KV Svalbard cruise 19-31 March 2007

Picture 1: Participants Bilde 1 av 5

We had about 10 days in the sea-ice south-east of Svalbard. We did three ice-stations with ~24 h duration. Ice conditions were quite strange this year, with thin fast iceand only very thin ice, or grease/frazil between Svalbard and Bjørn Øya. There were two other groups joining the cruise (DNV and SINTEF). Sea ice thickness measurements were made by Andreas Pfaffling and are available here. Andreas now has his own company called Pfaffling Geophysics. The efforts was along the lines of BIAC 'sea ice' with many processes being relevant, the CO2 etc. "Bipolar Atlantic thermohaline Circulation" The process studies that was worked on are listed below, for more on the different sensors we operate have a look at our Fieldwork page. The cruise narrative can be found here.

A) Atmospheric/flux measurements

Jochen Reuder (joachim.reuder@gfi.uib.no) and Anna Sjøblom (anna.sjoblom@unis.no) Tor DeLange (GFI technitian) and Charlotta Petterson (UNIS student)

Atmospheric fluxes of momentum, heat, moisture and CO2 by one eddy correlation system (Campbel CSAT3, Licor 7500) measured on the ice stations. Measurements with the inertial dissipation method were done from the bow of KV Svalbard. A sonic anemometer was placed approximately 9 meters above the water pointing in the ships travel direction. The measurements were done semi-continuously during the whole cruise, but intense measuring periods with the ship at rest in the wind were done especially in Storfjorden but also other places along the cruise track. The purpose is to evaluate the momentum and sensible heat fluxes over the air-ice-sea interface. Micrometeorological profiles at two locations with two measurement heights:

1m: temperature, humidity, pressure, wind speed
5m: temperature, humidity, wind speed, wind direction

These measurements will be done by our Aanderaa system. Therefore no special logistics concerning power supply are necessary for this. We intend to fix the masts by ice screws.

B) Oceanic Microstructure Profiles

Ilker Fer (BBCR) Help from Anna, Lars, Ragnheid along the way.

In addition to the eddy-correlation turbulence measurements conducted by Miles McPhee (see C), microstructure profiles were collected covering the full depth at three ice stations:

Station 1 in Van mijenfjorden fast-ice;
Station 2 near Freemansundet fast-ice; and
Station 3 from drifting ice east of Freemansundet in western Barents Sea.

An MSS90L loosely tethered free-fall profiler was used with a noise level for dissipation of about 3x10^-9 W/kg. Ice deployments were made from a hydrohole in the ice, within 30 m from TIC location and at least 150 m away from the research vessel. Background currents in the upper 30-60 m (depending on the scatterer strength) were monitored by acoustic Doppler profiler Aanderaa RDCP600 at Stations 1 & 2 and Sontek at Station 3, suspended from ice looking downwards. Additional microstructure profiles were collected from K.V. Svalbard along a section in the Storfjorden polynya and at several stations in the vicinity of the Storfjorden sill.

Station 1: Fast-ice station in Van mijenfjorden was occupied at 77deg 48.6075min N, 015deg 56.9013minE at water depth of about 65 m and ice thickness of 35-40 cm. In total, 63 casts were made between 200307 1926 – 210307 0914 UTC at an average sampling interval of 13 minutes between profiles.

Station 2: Fast-ice station in Freemansundet was occupied at 78deg 08.634min N, 020deg 52.009minE at water depth of about 46 m and ice thickness of 80 cm. In total, 5 casts were made between 220307 2309 – 230307 0008 UTC. Working conditions were difficult and the shear probes and microstructure sensors were vulnerable to slush continuously forming or advecting from below at the hydrohole. Time series were terminated after a mechanical failure of the MSS-winch system which was repaired on board K.V. Svalbard.

Station 3: Drift-ice station was occupied on a large ice floe with variable ice thickness (15 cm to 120 cm). At the MSS measurement site ice was about 30 cm thick and during the first cast position was approximately 78degN, 025deg 26minE at about 150 m water depth. 58 profiles were collected between 270307 1147 – 280307 0400 UTC.

See picture 2.

C) Turbulence and supercooling of the ocean boundary layer

During the cruise aboard the Norwegian Coast Guard icebreaker K/VSvalbard, we had the opportunity to deploy two turbulence instrumentclusters (TICs) during three short on-ice stations at different locations in ornear the Svalbard archipelago (see picture 3). The second station was situated near the edge offast ice approximately 45 cm thick in the northern end of Stor Fjord (betweenSpitsbergen and Edge Islands), near the mouth of Freeman Sound. We measuredthere at two lev­els, 1 and 3 m below the ice/water interface, for about 20hours, or slightly more than 11/2 tidal cycles. This is an area of much interest because the combination of strong tidal action and cold northerly winds often forms a polynya capable of producing exceptionally dense water that is both highly saline and cold. In winter the water is nearly always near its freezing temperature, and may become supercooled. In the measurements we made during our brief station in Freeman Sound, we observed what appear to be supercooled conditions, but also noticed a response of the SBE 04 conductivity meters in those conditions that may bear on other discussions of supercool­ing observed in polar waters, based on measurements made with Sea-Bird and similar conductivi­ty measuring instrumentation.

D) Sea ice / grease properties

Lars H. Smedsrud Johan Wåhlin (Nansen Centre, Master student)

The sea ice program included taking cores and measuring temperature, salinity, and ice thickness, as well as snow depths and floe size. Measurements were also planned to include new sea ice bulk salinity, grease and congelation ice samples. The warm temperatures during the cruise resulted in almost no mesurements of frazil ice and thin ice, so the main results were the measurements of the fast ice in Freemansundet, and of the floe from wich we were working east of Edge Øya in the Barents Sea. A detailed report is available here. At picture 4 you see Johan Wåhlin (Nansen Centre, supervised by Stein Sandveen) doing manual ice coring on the fast ice in Freemansundet. He also did snow measurements for validation of satellite data.

E) CTD profiles from the vessel

Full report here (PDF)
Skogseth, Ragnheid, (Ragnheid.Skogseth@unis.no), Smedsrud, Lars H., (larsh@gfi.uib.no), Wåhlin, Anna, (anna@gu.se) Fer, Ilker, (ilker.fer@gfi.uib.no)

The aim was to sample concurrent atmospheric and water properties in the area of open water in Storfjorden that is termed a polynya. Such a polynya forms due to winds, and partly currents, that transport sea ice away from land or fast ice areas. In order to enter the polynya area we were lucky to utilize the large and powerful icebreaker, K/V Svalbard. During the first days of the cruise the weather conditions were favourable for polynya activity, with strong north-easterly winds pushing the pack ice out of Storfjorden. Unfortunately, the wind became strong southerly when we left Van Mijenfjorden and entered Storfjorden and the polynya area. This gradually closed the polynya with thin ice and pack ice from south. Warmer and less saline water was measured to enter the shallow polynya area from south, while dense brine water formed on the shallow polynya area during the frazil ice polynya event, prior to the cruise, was measured along the bottom towards the deeper basin in Storfjorden (see picture 5).

http://www.uib.no/People/ngfls/KVSvalbardmarch07.html

By:
27-5 2008