CR
Cryospheric Sciences

Sea-ice

Camping on the Svalbard coast

Camping on the Svalbard coast

In early April 2015, a small team of 2 Belgian and 2 French researchers went to Svalbard. The goal? Testing new methods to measure sea-ice thickness and ice algal biomass, but also measuring greenhouse gases in the sea ice in relation with the ‘STeP’ (Storfjorden Polynya multidisciplinary study) campaign. With funding from the French Polar Institute (IPEV) and IPSL and logistical arrangements by the Laboratoire d’Océanographie et du Climat (LOCEAN, Paris), we had the opportunity to conduct a short field campaign, long enough to perform instrumental tests and ice coring.

The expedition was arranged with Stefano Poli – a tourist guide in Svalbard. People and equipment were driven on snow-mobiles to Agardhbukta, 100 km South East of Longyearbyen. The conditions for this expedition were quite rudimentary; a tent, a burner and sleeping bags. There are no human settlements in this remote location, so Stefano chose a camping spot, as safe as possible with respect to polar bears, right in front of the fjord, our working place…

Quite exciting, isn’t it? Let’s take a look at what we got up to:

Outside the tent (credit: A. Lourenço).

Setting up the Camp

How do you set up a camp in the Arctic? First, you look for a hidden place, ideal for bear watching (in our case we chose a place with a small hill on our back and open on a wide and flat area). Then the hard work starts:

  1. Build the body and the membrane of the tent.
  2. Dig a hole in the snow right under the entrance to allow carbonic gases to escape.
  3. Set up the oil burner circuit: the oil tank positioned outside the tent is sent to the burner through a pipe covered by snow to avoid spilling accidents, and another pipe made from superposition of aluminum cylindrical cans links the burner to the air above the tent. A hole in the membrane of the tent is designed for that purpose.
  4. Circle the tent with a bear alarm. This was totally handmade and consisted of a gun firecrackers guided by a thread, not really sufficient to stop a polar bear!

The daily life

Eating, sleeping, working, everything was adapted to Arctic conditions. The meals – morning, lunch and dinner – were just dry food in hermetic bags that you fill in with boiling water. Better choose the orange bags, chili con carne is the best. To sleep, reindeer skins were placed directly on the ground (i.e. snow) as mattresses, and sleeping bags were in natural bird feathers. The ideal position is when you find the perfect distance between your feet and the burner.

Inside the tent (credit: M. Kotovitch)

Inside the tent (credit: M. Kotovitch)

As the bear alarm might not be totally reliable, our guide offered us (well, without the possibility to decline or give up) a memorable nocturnal experiment, a series of 2-h bear-watching shifts, with a survival kit consisting of a flare gun, 2 tea thermos and 1 teddy polar bear for superstition.

In the Field

The objectives of this short campaign were (i) to sample early spring sea ice, snow and seawater in the Storfjorden region; (ii) to calibrate non-destructive methods for ice thickness and biomass retrievals in sea ice; and (iii) to measure greenhouse gases in sea ice in relation with the ‘STeP’ campaign. This cruise is scheduled for next summer in Storfjorden, led by IPSL-Paris and involves paleo-oceanographers, physical and chemical oceanographers as well as biogeochemists from several countries.

Why is it so important to develop a non-destructive method while working on sea ice? Because the general and only way known currently to sample sea ice in its entire thickness consists of coring, which destructs the site and can alter sea ice biogeochemical conditions.

With these goals in mind, the initial plan was to operate 2 or 3 stations per day on coastal landfast ice in Storfjorden. Agardhbukta was chosen for its situation (not too far from Longyearbyen) and as one of the locations in Storfjorden where we had good expectations to find practicable sea ice in this season, which was required to carry out our work. Our guide Stefano mentioned he saw a satellite image with new sea ice on March 23 in that location. And indeed, the sampled ice was probably not older than 2-3 weeks (Figure 4). Regarding the sampling planning, our expectations where a little bit overestimated. The weather conditions were so snowy and windy that we hardly had the time to sample one full station a day… This is how Polar Regions surprise us.

