NACLIM Deliverable D21.12
Deliverable title
Description of a monitoring system on the shallow East Greenland
shelf
This is a report describing the design of a new monitoring system to be
deployed on the East Greenland shelf
WP No.
2.1
Lead beneficiary:
WP title
Exchanges across the Greenland-Scotland-Ridge
Work duration
1)
12
x
NIOZ / Laura De Steur
15 October
Due delivery deadline:
2013
15
Actual delivery date: October
2013
R= report
P= prototype
Nature of the
deliverable
D= demonstrator
O= Other
PU = public
x
Dissemination
level
PP= restricted to other programme participants, including the
Commission services
RE= restricted to a group specified by the consortium, including the
Commission services
CO= confidential, only for members of the consortium, including the
Commission services
1) Work duration = project month
Lead beneficiary:
NIOZ
Laura De Steur
Other contributing
partners:
UHAM
Detlef Quadfasel team
UIB
K. Vǻge
UNIRES
S. Ǿsterhus
Page 1
Index
1. Executive summary ........................................................................................................... 3
2. Project objectives .............................................................................................................. 3
3. Detailed report on the deliverable ...................................................................................... 4
4. References ........................................................................................................................ 7
5. Dissemination and uptake ................................................................................................. 8
5.1 Dissemination .................................................................................................................. 8
5.2 Uptake by the targeted audience ...................................................................................... 8
6. The delivery is delayed:  Yes  No ............................................................................. 9
7. Changes made and difficulties encountered, if any............................................................ 9
8. Efforts for this deliverable .................................................................................................. 9
9. Sustainability ..................................................................................................................... 9
10. Dissemination activities ................................................................................................. 10
Description of the work package in the Description of Work (DOW) for reference .......... 11
Page 2
1. Executive summary
The Arctic Ocean is characterized by a large volume of freshwater stored in the upper ocean
originating from inflow of Pacific Water, input from the Siberian rivers, net precipitation, and
more recently, increases in sea-ice melt water. During the last decade a large amount of
freshwater has accumulated in the Arctic Ocean, particularly in the Canadian Basin but also in
the central Arctic. Estimates of the anomalous volume range from 1000 to 8000 km 3.
Freshwater anomalies from the Arctic released into the subpolar gyre in the North Atlantic
Ocean can alter upper ocean density and stratification, and potentially modify vertical motion
and hence the overturning circulation in the North Atlantic. Changes in the meridional
overturning circulation can ultimately influence the relatively mild climate we experience today in
Europe.
In order to quantify the amount of freshwater that presently flows from the Arctic through the
East Greenland Current (EGC) a mooring array of three moorings was initiated which may serve
as a basis for a future monitoring program near the Denmark Strait. This array will particularly
provide new information of the flow of freshwater on the shallow East Greenland shelf and adds
to existing knowledge of the shelf-break EGC in earlier years. The shelf is a hazardous region
for placing oceanic moorings since there are many icebergs and intensive fishing activities and
hence there are little data available from this region.
The present-day mooring array on the shelf at approximately 68̊N contains instrumentation to
measure the current velocities, pressure, salinity, and temperature and was deployed in 2013
for initially one year. These mooring data will be complemented with hydrographic data
(Conductivity, Temperature and Depth (CTD)) to incorporate vertical stratification between the
instruments which are at 80 m and 300 m (near the bottom) depth. Here we provide a report on
the design of these moorings which were deployed in August 2013. However, there are some
shortcomings related with the simple mooring set up that limit our ability to obtain exact flux
numbers which are discussed here. Hence, recommendations for future improvements of this
monitoring system are given.
2. Project objectives
With this deliverable, the project has contributed to the achievement of the following objectives
(see DOW Section B.1.1):
Page 3
Nr.
1.
