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IARC Technical Report # 1

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Cruise Report of the NABOS-03
Expeditionto the Northern Laptev Sea
aboard the Icebreaker Kapitan Dranitsyn September 2003

With support from the National Science FoundationGrant # 0327664

Igor Dmitrenko¹, Leonid Timokhov², Oleg Andreev², Robert Chadwell¹, Michael Dempsey³, Hajo Eicken⁴, Sergey Kirillov², Anatoly Klein², Sergey Mastrukov⁵, Miroslav Nitishinskiy², Igor Polyakov¹, Marc Ringuette⁶, Noryuki Tanaka¹, and David Walsh⁷

1 - International Arctic Research Center, University of Alaska Fairbanks, Fairbanks, Alaska, USA
2 - Arctic and Antarctic Research Institute St.Petersburg,Russia
3 - Oceanetic Measurement Ltd.Sidney, BC, Canada
4 - Geophysical Institute, University of Alaska Fairbanks, Fairbanks, Alaska, USA
5 - State Research Navigation and Hydrographic Institute, St.Petersburg, Russia
6 - Laval University, Quebec City, Quebec, Canada
7 - Naval Research Laboratory

USA Scientific Party and Deck Crew of the NABOS-03 Cruise to the Laptev Sea

IARC: International Arctic Research Center, University of Alaska Fairbanks, Alaska, USA
GI: Geophysical Institute, University of Alaska Fairbanks, Alaska,
USANLR: Naval Research Laboratory, USAOM: Oceanetic Measurement Ltd., Sidney, BC, Canada
LU: Laval University, Quebec City, Quebec, Canada
AARI: Arctic and Antarctic Research Institute, St.Petersburg, Russia
SRNHI: State Research Navigation and Hydrographic Institute, St.Petersburg, Russia

1. INTRODUCTION (I.Polyakov and I.Dmitrenko, IARC)

NABOS (Nansen and Amundsen Basins Observational System) is one of the major International Arctic Research Center (IARC) initiatives. NABOS is a full-scale long-term program aimed at providinga quantitative observationally based assessment of circulation, water mass transformations, and transformation mechanisms along the principal pathways transporting water from the Nordic Seas into the central Arctic Basin. The scientific objective was widely recognized as significant  - to measure water properties along the principal pathways transporting water from the Nordic Seas into the central Arctic Basin. The scope of the field problem clearly calls for international cooperation/coordination, a task commensurate with an international center. NABOS is currently conducted jointly by the IARC, the Institute of Marine Science (IMS), and the Arctic and Antarctic Research Institute (AARI), Russia. By now NABOS has become a major IARC initiative.

The primary monitoring tool of the NABOS program is the series of moorings placed at carefully chosen locations around the Arctic Ocean. Time series obtained from these moorings will allow separation of synoptic-scale signal (e.g., eddies, shelf waves) from longer-term climatic signal. Located along the major pathways of water, heat, and salt transport, such moorings should capture climatically important changes in oceanic conditions. The NABOS moorings will operate for one year at a time, with replacement every year. A gradual increase in the number of moorings is planned, from two deployed in summer 2002, to the full-scale monitoring system after several years.

This report describes field research during the oceanographic cruise NABOS-03aboard the Icebreaker "Kapitan Dranitsyn" in September 2003.It was the second NABOS expedition.  The overarching goal of the 2003 field program was to characterize the oceanographic, ice, and biological conditions in the northern part of the Laptev Sea in 2003.In addition, moorings were deployed and recovered.

2. RESEARCH VESSEL (I.Dmitrenko, IARC)

The Russian icebreaker "Kapitan Dranitsyn" (Figure 2.1) has been chartered by the University of Alaska Fairbanks to carry out oceanographic research over the continental slope of the Siberian Arctic shelf. The ship is under the operation of the Murmansk Shipping Company located in Murmansk, Russia. I/B "Kapitan Dranitsyn" is a powerful conventional propelled ice breaker, constructed in 1982. It was intended for working in the conditions of the Northern Sea Route and the Baltic Sea. The vessel was built at Wartsila Shipyard, Helsinki, Finland; on December 2, 1980 she was accepted by the crew and registered under Russia’s flag. In 1994 the icebreaker was remodeled in Finland; later she was reequipped for passenger operations. In 1999 she was updated in Norway and got a passenger vessel certificate. The icebreaker main technical characteristics are presented in Table 2.1.

