Jr271 physical oceanography analysis

JR271 Physical Oceanography Analysis

Finlo Cottier, Phil Hwang, Lewis Drysdale

Scottish Association for Marine Science

June 2014

Table of Contents

1 Introduction ....................................................................................................................... 3

2 Navigation Data ................................................................................................................. 3

3 Bathymetry Data ................................................................................................................ 3

4 Thermosalinograph (TSG) underway data ......................................................................... 3

4.1 Collection and Calibration ........................................................................................... 3

4.2 Analysis ........................................................................................................................ 4

4.3 Frontal identification ................................................................................................... 6

4.3.1 East Greenland Polar Front .................................................................................. 9

4.3.2 Iceland Faroes Front ............................................................................................ 9

4.3.3 Polar Front ........................................................................................................... 9

5 CTD data ............................................................................................................................. 9

5.1 Hydrography: water masses ........................................................................................ 9

5.1.1 North Atlantic ..................................................................................................... 10

5.1.2 Greenland Sea .................................................................................................... 10

5.1.3 Fram Strait.......................................................................................................... 11

5.1.4 Barents Sea/Norway Margin .............................................................................. 11

6 Sea Ice Conditions ............................................................................................................ 11

6.1 Station Descriptions .................................................................................................. 11

6.2 Sea Ice Maps .............................................................................................................. 13

7 Mixed Layer Depth ........................................................................................................... 23

7.1 MLD Quality Flags ...................................................................................................... 23

7.2 MLD Distributions...................................................................................................... 25

8 Acknowledgements .......................................................................................................... 31

9 References ....................................................................................................................... 31

List of Figures

Figure 4.1: TSG time series data ................................................................................................ 5

Figure 4.2: Temperature-Salinity distribution of TSG data ........................................................ 6

Figure 4.3: Surface temperature data ....................................................................................... 7

Figure 4.4: Surface salinity data ................................................................................................. 8

Figure 5.1: CTD data from casts 1 – 18 for the North Sea (red) and the North Atlantic (blue).

.................................................................................................................................................. 10

Figure 6.1: SIC (upper) and SIM (lower) for station 12 (overlaid) ........................................... 14









Figure 7.1: Exemplar CTD profile for MLD quality flag ‘A’ ....................................................... 24

Figure 7.2: Exemplar CTD profile for MLD quality flag ‘B’ ....................................................... 24

Figure 7.3: Exemplar CTD profile for MLD quality flag ‘C’ ....................................................... 25

Figure 7.4: Geographic distribution of MLD during JR271 ...................................................... 26

Figure 7.5: Mixed Layer Depth as function of ML temperature and salinity........................... 27

1 Introduction

In this report we provide an overview of the physical oceanographic data collected during

cruise JR271 (1 June – 2 July 2012) part of the UK Sea Surface Consortium Ocean

Acidification research project. We do not repeat the information provided in the cruise

report on instrumentation and sampling, rather give an overview of the physical

environments encountered along the cruise track.

In addition to the cruise data collected, we incorporate sea ice maps of key dates and areas

to provide the sea ice context to the sampling plan. Full data sets and high resolution

figures are provided as accompanying files.

2 Navigation Data

During the preparation of this report we used the navigation data provided by the Seatex

GPS (time, latitude, longitude). We have processed the data in a similar manner to that of

Thorpe [2014] to provide 1 minute averages of the navigation data.

3 Bathymetry Data

No bathymetry data have been accessed or processed as part of this report.

4 Thermosalinograph (TSG) underway data

4.1 Collection and Calibration

Underway data from the TSG system were recorded at 1 second intervals. Details on data

calibration are drawn from a technical report [Sanders and Palmer, 2013] obtained from

BODC. The underway data files provided by BODC cover the period from 01 June 2012 at

14:00 to 02 July 2012 at 18:30 with dates and times logged in GMT. Data were provided

from BODC at 1 minute intervals.

Conductivity and Temperature sensors on the TSG underway system were calibrated against

the equivalent values from both the Stainless Steel and the Titanium CTDs using data from

5m. Salinity data from the underway system was calibrated against the Stainless Steel CTD

only due to problems identified with the Titanium CTD. All data were calibrated by way of a

linear regression with r2 values of 0.97 (conductivity), 0.993 (hull temperature), 0.992

(thermosalinograph temperature) and 0.999 (salinity). It is these calibrated values that are

used. Suspect data (mainly due to changes in flow rate of the TSG, also noise in the

channels) were flagged.

