JERSTI L. D AAE LORIAN G EYER K I LKER F ER F J ULY -4 A UGUST 2007 H ÅKON M OSBY 10 ITH R.V. 2007 613 W D ATA R EPORT F ROM T HE C RUISE HM REPORTS IN METEOROLOGY AND OCEANOGRAPHY UNIVERSITY OF BERGEN

REPORTS IN METEOROLOGY AND OCEANOGRAPHY UNIVERSITY OF BERGEN

D ATA R EPORT F ROM T HE C RUISE

HM 2007 613 W ITH

R.V. H ÅKON M OSBY

10 J ULY -4 A UGUST 2007

I LKER F ER

F LORIAN G EYER

K JERSTI L. D AAE

Geophysical Institute, University of Bergen

October, 2008

Geophysical Institute

University of Bergen

Bergen, Norway

«REPORTS IN METEOROLOGY AND OCEANOGRAPHY»

utgis av Geofysisk Institutt ved Universitetet I Bergen.

Formålet med rapportserien er å publisere arbeider av personer som er tilknyttet avdelingen.

Redaksjonsutvalg:

Peter M. Haugan, Frank Cleveland, Arvid Skartveit og Endre Skaar.

Redaksjonens adresse er : «Reports in Meteorology and Oceanography», Geophysical Institute.

Allégaten 70

N-5007 Bergen, Norway

RAPPORT NR: 2 - 2008

ISBN 82-8116-014-4

Table of Contents

1. Introduction...4

2. Cruise Overview ...5

3. Environmental Conditions ...8

4. Measurements and Data Processing...10

4.1. Hydrography ...10

4.2. Microstructure Measurements ...12

4.3. Current Measurements ...15

4.4. Short-Term Mooring at Yermak Plateau ...16

5. Observations: Yermak Plateau Mooring...17

6. Observations : CTD ...19

7. Observations: Microstructure...28

7.1. Time-series stations 1-5 ...28

7.2. Sections A-J ...34

8. Observations: Currents...39

9. Time Line...41

10. Acknowledgements...46

11. References...47 Appendix A – Tables

Appendix B – Figures of CTD profiles for all CTD casts Appendix C – T-S diagrams for all CTD casts

Appendix D- ROSCOP Cruise Summary Report

1. Introduction

The cruise HM2007 613 with R.V. Håkon Mosby was organized by the Geophysical Institute (GFI) and the Bjerknes Centre for Climate Research, University of Bergen (UoB) to conduct field work planned under the projects Current Measurements North of Svalbard (CuNoS, funded by the Research Council of Norway) and DAMOCLES (funded by EU). The objectives and tasks of the cruise are therefore a subset of the mentioned projects. UoB field work activities in DAMOCLES include maintenance of two trawl-proof bottom frames equipped with acoustic Doppler current profilers (ADCPs), one at the Storfjorden sill and another at the shelf-break off Sørkapp, in order to provide near continuous time series of the cold Storfjorden overflow (Fer, 2007). The principal technical objective of CuNoS is to develop the capability for using electromagnetic current profilers, namely expendable current profilers (XCPs), in Bergen, with science objectives including internal wave induced mixing at the Yermak Plateau, north of Svalbard.

HM2007 613 is a physical oceanography cruise to conduct a hydrography survey of Storfjorden in Svalbard, and to investigate the dominant processes of mixing of the West Spitsbergen current and those at the Yermak Plateau. Main tasks comprised:

 recovery/service/redeployment of a bottom-mounted RDI ADCP at the Storfjorden sill

 Standard hydrography section Sørkapp-Vest

 Hydrography survey of Storfjorden and Storfjordrenna

 Current, hydrography and dissipation measurements across the West-Spitsbergen continental slope and at Yermak Plateau

 Ship-board XCP deployment at Yermak Plateau

 A short-term mooring deployment/recovery at Yermak Plateau

 A long-term moored profiler deployment at Yermak Plateau

The cruise is split into two legs. In the first leg (10-19 July 2007), Storfjorden hydrography survey and Sørkapp-Vest standard section were completed and the trawl-proof ADCP at the sill was recovered. Frank Cleveland was the sole participant and was responsible for the operation. During the second leg (20 July- 4 August 2007), Håkon Mosby accommodated all participants. The activities comprise the re-deployment of the Storfjorden sill ADCP, microstructure / hyrography and current measurements West of Spitsbergen and in Yermak Plateau, deployment of a short term mooring and a long term mooring (J.-C. Gascard, LOCEAN, France) at Yermak Plateau. The cruise track for both legs together with CTD stations are shown in Figure 1.

The list of participants is as follows:

Ilker Fer (GFI/UoB, cruise leader, scientist) Ragnheid Skogseth (UNIS, scientist)

Steinar Myking (GFI/UoB, engineer) Frank Cleveland (GFI/UoB, engineer) Florian Geyer (GFI/UoB, PhD student) Kjersti L. Daae (GFI/UoB, MSc student)

Jacky Lanoiselle (LOCEAN, France, guest engineer)

Mickael Beauverger (LOCEAN, France, guest engineer)

Figure 1. Cruise track of HM2007 613 between 10 July-4 August 2007, covering both legs. CTD stations are marked by z with chosen station numbers indicated.

2. Cruise Overview

A detailed timeline is given in Section 9 for both legs. Here, an overview is presented. The cruise summary report submitted to ROSCOP is given in Appendix D.

Leg 1. Longyearbyen- Longyearbyen (10-19 July 2007)

During the first leg, 97 CTD stations were occupied with focus on the West Spitsbergen

current and Storfjorden. The stations numbers (identical to filenames sta0XXX) cover 645 to

741. The station map is given in Figure 2. The standard section Sørkapp Vest and four zonal

sections along 78N, 7730, 77 and 7630N were collected on the way to Storfjordrenna. In Storfjordrenna and Storfjorden stations 691-741 were occupied.

The trawl-proof ADCP at the Storfjorden sill was successfully retrieved from the position 76

58.02 N, 019 18.31 E, on Monday 16/07-07 at 0104 local time. Prior to recovery ship- ADCP data were collected in the vicinity of the moored instrument, for compass correction purposes. The data are recovered from the sill-ADCP. Apparently, the trawl-proof frame was hit by a trawler. A SBE37 Microcat, which was not sufficiently protected, was lost. Cabling between the ADCP and the battery case was damaged. The lowermost battery pack in the battery case was damaged, however, inside the case, it was dry with no sign of leakage.