Figure 2.1: Icebreaker "Kapitan Dranitsyn" on NABOS-02 cruise in the northern Laptev Sea (photo by Stan Schwafel, IARC).

The ship may be navigated from two positions on the bridge and from an aft auxiliary bridge (ice can also be broken when traveling stern first). An air curtain system is applied to assist ice-breaking (air at 0.8 kg cm-2 is discharged through vents from forward to midships 2 m above the keel). Ice friction is reduced by polymeric coatings on the ice skirt. A cushioned stern allows close towing when vessels are being assisted through ice. Pumps can move 74 tonnes of water a minute between ballast and heeling tanks. Fresh water is provided from a vacuum distillation apparatus heated by exhaust gasses, which is supplemented by a reverse osmosis apparatus. A maximum of 80 tonnes a day can be produced. Two helicopters are carried to assist ice navigation. Safety equipment includes 4 fully enclosed life-boats and 4 inflatable life rafts (total capacity 264 persons). The fuel consumption rate is shown in Table 2.1. The icebreaker is equipped with 3 deck cranes. Two forward cranes can lift 3 tonnes each, and one on the helicopter deck lifts up to 10 tonnes.  

Table 2.1: The main technical characteristics of the I/B "Kapitan Dranitsyn".

Table 2.2: Fuel consumption of the I/B "Kapitan Dranitsyn". Data provided by Murmansk Shipping Company.

A LEBUS double drum electric oceanographic winch (Figure 2.2) manufactured by LEBUS Engineering International Ltd., England was additionally deployed on the helicopter deck of the icebreaker (Figure 2.3) in order to operate the conductivity/temperature/depth (CTD) profiler, biological nets and trawl and to deploy/recover the moorings. Winch electric motor power is 7.3 KW. Each drum capacity is 3500 m of 0.3-inch cable. The left drum (Figure 2.2) was used only for mooring recovery purposes. The right drum with spooling mechanism contains the mechanical cable of 3000 m length to carry the CTD probe, nets and trawl.

Figure 2.2: LEBUS double drum oceanographic winch on the helicopter deckof the I/B "Kapitan Dranitsyn".

Figure 2.3: CTD/Rosette winch site position on Deck 4 is shown by a red rectangle.

3. CRUISE TRACK (I.Dmitrenko, IARC)

The I/B "Kapitan Dranitsyn" left Kinkiness Harbor, Norway on 26 August 2003 and returned on 18 September 2003.The research area was over the continental slope of the Laptev Sea and the adjacent Eurasian Basin.CTD profiles were carried out on two transects across the continental slope in the central and eastern Laptev Sea and on another two transects approximately orientated along the continental slope. The survey within the Russian Exclusive Economical Zone was authorized by the Russian Ministry for Industry, Science and Technology. On the way to the research area the icebreaker passed along the Northern Sea Route through the Barents and Kara seas and entered the Laptev Sea through the Vilkitsky Strait on September 1, 2003. The scientific operationsbegan on September 1. Having completed the major goals of the cruise, the icebreaker left the Laptev Sea through the Vilkitsky Strait on 12 September (Figure 3.1).

Figure 3.1: NABOS-03 cruise track, 08/26/2003-09/17/2003.

4. SCIENTIFIC PARTY (I.Dmitrenko, IARC, and L.Timokhov, AARI)

5. ICE CONDITIONS (A.Klein, AARI)

The appearance of drifting ice along the route of the icebreaker was recorded in the northeastern part of the Kara Sea on the meridian of 83°12''E on August 30 (Figure 5.1, upper panel). Ice with coverage of 70 - 100% prevailed in the vicinity of Nordensheld Archipelago.Further in the Matisson Strait thick first-year land-fast ice with inclusions of up to 20% of two-year land-fast ice was observed. Sometimes the ice was in different stages of fracturing. Further in the vicinity of Vilkitskiy Strait and in the central part of the Laptev Sea the ice conditions along the ship track were characterized by alternation of zones with ice concentration of 0-10% and 20-30%. Within the research area after the northward turn the alternation of drifting ice with concentration of 70-80% and 90-100% was observed.