 

Bear watching (credit: A. Lourenço)

Edited by Sophie Berger and Nanna Karlsson


Marie Kotovitch is a PhD student at the Chemical Oceanography Unit, University of Liège, supervised by Bruno Delille. She is working with sea ice and gas transport (mostly greenhouse gases like CO2 and N2O). She has a collaboration with the Laboratory of Glaciology at the Université Libre de Bruxelles and was involved in this campaign in Svalbard to analyze the biological aspect of this study.

Cruising for mud: Sediments from the ocean floor as a climate indicator

Cruising for mud: Sediments from the ocean floor as a climate indicator

Going on a cruise for a month sounds tempting for most people and that is exactly how I spent one month of my summer. Instead of sunshine and 25 degrees, the temperature was closer to the freezing point on the thermometer and normal summer weather was replaced by milder weather conditions. The destination of the cruise was the western Nordic Sea and the east Greenland Margin. The ice2ice cruise was not a regular cruise, but a scientific cruise, starting in Reykjavik then heading towards the east coast of Greenland and ending in Tromsø, Northern Norway. Without the option to go ashore and far away from civilization, I spent four weeks aboard the Norwegian RV G.O. Sars. When I came home from the middle of the ocean, I realized that I had been part of a unique project.

The ice2ice cruise logo, where the red dots indicate the more than 30 sites of coring marine sediments under the ice2ice cruise. Photo credit: Amandine Tisserand

The ice2ice cruise logo, where the red dots indicate the more than 30 sites of coring marine sediments under the ice2ice cruise. Photo credit: Amandine Tisserand

Why are climate scientists going on a cruise?

The purpose of the cruise was to collect marine sediment cores in the western Nordic Seas and along the east Greenland Margin. The retrieved sediments can be used to document abrupt changes in sea ice cover and ocean circulation along the East Greenland continental margin, during glacial times and for the more recent past. For this purpose three different sediment coring systems were used. The multicore, which samples sediments, including the sediment/water interface at the sea floor, the gravity core that is used to get information about the deeper marine sediments (up to 5 meter), and the calypso core that could retrieve up to 20 m long sediment cores, containing muddy sediments from the ocean floor to the ship’s deck.

One of the main questions of the ice2ice project is why there are abrupt climate changes. The sediment cores should be ideal for correlation to the RECAP (http://recap.nbi.ku.dk/) ice core from Renland Ice Cap in Eastern Greenland, drilled earlier this year. Together it is a unique material, which hopefully can bring information of the sea ice cover and its extent back in time.

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Sediments: a split calypso core showing a clear pattern of a tephra layer from a volcanic eruption (left), and the multicore on the way up with four successful sediment cores (right). Photo credit: Iben Koldtoft and Ida Synnøve Olsen.

When everything is new – also the type of cruise

This was my first cruise ever, and before I boarded the ship in Reykjavik in mid-July, my knowledge of marine sediments and the ocean was very limited. Most of the people on board the ship were geologists who knew a lot about sediments from the ocean and had been on cruises before. Now a month later, my knowledge about sediments and the life aboard a research ship has become much larger. I think I had the steepest possible learning curve about sediments, because there were no stupid questions to ask, and everyone was very nice about answering questions, even if it was outside their area. Usually I work with ice cores and modelling of glacier ice and for me everything was new. This meant that I could contribute with knowledge about the RECAP ice core instead. Now I can take part in a conversation about sediments together with other geologist.

Normally when going on a cruise, there are only a few scientists on board on the ship. This means that there is only time to core the sediments and cut them into sections, while all the scientific work takes places later, when the sediments are in the lab. On this cruise, as something new, we were several scientists, so when the sediments were on deck, we immediately did a splendid job of handling the cores, describing and analysing the material. Thus, the detailed lab analyses can start right away after the material gets back to Bergen.

Shipboard analyses indicated that the material we have brought back to the laboratories in Bergen covers a time span from the present and probably a few hundred thousand years back in time. Not all the data have been analysed yet but we are looking forward to start and we are eager to see the results.

 Midnight sun over the Greenland Sea. Photo credit: Dag Inge Blindheim.