Figure 2. Overview of the CTD stations occupied during leg 1. Stations are marked by red circles.

Station names at the section start and end are marked. The zonal transect, marked by SV, is the Sørkapp Vest section.

Leg 2. Longyearbyen- Longyearbyen (20 July- 4 August 2007)

We departed on 21 July 0200, heading towards Storfjorden sill for redeployment of the bottom-mounted ADCP. Due to damaged cable described above, the ADCP was deployed with single battery without the external battery case.

During the second leg 88 CTD profiles were collected (stations 742 to 829). Additionally, 223 casts were made using the Microstructure profiler, MSS90L and 15 XCPs were dropped.

Ten sections, named A to J were taken with section H and I extending into Kongsfjorden and

Isfjorden, respectively. Section J was a section across Isfjorden. Additionally we occupied 5

day-long stations (numbered 1 to 5). The location of the Station 5 was chosen close to the

short-term mooring at Yermak Plateau. Section and station locations are summarized in

Figure 3.

Figure 3. Overview of the occupied stations during leg 2. Sections are labeled A to J with start and end station numbers indicated. Microstructure profiling was made at stations marked by red crosses.

Standard CTD profiling was made at stations marked by black circles. Day-long Stations 1 to 5 are

marked. Short-term mooring was deployed at Station 5 (red square). Green and black dashed lines

indicated the ice-edge digitized from met.no satellite-derived ice charts.

−0.5 0 0.5

Elevation (m)

1 2 A B C D 3 E 4 F 5 G H I J

AOTIM 5 / STATION 3 TIDES

20 21 22 23 24 25 26 27 28 29 30 31 01 02 03 04

−15

−10

−5 0 5 10 15

Velocity (cm/s)

Time, day 20 July to 4 August 2007 u

v

Figure 4. Spring-neap cycle at station 3, covering the cruise period. Tides are inferred from AOTIM 5km model at the location of station 3. Relative time of occupation of each section (A-J) and day-long station (1-5) is indicated. Of the day-long stations, only station 5 was close to spring tides.

3. Environmental Conditions

Here, the environmental conditions for the second leg are summarized. The forcing due to

tides and the atmosphere will have consequences for the internal wave field and turbulence,

hence are directly relevant for the finescale current and microstructure measurements carried

out in leg 2. The tides are inferred from the 5-km resolution AOTIM model at the location of

Station 3. The time series of inferred surface elevation and tidal currents are shown in Figure

4 covering one spring-neap cycle encountered during the survey. The surface elevation peak-

to-peak amplitude increases from about 30 cm in the neap to 90 cm in the spring tides. The

north component of the tidal currents is typically leading the east component. The barotropic

tidal currents are about ± 10 cm s

during the spring tides. Time of occupation of the sections

relative to the tidal cycles is marked in Figure 4. The first two day-long stations (Stations 1

and 2) are occupied during the neaps. Except from Station 5, near the mooring, all the

Yermak Plateau sections and time-series stations are occupied during transition from neap to

spring. Only the sections across the West-Spitsbergen Current, along 79.5N, 79N and 78N

(sections G, H, and I) are collected in spring tides. At the location of these sections, however,

the tidal signal can be different, as the presented tides were inferred for the Yermak Plateau.

−5 0 5 10 15

T a (°C)

−5 0 5 10

15 1 2 A B C D 3 E 4 F 5 G H I J

U 15 (m/s)

20 21 22 23 24 25 26 27 28 29 30 31 01 02 03 04

0 90 180 270 360

D 15(° T)

Time, day 20 July to 4 August 2007

Figure 5. Ship-based meteorological data, covering the cruise period. The measurements are taken 15 meters above the sea level, wind directions are clockwise from north. Relative time of occupation of each section (A-J) and day-long station (1-5) is indicated.

Ship-based meteorological data was recorded by an automatic Aanderaa weather station.

During the second leg of the cruise the weather conditions can be characterized by moderate to low wind speeds (Figure 5). This is especially true for the day-long stations. Temperatures were close to the freezing point near the ice edge and between 3 and 6 C elsewhere at Yermak Plateau, up to 10 C further south. The wind direction was NE to E for stations 1 to 3, changed to W during station 4 while being more variable at station 5.

Sensible and latent heat flux into the ocean were calculated from ship-based meteorological

measurements (air temperature, air pressure, humidity and wind speed) and sea-surface

temperatures using a simplified version of the Fairall et al (1996) TOGA/COARE algorithm

(Figure 6). Unfortunately shortwave radiation measurements are not available. The total heat

flux into the ocean was around 25 W m

at station 1, -40 W m

at station 2 and between -50

W m

and -20 W m

at station 3. Heat fluxes at station 4 and 5 were small.

20 21 22 23 24 25 26 27 28 29 30 31 01 02 03 04

0 5 10

Temperature ( ° C)

−60

−40

−20 0 20

40 1 2 3 4 5

Sensible and latent HF (W/m2 )

20 21 22 23 24 25 26 27 28 29 30 31 01 02 03 04

−100

−75

−50

−25 0 25 50

Total heat flux (W/m2 )

Time, day 20 July to 4 August 2007

Figure 6. Sensible (middle panel, black) and latent heat flux (middle panel, red) into the ocean inferred from air temperature at 15m above sea level (upper panel, black) and sea-surface temperature (upper panel, red). Total heat flux into the ocean (lower panel).

4. Measurements and Data Processing 4.1. Hydrography

Sampling - The CTD system used during the cruise was a SeaBird Electronics SBE911plus sonde mounted on a SBE32 Carousel Water Sampler, containing 12 3L Niskin bottles. The CTD was equipped with a standard pressure sensor, temperature sensor SBE 3 (SN1602), and conductivity sensor SBE 4 (SN1219).

A total of 185 CTD casts and 185 salinity bottle samples were collected during the cruise (97 in Leg 1 and 88 in Leg 2). All of the CTD stations covered from the surface to within about 20 m height above the bottom, except for 15 deep stations with echo depth greater than 2 km, profiles were taken down to about 1500 m. The CTD station overview is shown together with the cruise track on map in Figure 1, and a complete list is tabulated in Appendix A, Table A1 for Leg 1 and Table A2 for Leg 2.

