FS Polarstern PS94 (GN04, TransArc II)
Cruise summary report
|Ship name (ship code)||FS Polarstern (06AQ)|
|Cruise identifier||PS94 (GN04, TransArc II)|
|Cruise period||2015-08-17 — 2015-10-15|
|Port of departure||Tromsø, Norway|
|Port of return||Bremerhaven, Germany|
|Objectives||Trans-Arctic survey of the Arctic Ocean in transition (TransArc II) aiming to capture the physical, biological, and chemical changes of the Arctic Ocean. The retreat of the multi-year sea ice over the last decades, and the changes in ice and ocean circulation are tightly linked to changes in the heat and fresh water distribution with consequences for the gas exchange between ocean and atmosphere, for biogeochemical cycling and for organisms and ecosystems in the sea ice, in the water column and on the sea floor. To distinguish processes of multiyear variability from long-term, maybe anthropogenic, trends we capture in a distance of several years the regional distribution of the key components of the Arctic Ocean.
Specific goals of our programme were to determine if the water that is advected from the Atlantic and Pacific oceans continues to become warmer and whether this development has an impact on the sea ice decrease; whether the accumulation of fresh water in the Arctic that lasted over the past decades, as well as the related change of the upper ocean stratification has reached a turning point; whether besides the extent also the thickness of the sea ice continues to decrease. We also studied changes in the composition of phytoplankton in ice and water, and investigated the state of zooplankton. In the same time, PS94 was a central contribution to the international programme GEOTRACES which aims at determining the distribution and cycling of trace substances and their isotopes in the global ocean. In-situ measurements of the structure and the thickness of the sea ice served also as validation for remote sensing products, among them from the CryoSat2 mission.
To follow these goals, we conducted a number of long transects through the Eurasian part of the Arctic which extended from the Barents Sea and the Gakkel Ridge, respectively, into the Makarov Basin. From the ship, the helicopter and on ice stations we conducted in-situ measurements and sampled sea ice, water and sediment. We deployed a suite of autonomous platforms: observation systems installed on ice floes will record atmospheric, sea ice and water properties over the next months and - hopefully - years and send the data ashore while drifting with the host floes through the Arctic; two moorings were mounted at the sea floor to measure the seasonal cycle of hydrography, currents and vertical particle flux, and for the first time we will get once per week near-surface water samples from the central Arctic which will be analysed for their nutrient content after successful recovery in summer 2016. When operating in international or Norwegian waters, we recorded the sea floor topography with the multibeam echosounder to extend the still poor Arctic Ocean data coverage.
During the entire cruise, difficult ice conditions with concentration up to 100 % and new ice formation, as well as a continuously thickening snow layer on the ice hampered the sailing. In addition, the frequent snow fall and bad visibility limited the use of the helicopters. A highlight of the cruise was the meeting with the US coastguard ice breaker Healy at the North Pole on September 7, 2015. Also the Healy conducted a GEOTRACES programme and during the meeting an inter-calibration station right at the North Pole was conducted.
|Chief scientist||Ursula Schauer (Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research)|
|Project||GEOTRACES -Trace elements and their isotopes in the water column|
|Cruise report||(12.60 MB)|
|General||Laptev Sea (or Nordenskjold Sea)|
|Track charts||(0.41 MB)|
|Data held at BODC|
|93 CTD frame plus rosette sampler|
|7 Stand-alone pumps|