Objective
Assessing the predictability and quantifying the uncertainty in
forecasts of the North Atlantic/Arctic Ocean surface state
2. Assessing the atmospheric predictability related to the North
Atlantic/Arctic Ocean surface state
3. Monitoring of volume, heat and fresh water transports across key
sections in the North Atlantic
4. Quantifying the benefit of the different ocean observing system
components for the initialization of decadal climate predictions
5. Establishing the impact of an Arctic initialization on the forecast
skill in the North Atlantic/European sector
6. Quantifying the impact of predicted North Atlantic upper ocean
state changes on the oceanic ecosystem
7. Quantifying the impact of predicted North Atlantic upper ocean
state changes on socioeconomic systems in European urban
societies
8. Providing recommendations for observational and prediction
systems
9. Providing recommendations for predictions of the oceanic
ecosystem
10. Disseminating the key results to the climate service community
and relevant endusers/stakeholders
11. Constructing a dataset for sea surface and sea ice surface
temperatures in the Arctic
Yes
No
X
X
X
X
X
X
X
X
X
X
X
3. Detailed report on the deliverable
3.1 Introduction
The liquid freshwater content of the Beaufort Gyre in the Arctic Ocean increased with
approximately 1000 km3 between 2003 and 2007 (Proshutinsky et al., 2009) and with 8000 km3
by 2008 (McPhee et al., 2009). Riverine water has contributed to the observed accumulation in
particularly the Canada Basin (Yamamoto-Kawai et al., 2009, Morrison et al., 2012) under
strong anticyclonic wind forcing for several years (Giles et al., 2012). Freshwater increases have
also been observed in the central Arctic (Rabe et al., 2011), the Eurasian Basin (Timmermans
et al., 2011) and the Lincoln Sea (de Steur et al., 2013). Freshwater leaves the Arctic Ocean as
liquid freshwater and as sea ice through Fram Strait and the Canadian Arctic Archipelago
(Dickson et al., 2007). Anomalies in export have been related with atmospheric pressure and
circulation patterns in the high Arctic (Karcher et al., 2005, Jahn et al., 2009) and can be traced
down as far south as the North Atlantic (Dickson et al., 1988). External freshwater anomalies
Page 4
(e.g. large discharges from the Arctic or ice sheets) are thought to affect the subpolar gyre by
altering the upper ocean stratification and buoyancy which inhibits vertical motion and therefore
weaken the Atlantic Meridional Overturning Circulation (Manabe and Stouffer, 1999). It is
therefore essential to observe the present-day Arctic-Subarctic freshwater fluxes and changes
therein with respect to earlier estimates, in order to anticipate on potential future effects.
Presently our knowledge of year-round liquid freshwater flux in the East Greenland Current
between 1997 and 2008 comes from a mooring array in Fram Strait at 78.8°N (de Steur et al.,
2009). However, a portion of the freshwater in the EGC is thought to be advected into the
Nordic Seas, there is a large flux of sea ice in Fram Strait, and there is a substantial portion of
freshwater on the shelf contributing to southward flux as well. We therefore have little
knowledge of the net freshwater flux entering the subpolar gyre across the Greenland-Scotland
Ridge. Here we report on a new monitoring system that is developed under NACLIM that aims
to reduce one of the aforementioned uncertainties: the freshwater flux on the East Greenland
shelf near Denmark Strait.
3.2 Present mooring array on the East Greenland shelf
In order to increase our knowledge of the freshwater flux in the East Greenland Current (EGC)
north of Denmark Strait measurements are needed on the continental shelf where potentially a
substantial portion of southward transport of freshwater to the North Atlantic exists. Figure 1
illustrates the study region. The shelf region is characterized by ice bergs from the Greenlandic
glaciers, sea-ice cover for at least 6 months and by fishing activities (trawling) and is hence a
region from which it is difficult to install instrumentation to obtain continuous observations.
A relatively simple mooring array was deployed in August 2013 as a pilot survey of the flux on
the shelf. This small array consists of one bottom frame containing an 75 kHz Acoustic Doppler
Current Profiler (ADCP) and an SBE 37-SM Microcat, a two 200 m tall vertical moorings with
two ADCPs (600 and 1200 kHz respectively), an RCM-8 current meter and three SBE 37-SM
Microcats. The intention was to also add a previously deployed fourth mooring on the shelfbreak (~500 m tall), however, since this mooring was damaged and not recovered from the
previous year, the instruments were lost and it could not be included in the array described
here.