Data processing - SBEDataProcessing-Win32 version 5.26, standard Seabird Electronics

software for Windows, is used for data processing of the CTD data. Only data from

downcasts are used to avoid turbulence caused by rosette package on upcast. Raw data

(pressure, temperature and conductivity) are converted to physical units using calibration files

modified for air pressure and conductivity slope factor (DATCNV). Outliers, differing more

than 2 and 20 standard deviations for the first and second pass, respectively, from the mean of 100 scan windows are flagged and excluded from analysis (WILDEDIT). The thermal mass effects in the conductivity cell are corrected for (CELLTM, with parameters alpha = 0.03 and 1/beta = 7.0). Pressure is low pass filtered with a time constant of 0.15 s. Scans when the CTD is moving less than the minimum fall rate (0.25 m/s) are flagged to remove pressure reversals due to ship heave (LOOPEDIT). Data are then averaged into 1 dbar bins (BINAVG). Temperature is reported in ITS-68 scale. Salinity is reported on the practical salinity scale.

Conductivity correction from salinity bottle samples - Of the 185 salinity bottle samples, a total of 182 were analyzed at IMR with a Guildline Portasal 8410 salinometer. One reading (case 51, bottle 1140) appears erroneous and is excluded from the analysis. Salinity and conductivity values from each bottle were merged with the corresponding CTD data. Bottle conductivity is calculated from bottle salinity and CTD temperature and pressure. A full list of bottle and CTD-derived parameters are tabulated in Appendix A, Table A3. Following the procedure recommended by UNESCO (1988), only data within the 95% confidence interval are used to correct the calibration of the CTD conductivity. Histogram of ΔC = C

– C

, difference of conductivity measured by CTD and inferred from bottle salinity, is approximately normally distributed Following the recommendations given by Seabird Electronics, the conductivity values are corrected by the formula, C

= m C

, where m is the slope calculated by

n

i i

i 1 n

i i

i 1

a b

m

a a













 ^.

Here a

and b

are the CTD conductivity and the bottle conductivity, respectively and n is the total number of bottles. Using the 175 values inside the 95% confidence interval, the value for the slope is calculated to be m = 0.99995. Prior to correction, the conductivity difference between CTD and bottles, C = C

– C

averaged 1.4 (± 3.8) 10

(± 1 standard deviation, SD) over 175 samples. After correction C = 0.0 (± 3.8) 10

S/m.

-10 -5 0 5

x 10^-3 0

20 40 60 80 100

C = C_CTD-C

Bot (S/m)

Number of hits

0 50 100 150 200

-8 -6 -4 -2 0 2 4 6x 10^-3

C (S/m)

Bottles in chronological order

Figure 7. (Left) Histogram of CTD-derived and bottle conductivity differences. Red curve is the

normal-distribution fit for the sample mean and standard deviation. (Right) C in chronological order

with 95% confidence intervals on the mean indicated (black envelopes).

4.2. Microstructure Measurements

Instrument - The microstructure data were collected by the MSS90L profiler (S/N 33), a loosely-tethered free-fall instrument equipped with two airfoil probes (PNS98) aligned parallel to each other, a fast response conductivity (capillary type two electrode probe) and temperature (FP07), an acceleration sensor and conventional CTD sensors for precision measurements. The microstructure profiler, in addition to the turbulence data, returns about 10 cm resolution accurate CTD profiles, hence shipboard SBE-CTD profiler is often omitted when MSS was deployed. Occasional joint MSS-SBE casts were used for correction of MSS CTD data against the SBE. The specifications of the sensors can be found at http://www.isw- wasser.com/product1.htm. The sensors point downward when the instrument profiles vertically, and all sample at 1024 Hz to 16 bit resolution. An earlier version of the profiler is described by Prandke and Stips (1998). MSS90L is a longer, slightly heavier hence more stable version of MSS90. Results from a recent survey using MSS90 were reported e.g. in Fer (2006). The profiler is 1.25 m long and weighs  15 kg in air, hence can be handled by one person.

Sampling - The instrument is ballasted to free-fall at a typical fall speed of 0.6-0.7 m s

and is decoupled from operation induced tension by paying out cable at sufficient speed to keep it slack. The data are transmitted to a laptop acquisition PC on board the ship via the cable. The operational depth is about 520 m. In total 222 casts were made down to about 520 m depth in deep water or to within 10-15 m height above bottom for shallower depths. The profiler is equipped with a sensor protection cage at the leading end and occasionally the profiler landed at the bottom. The artifact of the protection cage is narrow band peaks in the shear spectra caused by von-Karman vortex shedding (at 24 Hz) and due to the cage’s oscillations (at higher frequency). With the mean fall speed of 0.65 m/s, the 24 Hz peak corresponds to a wavenumber of 37 cycles per meter (cpm). The wavenumber range chosen for the analysis is well below this peak. The sampling was made while the vessel was drifting with the engines and thrusters switched off. A full list of MSS casts is given in Table A4 of Appendix A.

Data processing - Full-scan (1024 Hz) data from all channels of the MSS profiler are edited for transmission errors and spikes and then averaged to 256 Hz to reduce noise. Time series are converted into vertical wavenumber space using a smooth fall-speed profile, invoking Taylor’s frozen turbulence hypothesis (valid at the fall speeds reported here). The fall speed is derived from the time derivative of the (2-Hz low passed) pressure record. The dissipation rate of turbulent kinetic energy per unit mass, , is calculated using the isotropic relation

2

7.5 u

   , where  is the viscosity of seawater (here, it is approximated as a function of temperature and ranges within 1.55-1.9×10

m

s

for the recorded range of temperatures), u

is the shear of the horizontal velocity resolved at cm-scales. Airfoil shear probes register

small scale velocity fluctuations by means of a piezoceramic beam. Due to its thermal

sensitivity, the measured raw shear is contaminated by the thermal changes as the probe

encounters temperature gradients during its descent. The thermal drift is eliminated by high-

pass filtering before deriving physical shear. Shear wavenumber spectra are calculated using

half overlapping 256-point Hanning windows. This corresponds to a 0.65-m window for a

nominal fall speed of 0.65 m s

. The shear variance is obtained by integrating the shear

wavenumber spectrum between 2 cpm (a limitation due to the length of the profiler) and an

upper cutoff number depending on the Kolmogorov wavenumber, (/

)