Midnight sun over the Greenland Sea. Photo credit: Dag Inge Blindheim.

The science

During the one month long cruise, we had collected numerous samples of shells from the ocean floor from 32 stations west of Iceland. We did CTD (Conductivity, Temperature and Depth) measurements, to get information about how the temperature, salinity, density and oxygen content of the water vary in the ocean, and we collected water samples at different depths to analyse oxygen and carbon isotopes. We also collected sediments from 31 stations and every core has passed the DNA sampling, color and MS measurements stations. The cores were then cut into sections, split down through the middle, logged and described so that we could  get an initial feel for the quality and utility of the samples we retrieved, before they are brought to shore for much more detailed analysis.

Ashley, Margit and Ida cut a gravity core into sections (left), while Alby brings a multicore from the deck down to the lab (right). Photo credit: Dag Inge Blindheim and Kerstin Perner.

Ashley, Margit and Ida cut a gravity core into sections (left), while Alby brings a multicore from the deck down to the lab (right). Photo credit: Dag Inge Blindheim and Kerstin Perner.

Working 24-hour shifts on the ship meant that we achieved a lot and we brought home more than 200 m of muddy sediment cores from the sea floor from the western Nordic Seas and the east Greenland Margin and more than 190 water samples.

Although it was 12 hours of hard work most of the days, it was a pleasure to be part of the cruise. It has certainly not been my last cruise, if it is up to me, and I will look forward to a new cruise if I am lucky enough to get the chance. Weather was nice most of the time, but of course, we had some days of rough seas.  The professionalism of the crew of G.O. Sars created an excellent atmosphere for work and time off, it was more like being on a real 4 star cruise if we ignore the time we worked.

Henrik is taking DNA samples of a gravity core (left) and water samples from the CTD (middle). Photo credit: Iben Koldtoft. I am happy after having packed one of the last sediment sections, which is now ready to be sent to Bergen and further analyzed (right). Photo credit: Kerstin Perner

Henrik is taking DNA samples of a gravity core (left) and water samples from the CTD (middle). Photo credit: Iben Koldtoft. I am happy after having packed one of the last sediment sections, which is now ready to be sent to Bergen and further analyzed (right). Photo credit: Kerstin Perner

On the ice2ice cruise the scientists were Eystein, Carin, Jørund, Dag Inge, Bjørg, Christian, Margit, and Amandine from Uni Research (Uni Research Climate, Norway), Stig, Sarah, Evangeline, Henrik, Ashley, and Ida from UiB (University of Bergen, Norway), Flor from GEUS (Geological Survey of Denmark and Greenland, Denmark), Mads from CIC (Centre for Ice and Climate, Denmark), Kerstin from IOW (Leibniz Institute for Baltic Sea Research Warnemünde, Germany), Albertine from Bris. (University of Bristol, UK), and myself Iben from DMI & CIC (Danish Meteorological Institute & Centre for Ice and Climate, Denmark). We were 19 participants, 8 men and 11 women, representing 8 different nationalities, and supported by a ship crew of 15. We were in good spirits all the time and a successful cruise!

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The scientific crew of the ice2ice cruise. Photo credit: Iben Koldtoft

The cruise would not be possible without support from the European Research Council Synergy project ice2ice (Danish-Norwegian), Bjerknes Centre for Climate Research (Norway) and Institute of Marine Research (Norway), who provided research vessel and crew onboard.

You can read more about the ice2ice project on its homepage https://ice2ice.b.uib.no/

Iben Koldtoft is PhD student within the ice2ice project at Danish Meteorological Institute and Centre for Ice and Climate, University of Copenhagen, Denmark and supervised by Jens H. Christensen and Christine S. Hvidberg. She is interested in modelling the dynamics of the Greenland Ice Sheet and the smaller glacier, Renland Ice Cap, in the Scoresbysund Fjord, Eastern Greenland. Currently she is coupling the ice sheet model PISM to the ocean by implementation of calving to the model. Surface mass balance simulations of the Greenland Ice Sheet will later be used to assess the quality of the interaction between the ice sheet model and a climate model in comparison to observations.

