Toktrapport/Havforskningsinstituttet/ISSN 1503-6294/Nr. 24 - 2003
INSTITUTE OF MARINE RESEARCH BERGEN, NORWAY
CRUISE REPORT
Environmental investigations in the Greenland Sea and northern Norwegian Sea.
May-June 2003.
By
Francisco Rey and Kjell Arne Mork
CRUISE NUMBER: JH2003206
VESSEL: R/V "JOHAN HJORT"
DEPARTURE: Ålesund, Norway on May 27, 2003 ARRIVAL: Tromsø, Norway on June 16, 2003 PORT OF CALL: Bodø, Norway on May 29, 2003 PARTICIPANTS:
Name Affiliation Responsability
Francisco Rey Institute of Marine Research Chief Scientist Kjell Arne Mork Institute of Marine Research Hydrography Penny Alvestad Institute of Marine Research Radioactivity Julio Erices Institute of Marine Research Technician Jarle Kristiansen Institute of Marine Research Instrument chief Lage Drivenes Institute of Marine Research Instrument operator Jean-Claude Gascard LODYC, France Scientist, hydrography Thierry Monglon LODYC, France Technician
Elodie Kestenare LODYC, France Technician Sandra Sequeira LODYC, France Technician
SCIENTIFIC OBJECTIVES
The cruise had several major objectives:
1) To carry out physical and chemical oceanographic investigations at selected stations in the Greenland Sea and northern Norwegian Sea.
2) To carry out physical, chemical and biological oceanographic observations at the standard Norwegian section Gimsøy-NW , Fugløya-Bjørnøya and Bjørnøya-W as part of IMR`s own monitoring activities.
3) To collect water and sediment samples for the determination of diverse radionuclides in the northern Norwegian Sea and Barents Sea, including monitoring activities at the site of a sunken Russian
submarine.
4) To deploy current meters (ARGOS) in the Greenland Sea.
5) To carry out detailed mapping of convective “chimneys” in the Greenland Sea.
CRUISE TRACK
Figure 1 shows the cruise track and the positions of the oceanographic stations where sampling was carried out.
SAMPLING METHODOLOGY Physical oceanography
The hydrographic work was carried out with a CTD-water sampling package from SeaBird Inc. with data being collected both during down- and upcast. The package consisted of a SBE 911plus CTD with double sensors for temperature and conductivity. All sensors were calibrated at the factory one month before the cruise. A LADCP was mounted on the CTD in order to obtain vertical current profiles.
The CTD was also equipped with a 12 position SBE 32 Caroussel with 10 liter Niskin bottles. At all stations water samples for calibration of the conductivity sensors were collected at all depths deeper than 1000 db or from the deepest sampling level. The samples will be analysed ashore. Three (3) sets of 20 salinity samples each from different areas were also collected in order to asses the influence of storage time on conductivity analyses.
A ship-mounted ADCP was used to measure current velocity and direction during the whole cruise. Data were averaged every ten minutes and stored. Due to the lack of a proper reference acoustic layer in the deeper waters of the Norwegian Sea, a DGPS positioning system was used to determine the exact position of the vessel during the measurements, especially during station work.
Chemical Oceanography
Oxygen concentration was measured using the Winkler method with visual determination of the titration end-point. Titration was done on whole samples ( about 120 ml) using a 1 ml automatic burette ( Metrohn) with a dispensing precision of 0.001 ml. Calibration of the thiosulfate solution (about 0.1 N ) was as done on each run. The reproducibility of the method estimated as the standard deviation of six replicates drawn from four different 10 l Niskin bottles was better than 0.3 micromol kg-1 at an oxygen concentration of about 300 micromol kg-1. Sampling procedures, reagents preparation and analyses were done following WOCE recommendations as stated in Culberson (1991). Conversion of volumetric to weight concentrations were done as recommended by WOCE using potential temperature from the CTD bottle
file. A test of a new type of oxygen sensor based on fluorescence yield (Optode, Anderaa Instr.) was planned to be carried out during the cruise. Unfortunately, defect connections hindered this.
Seawater samples for the analysis of nitrate, nitrite, phosphate and silicic acid were collected just after the sampling for oxygen. After rinsing three times, samples were drawn into 15 ml high-density
polyethylene test tubes with pressure caps added 0.2 ml chloroform as a preservative and kept dark and refrigerated at 4 °C until analysis ashore.
The nutrient analyses were performed using a system build up by the following items:
• Pump system from Ismatec, Switzerland.
•Reaction units of own fabrication
•Autosampling , detection and computing units from SANplus Segmented Flow Analyzer, Skalar Analytical B.V., The Netherlands.
The methods used were adaptations of standard methods ( Strickland and Parsons, 1972) slightly modified to the autoanalyzer system ( Føyn et al., 1981). The precision for the different analyses ( ten samples drawn from the same Niskin sampler) at full scale was less than 0.2% for nitrite, nitrate and silicic acid and less than 2 % for phosphate.
Biological oceanography
• Water sampling. Samples for biological analyses were obtained from the Niskin bottles on the Caroussel
• Chlorophyll
Samples for chlorophyll analyses were collected in 263 ml plastic bottles and filtered through glassfiber type F filters. The filters were inmediately frozen for analysis ashore.
• Phytoplankton taxonomy
Samples for quantitative analysis of phytoplankton were drawn from the Niskin bottles into 100 ml brown glass bottles and 20 % formaldehyde was added for conservation.
• Zooplankton
Samples for zooplankton biomass and species composition were collected by vertical tows at selected depth intervals by means of a 56 cm opening WP-2 plankton net with a 180 µm mesh size. The samples were split into two, one part being preserved with formaldehyde for later determination of species
composition. The other part was passed through three different meshsize nets, 2000, 1000 and 180 µm, and the fractions collected into preweighted aluminium containers, dried at 60 oC and then frozen, for later determination of dried weight ashore.
