Week 5: From Longyearbyen around Svalbard

From June 21st to June 23rd Polarstern stayed anchored in the Fjord of Longyearbyen. Here, a large part of the scientific crew of PS 106/1 left, and new cruise participants arrived. For those who remained on board for both legs, the stay in Longyearbyen was a most appreciated break, allowing for a walk on land and some relaxing moments before the new cruise leg would begin.

On Thursday June 22nd, my duty as a chief scientist of PS 106/2 began. The first scientific task of PS 106/2 was a delicate operation: Billiard ball-sized metal spheres hanging from fishing lines were manoeuvred precisely underneath the midline of Polarstern’s keel, using high-precision winches. Positioned in the centre of our EK60 echosounder’s sound beam, the characteristic echo of these spheres was used to calibrate the echosounder. This calibration exercise is very important for the accurate estimation of the biomass of fish and zooplankton from their acoustic signature in the water column.

With the successful completion of the echosounder calibration on the evening of June 22nd, Polarstern was ready for its second cruise leg PS 106/2. This cruise leg is in large parts dedicated to the SiPCA study (Survival of Polar Cod in a Changing Arctic Ocean), which aims to investigate the importance of sea ice for polar cod Boreogadus saida in the Barents Sea and the adjacent Arctic Ocean. Polar cod has a key role in Arctic ecosystems, because it constitutes the staple food of seals and seabirds. Young polar cod often live associated with the underside of sea ice for foraging and protection from higher predators. Due to climate change, the extent of the Arctic under-ice habitat is decreasing. The data obtained from this expedition will help understanding the susceptibility of polar cod populations to declining sea ice.

Leaving Longyearbyen, we sailed around the southern tip of Spitsbergen, before circumventing the Svalbard archipelago at its eastern side. As soon as we left the 12-mile zone of Norwegian waters, we resumed continuous measurements of the water and the atmosphere, as they had been conducted during PS 106/1. Now, an exciting new parameter was added to our programme: Colleagues from Wageningen Marine Research (WMR) in the Netherlands have been taking turns on the highest roof above the bridge, in order to conduct a seabird and mammal census. With these observations, SiPCA constitutes a full ecosystem survey covering organisms from small unicellular protists, zooplankton and fish, to warm-blooded top predators, such as wales and polar bears. With two to three people counting on the ship’s highest deck and from the helicopter, WMR aims to survey seabirds, whales, seals and polar bears 24 hours a day. Since leaving Longyearbyen, large numbers of different birds and marine mammal species were already observed. Just south of Svalbard, big groups of foraging blue whales, humpbacks, fin and minke whales together with white-beaked dolphins were observed. In this region, hundreds of little auks, fulmars and kittiwakes were also recorded. Several kittiwakes, ivory gulls, glaucous gulls and fulmars follow our ship, catching polar cod washed to the surface during ice-breaking (Picture 2). Since entering the ice-covered sea, 16 polar bears were observed.

The first official station of PS 106/2 was accomplished on June 24th, 2017, as part of a daily sampling campaign of chemical compounds in the surface microlayer with Polarstern’s zodiac Laura, accompanied by CTD casts and water sampling.

Ten days after leaving the drift station of PS 106/1, we continued our work on and under the sea ice with our first ice station of PS 106/2 on June 26th. In the meantime, summer melt of the sea ice has progressed, and the sea ice surface is increasingly covered with melt ponds. Overall, the sea ice in this region east of Svalbard is much more eroded than the ice of ‘our’ PS 106/1 floe north of 82°N. The routine in sea ice work we had built up during the previous cruise leg constituted a solid foundation for efficient sea ice work, allowing a seamless integration of the many new participants in the different groups working on the ice. In general, we conducted the same measurements as during PS 106/1. Rather than 13 days, however, this time we were left with 10 hours to set up, measure and take samples before the ship resumed its course. At first, instruments were set up that needed to be deployed under the ice for several hours in order to collect sufficient sample material, or to conduct in situ experiments. The ROV Beast was deployed to investigate the properties of sea ice and the upper ocean layer, and to collect samples of ice algae, zooplankton and under-ice fauna. Numerous sea ice and snow samples were collected for physical, biological and chemical analyses. An intense sampling programme focused on melt ponds. Good weather conditions enabled us to conduct measurements of the sampled ice floe and its surroundings by helicopter.

First analyses showed how the on-going melting of the sea ice is affecting the ecosystem and the interplay of sea ice and ocean. This region is strongly influenced by the nearby open Barents Sea and will be completely free of ice in the coming weeks – as it is every summer.

With contributions from Susanne Kühn and Marcel Nicolaus.

Best regards from scientists and crew,

Hauke Flores, chief scientist