RV LANCE Cruise Report

18^th May - 04^th June 2005

Hydrography and Ice Observations in the Fram Strait

Report prepared by: Vladimir Pavlov, Harvey Goodwin, Jürgen Holfort, Kristen Fossan, Olga Pavlova, Marzena Kaczmarska and Roman Vlasenkov

Funded by
Norsk Polarinstitutt

Table of contents

List of Participants

Work performed, data acquired

Cruise track and station positions

Mooring Search

CTD_Work

CTD data acquisition

Grid survey

Station information and Water sampling (Table 1)

Temperature and salinity distribution at the transects through the West Spitsbergen Current

Vertical profiles of potential temperature and salinity at the stations in the branches of the West Spitsbergen Current

Some comparisons between Lance CTD observations and historical hydrography in the Fram Strait

ADCP Data

Sea Ice Work

IceCam ice observations

Ice Stations

Ice thickness drilling

Snow properties

Water temperature

Air temperature

Ice Cores

Water samples

Measurements of the relative seawater transparency

Satellite imagery

Meteorology

Acknowledgements

List of Participants

Cruise Leader

Vladimir Pavlov
Norsk Polarinstitutt
Tromsø, Norway
pavlov@npolar.no

Scientists:

Harvey Goodwin
Norsk Polarinstitutt
Tromsø, Norway
goodwin@npolar.no

Jürgen Holfort
Norsk Polarinstitutt
Tromsø, Norway
holfort@npolar.no

Olga Pavlova
Norsk Polarinstitutt
Tromsø, Norway
olga@npolar.no

Marzena Kaczmarska
Norsk Polarinstitutt
Tromsø, Norway
marzena.kaczmarska@npolar.no

Engineer

Kristen Fossan
Norsk Polarinstitutt
Tromsø
kfossan@npolar.no

PhD student

Roman Vlasenkov
Arctic and Antarctic Research Institute
St.Petersburg, Russia
vlasenkov@list.ru

Work performed, data acquired

Our survey of the Fram Strait continues the annual NP hydrographic observation and monitoring of ice in this region.

The locations of the profiles were at the positions of the stations performed in grid survey of FRAM2005 expedition plan (see Fig.1). The Lance CTD stations were a mixture of near full depth (3500 m) and shallower depth (100m) stations.

Additional stations extending this grid were also performed (Transect 7: Sts. 51-59) as well as CTD stations near ice stations. All data were acquired using aSeabird 911 plus fitted with a Seabird, pressure, temperature, conductivity cell and pump. The CTD was installed at the bottom of a CTD frame which included a carousal water sampler above it. Water samples for salinity calibration were obtained at most stations (See Table 1 for full listing).The ADCP records were obtained throughout the cruise.

During the cruise CTD data was transmitted to KV Svalbard and H.U.Sverdrup II.

Fig. 1 CTD station layout - bathymetry.
Red circles: Lance CTD stations
Green circles: H. U. Sverdrup II CTD stations
Yellow circles: Helicopter CTD stations from KV Svalbard
Red squares: NPI moorings
Black rectangle: Likely operating area of KV Svalbard, depending on sea ice conditions.

10 ice stations were visited. 6 in the MIZ near 79°N and between 0°W and 2°W, and 4 stations in the MIZ northwest of Svalbard at approximately 80°N. The main aim of the ice station work was to obtain data regarding ice thickness from representative large ice floes in the Fram Strait. In addition temperature and salinity samples were taken along with physical properties of the snow cover.

Lance is also equipped with an automatic weather station which records meteorological parameters and digital photographs every 5 minutes which are used to calculate sea ice concentration. Navigational parameters are also recorded in parallel.

To aid our operational efficiency ice charts and satellite imagery were obtained daily via email.

At each CTD station Sekki disk observations of relative seawater transparency was carried out.

Cruise track and station positions

Below is a map showing the location of all CTD and Ice stations performed during the cruise.

Fig.2 Cruise track and station positions

Mooring search

In the beginning of the cruise, on 19^th May at 11:00, the successful recovery of the University Pierre et Marie Curie mooring station was undertaken. The mooring was deployed in 2003. The depth and position are noted in table below.