Do Beers Go Stale in the Arctic? – Jakob Sievers

Do Beers Go Stale in the Arctic? – Jakob Sievers

A story about CO2 -fluxes between sea-ice and the atmosphere

What’s it all about?

Whenever I have had to describe my PhD research project to people outside of my research community, I have always found it useful to use an analogy most people are familiar with, namely beers. Now that I have the full attention of the entire class, allow me to explain. Say you were to find yourself at an outside café, grabbing a beer in the beautiful weather with your friends. You get caught up in the conversation and soon your beer is lukewarm and stale and you struggle with the last few drops while gesturing somewhat frantically at the waitress to bring you a new beer. What has happened? Well, the partial pressure of CO2 (pCO2) in the beer is much larger, relative to that of the atmosphere. This leads to gradual diffusion (or flux) of CO2 from the surface of the beer into the atmosphere, and eventually the establishment of an equilibrium pCO2 in the beer, similar to that of the atmosphere. Of course, you have probably been waving at the waitress long before the equilibrium is reached. Now imagine that you had performed this experiment in the cold of winter. The waitress brings you a beer and from the moment it reaches your table a thin layer of ice starts forming on the top. What happens with the CO2 levels now?

Though a bar would probably have been a nice place for fieldwork, obviously my fieldwork took place in a much colder environment, namely the arctic sea-ice in northeast Greenland. The kingdom of the sort of curious four-legged fella shown in the photo above. And the answer to the above question might be “nothing” in the case of a beer. I.e., the ice works as a sort of lid on the beer, preventing any fluxes of CO2 from occurring, but what about in a sea-ice environment? Until very recently the beer analogy would have applied equally well here, as most scientists would have told you that no CO2 fluxes could take place in this sort of environment. Accordingly, all climate models currently treat sea-ice covered regions as regions of no exchange in terms of CO2. Lately, however, a number of papers have been published, suggesting that fluxes can occur at different stages of the annual sea-ice cycle. The paradigm shift occurred when it was discovered that CO2 may be transported through brine channels within the sea-ice. Brine channels form within sea-ice because of the salt in the sea-water, and they tend to be larger if the temperature is higher. So, at the bottom of the ice where the ambient temperature is a balmy 0°C, the channels are largest (Fig. 1).

Figure 1: An actual photo of brine channels within sea-ice [Junge et al., 2001, Annals of Glaciology]

Figure 1: An actual photo of brine channels within sea-ice [Junge et al., 2001, Annals of Glaciology]

Processes – scratching the surface

It is thought that the bulk of fluxes occur primarily in the spring during sea-ice melting. To understand why, we have to go back to when the sea-ice is formed during wintertime. As the ice forms, salts and CO2 are concentrated in the brine channels, and are expelled into the ocean through the larger brine channels in the bottom of the ice. The process is called gravity drainage and refers to the sinking of the highly saline and cold brine water which is denser relative to the underlying sea-water. Some of the expelled CO2 will continue to the deeper ocean column and as such lead to a CO2 loss of the original surface system. Hence, upon springtime melting, the upper water column has less CO2 than the atmosphere, which then causes an uptake of CO2 from the atmosphere. I.e.: a re-carbonization of the beer, so to speak. The mechanism has been coined the sea-ice driven carbon pump and has been estimated to drive an annual uptake of 50 million tons of carbon annually in the arctic alone, constituting a significant fraction of the total CO2 uptake of the arctic ocean which is estimated to be 66-199 million tons of carbon annually. Hence, understanding the impact of this carbon pump is important, particularly because the impact of climate change is felt more dramatically in the arctic compared to the rest of the world. Sea-ice cover is becoming increasingly ephemeral and glacial freshwater runoff, which inherently has a low partial pressure of CO2, is becoming increasingly ubiquitous in the fjord systems.

What are the challenges in this field of study?

