Assessing the effects of climate change in the Arctic

The volume of Arctic sea ice has dropped by 75% over the last 40 years. It is really sad to think that the ice habitat we saw last summer just won’t be there any more in 10-15 years. But it makes the work we are doing all the more important.

Dr Katrin Schmidt, School of Geography, Earth and Environmental Sciences


Charting changes in the Arctic

In 2020, Dr Katrin Schmidt spent two months in the Arctic as part of the international MOSAiC expedition examining the effects of climate change. Stationed on board the research vessel Polarstern, along with 100 other scientists and crew, she collected a range of samples containing ice algae and zooplankton which will now be analysed in a joint Natural Environment Research Council-funded project between the University of Plymouth, Plymouth Marine Laboratory and the Alfred-Wegener-Institute (Germany). The aim of the expedition is to provide a process-level understanding of the Arctic climate system and how the ongoing changes are impacting species that live there and the planet as a whole.

Here is Katrin's story.

Katrin inspecting a plankton catch (Credit: Lianna Nixon)

Katrin inspecting a plankton catch (Credit: Lianna Nixon)

Climate science during a pandemic

The one-year expedition had been 10 years in planning and started in September 2019. When the COVID-19 pandemic hit in February 2020, the organisers had to negotiate options to carry on or terminate early. It carried on and I was really happy it did. At the end of the day, climate change will be around a lot longer than COVID.

Before going on board we had two weeks of quarantine in a hotel in Bremerhaven, Germany, and three COVID tests. Some of my colleagues – for example, those from China or New Zealand – had to quarantine again when returning home, but I was lucky as there was a travel corridor from Germany to UK.

But on the ship, it was really easy because you know everyone on board is clear. And in all honesty, we tried to avoid talking about it as much as possible, and even not reading the news, because we had so much work to do. When I came back the news hadn’t really changed.

Setting sail for the Arctic

We left on the Russian icebreaker Tryoshnikov from Bremerhaven on the 3rd of August and had a few days of handover with the previous Polarstern scientists and crew on the north Greenland shelf.

By this time, the original ice floe that the MOSAiC expedition had been studying for the past 10 months had disintegrated. So we went further north in search of another multi-year ice floe to study the freeze-up, a process that was still missing from our annual cycle.

Arriving at the new floe, we had open melt ponds and leads that restricted our movements across the ice. Then temperatures dropped, we had a lot of wind and snow, and all was covered in white. It was really amazing to see this fast transition.

Living and working on board the RV Polarstern

Life on board the ship is quite restricted. You have two people per cabin, with two bunk beds, a toilet and shower, a desk and somewhere to sit. Outside that, there are always places you can go, such as your lab space, quiet areas, a mini swimming pool and a sauna and gym.

If you want to chill you can go outside but we also had the red saloon, next to where you eat, and there are coffee machines and sofas. The blue saloon has tables where people sit and chat and a library where you can read.

But overall, you have to keep within the ship’s rules. There were 101 people on board – including 40 crew – and some people mix more than others but you all find ways to get along.

An aerial view of Polarstern and the ice camp (Credit: Jan Rohde)

An aerial view of Polarstern and the ice camp (Credit: Jan Rohde)

Katrin's daily routine

0715. Meeting on the bridge to decide what work can take place that day. This is based on predictions from weather forecasters on board, and will determine – for example – if helicopters are able to fly in that day’s conditions.

0830. General meeting for scientists to discuss who will be working on the ice. An important issue was always to ensure safety from polar bears. Therefore we needed trained polar bear guards on the ice and several look-outs from the ship’s bridge. Due to COVID, training courses on land had to be cancelled and there were fewer guards than we would have had normally, so the coordination of activities on the ice was sometimes tricky. If a polar bear arrived at the floe, everybody had to return to the ship immediately.

0900. Head out onto the ice and begin work.

1130-1230. Stop for lunch. If you were close to the ship you would return, but otherwise you would eat your packed lunch on the floe and spend the maximum amount of time at work. If you did go back to the ship you would have some time to unwind, perhaps playing table tennis, before getting back to work.