/2 cpm. The upper

cutoff is determined by iteration, similar to that described in Moum et al. (1995), and is set to

maximum 30 cpm or 14 cpm when 2-14 cpm integrated  < 2  10

W kg

. This range is not affected by the narrowband noise peaks. A small correction (typically within a factor of 1.2 for  < 10

W kg

and about a factor of 1.7 for   10

W kg

) is applied for the lost variance assuming the Nasmyth’s form as tabulated in Oakey (1982). We used the functional form of this universal curve (Wolk et al., 2002). Independent estimates using non-linear least- squares fit to the Nasmyth’s form give comparable values for dissipation. A further check is employed by comparing dissipation values from both probes, and anomalous data were discarded prior to averaging at 1 m resolution. The noise level measured in quiet regions appears to be about  3-510

W kg

. The typical “pseudo” dissipation rates, derived identically from spectral analysis of the acceleration sensor divided by the fall speed (Moum and Lueck, 1985), are < 10

W kg

. The vertical diffusivity for mass is approximated using K

= /N

(Osborn, 1980), where  is related to the mixing efficiency. We employ the widely used value  = 0.2 (Moum, 1996). An independent estimate of vertical diffusivity (for heat) K

(typically  K

) using the Osborn-Cox model (Osborn and Cox, 1972) is not attempted here.

256 Hz sampled data from the MSS precision CTD sensors are low-passed at 10 Hz. Data from the precision conductivity sensor is corrected for sensor response with respect to temperature sensor using a single pole recursive filter with time constant corresponding to 55 scans. CTD data are then averaged at 10-cm intervals prior to calculating spike-free salinity.

Salinity profile is further smoothed using a 5 scan (0.5 m) median filter. Buoyancy frequency, N(z), is calculated using the Thorpe ordered density profiles (Thorpe, 1977).

Correction against SBE-CTD – The precision conductivity, hence salinity data from SeaBird sensors are more reliable, particularly because they are corrected against salinity bottles. We correct the MSS-conductivity record against SBE profiles. For the purpose, we use the MSS casts with subsequent SBE-CTD casts. Most SBE profiles were collected deliberately after or prior to an MSS cast, for calibration purposes. In total 86 MSS-SBE casts are matched, with sampling time separation within 1.5 hours, and portions of the profiles where the salinity was nearly homogeneous were chosen for the analysis. In total 503 segments of various length (but > 3 m) were detected where the vertical salinity gradient (derived by line fits over 10-m moving windows) was less than twice its standard error.

Averages properties for the detected segments and the corresponding values from the SBE

sensors are calculated and compared. The histogram and the time series for the conductivity

difference C = C

– C

are shown in Figure 8. The correction slope is calculated as it

was described for SBE-bottle correction. Ignoring outliers, using 462 data points in total, m =

1.001. Prior to correction, C = - 0.002 (± 0.007) S/m. After correction C = 8 ( ± 60) 10

S/m.

−1 −0.5 0 0.5 1 0

50 100 150

ΔC = C_MSS−C_SBE (S/m)

Number of hits

0 200 400 600

−1

−0.5 0 0.5 1

ΔC (S/m)

Bins in chronological order

Figure 8. (Left) Histogram of MSS and CTD conductivity differences. Red curve is the normal- distribution fit for the sample mean and standard deviation. (Right) C in chronological order with 95% confidence intervals (from normal distribution, i.e. ±2SD) on the mean indicated. Values plotted are 10

times C.

On the other hand a comparison of the salinity for the same detected segments shows a

significant drift starting with section H (not shown). MSS-derived salinity towards the end of

the cruise is as much as 0.4 practical salinity units off. This is found to be related to the drift

in the temperature data recorded by the MSS-precision T sensor. Report from the post-cruise

service of the profiler confirms that the T-sensor flooded. The fast-response FP07

temperature sensor did not show such drift. We use the FP07 sensor to calculate and correct

for the drift in the T sensor. Depth averaged temperature difference between the T sensor and

FP07 (mT) sensor for each MSS cast is shown in Figure 9. We therefore corrected the

temperature record for each cast for the corresponding T-mT difference. Resulting MSS-T

profiles are compared to SBE-T profiles to find a mean offset of 0.04 K. After the final

corrections on temperature and conductivity slope correction, salinity and density are derived,

which compare well with the SBE data. In summary following corrections are applied to

MSS-CTD: Conductivity values are corrected using a slope of m = 1.001. Temperature

values are corrected with a constant offset of - 0.03 K (-0.07 K for mean T-mT offset and

0.04K for SBE-MSS offset) plus the negative T-mT values given in Figure 9.

202 204 206 208 210 212 214 216

−0.4

−0.3

−0.2

−0.1 0

Decimal Day (2007)

T − mT (K)

Figure 9. Depth averaged temperature difference between the T sensor and FP07 (mT) sensor for each MSS cast. A mean difference of 0.07 K, due to the fact that FP07 is calibrated for surface pressure, is removed before plotting. Note the significant deviation towards the end of the cruise.

4.3. Current Measurements

The vessel was equipped with a RD-Instruments Narrowband ADCP with 150kHz frequency.

ADCP was operational; however the data are not processed before the completion of this report.

Additionally current measurements were made by expendable current profilers (XCPs, Lockheed Martin Sippican, Inc.). The XCP measurement of velocity is based on electromagnetic induction: water velocity relative to a depth independent mean is inferred from sensing the electric current induced in seawater by its motion through the earth’s magnetic field (Sanford et al., 1993). The XCP falls through the water at about 4.5 m/s, and samples relative horizontal velocity, compass, and temperature to a depth of 1500m. Depth is inferred from time of fall and a known fall rate, velocity resolution is 1.0 cm/s rms and is output with a vertical resolution of 0.4 m. Use of XCPs is well established in mid-latitudes, for example in measurements of internal wave shear (e.g., Kunze et al., 2002), but they have also been used successfully at Arctic latitudes (e.g., D'Asaro and Morison, 1992). XCP velocity measurement depends on the non-zero amplitude of the vertical component of the magnetic field, which is large at high latitudes; however compass errors due to the decreasing size of the horizontal component of the magnetic field will result in increasing errors in velocity direction as the magnetic pole is approached. The survey site is sufficiently far from the magnetic pole and compass errors are not of concern, but the velocity components must be corrected for the magnetic declination, as they are relative to magnetic coordinates.

