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The perfect ice floe

The perfect ice floe

Current position: 89°31.85 N, 62°0.45 E, drifting with a multi-year ice floe (24th August 2018)

With a little more than three weeks into the Arctic Ocean 2018 Expedition, the team has found the right ice floe and settled down to routine operations.

Finding the perfect ice floe for an interdisciplinary science cruise is not an easy task. The Arctic Ocean 2018 Expedition aims to understand the linkages between the sea, microbial life, the chemical composition of the lower atmosphere and clouds (see previous blog entry) in the high Arctic. This means that the “perfect floe” needs to serve a multitude of scientific activities that involve sampling from open water, drilling ice cores, setting up a meteorological tower, installing balloons, driving a remotely operated vehicle, measuring fluxes from open leads and sampling air uncontaminated from the expedition activities. The floe hence needs to be composed of multi-year ice, be thick enough to carry all installations but not too thick to allow for drilling through it. There should also be an open lead large enough for floating platforms and the shape of the floe needs to be such that the icebreaker can be moored against it on the port or starboard side facing all for cardinal directions depending on where the wind is coming from.

The search for the ice floe actually turned out to be more challenging than expected. The tricky task was not only to find a floe that would satisfy all scientific needs, but getting to it north of 89°N proved exceptionally difficult this year. After passing the marginal ice zone north of Svalbard, see blue line on the track (Figure 2), progress through the first year ice was relatively easy. Advancing with roughly 6 knots, that is about 12 km/h, we advanced quickly. After a couple of days however, the ice became unexpectedly thick with up to three meters. This made progress difficult and slow, even for Oden with her 24,500 horse powers. In such conditions the strategy is to send a helicopter ahead to scout for a convenient route through cracks and thinner ice. However, persistent fog kept the pilot from taking off which meant for the expedition to sit and wait in the same spot. For us aerosol scientists looking at aerosol-cloud interactions this was a welcome occasion to get hand on the first exciting data. In the meantime, strong winds from the east pushed the pack ice together even harder, producing ridges that are hard to overcome with the ship. But with a bit of patience and improved weather conditions, we progressed northwards keeping our eyes open for the floe.

Figure 2: Cruise track with drift. The light red line indicates the track to the ice floe, the dark red line indicates the drift with the floe. The thin blue line is the marginal ice zone from the beginning of August.

As it happened, we met unsurmountable ice conditions at 89°54’ N, 38°32’ E, just about 12 km from the North Pole – reason enough to celebrate the farthest North.

Figure 3: Expedition picture at the North Pole. (Credit: SPRS)

Going back South from there it just took a bit more than a day with helicopter flights and good visibility until we finally found ice conditions featuring multiple floes.

And here we are. After a week of intense mobilization on the floe, the four sites on the ice and the instrumentation on the ship are now in full operation and routine, if you stretch the meaning of the term a bit, has taken over. A normal day looks approximately like this:

7:45:  breakfast, meteorological briefing, information about plan of the day; 8:30 – 9:00: heavy lifting of material from the ship to the ice floe with the crane; 9:00 (or later): weather permitting, teams go to the their sites, CTDs are casted from the ship if the aft is not covered by ice; 11:45: lunch for all on board and pick-nick on the floe; 17:30: end of day activities on the ice, lifting of the gangway to prevent polar bear visits on the ship; 17:45: dinner; evening: science meetings, data crunching, lab work or recreation.

Figure 4: Sites on the floe, nearby the ship. (Credit: Mario Hoppmann)

At the balloon site, about 200 m from the ship, one balloon and one heli-kite are lifted alternately to take profiles of radiation, basic meteorological variables and aerosol concentrations. Other instruments are lifted up to sit over hours in and above clouds to sample cloud water and ice nucleating particles, respectively. At the met alley, a 15 m tall mast carries radiation and flux instrumentation to characterize heat fluxes in the boundary layer. The red tent at the remotely operated vehicle (ROV) site houses a pool through which the ROV dives under the flow to measure physical properties of the water. The longest walk, about 20 minutes, is to the open lead site, where a catamaran takes sea surface micro layer samples, a floating platform observes aerosol production and cameras image underwater bubbles. The ice core drilling team visits different sites on the floe to take samples for microbial and halogen analyses.

Open Lead site. (Credit: Julia Schmale)

Importantly, all activities on the ice need to be accompanied by bear guards. Everybody carries a radio and needs to report when they go off the ship and come back. If the visibility decreases, all need to come in for safety reasons. Lab work and continuous measurements on the ship happen throughout the day and night. More details on the ship-based aerosol laboratory follow in the next contribution.

Edited by Dasaraden Mauree


Julia Schmale is an atmospheric scientist at the Paul Scherrer Institute in Switzerland. Her research focuses on aerosol-cloud interactions in extreme environments. She is a member of the Atmosphere Working Group of the International Arctic Science Committee and a member of the Arctic Monitoring and Assessment Programme Expert Group on Short-lived Climate Forcers .

