Polar Notes

Feb 2024

Polar Note: Getting to the core of environmental change: how lake sediment cores are being used to bring the hidden depths of Arctic climate change to the surface

Polar Note: Getting to the core of environmental change

Getting to the core of environmental change: how lake sediment cores are being used to bring the hidden depths of Arctic climate change to the surface

Polar Regions APPG Research Specialist, Amy Gray

Research Specialist of the APPG for the Polar Regions, Amy Gray, is currently completing the final year of her PhD at Loughborough University, studying High Arctic climate and environmental change. Here, she explains why studying mud from the bottom of polar lakes can help scientists work out what's going on with the climate in the Arctic.

Project context

Climate change is arguably one of humanity’s greatest threats, with anthropogenic activity widely recognised to be driving the current discrepancies between natural cyclic planetary changes and current warming. As such, one of science’s greatest challenges is trying to determine how climate change is going to impact upon Earth’s biome and the ecological systems upon which we depend, with a view to ensuring that humanity doesn’t irreparably damage our planet’s biological functionality.

When looking at patterns of climate change globally, over the last century, the High Arctic has experienced rapid warming at a rate almost four times higher than the global average. This makes the Arctic a prime location to study in order to better understand the immediate environmental impacts of climate change. However, unlike more populated parts of the world, the Arctic is relatively sparsely monitored, and as such, documenting environmental changes and their impacts remains challenging. Consequently, more effort needs to be made to study this remote and challenging environment in order to  refine our understanding of the science behind climate change and its planetary and humanitarian consequences.

Aerial views of the Brögger Peninsula and the research village of Ny-Ålesund

Study site

My research takes place in Svalbard: a Norwegian archipelago situated in the high Arctic (between 74°N and 81°N, and between 10°E and 35°E), approximately midway between the northern tip of mainland Norway and the North Pole. The archipelago itself is still sometimes referred to as Spitsbergen (or Spitzbergen), so named by Dutch navigator and explorer, Willem Barentsz, who is recognised as the first person to have discovered the islands. However, when the Norwegian sovereignty of the archipelago was finalised at the signing of the Svalbard Treaty in 1920, the Norwegians renamed it Svalbard to commemorate the occasion.

My study is centred around the glacial fjord, Kongsfjorden, which is situated on the northwest coast of Spitsbergen, Svalbard’s largest island. Kongsfjorden’s south shore (the Brögger Peninsula) has been the site of the world’s most northerly town, Ny-Ålesund, since 1917, when the Kings Bay Kull Company started mining in the vicinity. The town has since been transformed into a research settlement hosting institutions from ten nations from around the world, and it was from here that I conducted my research.

I sampled four lakes within a 14km2 radius of Ny-Ålesund between 7th July 2019 and 20th July 2019, the locations of which are mapped in the following figure. Of these, three lakes (Tvillingvatnet, Ossian Sarsvatnet and Pedersenvatnet) were cored. This means collecting sediment cores from the deepest point of the lake basin. These cores were subsampled to the highest resolution possible (0.25cm) to capture the most detailed amount of changes documented in the lake sediments and transported back to the UK to analyse for various properties that can help create a picture of past environmental and climatic changes in those lake catchments.

How can this research help?

Map depicting the locations of the four lakes studied for this thesis

My project aims to overcome the challenges associated with the lack of high-resolution, long-term environmental monitoring in the Arctic by developing a state-of-the-art, multi-proxy approach to analysing lake sediment cores. Specifically, this project focusses upon detailing centennial/millennial records of sedimentological, chemical and ecological changes in three High Arctic lakes located near Ny-Ålesund, Svalbard, spanning the last ~3,300 years.

Diatom species (Pinnularia interrupta) found in Svalbard lakes

As well as looking at the physical properties of the sediments (such as organic content, particle size fluctuations, magnetic susceptibility, elemental composition, and pollutant levels), I am also looking at diatoms, single celled silica-based micro-algae that are key primary producers in Arctic environments. These unicellular phytoplanktonic photosynthesisers leave behind their glassy cell walls when they die, becoming microfossils that can help scientists understand the environmental conditions within the waterbodies they inhabit. There are tens of thousands of species found across the globe, and each species has unique characteristics that help enable identification. By creating a profile of which species of diatoms were thriving or missing at any one time, we can create picture of how conditions in the lakes changed over time.

Layers of sediment built up over approximately 3,300 years visible using an X-ray scan of the Ossian core

Why look at lake sediments?

Suspended sediments accumulate sequentially on the lake floor, forming a chronological record that encapsulates details of past environments. Once dated, environmental conditions can be deduced by analysing various properties of the core’s sediments. In the case of this project, analyses of grain size, magnetic susceptibility, geochemical composition (via XRF), mercury (Hg) concentrations, organic content and diatom assemblages have, where possible, been conducted at the highest resolution (0.25 cm or 200 µm for XRF), providing a detailed insight into how natural environmental (especially climate) change and more recent anthropogenic impacts and atmospheric contamination in the Arctic affect physical and environmental processes in this region.

Why does this matter?

By understanding past climate-driven environmental changes (and how recent man-made changes are influencing the Arctic environment), it is then possible to develop more accurate impact-assessment models to anticipate future environmental responses to climate change. This improved understanding will help influence policies on global carbon reduction targets and the relative importance of encouraging sustainability and innovation in carbon neutral industries.

Finding the deepest point of the lake to take sediment core samples at Ossian Sarsvatnet