1300-1700. Work on the ice.

1730-1830. Dinner. Mealtimes are quite brief and everyone (scientists and crew) has their own set places where they eat.

1830. General meeting to discuss the following day’s activities and look at the weather forecast.

1900. The ship’s shop opened occasionally - this would often be the highlight of the day. There would be souvenirs or we could re-stock on goodies.

Evening. Often people had to work through the evening in the ship’s labs or on data entry, but twice a week the bar opened. We would celebrate if someone had a birthday. There were also dance parties, quizzes, science talks, movies and other events, or people played guitar. Such downtime is really important for your mental health.

Coping with the Arctic conditions

The lowest temperature we saw was only -15°C. But we had good clothing and face coverings, so it was comfortable – you never felt really cold. The coldest that other cruise legs experienced was -40°C (but -65°C with added wind-chill), and then nobody was allowed outside. Despite that, there were a few incidents of frostbite.

During our time on board, the sun never set and it was much easier to work outside than what other legs experienced during the winter months. There was a great communal spirit on board; teams helped each other, our plans were achieved and a huge number of samples and data were collected.  Other legs were more affected by changing ice conditions, bad weather or polar bears nearby.

Katrin and colleagues with a zooplankton catch on the ice (Credit: Jan Rohde)

Katrin and colleagues with a zooplankton catch on the ice (Credit: Jan Rohde)

Capturing data on ice algae and zooplankton

There are five teams in MOSAiC (Team Atmosphere, Team Snow and Ice, Team Ocean, Team Ecosystem and Team Biogeochemistry) looking at the Arctic climate system.

I was in Team Eco and our project is looking specifically at the role of ice algae (those that grow in or around sea ice) within the Arctic foodweb and in carbon export. With the loss of sea ice, other primary producers are taking over, but we don’t know how this affects the Arctic ecosystem.

During the cruise, we sampled ice algae and water column algae as well as zooplankton and fish. To do this, we used ice corers, water-column samplers, various nets that could sample from the ice underside to water depths of 2000m, along with visual and acoustic devices.

On board, we separated the different zooplankton species, and preserved them in the -80°C freezer for subsequent analysis on land.

A lot of teams got their full dataset while in the field and we were quite jealous of them, as our work was really only just beginning. There simply wasn’t the time and space on the ship for the complicated analyses involved, so our lab work will take place in Plymouth.

<p>The lipid-rich copepod Calanus hyperboreus (Credit: Bob Campbell)<br></p>
<p>The ice-associated amphipod Apherusa glacialis (Credit: Katrin Schmidt)<br></p>
<p>A juvenile of the squid Gonatus fabricii (Credit: Jo Käßbohrer)<br></p>

Above (from left): the lipid-rich copepod Calanus hyperboreus (Credit: Bob Campbell); the ice-associated amphipod Apherusa glacialis (Credit: Katrin Schmidt); a juvenile of the squid Gonatus fabricii (Credit: Jo Käßbohrer)

Appreciating the environment

Every day brought new challenges, so for much of the time we ran on adrenaline. Arctic sea ice is such a unique environment and even now, two months after being back, I think of it almost every day.

I have been to the Antarctic before but there it was quite different. For example, you didn’t see so many facets in the ice structure and how the colours changed day by day. But when you stand on the bridge in the Arctic, the landscape is so beautiful and you just try to take it all in.

I think it is important that this expedition happened and that we were able to sample the Arctic at this benchmark in time.

In the past, the Arctic was dominated by thick multi-year ice up to seven years old, but now there is hardly any ice older than two years. In winter, thinner ice cracks more easily and heat can escape from the warmer ocean to the much colder atmosphere, while in summer four times more light is absorbed by dark open water compared to snow and ice.

You only fully realise when you are there how the ice acts as an insulating cap between ocean and atmosphere.