In total 17 XCPs (channel 14 with 40s delay) were deployed (Table 1). Six probes were

dropped at Station 1, at approximately 4 hour interval, and all probes functioned properly. At

Stations 3, on the other hand, only two out of seven deployments returned useable data. The

first and last drops at Station 3 (SN 07061007, 06051108) failed due to operator error. The

third drop returned data only in the upper 60 m and is omitted in the report. The remaining

probes had damaged release mechanism. The final three XCPs were deployed successfully at

section F, stations F7 to F9.

Table 1. XCP deployments. Fh and Fz are the horizontal and vertical components of the magnetic field at the given time and position. The probes identified by italic case (serial numbers in bold case) malfunctioned returning no or not-usable data.

Sta- tion

XCP

S/N Drop Date-Time (UTC)

Depth

(m) Latitude (deg min)

Longitude (deg min)

F

nT

-F

nT St1 06051107 St1_1 23.7.2007 13:47 1208 80 08.58 N 004 21.48 E 6703.7 -54464.7 St1 06051053 St1_2 23.7.2007 18:30 1254 80 07.90 N 004 18.50 E 6708.5 -54461.2 St1 07011013 St1_3 23.7.2007 22:08 1344 80 07.06 N 004 10.36 E 6714.2 -54456.3 St1 06051025 St1_4 24.7.2007 02:40 1388 80 06.07 N 004 09.27 E 6721.5 -54452.0 St1 06051003 St1_5 24.7.2007 06:43 1226 80 08.49 N 004 19.91 E 6704.4 -54464.2 St1 06051004 St1_6 24.7.2007 10:10 1364 80 07.29 N 004 07.85 E 6712.5 -54457.0

St3 07031011 St3_1 27.7.2007 10:49 960 80 33.99 N 009 48.90 E St3 07061005 - 27.7.2007 14:02 1068 80 33.85 N 009 38.84 E

St3 07061003 St3_2 27.7.2007 14:44 1048 80 33.61 N 009 36.75 E 6520.4 -54642.6 St3 07061002 St3_3 27.7.2007 18:25 978 80 33.96 N 009 46.55 E 6428.6 -54378.3

St3 06051109 St3_4 27.7.2007 22:09 1015 80 34.29 N 009 46.29 E 6426.3 -54379.6 St3 05121030 St3_5 28.7.2007 02:24 1164 80 34.45 N 009 36.14 E 6425.5 -54377.6

F7 06051089 F7 30.7.2007 04:10 872 79 59.90 N 006 01.40 E 6680.2 -54188.0 F8 06051110 F8 30.7.2007 06:45 1142 79 59.70 N 004 59.64 E 6679.9 -54175.2 F9 07011015 F9 30.7.2007 09:17 1780 80 00.00 N 003 58.70 E 7105.6 -53919.3

4.4. Short-Term Mooring at Yermak Plateau

In order to record isotherm displacements and current fluctuations at Yermak Plateau, a short-

term mooring was deployed at 79N 59.78N, 5 55.95E at 889 m isobath on 23 July 2007

1039 UTC. The mooring was retrieved on 31 July 2007 1424 UTC. In total, the mooring

consisted of a line of 19 SBE37 Microcats, a RD-Instruments 75 kHz Longranger ADCP and

an Aanderaa RCM Seaguard. The deployment depth and details of the instruments are given

in Table 2. Microcats were set to sample 10 point averages every one minute. The

Longranger sampled 1 min averages of 27 pings per ensemble, in earth coordinates, in 8-m

size depth cells. The Longranger was damaged and leaked seawater from the pressure

sensors. It returned only 16.8 h of data early in the deployment.

Table 2. Yermak Plateau Mooring Set-up. Ballast is 800 kg. 8-mm steel wire is used. 260N buoyancy is placed about 3-m above the Longranger. The uppermost buoyancy element is SS41 at 15 m depth.

Instrument depth given is the depth inferred from the average pressure record when available, or the target depth (in bracets).

Instrument S/N Depth (m) Height above

bottom (m) Comments

RCM SeaGuard 16 23 865 U-V-C-T-P

SBE37 5453 99 789 C-T-P

SBE37 5396 (125) 763 C-T

SBE37 5454 145 743 C-T-P

SBE37 5397 (163) 725 C-T

SBE37 5455 183 705 C-T-P

SBE37 5398 - - Did not log

SBE37 5456 230 658 C-T-P

SBE37 5399 (260) 628 C-T

SBE37 5457 286 602 C-T-P

SBE37 5458 315 573 C-T-P

SBE37 5459 362 526 C-T-P

SBE37 5445 409 479 C-T-P

SBE37 5446 456 432 C-T-P

SBE37 5447 507 381 C-T-P

SBE37 5448 560 328 C-T-P

SBE37 5449 610 278 C-T-P

SBE37 5450 708 180 C-T-P

SBE37 5451 805 83 C-T-P

Longranger 868 20 16.8h of data

SBE37 5452 873 15 C-T-P

5. Observations: Yermak Plateau Mooring

The mean temperature and salinity profile derived from the Microcat records compare well with the average CTD profile in the vicinity measured by the ship-board SBE911+ system Figure 10, hence no corrections were made to the mooring temperature and salinity data.

Time series of isotherms and isohalines over the duration of the deployment is shown in

Figure 11 and a summary of the parameters measured by the Seaguard at about 23 m depth is

shown in Figure 12.

Figure 10. Comparison of (left) T, (right) S profiles derived from the Microcats (yellow: all 1-min profiles, red: time average) and (black) Sea-Bird CTD casts 792-796. Mean temperature and salinity recorded by the RCM SeaGuard are indicated by the green rectangle.