4.2 Analysis

Good data was collected for 90% of the cruise with most of the data loss occurring whilst

the ship was in ice conditions (15 – 18 June). It is not known what caused the data drop-out

during other periods.

Hourly mean values of the original 1 minute TSG data were calculated by extracting

temperature and salinity data 30 minutes either side of each hour. Data from the TSG also

appeared to be rather variable whilst the ship was stationary and so the data were further

reduced by removing data collected whilst the ship was on station or manoeuvring at very

slow speed. The result is 466 hourly TS pairs for the surface water (approximately 7m

depth) from a possible 709 pairs (65% data collection). Fluorescence data were also

recorded by the TSG but it has not been processed or plotted here.

The resulting hourly temperature and salinity data are plotted in two formats (i) as time

series in Figure 4.1 and (ii) as a Temperature-Salinity (TS) diagram in Figure 4.2. As a guide,

the data points corresponding to the 5 Bioassay stations are marked in red to show the

relative distribution of surface TS conditions for these key stations. Figure 4.2 shows that

there is a good spread of temperatures (at similar salinities) from stations #1 - #2 - #5 - #3.

There is also a salinity contrast between the two stations in relatively cold waters from #3 to

#4.

Figure 4.1: TSG time series data

Upper panel shows the underway surface temperature data and the lower panel shows the underway salinity data for the duration of the cruise. Times when the bioassay CTD profiles were taken are shown in red.

Figure 4.2: Temperature-Salinity distribution of TSG data

1 hour TSG data for the duration of the cruise represented in a T-S diagram illustrating the range of surface hydrographic characteristic encountered. The T-S surface properties of the 5 Bioassay stations are shown in red.

4.3 Frontal identification

The TSG data along the cruise track for temperature and salinity are presented below in

Figures Figure 4.3 and Figure 4.4 respectively. From the TSG data we are able to identify a

number of frontal regions along the ship’s track. In the Nordic Seas we can identify three

major fronts (i) the East Greenland Polar Front (ii) the Iceland-Faroe Front and (iii) the

Barents Sea Polar Front. These are principally evident in the salinity variations.

Figure 4.3: Surface temperature data

1 hour TSG temperature data along the cruise track. Bioassay stations are marked as large open circles

Figure 4.4: Surface salinity data

TSG salinity data along the cruise track. Bioassay stations are marked as large open circles. The red and blue dashed lines are schematic representations of Atlantic Waters and Polar Waters respectively. The position of three significant fronts are shown: East Greenland Front (EGF), Polar Front (PF) and Iceland Faroe Front (IFF).

4.3.1 East Greenland Polar Front

The East Greenland Front develops fringes of the East Greenland Shelf as far as Cape

Farewell at the southern end of Greenland. The front is between the East Greenland Current

which exports low salinity water from the Arctic southward along the shelf break, and the

recirculating relatively warm and saline Atlantic Water [Rudels et al., 2005]. Horizontal

gradients here can be significant, temperature 0.1-0.3 ⁰C/km, salinity 0.1-0.2 PSU/km in the

summer [Kostianoy et al., 2004]. The cruise track crosses this front in three places (south to

north); in the Denmark Strait northeast of Iceland, northeast of Jan Mayen Island and in the

Fram Strait. Here we assume that all waters with salinity ≤ 34.5 [Hopkins, 1991; Nilsson et

al., 2008] represent Polar Surface Water that has been carried south by the EGC. We

provide an indicative position of the front in Figure 4.4 and the actual situation will be more

complex with smaller fronts forming and propagating at the edges of streams and eddies at

the edge of the EGC.

4.3.2 Iceland Faroes Front

A bifurcation of the EGC flows north of Iceland towards the Iceland Faroes Ridge to form the

Iceland-Faroe Front (IFF). The IFF is a boundary between warm and saline Atlantic Water to

the south and cold and fresh Polar Waters (originally from the EGC and sometimes referred

to as East Icelandic Current Water [Kostianoy et al., 2004]) to the north in the Iceland Sea.

The IFF is strongly visible as a temperature front in Figure 4.3 and has also been defined by

the outcropping of the S = 35 isohaline [Hansen and Østerhus, 2000; Hopkins, 1991] as

shown in Figure 4.4.

4.3.3 Polar Front

In the northeaster part of the cruise area we identify the Polar Front in the Barents Sea,

south of Svalbard. Here the Barents Sea branch of the north flowing Atlantic Water meets

the cold and fresh polar waters from the north and east of the Barents Sea. It appears as a

surface front in both temperature (Figure 4.3) and salinity (Figure 4.4) and tends to follow

the depth contours of the Bear Island trough [Schauer, 1995].