Into the mist of studying the mystery of Arctic low level clouds

Into the mist of studying the mystery of Arctic low level clouds

This post is the first of a “live-series of blog post” that will be written by Julia Schmale while she is participating in the Arctic Ocean 2018 expedition.

Low level Arctic clouds are still a mystery to the atmospheric science community. To understand their role the present and future Arctic climate, the Arctic Ocean 2018 Expedition is currently under way with an international group of scientists to study the ocean, lower atmosphere, clouds and aerosols.

Low level clouds in the high Arctic influence the energy budget of the region and they hence play an important role for the Arctic climate. The Arctic is warming about twice as fast as the global average, a phenomenon called Arctic amplification. The role of clouds for climate is linked to their interaction with solar radiation. They reflect short-wave radiation, thereby sending energy back to space and cooling the surface. In the case of longwave radiation, clouds reflect it back to the surface which causes a greenhouse effect that is warming the surface. The top of the clouds cools during this process, which makes air parcels surrounding the top cool as well and sink to the surface. These air masses are replaced by warmer surface air which rises. This can cause a well-mixed Arctic boundary layer. Most of the time, however, the cloud level is decoupled from the surface due to temperature inversions. This is possible when clouds are thin. In this case, clouds cannot feed on the water vapor from the surface and they might dissipate. Interaction of clouds with short-wave radiation in the summer is most of the time less important than their interaction with long-wave radiation. This is because the cloud albedo is similar to the sea ice albedo. Hence clouds do not have a strong cooling effect. However, as summer sea ice retreats and the surface gets darker, clouds may contribute to surface cooling in the future.

The overall radiative properties of clouds are further influenced by the phase of the clouds. Arctic summer clouds are normally mixed-phased, that is liquid droplets co-exist with ice crystals. Usually, ice and liquid water do not co-exist, because the ice crystals grow at the expense of liquid droplets that evaporate (because the saturation water vapor pressure is higher of liquid droplets than ice crystals). However, in simple words, in the summertime Arctic, when mixing of air masses occurs, liquid droplets form in rising air parcels that sustain the liquid layer at the bottom of the cloud which in turn feeds the ice crystal growth.

As cloud droplets and ice crystals only form on cloud condensation nuclei (CCN) and ice nucleating particles (INP), the whole complexity described above, depends on the presence of aerosol particles. But the central Arctic Ocean has an extremely limited supply of CCN and INP. Potential sources include locally produced or long-range transported particles. Long-range transport of particles – or precursor gases that form particles – to the high Arctic in the free troposphere can contribute to the number of CCN and INP. However, in the summer Arctic atmosphere precipitation is frequent and particles can be washed out along their way north. Regional transport of trace gases such as dimethyl sulfide (DMS), which is emitted from phytoplankton blooms in the marginal ice zone, can contribute to the CCN after atmospheric oxidation. Local sources in the high Arctic are however, extremely limited. Open leads, those are areas of open water which form as the sea ice is moving, can produce particles through bubble bursting. These bursting bubbles expel material such as sea salt and organic particles contained in the surface water into the air from where they might be transported to the cloud level. Another conceivable source of particles is new particle formation. This means that particles are freshly formed purely from gases. This process and the chemical nature and sources of the gases are however poorly understood.

To shed light on how cloud formation works in the summer time high Arctic and how this might change in the future with changing climatic conditions the Arctic Ocean 2018 Expedition is designed to investigate physical, chemical and biological processes from the water column to the free troposphere. The graphic below provides a schematic of the planned activities.

Arctic ocean setup by Paul Zieger

 

On 1 August, we left Longyearbyen. After a 24 hour station in the marginal ice zone, we are now heading towards the North Pole area where we look for a stable multi-year ice floe against which the ship will be moored for several weeks to drift along. This strategy will give us the opportunity for detailed process studies. In the upcoming blog contributions, several of these process studies will be featured.

Further links:
Expedition website:
https://polarforskningsportalen.se/en/arctic/expeditions/arctic-ocean-2018
Arctic ocean blog of the Paul Scherrer Institute:
https://www.psi.ch/lac/arctic-ocean-blog
Stockholm University Expedition Webpage:
https://www.aces.su.se/research/projects/microbiology-ocean-cloud-coupling-in-the-high-arctic-moccha/

Edited by Dasaraden Mauree


Julia Schmale is an atmospheric scientist at the Paul Scherrer Institute in Switzerland. Her research focuses on aerosol-cloud interactions in extreme environments. She is a member of the Atmosphere Working Group of the International Arctic Science Committee and a member of the Arctic Monitoring and Assessment Programme Expert Group on Short-lived Climate Forcers .