New study refines our understanding of biogenic indicators to reconstruct past sea-ice conditions


A collaborative study led by GEUS researchers from the Glaciology and Climate Department provides important new information for reconstructing past ice cover conditions in Arctic fjords.


Arctic sea ice is one of the most sensitive indicators of climate change. During the satellite era, the Arctic region has lost nearly half of its seasonal sea ice, and it continues to warm at a rate 2-3 times faster than the global average. Extrapolations of recent observed data suggest a seasonally ice-free Arctic Ocean by the late 2030s, earlier than projected by most climate models.

For improved future predictions, it is necessary to place recent antropogenic change in a broader context and document sea ice variability on historical and geological timescales, as the natural dynamics of the climate system are poorly understood.

Paleo-records such as marine sediment cores can help extend time-series of sea-ice cover to the pre-instrumental era, and scientists have been working on developing new proxies or indicators that can trace past sea ice evolution.

Sea ice is the habitat of highly specialised microalgae (mainly diatoms). Some sea ice diatoms produce a unique compound (IP25 – ice proxy with 25 carbon atoms) that can remain stable in the sediments for millions of years. This has proven to be a useful indicator in marine settings, but its applicability in Arctic fjord sediments has been questioned.