5 CTD data

CTD data came from two systems, one with a stainless steel rosette and the other with a

titanium rosette. All details of the calibration for these data are contained in the cruise

report for JR271. The only cast of note is CTD004 which has a big salinity offset compared to

other profiles from that station. The CTD data have been broadly grouped into common

areas for descriptive purposes.

5.1 Hydrography: water masses

5.1.1 North Atlantic

The water masses of the North Sea in Figure 5.1 are subject to inputs of Atlantic Water from

the Norwegian Sea, the Scottish Coastal Current and the English Channel. Run-off from the

Baltic Sea dilutes the water lowering its salinity while atmospheric mixing homogenises the

water down to shelf depth. In the North Atlantic, the warmest and most saline water

masses are found in the surface of the Faroe-Shetland Channel (T= 10°C, S=35.45) becoming

progressively less saline to the west (stations 12-18). The deep water in the Faroe-Shetland

channel is the cold outflow from the Nordic Seas. At Bioassay station in the Iceland Basin the

water is from the North Atlantic Current as it bifurcates south of the Iceland Faroese Ridge

and is topographically steered south round the Reykjanes Ridge into the Irminger Basin.

Water between 0-500 m depth in this region is mostly homogenous [Hansen and Østerhus,

2000] and is warm and saline (T > 8 ⁰C, S > 35.3).

5.1.2 Greenland Sea

In the Greenland Sea station the water is generally bounded by Atlantic Waters to the east

and Polar waters to the west. The sea here is occupied by a mixture of these boundary

waters that have been exposed to atmospheric exchanges [Hopkins, 1991]. The salinity and

temperature range reported by Hopkins [1991] for this area is between 34.4 to 35 and -1.8

Figure 5.1: CTD data from casts 1 – 18 for the North Sea (red) and the North Atlantic (blue).

to 4 ⁰C respectively, although much higher temperatures may be found. There is a rather

complex series of recirculation, atmospheric exchanges, interleaving and mixing which gives

rise to a broad variety of water masses in this region e.g. [Rudels et al., 2005]. Typically the

surface will have some form of cold and fresh polar derived surface water overlying a

heavily modified form of Atlantic water which will be warm and more saline in nature. IN

the deeper waters, below 1000 m will be the Artic intermediate water. Where sea ice

formation has taken place in situ there may be the characteristic signature of a cold

halocline layer with very cold and water increasing rapidly in salinity in the upper 200m.

5.1.3 Fram Strait

The Fram Strait surface waters are generally low salinity and low temperature on the west,

increasing in both temperature and salinity to the east. The presence of fresh surface water

is likely to be influenced strongly by the melting of sea ice in situ. Given the time of year of

the cruise, ice melt is a major contributor to a stable surface layer. Further, it is expected

that the water will be generally cooler and fresher to the west towards the East Greenland

Shelf. Close to Svalbard, the surface waters may freshen slightly due to the nearby Barents

Sea Polar Front separating the East Spitsbergen Current and West Spitsbergen Current,

which is approximately located over the shelf break. The shelf resident East Spitsbergen

Current here can be strongly freshened during the summer months. Again, deeper waters

are generally some form of Arctic Intermediate water [Rudels et al., 2005] below 1000 m.

5.1.4 Barents Sea/Norway Margin

The water around the Barents Sea station has a strong influence from the North Atlantic

Water. It has been defined by [Loeng, 1991] as salinity greater than 35 and temperature

between 3.5 to 6.5 ⁰C. Closer inshore the coastal current has a similar temperature but the

salinity is much reduced due to run off.

6 Sea Ice Conditions

Here we consider those stations where sea ice cover is an important aspect of their

oceanography. The description of sea ice condition is based on both passive microwave

SSMIS ASI sea ice concentration (SIC) from University of Bremen as well as sea ice map (SIM)

from Norwegian Ice Service.

6.1 Station Descriptions

A descriptive summary for each station is given in Table 6.1 and the relevant imagery for

each station is then provided in the series of figures below.

Table 6.1: Summary of sea ice conditions at relevant JR271 stations

Date Station Latitude Longitude Descriptor Figure

15/06/12 12 78.24771 N 5.54734 W ST12 was located within the closely packed drift ice. SIC in surrounding area was 70-100%. The nearest ice edge was located about 30 km to the east. *both SIC and SIM based on 15/06/12.