To incorporate the carbon pump into existing climate models we need first to understand the physical and biogeochemical processes which drive sea-ice carbon fluxes in both coastal and open water conditions as well as during the entire life-cycle of sea-ice. Sounds simple, right? Of course not. Like most experimental investigators in cryospheric sciences we are struggling with considerable logistical challenges in a vast and unforgiving environment, where temperature conditions often have instrument-developers shaking their head in disbelief. “We didn’t test the instrument for that sort of thing”. How reassuring. Secondly, there are substantial risks involved, both for people and instruments, when conducting experiments during periods of thin sea-ice, which also happen to be the periods in which fluxes are most pronounced, and thus all the more important to understand. Fortunately we are equipped with fairly unique vehicles for transportation during these conditions (Fig. 2). Finally, the fluxes that are reported on sea-ice are often significantly smaller than what is typically reported in terrestrial environments, leaving investigators at times struggling to discern actual measurements from artificial noise.

Figure 2: Our polar air-boat for safe and fast transportation on thin sea-ice. During the experiment this bad boy was typically referred to as a gasoline-to-noise converter. In this particular picture the air-boat is pictured on thick sea-ice, hence the use of normal winter clothing instead of marine safety suits. Photo: Jakob Sievers.

Figure 2: Our polar air-boat for safe and fast transportation on thin sea-ice. During the experiment this bad boy was typically referred to as a gasoline-to-noise converter. In this particular picture the air-boat is pictured on thick sea-ice, hence the use of normal winter clothing instead of marine safety suits. Photo: Jakob Sievers.

What did I focus on during my PhD?

A common method for flux-observation is the micrometeorological Eddy Covariance method. It involves setting up a 2-5m high tower on a surface of interest and at the top installing:

(1) A three-dimensional ultrasonic anemometer, which measures 3D wind patterns,

(2) A gas analyzer, which measures the atmospheric concentration of e.g. H2O, CO2 or CH4 depending on which type of flux you are interested in.

Figure 3: Our eddy covariance tower on thin ice (20cm) in the outermost region of Young Sound (NE Greenland). Photo: Jakob Sievers.

Figure 3: Our eddy covariance tower on thin ice (20cm) in the outermost region of Young Sound (NE Greenland). Photo: Jakob Sievers.

Together they allow for calculation of the average flux in an upwind area in front of the tower. This area will vary in size depending on the height of the tower and wind-conditions. One of our instrument towers are shown in Fig. 3. From a mathematical standpoint the method is very simple, but it requires a number of quite complicated assumptions concerning the characteristic wind-patterns of the environment in question. Often these assumptions are not discussed in detail in papers. During my PhD I found that because most fluxes in a sea-ice environment are so small the critical assumptions began breaking down. It seemed that nearly all observations reflected large-scale meteorological patterns and flow-characteristics of the topography instead of fluxes in the local area of interest. Realizing this, I successfully developed and tested a very comprehensive data-analysis method to disentangle contributions of interest and contributions which were not reflective of the local environment of interest. Due to the technical nature of this new method I will not elaborate here, except to say that it was recently published in the Journal of Atmospheric Chemistry and Physics. Subsequently I was able to analyze simultaneous observations of CO2-fluxes and environmental parameters such as site energy balance and wind-speed to achieve a better understanding of some basic causal relationships for CO2 fluxes in a sea-ice environment.

Because this field of study is so new, and in-situ experiments are so challenging, much work is still needed but hopefully we will soon have a sufficiently detailed understanding of the physical and biogeochemical factors driving CO2 fluxes in the sea-ice environment, to be able to develop a model relationship and upscale that to all polar regions in which sea-ice exist.

Figure 4: An unexpected challenge during fieldwork: invasion by sled dog pups. Photo: Karl Attard.

Figure 4: An unexpected challenge during fieldwork: invasion by sled dog pups. Photo: Karl Attard.

I would like to leave you with one final picture illustrating a somewhat unexpected challenge during our experiment: having to reclaim our instruments and tools from the sled dog pups (Fig. 4).

Jakob Sievers ( Arctic Research Centre / Aarhus University) has just completed his PhD at Aarhus University in Denmark as part of the DEFROST project. He is interested in the physical and biogeochemical drivers of CO2 cycling in sea-ice environments and the development of flux models and flux observation methods under these challenging circumstances. He is currently seeking funding for the purpose of continuing his research in northern Norway.