CTD Work

CTD data Acquisition

In order to obtain round the clock CTD data the scientific personnel was divided into two groups. Team 1 (Vladimir, Kristen and Roman) performed the 6 to 12 shift whilst Team 2 (Jürgen and Olga) ran the 12 - 6 shift. In the calm weather the swinging of the CTD was not a problem. When the weather was bad an extra person from the crew or Harvey or Roman helped Team 2 with this procedure and we are indebted to them for their help.

Once in the water the logging was initiated using SeaSave the Seabird data acquisition software. The salinity and temperature values were monitored until they were stable and then the CTD was lowered at about 1m/s. Water samples were fired& on the upcast.

At the end of a station the CTD was taken back on deck, wheeled into the shelter where it could be fastened to the ship before Lance headed to the next station. After which the data was downloaded, changed to ASCII using Data Conversion (DatConv) on the SBE data processing software. The resultant CNV file was used for plotting of TS vertical profiles and transects. At this stage no other processing was performed to the data.

Grid survey

The main thrust of the cruise was to characterise the oceanographic properties of the Eastern part of the Fram Strait. In particular it was to identify and survey features of the West Spitsbergen Current. In order to identify the Atlantic water masses there were performed 8 transects through the West Spitsbergen Current (Fig.2). The CTD data from these transects (Fig. 3-10) allowed us to identify pathways of the Atlantic waters and reconstruct the main branches of the West Spitsbergen Current (Fig. 11). In the core the temperature is changing from 5.1-5.2 at latitudes 76 30N - 77N to 3.4-4.3 at the latitudes 80N-80 30N. At the latitude 79 30N the branching of the West Spitsbergen Current occurs. Eastern branch turns over Svalbard trough Yermak Plateau along isobaths 500 m and its western branch follows to the north.

Figures 12-22 shows vertical profiles of the potential temperature and salinity at the stations in the branches of the West Spitsbergen Current.

Table. 1 Water sampling and Station information

Temperature and salinity distribution at the transects through the West Spitsbergen Current

Fig. 3 Temperature and salinity distribution at Transect 1 (transect location is shown in Fig. 2)

Fig. 4 Temperature and salinity distribution at Transect 2 (transect location is shown in Fig. 2)

Fig. 5 Temperature and salinity distribution at Transect 3 (transect location is shown in Fig. 2)

Fig. 6 Temperature (upper panel) and salinity (bottom panel) distribution at Transect 4 (transect location is shown in Fig. 2)

Fig. 7 Temperature and salinity distribution at Transect 5 (transect location is shown in Fig. 2)

Fig. 8 Temperature and salinity distribution at Transect 6 (transect location is shown in Fig. 2)

Fig. 9 Temperature and salinity distribution at Transect 7 (transect location is shown in Fig. 2)

Fig. 10 Temperature and salinity distribution at Transect 8 (transect location is shown in Fig. 2)

Fig. 11 Reconstructed location of the main branches of the West Spitsbergen Current

Vertical profiles of potential temperature and salinity at the stations in the branches of the West Spitsbergen Current

Fig. 12 Potential temperature and salinity profiles at the standard levels
(Station number Fr02, Transect 1)

Fig. 13 Potential temperature and salinity profiles at the standard levels
(Station number Fr05, Transect 1)

Fig. 14 Potential temperature and salinity profiles at the standard levels
(Station number Fr15, Transect 2)

Fig. 15 Potential temperature and salinity profiles at the standard levels
(Station number Fr18, Transect 3)

Fig. 16 Potential temperature and salinity profiles at the standard levels
(Station number Fr34, Transect 4)

Fig. 17 Potential temperature and salinity profiles at the standard levels
(Station number Fr56, Transect 7)

Fig. 18 Potential temperature and salinity profiles at the standard levels
(Station number Fr61, Transect 6)

Fig. 19 Potential temperature and salinity profiles at the standard levels
(Station number Fr63, Transect 6)

Fig. 20 Potential temperature and salinity profiles at the standard levels
(Station number Fr67, Transect 8)

Fig. 21 Potential temperature and salinity profiles at the standard levels
(Station number Fr71, Transect 5)

Fig. 22 Potential temperature and salinity profiles at the standard levels
(Station number Fr77, Transect 5)

Some comparisons between Lance CTD observations and historical hydrography in the Fram Strait

Our primary focus is on the section along 79ºN as this is a regular section surveyed by the September cruises in recent years and it also covers the largest part of the basin. An important task of these comparisons is the differentiation between seasonal and longer term changes. To see what part of the observed changes is due to seasonal variations we will compare the changes from September 2004 to May 2005 with changes from September 1998 to May 1999 and look for similarities. Both September cruises were done while servicing the NPI mooring array in the East Greenland current, the May 1999 cruise was a VEINS cruise (data from the VEINS CD-ROM).