Figure 6.1

15/06/12 13 78.30724 N 6.08104 W ST13 was located within the closely packed drift ice. SIC in surrounding area was more than 90%. The nearest ice edge was about 45 km to the east. *both SIC and SIM based on 15/06/12.

Figure 6.2

16/06/12 14 78.21569 N 6.00632 W ST14 was located within the closely packed drift ice. SIC in surrounding area was more than 90%. The nearest ice edge was about 40 km to the east. *SIC based on 16/06/12 and SIM based on 15/06/12.

Figure 6.3

17/06/12 15 77.83088 N 5.03106 W ST15 was located within the closely packed drift ice. SIC in surrounding area was 70-100%. The nearest ice edge was about 35 km to the east. *SIC based on 17/06/12 and SIM based on 18/06/12.

Figure 6.4

17/06/12 16 77.77939 N 3.07602 W ST16 was located at the ice edge. In fact based on detailed SIM, the station was located in open water area where the ice edge was about 10 km away to the west. SIC in surrounding area was highly variable (from 0% in the east to 70% in the west). *SIC based on 17/06/12 and SIM based on 18/06/12.

Figure 6.5

18/06/12 17 78.35248 N 3.66429 W ST17 was located within the closely packed drift ice. SIC in surrounding area was more than 90%. The nearest ice edge was about 35 km to the east. *both SIC and SIM based on 18/06/12.

Figure 6.6

18/06/12 18 78.35256 N 4.16800 W ST18 was located within the closely packed drift ice. SIC in surrounding area was more than 90%. The nearest ice edge was about 45 km to the east. About 10 km into ice interior compared to ST17. *both SIC and SIM based on 18/06/12.

Figure 6.7

01/07/12 44 67.26234 N 24.03624 W ST44 was located at the ice edge. SIC in surrounding area was highly variable (from 0% in the south to 70% in the north) – a very sharp change. Closely packed ice in the north and open water in the south. *both SIC and SIM based on 01/07/12.

Figure 6.8

01/07/12 45 66.79138 N 25.14132 W ST45 was located very close to the ice edge. In fact based on detailed SIM, the station was located in open water area and the ice edge was about 10 km away to the north. SIC in surrounding area was highly variable (from 0% in the south to 50% in the north) *both SIC and SIM based on

Figure 6.9

01/07/12.

6.2 Sea Ice Maps

In the following sequence of figures we show sea ice concentration (SIC) data derived from

SSMIS ASI sea ice maps from University of Bremen (http://www.iup.uni-

bremen.de:8084/ssmisdata/asi_daygrid_swath/n6250/, [Spreen et al., 2008]). The black

line on the maps indicates the ice edge, defined as the contour line of SIC of 15%. We also

show a sea ice map (SIM) produced by the Norwegian Meteorological Institute

(www.met.no), using various data sources including satellite Synthetic Aperture Radar (SAR)

images. The colour in the map indicates ice type according to: Dark grey: Fast Ice, Red: Very

Close Drift ice (90-100%), Orange: Close Drift Ice (70-90%), Yellow: Open Drift (40-70%),

Green: Very Open Drift Ice (10-40%). Blue: Open Water (0-10%). The ice edge is defined

between Green and Blue areas. Vector file was obtained from Nick Hughes at Norwegian

Ice Service.

Figure 6.1: SIC (upper) and SIM (lower) for station 12 (overlaid)

7 Mixed Layer Depth

The depth of the surface mixed layer is an important property of the water column. The

mixed layer (ML) conditions are set by processes acting on the surface such as wind mixing

and density-driven convection. The mixed layer depth (MLD) was calculated for each CTD

profile using a standard difference criterion described by [Nilsen and Falck, 2006] and

adopting the criterion of the MLD being where the potential density has increased from the

surface value by 0.05 kg m-3. This criterion has been used by Thorpe [2014] for the Antarctic

OA cruise (JR274) and in European waters by Hickman et al [2012]. A summary of the

resulting MLD analysis is provided in Table 7.1 below.

7.1 MLD Quality Flags

During the course of the analysis for MLD we identify three classes of profile and these are

given an associated quality flag. Quality Flag A represents a well-defined ML with

homogeneous properties in temperature and salinity throughout the ML. This conforms to

the ‘classic’ ML conditions and an exemplar from CTD 22 (station 9) is given in Figure 7.1:

Exemplar CTD profile for MLD quality flag ‘A’Figure 7.1. We note also that the algorithm for

determining the MLD has derived a MLD of 37 m. However, it is clear from the profile that

the actual layer that is mixed is somewhat shallower at around 30 m. Such a manual

estimate is provided in Table 7.1: Summary of Mixed Layer Depth properties at JR271

stations..