Figure 5.1: Ice extent mosaics along the NABOS-03 cruise track. The upper and lower panels correspond to August 31 and September 11, 2003. The SSM/I information was processed and plotted by Dr. V.Smolyanitskiy, AARI.

On the way back from the Laptev Sea to the Kara Sea (Figure 5.1, lower panel) the ice conditions were different from those which were observed before. The Kara Sea near Vilkitskiy Strait was practically clear of compact drifting ice. In the vicinity of Nordensheld Archipelago there was no land-fast ice. The general ice cover decrease was also observed there. Westward from the meridian of 95°E no compact drifting ice was observed.  As a whole, the first-year thick ice predominated. Ice thickness varied in a wide range from 80-100 cm to up to 180-200 cm. The amount of hummocked ice was estimated to fall within the range of from 0-10% to 20-30%. The fracturing was estimated to be as much as 30%. The presence of significant amounts (sometimes up to 50% of the total) of two-year-old ice with a thickness of more than 2 m is considered to be the characteristic feature of September 2003 sea-ice conditions along the ship track in September, 2003.

6. METEOROLOGICAL CONDITIONS (O.Andreev, AARI)

As a whole, the synoptic regime over the Laptev Sea during the period of research was characterized by high cyclonic activity (Figure 6.1). Within the Icelandic Low intensive processes of cyclogenesis occurred. The hollow of low pressure stretched from Iceland along Greenland to the south of Archipelago Spitsbergen to Novaya Zemlya Island.  The cyclones traveled in this direction. As they approached the Laptev Sea area across the Taimyr Peninsula, the cyclones were amplified by local synoptic conditions.During August 31 - September 1 the weather conditions on the route towards and within the research area were defined by an inactive filling cyclone. Atmospheric pressure varied between 993-995 mb. The weather was characterized by continuous overcast and gusty southern and southwest wind of 5-12 m/s. The air temperature decreased from +3.0°C at Vilkitski Strait, down to 0.0°C in the research area (Figure 6.2). Further, this cyclone was displaced by an area of high atmospheric pressure (1005-1011 mb) stretched from the Taymyr Peninsula to the northern Laptev Sea. The weather conditions on September 2 and 3 were characterized by continuous overcast and strong (12-15 m/s) gusty northern winds, and later northwest and western winds. The air temperature decreased to -2 to -4°C. On September 4-7 the next cyclone reached the Laptev Sea. Atmospheric pressure dropped down to 987-994 mb. The weather became cloudy, with precipitation, and a steady northwest wind blew at up to 14-19 m/s. The air temperature continued to decrease to -3 to -5°C.

Figure 6.1: National Center for Environmental Protection (NCEP)/National Center for Atmospheric Research (NCAR) Sea level pressure averaged over September 1-11, 2003.

During September 8-11 the weather conditions in the research area were dominated by high atmospheric pressure (1004 -1011 mb). The cloud cover became broken, and snow fell a couple of times. On September 8-10 the wind varied from northwestto northeast with a speed of 6-8 m/s. On September 11 it had returned to the northwesterly direction and finally dropped down to 1-3 m/s with variable direction. During September 8-10 the air temperature was recorded as low as -1 to -3°C. Along the way to Vilkitski Strait on September 11, temperatures rose to +1to +4.0°C.

Figure 6.2: Variation of the main meteorological parameters along the NABOS-03 cruise track. The measurements were carried out from the upper deck of the icebreaker by the WM-918 weather station. The gray strip corresponds to the time of operation within the area of oceanographic research.

7. OBSERVATIONS (I.Dmitrenko, IARC, and L.Timokhov, AARI)

The NABOS-03 program included routine CTD observations and water sampling, recovery and deployment of oceanographic moorings, ARGOS ice buoy deployments, biological observations, and ice sampling, along with routine ice and meteorological observations.  Measurements made during the NABOS-03 cruise on the I/B "Kapitan Dranitsyn" are described in Table 7.1. The full information about all research activities during the cruise is summarized in Appendix 2. The information in Table 7.1 and Appendix 1 is presented in chronological order.