Figure 2 shows the vertical set up of the three moorings presently on the shelf. The
bottom frame (KGA12) is designed to protect the ACDP from icebergs and trawling. The two
shallow vertical moorings (KGA13 and KGA14) extend up to 80 m below the surface which is as
Page 5
high in the water column as we wanted to place our instruments with respect to the risks related
with icebergs. The upward looking ADCPs measure velocities towards the surface and allows
us to estimate the upper ocean flux. The current meters measure each hour and the Microcats
measure salinity, temperature and pressure each 15 minutes. These moorings shall be in place
for one year and they all contain ARGOS beacons. Once recovered in August 2014 the data
shall be processed and quality controlled and merged with hydrographic data to improve vertical
stratification. In addition, regression of the time series of two neighbouring moorings (KGA12
and one east of it, not shown here) from an array that was present on the shelf slope in 20112012 could provide an eastward extension of the flow field on the shelf slope and add to the flux
estimate on the East Greenland shelf.
3.3 Future improvement of a monitoring array in the EGC and on the shelf
The present array has two weaknesses: 1) the measurements (particularly of salinity) do not
span the water column close to the surface (i.e. above 80 m) in order to stay away from
icebergs but it is here where the largest amount of freshwater resides, and 2) the lateral spacing
between the two moorings is of low resolution (20 km apart) which is larger than the Rossby
radius of deformation, and hence not all features and variability of the current on the ~60 km
broad shelf can be captured. Here we provide some recommendations to improve a future
monitoring system in the EGC and particularly on the shelf.
The first difficulty, to measure closer to the surface, can be approached by including
mooring extensions with TC sensors (Temperature-Conductivity) that are flexible enough to
bend but also strong enough to not break under large strain from ice. An example of this is
shown in Figure 4. The so-called Ice Snake from Aanderaa connects the different TC sensors
with a conducting cable such that the data is stored in a data-logger with floatation at larger
depth below the surface. The top of the Ice Snake contains a Pressure sensor too such that
information is obtained about how often and how deep the top of the line is pushed down. The
second problem of too low resolution of the array requires simply more instrumentation and
moorings. For better resolution of the EGC on the shelf and the shelf slope, an array with at
least 5 moorings are recommended for one year to obtain a time series of the current structure
and variability on the whole shelf.
In addition, higher resolution and improved insight in the spatial and temporal variability of
salinity and temperature on the shelf could be obtained by the introduction of a sea glider. The
glider could initially be deployed and tested for a period of two weeks during an oceanographic
Page 6
cruise in the area. The use of a glider in winter, when the region is covered with sea ice, would
be the ultimate goal to obtain more, highly essential winter data.
Figure 3: The Aanderaa Ice Snake with Temperature-Conductivity (TC) sensors
4. References
Dickson et al., 1988. The "Great Salinity Anomalies" in the northern North Atlantic, 1968- 1982, J. Phys.
Oceanogr., 20, pages 103–151.
Dickson et al., 2007. Current estimates of freshwater flux through Arctic and subarctic seas,
Prog.
Oceanog., 73, pages 210–230.
Giles et al., 2012. Western Arctic Ocean freshwater storage increased by wind-driven spin-up of the
Beaufort Gyre, Nature Geoscience, doi:10.1038/NGEO1379.
Jahn et al., 2009. Effect of the large-scale atmospheric circulation on the variability of the Arctic Ocean
freshwater export, Clim. Dynam., doi:10.1007/s00382-009-0558-z.
Karcher et al., 2005. Arctic Ocean change heralds North Atlantic freshening, Geophys. Res.
32, L21606, doi:10.1029/2005GL023861.
Page 7
Lett.,
Manabe and Stouffer, 1999. The role of thermohaline circulation in climate, Tellus, 51A-B, 91-109.
doi:10.1034/j.1600-0889.1999.00008.x
McPhee et al., 2009. Rapid change in freshwater content of the Arctic Ocean, Geophys.. Res. Lett., 36,
L10602, doi: 10.1029/2009GL037525.
Morrison et al., 2012. Changing Arctic Ocean freshwater pathways, Nature, 481, doi:
10.1038/nature10705.
Proshutinsky et al., 2009. The Beaufort Gyre freshwater reservoir: State and variability from
observations, J. Geophys. Res., 114, C00A10, doi:10.1029/2008JC005104.
Rabe et al., 2011. An assessment of pan-Arctic Ocean freshwater content changes from the
1990s
to the IPY period, Deep-Sea. Res. I, 58, doi: 10.1016/j.dsr.2012.12.002.
de Steur et al., 2009. Freshwater fluxes in the East Greenland Current: A decade of observations.
