It has never been so heavily investigated. Why the sudden rush?
A perfect storm of stimuli came together…
It was realised that, spread over numerous publications (over 1000), fragments of the jigsaw puzzle that is – ‘ice sheet information’ – had never been assembled. This was put right in BRITICE, a previous project compiling over 20,000 landforms (eg moraines, drumlins) into a map and as downloadable data (GIS) layers.
This brought value to over 100 years of fieldwork, but what about the blanks on the map? Using satellite images and elevation models of the land and seafloor, the whole ice sheet bed was mapped afresh.
Pattern of ice retreat
For the first time, a detailed map of the pattern of ice margin retreat was assembled. This was based on, and traceable back to, the underlying landform evidence. Once this was assembled we wondered about the timescale; what was the rate of retreat, how and why did it vary, did anything catastrophic happen when North Sea ice broke up?
Whilst this curiosity-driven academic research on our palaeo ice sheet progressed, human driven global warming continued. We now know this to be melting ice sheets in Antarctica and Greenland at a rate faster than can be replenished by snowfall, with losses exceeding 100 Gigatonnes per year (100 kilometre-sized ice cubes every year) with indications of acceleration.
The melted ice ends up in the sea, contributing to rising sea levels. Forecasting is difficult because the complex-interacting Earth systems have yet to be completely understood. It is hard to know when people will start responding to the now-obvious signs.
Both uncertainties make forecasting difficult, but the best current estimates predict a sea level rise by the year 2100 of between half a metre and one metre.
… and sea level rise …
A rapid rise in sea level will have a huge impact on people around the world, most of whom have built their existence in a world of slow change. This dramatic effect has focussed the minds of scientists who now need to improve understanding to make more precise forecasts.
Just as our weather forecasters use a mix of data and computer models, our glaciologists do likewise with their ice sheet models. These track fallen snowflakes, on their journey of flow as ice, until they reach the sea, as water.
So the BRITICE-CHRONO team was frantically busy, setting out to do 50 years work in five, because glaciologists urgently need a data-rich playground of information regarding the timing of a retreating ice sheet. This information would be essential to test and improve their forecasting models.
Weather forecasters get to know whether they were correct or not in a few days’ time, which allows them to keep improving their models. We aimed to do similar for ice sheet forecasters, who instead need data on timesteps of thousands of years rather than daily.
BRITICE-CHRONO looked to achieve this by collecting samples of rock, sand and organics, analysing these in our labs (eg radiocarbon) to provide dates on the pattern of retreat. So how fast did the British-Irish ice sheet retreat?