Some CTD profiles yielded a density profile that looked like a classic ML but on inspection of

the temperature and salinity profiles it was clear that the water was not homogeneous

within the apparent ML. The existence of gradients in temperature and salinity throughout

the ML indicate that this body of water is not fully mixed; rather it is likely to have

developed through some diffusive effects to create uniform gradients in T&S. It may not

require much external forcing to fully mix this layer of water but when sampled it could not

be considered as a properly mixed layer. An example profile is given in Figure 7.2 which is

CTD 08 (station 3).

Finally there are a class of CTD profiles where the concept of a ML is not appropriate as

there is either an increase in density throughout the upper part of the profile or there is a

substantial density inversion indicating a poorly mixed layer. An example of this type of

profile is given in Figure 7.3 which is for CTD 70 (station 45).

Care needs to be exercised when making use of the concept of Mixed Layer Depth. It is

always possible to calculate the depth at which the density exceeds the surface by a certain

criterion. However, the details of the temperature, salinity and density profiles will indicate

whether this constitutes a properly defined mixed layer or it is merely some depth in a

profile of a poorly mixed column of water.

Figure 7.1: Exemplar CTD profile for MLD quality flag ‘A’

Profiles of temperature, salinity, potential density and output from the fluorometer are plotted for the upper 100 m of CTD profile 22 (station 9). The calculated MLD is indicated by the horizontal red line.

Figure 7.2: Exemplar CTD profile for MLD quality flag ‘B’


Figure 7.3: Exemplar CTD profile for MLD quality flag ‘C’


7.2 MLD Distributions

In addition to calculating the MLD we illustrate the range of MLD values in both geographic

space, Figure 7.4, and with respect to the mean temperature and salinity of the ML, Figure

7.5. We can see that the deepest MLs are dominated by those station which have a strong

Atlantic Water contribution in the surface waters; south of Iceland and in the Barents Sea

Opening. The deepest MLs generally have a mean salinity of > 34.8 which is often used

(particularly in polar waters) as being the lower limit for Atlantic Water. Even so, there are

some stations which have strong Atlantic characteristics which have rather shallow mixed

layers, e.g. the northern North Sea. In general those stations with shallow MLs are those

dominated by cool and fresh polar waters which form a strong and shallow gradient deeper

than which mixing processes are ineffective. Most of these stations are in the western part

of the Greenland Sea.

Figure 7.4: Geographic distribution of MLD during JR271

The value of MLD for those profiles with a ML flag of ‘A’ or ‘B’ along the cruise track.

Figure 7.5: Mixed Layer Depth as function of ML temperature and salinity

The value of MLD for those profiles with a ML flag of ‘A’ or ‘B’ plotted against the mean temperature and salinity calculated for the ML.

Table 7.1: Summary of Mixed Layer Depth properties at JR271 stations.

The flag status codes are: A = Well-defined ML, B = Poorly mixed ML, C = No ML evident in the profile. All ML depths derived by the density criterion algorithm are listed. Where the ML depth appears to vary from this by manual inspection of the profiles, this manual value is also listed.

Station CTD Depth of minimum density (m)

Mixed Layer Depth (m) algorithm

Mixed Layer Depth (m) manual

Mean ML in situ temp (°C)

Mean ML salinity Caution – see note

Mean ML pot. Density (kg m

-3)

Mean ML dissolved oxygen (µmol L

-1)