Figure 11. Contours of (top) temperature and (bottom) salinity derived from Microcats deployed at the

Yermak Plateau. Temperature is shown for 1-min sampling. Salinity is 15-min averaged.

Figure 12. Time series of pressure, temperature, salinity and East (black) and North (red) component of the velocity recorded by the RCM Seaguard.

6. Observations : CTD

Figures of all CTD profiles and the T-S plots for each section are provided in Appendix B and C, respectively. Here we present the hydrography contoured for each section.

Figure 13 (next page). Temperature (upper panel) and salinity (lower panel) contours for the sections

worked in Leg 1. For deep sections the depth scale for the upper and deeper layers are different at the

level marked by the dashed horizon. Arrow heads mark the position of the CTD stations with station

names indicated. Bathymetry is ETOPO2 interpolated along the section modified with actual ship

echo sounder depth at the station (circles).

T(°C)

−1 0 1 2 3 4 5 6 7 8

0

0

2

2 4

6 4 6 6

Depth (m)

0 50 100 150 200 250 500 750 1000 1250 1500

a10 a9 a8 a7 a6a5a4a3a2 a1

S

34.8 34.85 34.9 34.95 35 35.05 35.1 35.15

34.85 34.85

34.95

34.95 35.05 35.05

Depth (m)

Distance (km)

0 20 40 60 80 100

0 50 100 150 200 250 500 750 1000 1250 1500

HM6132007 Leg 1 − Section a (78N)

T(°C)

−1 0 1 2 3 4 5 6 7 8

0

0

2

2

4

4 6

6 6

Depth (m)

0 50 100 150 200 250 500 750 1000 1250 1500 1750

b1 b2 b3 b4 b5 b6b7 b8 b9b10

S

34.85 34.9 34.95 35 35.05 35.1 35.15

34.875

34.875

34.925 34.975

34.975

35.025

35.025

35.075 35.075 35.125

35.125

35.125 35.125

Depth (m)

Distance (km)

0 10 20 30 40 50 60 70 80 90

0 50 100 150 200 250 500 750 1000 1250 1500 1750

HM6132007 Leg 1 − Section b (77N30)

T(°C)

−1 0 1 2 3 4 5 6 7 8

0

0

2

2

4 4

6 6

Depth (m)

0 50 100 150 200 250 500 750 1000 1250 1500

c10 c9 c8 c7 c6 c5 c4c3 c2 c1

S

34.8 34.85 34.9 34.95 35 35.05 35.1 35.15 35.2

34.85 34.85

34.95 34.95

35.05 35.05

Depth (m)

Distance (km)

0 10 20 30 40 50 60 70 80 90 100

0 50 100 150 200 250 500 750 1000 1250 1500

HM6132007 Leg 1 − Section c (77N)

T(°C)

−1 0 1 2 3 4 5 6 7 8

0

0

2

2

4

4 6

6

Depth (m)

0 50 100 150 200 250 500 750 1000 1250 1500

d1 d2 d3 d4 d5 d6 d7 d8 d9d10

S

34.4 34.5 34.6 34.7 34.8 34.9 35 35.1 35.2

34.5 34.5

34.7 34.7

34.9 34.9

34.9

35.1

35.1 35.1

35.1

Depth (m)

Distance (km)

0 10 20 30 40 50 60 70 80 90 100

0 50 100 150 200 250 500 750 1000 1250 1500

HM6132007 Leg 1 − Section d)

T(°C)

−2

−1 0 1 2 3 4 5

−1

−1 1

1 1

3 3 3

−1 1

Depth (m)

0

50

100

150

e1 e2 e3 e4 e5 e6 e7 e8 e9

S

33.4 33.6 33.8 34 34.2 34.4 34.6 34.8 35 35.2

33.6 33.6

34

34

34.4 34.4

34.8 34.8

Depth (m)

Distance (km)

0 10 20 30 40 50 60 70 80 90

0

50

100

150

HM6132007 Leg 1 − Section e (Storfjorden Sill)

T(°C)

−2

−1 0 1 2 3 4 5 6

−1

−1 1

1 3

3

−1 5

−1

Depth (m)

0

50

100

150

f1 f2 f3 f4 f5f6 f7 f8

S

33.4 33.8 34.2 34.6 35 35.4

33.6 33.6

34

34

34.4

34.4

34.8

34.8 34.8 34.8

35.2

Depth (m)

Distance (km)

0 10 20 30 40 50

0

50

100

150

HM6132007 Leg 1 − Section f

T(°C)

−2

−1 0 1 2 3 4 5

−1

−1

1 1

3 3

1

Depth (m)

0 20 40 60 80

g1 g2 g3 g4 g5

S

33.7 33.9 34.1 34.3 34.5 34.7 34.9

33.8 33.8

34 34

34.2 34.2

34.4 34.4

34.6

34.8

Depth (m)

Distance (km)

0 5 10 15 20 25 30 35

0 20 40 60 80

HM6132007 Leg 1 − Section g

T(°C)

−1.5

−0.5 0.5 1.5 2.5 3.5 4.5

−1

−1

0

0

1

1

2 2

3

2

3 4

1 4

2 3 4

Depth (m)

0 50 100 150 200

h1 h3 h5 h7 h9 h11

S

34.3 34.4 34.5 34.6 34.7 34.8 34.9 35 35.1

34.4 34.4

34.6 34.6

34.8 35 34.8

34.8

34.8

Depth (m)

Distance (km)

0 10 20 30 40 50 60 70 80 90

0 50 100 150 200

HM6132007 Leg 1 − Section h

T(°C)

−0.5 0.5 1.5 2.5 3.5 4.5 5.5

0 0

1

1

2 2

3 3

4 4

5

5 5

5 5

Depth (m)

0 50 100 150 200 250

i1 i2 i3 i4 i5 i6 i7 i8

S

34.4 34.5 34.6 34.7 34.8 34.9 35 35.1 35.2

34.5

34.5

34.7

34.7

34.9 34.9

35.1

Depth (m)

Distance (km)

0 10 20 30 40 50 60

0 50 100 150 200 250

HM6132007 Leg 1 − Section i

(end of Figure 13.)

Figure 14. (next page) Same as Figure 13 but for Leg 2.