Fig.23: Positions of the CTD stations used in the comparison.

The individual sections were first interpolated onto a regular longitude-pressure grid (irrespective of latitude) and these grids were then used for the comparison. The latitudinal difference between sections is at most 10 minutes (Fig.23), the errors due to this separation should be small. As the difference sections (Fig.24) are quite noisy due to frontal shifts and eddy activity, means of different hydrographic regions were calculated. The 79ºN section was divided into three regions, a shelf region (east of 9ºE), the West-Spitsbergen current (3ºE-9ºE) and the mid Fram Strait (west of 3ºE till about 2ºW).

Fig.24 Sections of the differences between May 05 and September 04 in temperature, salinity and density (from left to right). Red colours indicate higher values in May 05, blue values values that are lower in May 05 then in September 04.

In all regions the uppermost water column (till about 50m) has higher salinities than in September (Fig.25). The middle of the Fram Strait has a pronounced decrease in salinity. This can be attributed to an eastward shift of the East Greenland front, which brings the cold and less saline Polar Water (PW) into regions up to 0ºW. As expected the surface waters are colder in May then in September, this cooling reaches depths of about 300 m in the West Spitsbergen region and 700m in the middle Fram Strait region (Fig.26). Associated with this cooling is an increase in density. The largest density increase is found at the surface due to the combined effect of cooling and higher salinities.

At mid-depths (400-800m) the warm AW is further east in May then in September, leading to colder waters in May at the continental slope and warmer waters further east. The mean temperature is higher in May east of 3ºW and colder west of 3ºW. The total change is small. The salinity signal corresponds to the temperature signal.

The deep waters (1800-2400m) are warmer (0.02) and less saline (-0.01) in May than in September.

The deepest waters near the bottom show negligible salinity changes, an increase in temperature in the West-Spitsbergen current region and none in the middle region.

Many features of the 2005-2004 comparison can also be found in the 1999-1998 differences, and therefore are probably mostly signs of the seasonal cycle. The two strongest of these features are the colder and more saline upper waters and the warmer and more saline waters at mid-depths in the West-Spitsbergen current.

Fig.25 Salinity differences in the 79ºN regions between May 05 and September 04 (left), May 99 and September 98 (middle) and between May 05 and May 99 (right).

Fig.26 Temperature differences in the 79ºN regions between May 05 and September 04 (left), May 99 and September 98 (middle) and between May 05 and May 99 (right).

Comparing the May measurements from 2005 and 1999 we see a strong warming reaching more than 1ºC at depths of more then 500m. This warming is accompanied with a salinity increase. Comparing the maximum temperature in the core of the Atlantic Water with previous measurements in this area from May to June (Fig.27) the temperature is high (4.77ºC) in 2005. Just twice, in 1984 and 1990 higher temperatures (5.24ºC and 5.90ºC) were observed here in these months.

Fig. 27 Maximal temperature in the core of the West Spitsbergen Current at latitude 79ºN in this cruise (red bar) and in previous years (blue bars)

ADCP Data

The ADCP recorded data throughout the cruise. The ADCP is a broadband 150kHz type and was set to 8m bins and an averaging interval of 300 seconds. The attained vertical range was about 200m. Just a first data check was made onboard. Along the 79ºN section (Fig.XX) two regions of larger northward velocity are apparent. The first at about 6ºW can be associated with the main core of the AW and the second region at about 8ºW is situated near the shelf break and the front between warm and saline AW and cold and fresh shelf water. The later is also visible at 78º 20'N at about 9ºW.

Fig. 28 Near surface velocities (9-97m) from the vessel mounted ADCP.

Sea Ice Work

IceCam ice observations

An IceCam is permanently installed onboard Lance and is set to record an image every 5 minutes via a web camera mounted on the bridge and looking to the starboard side. In addition GPS, time, pitch and roll are recorded. This data can later be analysed to give ice concentration.

Ice Stations

A total of 10 stations were taken, 6 full stations and 4 short stations. At each station the minimum work done was an ice thickness profile, and snow properties. For short stations the salinity and ice core temperature were dropped when time was limited.

The aim was to record the following data for each full station.