UNDERWAY MEASUREMENTS
Chlorophyll in vivo fluorescence ( WebStar Mini fluorometer), temperature and salinity ( SBE 21
Thermosalinograph, Seabird Inc.) were continously monitored on water from the ship´s water intake at 5 meters depth.
PRELIMINARY RESULTS
The hydrographical conditions along the section from Gimsøy and northwestwards are shown in Figs 2 to 4. As in previous years it was easy to identify the main watermasses in the area, the Atlantic water ( T>0.5°C; S> 35.0) and the Greenland Sea water (T<0.5°C; S<34.9) in the upper 500 meters. The area between these two water masses is called Arctic Front.
100 200 300 400 500 600 700 800
De p th [ m ]
-0. 8
-0.5 0
7
6
7
4 5 3 0 .5 1 2 -0.8
-1.1
387 384 381 378 375 372 369 363
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D e pt h [ m ]
-1
-0.9
-0.8 -0.5 0
5
-1.6143 -1.1 -1.05 -1 -0.9 -0.8 -0.5 0 0.5 1 2 3 4 5 6 7 8 9
Figure 2. Potential temperature in the Gimsøy-NW section during May/June 2003
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D e pt h [ m ]
34 .7 34.85 34.8
34 .88 3
4 .9 34
.90
5
3 5 .2
3 5 .1
3 5 .1
3 5
387 384 381 378 375 372 369 363
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Distance [km]
D ept h [ m ]
34.905 34.9
34.9 35.1
33.795 34.5 34.7 34.8 34.85 34.88 34.9 34.905 34.91 34.912 34.913 34.95 35 35.1 35.2 35.25
Figure 3. Salinity in the Gimsøy-NW section during May/June 2003.
100 200 300 400 500 600 700 800
D e pt h [ m ]
28 .05
2 8 .0 3
2 8 27
.9
27 .8
2 7 .7
2 7 .5
387 384 381 378 375 372 369 363
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Distance [km]
D ept h [ m ]
28.077 28.07 28.06
28.05
28 27.9
26 26.5 27 27.5 27.7 27.8 27.9 28 28.03 28.05 28.06 28.07 28.077 28.08
Figure 4. Sigma-theta in the Gimsøy-NW section during May/June 2003.
The nutrient distribution along the section is shown in Figs. 5 and 6. The distribution pattern of nitrate and silicate suggest that the phytoplankton spring bloom was well developed at both ends of the section in the areas. At the continental shelf the strong decline in both nitrate and silicate concentrations
indicates that the spring bloom was dominated by a mixed phytoplankton population. On the Greenland Sea side however, the relative higher nitrate concentrations with respect to silicate suggest that here the spring bloom was strongly dominated by diatoms. Microscopical observations of the phytoplankton species composition made onboard confirmed this assumption. At the Atlantic water area close to the Arctic Front the relative higher nutrient concentrations suggest a later phytoplankton development.
0 100 200 300 400 500 600 700 800 900 Distance (km)
800 700 600 500 400 300 200 100 0
Depth (m)
Figure 5. Nitrate in the Gimsøy-NW section during May/June 2003.
0 100 200 300 400 500 600 700 800 900 Distance (km)
800 700 600 500 400 300 200 100 0
Depth (m)
Figure 6. Silicate in the Gimsøy-NW section during May/June 2003
One of the purposes of the cruise was to deploy Argos drifting CTD-buoys in the Greenland Sea. In connection with this work we were informed of the presence of an eddy in the area with deep convection down to about 2500 meters. We used the opportunity of being in the vicinity to have a closer look to this phenomen since its importance for deep water formation. We found the “chimney” at 74°40`N and 0°30`W and a series of transects were designed to map the chimney. Fig. 7 shows the hydrography of the chimney on a east-west section.
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K ilom etre
Depth [m]
28 .07 5 28.07 28.06
28 .05 5 28 .05
28 .04 5 28 .04 28 .03 5
9 8 7 6 5 4 3 2 st. 411 1
st. 419
0 5
1 0 1 5
20 25
0
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K ilom etre
Depth [m]
-1 -0 .95
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-0 .85 -0 .9
-0 .9 -0 .85
-0 .9 -0 .85
-0 .8
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9 8 7 6 5 4 3 2 st. 411 1
st. 419
0 5
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0
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K ilom etre
Depth [m]
34 .875 34 .88
34 .88
34 .88 5 34 .89
34 .9 34 .90 5
34 .90 5
34 .88 5
9 8 7 6 5 4 3 2 st. 411 1
st. 419
Figure 7. Hydrographic sections across the chimney.
REFERENCES
Culberson, C.H. (1991) Dissolved oxygen. In: WOCE Operations Manual. Vol.3, Section 3.1, Part 3.1.3:
WHP Operations and Methods. WOCE Report No. 68/91, Woods Hole.
Føyn, L., M. Magnussen and K. Seglem (1981). Automatic analysis of nutrients with an on-line
dataprocessing. A presentation of the building and functioning of the system used at the Institute of Marine Research. Fisken Hav., Serie B, 1981 (4) : 1-39.( In Norwegian).
Strickland, J.D.H. and T.R. Parsons (1972) A practical handbook of seawater analysys. Bull. Fish. Res. Bd.
Canada. 167: 1-311.
WHPO (1991) WOCE Operations Manual. WHP Office Report WHPO 91-1 WOCE Report No. 68/91. Woods Hole Mass, USA.
ACKNOWLEDGEMENTS.
We would like to thank Mr. Magnar Hagebø of IMR for the nutrient analyses.
