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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.
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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 6.2: SIC (upper) and SIM (lower) for station 13 (overlaid) ........................................... 15
Figure 6.3: SIC (upper) and SIM (lower) for station 14 (overlaid) ........................................... 16
Figure 6.4: SIC (upper) and SIM (lower) for station 15 (overlaid) ........................................... 17
Figure 6.5: SIC (upper) and SIM (lower) for station 16 (overlaid) ........................................... 18
Figure 6.6: SIC (upper) and SIM (lower) for station 17 (overlaid) ........................................... 19
Figure 6.7: SIC (upper) and SIM (lower) for station 18 (overlaid) ........................................... 20
Figure 6.8: SIC (upper) and SIM (lower) for station 44 (overlaid) ........................................... 21
Figure 6.9: SIC (upper) and SIM (lower) for station 45 (overlaid) ........................................... 22
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)
Figure 6.2: SIC (upper) and SIM (lower) for station 13 (overlaid)
Figure 6.3: SIC (upper) and SIM (lower) for station 14 (overlaid)
Figure 6.4: SIC (upper) and SIM (lower) for station 15 (overlaid)
Figure 6.5: SIC (upper) and SIM (lower) for station 16 (overlaid)
Figure 6.6: SIC (upper) and SIM (lower) for station 17 (overlaid)
Figure 6.7: SIC (upper) and SIM (lower) for station 18 (overlaid)
Figure 6.8: SIC (upper) and SIM (lower) for station 44 (overlaid)
Figure 6.9: SIC (upper) and SIM (lower) for station 45 (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’
Profiles of temperature, salinity, potential density and output from the fluorometer are plotted for the upper 100 m of CTD profile 08 (station 3). The calculated MLD is indicated by the horizontal red line.
Figure 7.3: Exemplar CTD profile for MLD quality flag ‘C’
Profiles of temperature, salinity, potential density and output from the fluorometer are plotted for the upper 100 m of CTD profile 70 (station 45). The calculated MLD is indicated by the horizontal red line.
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 2 1 11 10.6 35.1 26.94 12 A Mainly temperature stratified
1 3 3 12 10.7 35.1 26.93 12 A Mainly temperature stratified
1 4 12 13 10.8 34.0 25.99 318 C Mainly temperature stratified
1 5 3 15 10.7 35.1 26.93 12 A Mainly temperature stratified
2 6 9 12 9.8 35.3 27.25 325 B Density inversion within ML
2 7 10 15 10.2 35.3 27.18 325 A Mainly temperature stratified
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
4 10 4 48 10.6 35.3 27.09 336 B Gradients in T, S throughout ML
4 11 6 54 10.6 35.3 27.10 316 B Gradients in T, S throughout ML
5 12 5 28 10.2 35.2 27.05 320 B Gradients in T, S throughout ML
5 13 9 25 22 10.3 35.2 27.05 307 A
6 14 10 35 10.7 35.2 27.03 307 B Gradients in T, S throughout ML
6 15 14 35 10.6 35.3 27.04 306 B Gradients in T, S throughout ML
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
8 20 13 15 3.4 35.0 27.87 369 C Continuous gradients in T and S
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
11 29 5 40 3.3 35.0 27.83 412 C Continuous gradients in T and S
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
14 32 5 6 -1.5 32.4 26.03 362 C Density inversion and T,S gradients within ML
15 33 6 8 -1.4 32.5 26.14 363 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
17 35 5 6 0.2 33.3 26.73 395 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
19 40 7 9 2.4 34.2 27.27 378 C Density inversion and T,S gradients within ML
20 41 5 20 4.2 35.1 27.84 360 C Continuous gradients in T and S
21 42 3 21 6.0 35.1 27.61 376 A
22 43 6 8 4.9 34.5 27.31 353 C Density inversion and T,S gradients within ML
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
28 47 4 18 1.0 34.4 27.56 367 B Gradients in T, S throughout ML
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 50 3 48 6.5 35.0 27.48 317 B Gradients in T, S 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
31 53 4 24 7.1 34.6 27.06 331 B Gradients in T, S throughout ML
32 54 5 16 7.8 35.0 27.26 312 C Continuous gradients in T and S
33 55 5 9 8.3 35.0 27.22 330 C Density inversion and T,S gradients within ML
34 56 4 24 18 6.7 35.2 27.59 326 B Gradients in T, S in lower part of ML
35 57 5 26 6.7 35.2 27.61 328 B Gradients in T throughout ML
36 58 4 33 5.8 35.1 27.70 339 B Gradients in T throughout ML
37 59 4 18 4.0 34.9 27.73 377 C Continuous gradients in T and S
38 60 5 12 3.2 34.4 27.36 361 B Gradients in T, S throughout ML
38 61 5 7 2.9 34.4 27.42 366 C Continuous gradients in T and S
39 62 5 15 4.2 34.9 27.68 394 C Continuous gradients in T and S
40 63 4 20 4.2 34.8 27.62 356 B Gradients in T throughout ML
41 64 5 7 5.6 34.8 27.44 345 C Density inversion and T,S gradients within 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
43 67 4 13 7.6 34.7 27.12 332 B Gradients in T, S throughout ML
44 68 6 7 3.7 33.0 26.26 355 C Density inversion and T,S gradients within ML
44 69 5 7 4.2 33.3 26.42 356 C Density inversion and T,S gradients within ML
45 70 6 7 4.6 33.5 26.50 352 C Density inversion and T,S gradients within ML
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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