Stockholm university
Department of Meteorology

The expedition Arctic Ocean 2025, post 4: Sediment samples – climate archive millions of years old

Over three weeks have gone for this years Oden expedition to the central Arctic Ocean and we have passed the midpoint with less time left than spent. We have managed to take some more sediment samples; the several meters deep samples represents a climate archive that may go millions of years back in time. Also a rare spotting of the sun, this time with two so-called "sundogs".

Cloudy sky, blue ice, bright sun, "sundogs" to the left and right, rainbow coloured.
A rare spotting of the sun, this time with two so-called "sundogs", that occurs as solar radiation is refracted in ice particles in the atmosphere. Photo: Michael Tjernström.

Over three weeks have gone for this years Oden expedition to the central Arctic Ocean and we have passed the midpoint with less time left than spent. We are still on "the other side" of the pole which means a flipped day, with the darkest hours in the middle of the day, but we are now heading back towards the area around the pole again before heading back home. It has continued to be a lot of fog and other adverse weather, that complicates some of the work since we cannot use the helicopter for work on the ice as much as planned.

A man in lifewest, safety belt and helmet holding the sediment core.
A sediment core is being retrieved from the sea floor thousands of meters below the ship. Photo: Michael Tjernström.

We have managed to take some more sediment samples; the several meters deep samples represents a climate archive that may go millions of years back in time. We also have several more water samples from different depths and some new ice cores from the sea ice. We also continuously sample the surface water and continues to send weather balloons and to monitor the energy exchange between the atmosphere and the ocean.

In addition to learning about ocean, sea ice and atmosphere there has been lectures on the sediments och biology, seismology och sea floor mapping, and a lot more.

Students bending over a tale jammed with puzzle pieces.
Puzzle-laying students on icebreaker Oden. Photo: Michael Tjernström.

An important aspect of this years expedition is the research school. Much of the research is carried out by the students that also have lectures on different topics. In addition to learning about ocean, sea ice and atmosphere there has been lectures on the sediments och biology, seismology och sea floor mapping, and a lot more. The past week the students have had a workshop on UNCLOS – United Nations Convention on the Law of the Sea – the international agreement that regulates how the oceans can be used. Between work and lectures there is time for social life; the cinema is on every night, there's a ping-pong tournament and we have had salsa dans lectures on two occasions. And tonight is the traditional crayfish party!

(Michael Tjernström, 1 September 2025)

The stern deck of Oden, and St Laurent in the distance at the other end of the ice tunnel.
Oden is breaking ice for Louis S. St Laurent, conducting measurements of the sea floor with seismology. Photo: Michael Tjernström.

UNCLOS – United Nations Convention on the Law of the Sea

The icebreaker Oden has set sail and is heading for the Arctic to map the seabed. On board are 18 PhD students from various countries attending a research school where practical work is combined with lectures. Follow their journey in our blog, with weekly reports by Michael Tjernström, professor emeritus of meteorology at Stockholm University with extensive experience of Arctic expeditions, and responsible for the research school.

UNCLOS – United Nations Convention on the Law of the Sea

Blog and more articles about the expedition AO25

The AO25 blog: The expedition Arctic Ocean 2025

Theme
Atmosphere and Weather - Theme page Climate and Environment - Theme page Oceans and Lakes - Theme page
Research subjects
Climate dynamics and climate change Meteorology and atmospheric science Oceanography

Last updated: September 2, 2025

Source: MISU

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