• GPS position and time (start and end position of the ice floe to record ice drift)

• Ice thickness

• Snow thickness and physical properties

• Ice cores â?" length, stratigraphy, temperature, photo

• Air and water temperature

• Salinity

• Water samples

Ice thickness drilling

Floes were chosen as large as possible and were accessed either directly from Lance or by Zodiac. Thickness profiles 50-100m in length were measured with profiling every 10m. We used a Covacs thickness drill. Together with ice thickness we also recorded snow cover thickness and freeboard.

Snow properties

Physical snow properties were recorded at every station. The site chosen for the snow pit was selected as representative for the floe.

The following parameters were recorded

• Snow description:

  • Snow type

  • Avg, min, max grain diameter

  • Hardness test

  • Draw / photograph stratigraphy profile

• Snow temperature every 2-5cm (depending on snow pack thickness and layering)

• Snow density â?" no. of samples depending on the snow thickness

• Salinity measurements every 10cm in the snow pack at stations where ice core salinity is measured

Water temperature

Water temperature was taken from the side of the floe if possible. Sometimes the ice station corresponded with a CTD station and therefore both temperature and salinity measurements can be obtained from this data

Air temperature

Air temperature was recorded at 1m above the surface in the body shadow

Ice Cores

8 ice cores were drilled at stations 1, 3, 4, 5, 7, 8, 9, and 10 in level ice of average thickness. The core was photographed and the total length recorded. The temperature approximately every 10cm was measured by drilling a hole with a hand drill in the core and inserting the temperature probe. This was done quickly section for section to avoid temp changes. The stratigraphy of the core was noted and peculiarities marked such as sediment or algae were recorded

To measure salinity along sections of the ice core we cut the core into ca. 7-10cm sections and then bagged and labelled each section. Onboard Lance the samples were melted and bottled so that salinity could be measured in Tromsø. No salinity samples were taken for cores 9 and 10.

Traces of green algae were found in core 7.

Water samples

2 x 50 liter samples were taken with a bucket from the side of the ship for analysis in Tromsø for traces of radionuclides.

1. West Spitsbergen current off Kongsfjorden N79deg 00â?™, E08deg 30â?™

   • Date: 22.05.2005

   • Time: 20:30

2. N80deg 16.9â?™, E06deg 18â?™

   • Date: 27.05.2005

   • Time: 00:45

   • Sea ice 1^st year, 10m floes, 0.5m thick, 20cm snow cover

Measurements of the relative seawater transparency

Long before the beginning of precise instrumental observations, simple optical observations of seawater visibility depth through a white so-called Sekki disk (see picture below) were used.

Sekki disc view

The transparency characterises properties of the physical environment to loosen electromagnetic radiation in the optical range. The spatial and temporal allocation of optical properties of seawater is defined by the allocation of a dissolved organic material and suspended sediments concentration. In the open sea these are defined by the concentration of organic and non-organic material, water dynamics and turbulence. The last two factors are responsible for the transport and distribution of this material. Shore and shelf erosion, along with river discharge provide the major contribution to the optical properties of seawater.

During the Lance cruise 40 relative seawater transparencies were taken. Station positions and transparency value are listed in the Table 2 and shown in Fig 29.

Table 2 Station positions and value of the relative seawater transparency

Fig. 29 Relative seawater transparency distribution.

Satellite imagery

Processed MODIS satellite images were received daily from Nick Hughs from SAMS and were a useful tool for the daily operation of the cruise. Met.no provided daily ice charts useful for anticipating encounters with the sea ice edge and for planning ice stations. In addition we received Radarsat and Envisat high resolution SAR imagery for the area of operation. These were not available daily for the particular area Lance was operating in but were extremely useful for assessing ice conditions when entering the marginal ice zone. The SAR imagery was processed by Mohamed Keyse at NP

Meteorology

An automatic weather station is installed on Lance and logs data continuously. The system records air temperature, sea water temperature, humidity, wind speed and direction, and air pressure. During a period of bad weather we received synoptic weather forecast charts from met.no which helped in planning the next phase of the cruise. These charts would have been beneficial on a daily basis and should be acquired on future cruises.

Acknowledgements

We are very grateful for the excellent support and the splendid seamanship of the captain, officers and crew of Lance. Their professional conduct and willingness to help made this cruise extremely successful. In fact without their help we could not have accomplished our mission.