T(°C)

−1 0 1 2 3 4 5 6 7

0 0

2 2

4

4 4

6

2

2

4

Depth (m)

0 50 100 150 200 250 500 750

A1 A2 A3 A4

S

32.8 33.2 33.6 34 34.4 34.8 35.2

33 33

33.4

33.4

33.8 33.8

34.2 34.2

34.6

34.6

35 35 35

35

35 34.6

33.8

Depth (m)

Distance (km)

0 5 10 15 20

0 50 100 150 200 250 500 750

HM6132007 Leg 2 − Section A

T(°C)

−2

−1 0 1 2 3 4 5 6

−1

−1 −1

1

1 1

3 3

3 3

−1 1 1

3

1 1

3 5

Depth (m) 1

0 50 100 150 200 250 500 750 1000

B1 B2 B3 B4 B5 B6 B7

S

32.25 32.75 33.25 33.75 34.25 34.75 35.25

33 33

33.5 33.5

34

34 34.5

35

35 35

35

34.5

Depth (m)

Distance (km)

0 20 40 60 80 100

0 50 100 150 200 250 500 750 1000

HM6132007 Leg 2 − Section B

T(°C)

−2

−1 0 1 2 3 4 5 6 7

−1

−1

1 1

3

3

5 3 5

5

Depth (m) 1

0 50 100 150 200 250 500 750 1000

C7 C6 C5 C4 C3 C2 C1

S

33.4 33.6 33.8 34 34.2 34.4 34.6 34.8 35 35.2

33.6

33.6

34

34

34.4

34.4

34.8

34.8

Depth (m)

Distance (km)

0 10 20 30 40 50 60 70

0 50 100 150 200 250 500 750 1000

HM6132007 Leg 2 − Section C

T(°C)

−1 0 1 2 3 4 5 6 7

0 0

2 2

4 4

6 6

Depth (m)

0 50 100 150 200 250 500 750

D7 D6 D5 D4 D3 D3 D1

S

34.3 34.4 34.5 34.6 34.7 34.8 34.9 35 35.1 35.2

34.4 34.4

34.6 34.6

34.8 34.8

35 35

Depth (m)

Distance (km)

0 10 20 30 40 50 60 70

0 50 100 150 200 250 500 750

HM6132007 Leg 2 − Section D

T(°C)

−1 0 1 2 3 4 5 6 7

0 0

2

2

4

4 6 6

6

Depth (m)

0 50 100 150 200 250 500 750 1000

E5 E3 E2 E1

S

34.75 34.8 34.85 34.9 34.95 35 35.05 35.1 35.15

34.8

34.8

34.9

34.9

35 35

35.1 35.1

35.1 35.1

35.1

35.1

Depth (m)

Distance (km)

0 10 20 30 40 50 60

0 50 100 150 200 250 500 750 1000

HM6132007 Leg 2 − Section E

T(°C)

−2 0 2 4 6 8

−1

−1

1

1 1

3

3 7 55

33

Depth (m)

0 50 100 150 200 250 500 750 1000 1250 1500 1750

F9 F8 F7 F6 F5 F4 F3 F2 F1

S

31.5 32 32.5 33 33.5 34 34.5 35 35.5

32 32

33

33

34

34

35

35 35

35

Depth (m)

Distance (km)

0 50 100 150

0 50 100 150 200 250 500 750 1000 1250 1500 1750

HM6132007 Leg 2 − Section F

T(°C)

−1 1 3 5 7 9

0

2 2

4

4 4

6

6

44

2

4

Depth (m)

0 50 100 150 200 250 500 750 1000 1250 1500

I1 I3 I5 I7 I9 I11 I13 I15 I17 I19 I21 I23

S

32.5 33 33.5 34 34.5 35

32.75

32.75

33.25 33.25

33.75

33.75

34.25 34.25

34.75 34.75

34.75

Depth (m)

Distance (km)

0 20 40 60 80 100 120 140 160

0 50 100 150 200 250 500 750 1000 1250 1500

HM6132007 Leg 2 − Section I

(end of Figure 14.)

7. Observations: Microstructure 7.1. Time-series stations 1-5

In Figures 15-19, time-depth maps of temperature and salinity (upper panels) and the

dissipation rate of turbulent kinetic energy (TKE) per unit mass together with the isopycnals

(lower panels) are shown for stations 1 to 5. The corresponding time-averaged profiles of

temperature, T, salinity, S, buoyancy frequency, N, density, 

, dissipation rate of TKE,  and

diapycnal eddy diffusivity, K

. are given in Figures 20-24. Subsequently, Figure 25 shows the

depth-distance contours of temperature and salinity (upper panels) and the dissipation rate of

turbulent kinetic energy (TKE) per unit mass together with the isopycnals (lower panels) for

all MSS sections occupied during Leg 2.

T (°C)

−2

−1 0 1 2 3

Depth (m)

35 35

35 35

34

34.8 33.5

100 34.9

200 300 400 500

log

10(ε)

−9

−8.5 −8

−7.5 −7

−6.5 −6

Decimal Day 2007

Depth (m)

27.9 27.9

27.5 27.6

203.6 203.7 203.8 203.9 204 204.1 204.2 204.3 204.4 204.5 100

200 300 400 500

Figure 15.

irregular contour interval) and (bottom) log10 base dissipation rate of turbulent kinetic energy (color) and density (

, black, irregular contour interval).

T (°C)

0.5 1.5 2.5 3.5 4.5 5.5 6.5

Depth (m)

35 35

35.1 35.1

35.1 35.1

34.7

100 200 300 400 500

log

10(ε)

−9

−8.5 −8

−7.5 −7

−6.5 −6

Decimal Day 2007

Depth (m)

28 28

27.9 27.8

27.6 27.5

204.8 204.9 205 205.1 205.2 205.3 205.4 205.5 205.6 100

200 300 400 500

Figure 16. Same as Figure 15 but for Station 2.

T (°C)

0.5 1.5 2.5 3.5 4.5 5.5 6.5

Depth (m)

35

35 34.9 34.9

35.1

35

100 200 300 400 500

log

10(ε)

−9

−8.5 −8

−7.5 −7

−6.5 −6

Decimal Day 2007

Depth (m)

28

27.9 27.9

27.8 27.6 27.7

207.4 207.5 207.6 207.7 207.8 207.9 208 208.1 208.2 100

200 300 400 500

Figure 17. Same as Figure 15 but for Station 3.