Caution – see note

FLAG

Notes

1 1 5 17 10.7 35.1 26.92 12 A Mainly temperature stratified



1 4 12 13 10.8 34.0 25.99 318 C Mainly temperature stratified


2 6 9 12 9.8 35.3 27.25 325 B Density inversion within ML


3 8 5 28 10.3 35.4 27.23 311 B Gradients in T, S throughout ML

3 9 7 57 50 10.4 35.4 27.22 309 A Mainly temperature stratified




5 13 9 25 22 10.3 35.2 27.05 307 A



6 16 12 38 30 10.5 35.2 27.05 305 A

6 17 11 32 10.5 35.2 27.04 322 C Continuous gradients in T and S

6 18 11 39 32 10.4 35.2 27.05 304 A

7 19 5 15 13 4.5 34.9 27.62 397 A


9 21 6 24 19 0.9 34.9 27.97 392 B Gradients in T, S throughout ML

9 22 4 37 30 0.8 34.9 27.97 372 A

trans 10 23 5 29 1.3 34.9 27.93 391 C Continuous gradients in T and S

10 24 4 45 37 1.5 34.9 27.95 363 A

10 25 4 32 22 1.5 34.9 27.95 362 A

10 26 5 C Density doesn't increase > 0.05 kg m^-3

10 27 4 33 30 1.6 34.9 27.95 388 B Gradients in T throughout ML

10 28 4 28 1.5 34.9 27.95 364 A


12 30 5 22 -1.5 33.3 26.76 384 B Gradients in T, S throughout ML

13 31 6 8 -1.5 32.3 26.01 368 C Density inversion and T,S gradients within ML



16 34 6 7 1.6 33.9 27.13 390 C Density inversion and T,S gradients within ML


18 36 4 9 -1.6 32.6 26.19 373 A Defined ML above the main pycnocline

18 37 4 12 -1.6 32.7 26.28 373 A

18 38 4 11 -1.5 32.6 26.20 375 A

18 39 5 12 -1.6 32.6 26.20 371 A



21 42 3 21 6.0 35.1 27.61 376 A


25 44 5 37 26 5.8 35.1 27.68 331 A

26 45 6 46 5.7 35.2 27.71 330 A

27 46 7 55 4.4 35.0 27.77 375 A


29 48 5 49 25 5.7 35.1 27.66 328 B Shallower ML down to 25m

30 49 3 39 6.5 35.0 27.47 318 B Gradients in T throughout ML


30 51 3 48 40 6.4 35.0 27.51 317 A

30 52 5 45 6.4 35.0 27.51 318 A




34 56 4 24 18 6.7 35.2 27.59 326 B Gradients in T, S in lower part of ML









42 65 4 16 12 6.9 34.9 27.38 329 A

42 66 3 18 6.9 34.9 27.37 334 A





NB: In the JR271 cruise report, section on CTD data processing there was an alignment problem for the oxygen sensor on the Stainless Steel CTD. The

cautionary note was “… caution should be applied when requiring high accuracy oxygen concentrations from this CTD.”

Further, lack of salinity bottles from the titanium CTD meant that no calibration correction could be applied to this instrument, again “Caution should be

applied when using high accuracy salinity from this CTD.”

8 Acknowledgements

Digital Ice Charts from Norwegian Ice Service was obtained from Nick Hughes at met.no. The sea ice

concentration (SIC) data was obtained from the University of Bremen (http://www.iup.uni-

bremen.de:8084/ssmisdata/asi_daygrid_swath/n6250/).

9 References

Hansen, B., and S. Østerhus (2000), North Atlantic-Nordic Seas exchanges, Prog. Oceanogr., 45(2), 109-208. Hickman, A., et al. (2012), Primary production and nitrate uptake within the seasonal thermocline of a stratified shelf sea, Marine Ecology Progress Series, 463, 39-57. Hopkins, T. S. (1991), The GIN Sea A synthesis of its physical oceanography and literature review 1972-1985, Earth Science Reviews, 30, 175-318. Kostianoy, A. G., et al. (2004), Physical Oceanography of Frontal Zones in the Subarctic Seas, Elsevier. Loeng, H. (1991), Features of the physical oceanographic conditions of the Barents Sea, Polar Research, 10(1), 5-18. Nilsen, J. E. Ø., and E. Falck (2006), Variations of Mixed Layer Properties in the Norwegian Sea for the Period 1948–1999, Prog. Oceanogr., 70(1), 58-90. Nilsson, J., et al. (2008), Liquid freshwater transport and Polar Surface Water characteristics in the East Greenland Current during the AO02 Oden expedition, Prog. Oceanogr., 78(1), 45-57. Rudels, B., et al. (2005), The interaction between water from the Arctic Ocean and the Nordic Seas north of Fram Strait and along the East Greenland Current: results from the Arctic Ocean-02 Oden expedition, J. Mar. Syst., 55, 1-30. Sanders, R., and M. R. Palmer (2013), JR271 Underway Data Processing, 4 pp, National Oceanography Centre, Liverpool. Schauer, U. (1995), The release of brine-enriched shelf water from Storfjord into the Norwegian Sea, J. Geophys. Res.-Oceans, 100(C8), 16,015-016,028. Spreen, G., et al. (2008), Sea ice remote sensing using AMSR-E 89 GHz channels, J. Geophys. Res.-Oceans, 113, C02S03. Thorpe, S. (2014), JR274 Physical Oceanographic Analyses, 24 pp, British Antarctic Survey.

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