Table 7.1: Observations during NABOS-03 cruise on I/B "Kapitan Dranitsyn".

7.1. OCEANOGRAPHIC OBSERVATIONS

7.1.1. Background information (I.Polyakov, IARC, and D.Walsh, NRL)

Observations made from ice buoys, manned drifting stations, and satellites show that near-freezing surface waters, driven by surface winds and ice drift, exhibit a trans-polar drift from Siberian Arctic toward Fram Strait [Rigor et al., 2002].In the eastern part of the Eurasian Basin this flow merges with several branches coming from marginal arctic seas (the East Siberian and Laptev Sea branches, and further west the Barents Sea branch). The basic features of the circulation in the Nansen and Amundsen Basins are shown by blue arrows in Figure 7.1. Nansen was the first to identify Atlantic Water (AW) in the Arctic Ocean during his drift on board the Fram in 1893-1896. Later observations provided evidence that the AW spreads cyclonically around the Arctic Basin and is its major source of heat [Timofeev, 1960; Coachman and Barnes, 1963], and clarified the properties of AW circulation. Aagaard [1989] used moored current measurements and hypothesized that major subsurface water transports occur in the form of narrow near-slope cyclonic boundary currents (Figure 7.1, red arrows). Two major inflows supply the polar basins with AW - the Fram Strait AW branch and the Barents Sea AW branch [Rudels et al., 1994]. The Fram Strait branch enters the Nansen Basin through Fram Strait and follows the slope until it encounters the Barents Sea branch north of the Kara Sea, an area characterized by strong water-mass mixing and thermohaline interleaving.The two merged branches follow the Eurasian Basin bathymetry in a cyclonic sense, forming a narrow topographically trapped boundary current which flows at about 5 cm/s [Woodgate et al., 2001]. Near the Lomonosov Ridge the flow bifurcates, with part turning north and following the Lomonosov Ridge and another part entering the Canadian Basin [Woodgate et al., 2001].Jones [2001] stresses that the circulation in the deep waters (>1700m) has not been well determined.

Figure 7.1: Water mass circulation patterns in the Nansen Basin and adjacent arctic seas.Surface and subsurface circulation shown by blue and red arrows respectively.   

The area of the northern Laptev Sea and adjacent Eurasian basin has complex water-mass characteristics [Pfirman et al., 1994; Schauer et al.,1997; Schauer et al., 2002]. Atlantic Waters originating in Fram Strait are found between 150 and 800 m depth in this region (Figure 7.2, left panel).Lower Halocline Water (LHW) lies at thebase of the permanent halocline, occupying the region of temperature(T)-salinity (S) space defined by 34.0<S<34.5 psu, and temperature less than -1.0 °C [Woodgate et al., 2001]. Below the AW layer lie the Bottom Water (BW) layers, with potential temperatures down to -0.95°C. The locations of these water masses in the T-S plane are shown in Figure 7.2, right panel.

Figure 7.2: Location of Low Halocline Water (LHW), Atlantic Water (AW), and Bottom Water (BW) on the typical vertical temperature and salinity distribution and T-S curve in the research area.

 Little is known about temporal variability of thermohaline structure in the Eurasian Basin.An early attempt to quantify interannual variability of water-mass structure in this region is due to Quadfasel et al. [1993], who compared measurements from cruises in different years, finding significant year-to-year variability in the core temperature of the AW layer.However, because Quadfasel et al. compared measurements taken in different years and at different locations in the Nansen Basin, it is difficult to determine the extent to which their conclusions were influenced by aliasing of spatial and temporal variability, especially as the AW layer is known to cool dramatically as it flows through the Nansen Basin. [Polyakov et al., 2003] emphasize that quantifying interannual variability in this region is substantially complicated by the large spatial gradients in the area. Processes which affect fresh-water content (e.g., freezing, melting, and riverine inflow) are of first-order importance to Arctic Ocean dynamics [Aagaard, 1989]. Large amounts of ice form in winter on the wide continental shelves on the periphery of the Arctic Ocean, in some cases producing dense, briny waters which flow off the shelves and significantly influence the T-S structure in the interior.

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Last modified: March 08, 2004. 15:07:50 pm