T (°C)

0 1 2 3 4 5 6 7

Depth (m)

35 35

35.1 35.1 35.1

35 35

100 200 300 400

log

10(ε)

−9

−8.5 −8

−7.5 −7

−6.5 −6

Decimal Day 2007

Depth (m)

28

27.9

27.8 27.7

27.6

208.6 208.7 208.8 208.9 209 209.1 209.2 209.3 209.4 209.5 100

200 300 400

Figure 18. Same as Figure 15 but for Station 4.

T (°C)

−2

−1 0 1 2 3 4 5 6

Depth (m)

35 35

34.8

34.5

100 34.9

200 300 400 500

log

10(ε)

−9

−8.5 −8

−7.5 −7

−6.5 −6

Decimal Day 2007

Depth (m)

28

27.9 27.9

27.6 27.8 27.5

210.6 210.7 210.8 210.9 211 211.1 211.2 211.3 211.4 211.5 100

200 300 400 500

Figure 19. Same as Figure 15 but for Station 5.

−1.5 0 1.5 0

50 100 150 200 250 300 350 400 450 500 550

T (°C)

Depth (m)

32 33.5 35 S

25.526.2527 27.75 σ_θ

0 10 20

N (cph)

−9 −8 −7 log10ε (W kg⁻¹) AVERAGE PROFILES: STATION 1

−5 −4 −3 log10K

ρ (m² s⁻¹)

Figure 20.

density, 

, dissipation rate of TKE,  and diapycnal eddy diffusivity, K

.

1.5 3 4.5 6 0

50 100 150 200 250 300 350 400 450 500 550

T (°C)

Depth (m)

33.6 34.2 34.8 S

26.8 27.4 28 σ_θ

0 10 20

N (cph)

−9 −8 −7 log₁₀ε (W kg⁻¹) AVERAGE PROFILES: STATION 2

−5 −4 −3 log₁₀K_ρ (m² s⁻¹)

Figure 21. Same as Figure 20 but for Station 2.

1 2.5 4 5.5 0

50 100 150 200 250 300 350 400 450 500 550

T (°C)

Depth (m)

34.6534.834.95 S

27.3 27.6 27.9 σ_θ

0 5

N (cph)

−9 −8 −7 log₁₀ε (W kg⁻¹) AVERAGE PROFILES: STATION 3

−5 −4 −3 log₁₀K_ρ (m² s⁻¹)

Figure 22. Same as Figure 20 but for Station 3.

1 4 0

50 100 150 200 250 300 350 400 450 500

T (°C)

Depth (m)

34.8534.9253535.075 S

27.5 27.8 σ_θ

0 2 4

N (cph)

−9 −8 −7 log₁₀ε (W kg⁻¹) AVERAGE PROFILES: STATION 4

−5 −4 −3 log₁₀K_ρ (m² s⁻¹)

Figure 23. Same as Figure 20 but for Station 4.

0.75 1.5 2.25 3 0

50 100 150 200 250 300 350 400 450 500 550

T (°C)

Depth (m)

32 33.5 35 S

25.7526.527.2528 σ_θ

0 10 20

N (cph)

−9 −8 −7 log₁₀ε (W kg⁻¹) AVERAGE PROFILES: STATION 5

−5 −4 −3 log₁₀K_ρ (m² s⁻¹)

Figure 24. Same as Figure 20 but for Station 5.

7.2. Sections A-J

T (°C)

−1 0 1 2 3 4 5 6 7

Depth (m)

35 35

34.9 35 34.9 35

100 200 300 400 500

A1 A2 A3 A4

log

10(ε)

−9

−8.5 −8

−7.5 −7

−6.5 −6

Distance (km)

Depth (m)

28

28 27.9

27.8

27.5 27.5

0 5 10 15 20

100 200 300 400 500

T (°C)

−2

−1 0 1 2 3 4 5 6

Depth (m)

35

35 35

34.5 34.9

34.5

100 200 300 400 500

B1 B2 B3 B4 B5 B6 B7

log

10(ε)

−9

−8.5 −8

−7.5 −7

−6.5 −6

Distance (km)

Depth (m)

28

27.9

27.8 27.7

27.9

0 20 40 60 80 100

100 200 300 400 500

Figure 25.

(black, irregular contour interval) and (bottom) log10 base dissipation rate of turbulent kinetic energy (color)

and density (

, black, irregular contour interval). Station names are marked on top (see station map for the

position of the sections and end stations).

T (°C)

−2

−1 0 1 2 3 4 5 6 7

Depth (m)

35

35 35.1 35

34.7

100 200 300 400 500

C7 C6 C5 C4 C3 C2 C1

log

10(ε)

−9

−8.5 −8

−7.5 −7

−6.5 −6

Distance (km)

Depth (m)

28

27.9 27.8 27.5 27.7

0 10 20 30 40 50 60 70

100 200 300 400 500

T (°C)

0.5 1.5 2.5 3.5 4.5 5.5 6.5

Depth (m)

35.1

35

35.1 35

100 200 300 400 500

D7 D6 D5 D4 D3 D2 D1

log₁₀(ε)

−9

−8.5 −8

−7.5 −7

−6.5 −6

Distance (km)

Depth (m)

27.9

27.8

27.6 27.7 27.6

0 10 20 30 40 50 60 70

100 200 300 400 500

T (°C)

0.5 1.5 2.5 3.5 4.5 5.5 6.5

Depth (m)

35

35.1

35

100 200 300 400 500

E5 E4 E3 E2 E1

log

10(ε)

−9

−8.5 −8

−7.5 −7

−6.5 −6

Distance (km)

Depth (m)

28

27.9

27.8

27.7 27.6

0 10 20 30 40 50 60

100 200 300 400 500

T (°C)

−2 0 2 4 6 8

Depth (m)

35

35.1 34.9

100 35

200 300 400 500

F9 F8 F7 F6 F5 F4 F3 F2 F1

log₁₀(ε)

−9

−8.5 −8

−7.5 −7

−6.5 −6

Distance (km)

Depth (m)

28

28

27.9 27.9

27.6

27.7

0 50 100 150

100 200 300 400 500