If you have less ice, the algae we are studying lose their habitat, but there is a whole community that lives in and around the sea ice. The underside is nursery and foraging area for zooplankton and fish, the ice above is hunting ground for polar bears.

Species have adapted to hide in and on the ice, something you can see in their pale coloration.  Others have adapted to cling onto the ice-underside, which you can see in the morphology of their limbs or are adapted to the extreme salinity or temperatures that you find in the ice.

As a region, the Arctic is warming twice as fast as the global average. This is because its warming has multiple positive feedbacks that lead to even more warming – for instance, the loss of ice and therefore decrease in albedo, or the thawing of permafrost that can lead to wildfires and the release of greenhouse gases.

The consequences, however, are not restricted to the Arctic but affect the rest of our planet – for instance, through weakening of the jet stream that promotes extreme weather patterns in the northern hemisphere, through the melt of the Greenland Ice Sheet that leads to sea level rises and through enhanced greenhouse gas emission.

My highlight of the trip

Our work was always pretty intense, but we did one period where we sampled a range of ecological variables every hour for 36 hours. We worked in tents on the ice and I had the shift from midnight to 4am, and the wind was really strong and rattling on the tent. Because of the strong wind and pressure, the ice cracked and when we opened the tent at the end of our shift a small lead had turned into big open water in front of us – it showed how fast the landscape could change.

I then had another shift from 8pm to midnight, which marked the end of that period of study. When we finished, the wind had dropped and there were new frozen features on some of the melt ponds. The sun was just over the horizon but the light so strong that it felt like we were in a desert – a desert of ice. We explored and ran barefoot through the snow. We were so tired from the work but happy that we did it – that was really cool.

The ladies of Team Ecosystem, with Katrin third from right (Credit: Lianna Nixon)

The ladies of Team Ecosystem, with Katrin third from right (Credit: Lianna Nixon)

What happens next?

Once we get the samples shipped from Germany, we will be spending about a year analysing a range of biomarkers such as highly-branched isoprenoids, sterols, fatty acids, bulk- and compound-specific stable isotopes. The various biomarkers help us to trace traditional (e.g. ice algae) and new (e.g. Phaeocyctis spp. or Melosira arctica) Arctic food sources within the food web. This way we will find out which zooplankton species are the winners and losers of the Arctic climate change.

One of the questions I’m most interested in is whether ice algae fuel the lipid pump in the Central Arctic Ocean? The lipid pump is in action when copepods turn their food in surface waters into lipid stores and spend several winter months dormant in the deep ocean respiring those reserves.

This pathway may sequester more carbon than any other process of the biological carbon pump. Key is that the copepods' life at depth relies on high levels of polyunsaturated fatty acids (PUFA) which they can only gain from their diet and that ice algae are considered a valuable source of such PUFA.

Find out more about the MOSAiC expedition

RV Polarstern set sail from Tromsø, Norway, in September 2019 to spend a year drifting through the Arctic Ocean – trapped in ice. The goal was to take the closest look ever at the Arctic as the epicentre of global warming and to gain fundamental insights that are key to better understand global climate change.

Following in the footsteps of Fridtjof Nansen's ground-breaking expedition with his wooden sailing ship Fram in 1893-1896, the MOSAiC expedition brought a modern research icebreaker close to the North Pole for a full year including, for the first time, in polar winter. The data gathered will be used by scientists around the globe to take climate research to a completely new level.


Read more about the expedition

<p>Tents on the ice</p>
<p>Ice floe during the Polarstern voyage</p>
<p>The MOSAiC scientists and crew</p>
<p>An aerial view of the Polarstern and its ice floe. iceberg boat</p>
<p>Scientists on the ice</p>
<p>Polarstern trapped in sea ice<br></p>

These images show the Polarstern, the ice floe, and the scientists and crew of MOSAiC leg 5 (Credits: Lianna Nixon, Steffen Graupner, Daiki Nomura, Katrin Schmidt).

For more information on anything featured in this article, and the ongoing SYM-PEL research project, please email katrin.schmidt@plymouth.ac.uk.

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