A 12-meter sediment core retrieved in 2019 from the Fram Strait, between Svalbard and Greenland, is under meticulous analysis by Jochen Knies and his team from our Polar Research Hub. Extracted from a depth of 2,500 meters, the core preserves a climate record spanning up to 400,000 years. Its sediment layers offer crucial insights into the Arctic’s past, addressing an important question: Was the Arctic ever ice-free during past warm periods?
Photo taken by the author
Proxies: Unlocking climate history
The core undergoes a series of detailed analyses to reconstruct its climate history, starting with the use of proxies —specific markers like paleomagnetic data, microfossils, and stable isotopes—that allow scientists to infer past environmental conditions. Proxies help determine the age of each layer and uncover significant climate events, such as shifts in temperature, ice cover, and ocean dynamics.
For instance, paleomagnetic data reveal changes in Earth’s magnetic field, aiding in dating specific layers. Microfossils, such as marine organisms, provide clues about past ocean temperatures and productivity. Stable isotopes further detail historical water temperatures and ice volume. By integrating these data, the team constructs a detailed timeline of Arctic climate changes spanning hundreds of thousands of years.
High-Resolution Sampling: Precision matters
To maximize precision, the core is cut into small segments, typically every centimeter, for analysis. This high-resolution sampling captures intricate climate details from each layer.
Photo taken by the author
“We are particularly focused on warm climate periods like the last interglacial (~130,000 years ago) and the one before (~400,000 years ago),” explained Jochen Knies. “Examining these fine-scale samples allows us to gather a wealth of information about the Arctic’s climate during these critical times.”
In some cases, segments are sampled every half centimetre to detect even the most subtle climate shifts.
Measuring water content
Photo taken by the author
After analyzing proxies, the team measures the core’s water content. Sediment samples are weighed wet, dried, and reweighed to calculate water content, which reveals sediment density. This data helps determine sediment accumulation rates over time.
“Understanding how sediment accumulated during specific periods provides insight into past environmental conditions, including deposition rates of various materials,” noted Jochen Knies.
Photo taken by the author depicting 1cm – sediments samples ready to be weighted wet.
Feeding climate models
Though this core reflects a single Arctic location, it forms a vital piece of a larger puzzle. “The data will feed into climate models, enhancing our understanding of the Arctic’s climate history and refining predictions for its future”, said Jochen Knies.
Incorporating these findings into models helps scientists anticipate how the Arctic might respond to rising global temperatures.
Expanding the research
The current core is just the beginning. Next year, the team plans another expedition to gather additional sediment cores from various Arctic regions. These new samples will expand the dataset, offering a more comprehensive picture of Arctic climate during past interglacial periods.
Jochen Knies and his team aim to determine whether the Arctic has been ice-free in the past while uncovering valuable insights into how the region may evolve under ongoing climate change. Their research is vital to understanding the complexities of global climate dynamics and enhancing predictive models for the Arctic’s future.
Jochen Knies is a member of the new centre for ice, Cryosphere, Carbon and Climate (iC3), which investigates how the links between ice sheets, carbon cycles and ocean ecosystems affect life on Earth. He is also project leads of the new project into the Blue (i2B), which aims at resolving past Arctic greenhouse climates.