Geophys. Res. Lett. 36, doi:10.1029/2009GL041278
de Steur et al., 2013. Hydrographic changes in the Lincoln Sea in the Arctic Ocean with focus on an
upper ocean freshwater anomaly between 2007-2010. J. Geophys. Res. Accepted. doi:
10.1002/jgrc.20341
Timmermans et al., 2011. Surface freshening in the Arctic Ocean’s Eurasian Basin: An apparent
consequence of recent change in the wind-driven circulation, J. Geophys. Res., 116, C00D03,
doi:10.1029/2011JC006975.
Yamamoto-Kawai et al., 2009. Surface freshening of the Canada Basin, 2003-2007: River
runoff
versus sea ice meltwater, J. Geophys. Res., 114, C00A05, doi:10.1029/2008JC005000.
5. Dissemination and uptake
5.1 Dissemination
Peer reviewed articles:
None so far.
Publications in preparation OR submitted:
In preparation
OR submitted?
Title
All authors
Title of the periodical
or the series
Is/Will open access be provided
to this publication?
Planned: 2014
Freshwater flux on the
East Greenland shelf at
68.3°N
L. de Steur and others
Ocean Sciences
Discussion Paper
Yes
5.2 Uptake by the targeted audience
According to the DOW, your audience for this deliverable is:
Page 8
The general public (PU)
X
The project partners, including the Commission services (PP)
A group specified by the consortium, including the Commission services (RE)
This reports is confidential, only for members of the consortium, including the Commission services
(CO)
How are you going to ensure the uptake of the deliverables by the targeted audience?
The report will be sent around to NACLIM partners and will be published on the NACLIM
website.
6. The delivery is delayed:  Yes
 No
7. Changes made and difficulties encountered, if any
If you have encountered difficulties or made changes, please write four lines of explanation.
One planned mooring for 2013-2014 could not be redeployed in the shelf-slope EGC since the
mooring that was there the year before was lost and thus the instrumentation that would be
used for this mooring was not available. The mooring was likely lost in early 2013 due to an
iceberg encounter. This illustrates exactly how difficult it is to obtain measurements from this
region.
8. Efforts for this deliverable
How many person-months have been used up for this deliverable?
Partner
Person-months
NIOZ
UHAM
UIB
UNIRES
Total
0.5
1
1
2
4.5
Period covered
From 01/11/2012- to 15/10/2013
From 01/11/2012- to 15/10/2013
From 01/11/2012- to 15/10/2013
From 01/11/2012- to 15/10/2013
Total estimated effort for this deliverable (DOW) was 4.5 person-months.
9. Sustainability
The present system performance will be evaluated in D21.21, daily time series of the freshwater
flux will be delivered to the NACLIM data base under D21.34, and ultimately an assessment of
the year-round freshwater flux on the shelf will be added to D21.53.
Page 9
10. Dissemination activities
Add the dissemination activities (starting from November 2012) related to this deliverable.
Fill in the table below in all its parts.
[3] Indicate here which type of activities from the following list: Publications, conferences, workshops, web, press releases, flyers, articles published
in the popular press, videos, media briefings, presentations, exhibitions, thesis, interviews, films, TV clips, posters, Other.
[4] Indicate here which type of audience: Scientific Community (higher education, Research), Industry, Civil Society, Policy makers, Medias ('multiple
choices' is possible.
Type of
activities[3]
Main leader
Title (+website
reference)
Date
Place
Type of
audience[4]
Presentation
Laura de
Steur
(NIOZ)
Freshwater
components in
the East
Greenland
Current
between
Denmark and
Fram Strait
2012
22-26 July
2013
Knowledge of
the future/North
Atlantic and
Climate Change,
at IUGG
Meeting,
Gothenburg
(SE)
Scientific
Community
Page
10
Size of
audience
Countries
addressed
Have you
sent a copy
to Chiara
(project
office) via
mail?
All
Yes
Description of the work package in the Description of Work (DOW) for
reference
Objectives WP 2.1
• To modify existing measuring systems in order to make them more accurate and more sustainable for
long-term monitoring of the exchanges across the Greenland-Scotland Ridge
• To provide updated time series of mass and heat transport for all the Atlantic inflow branches to the
Nordic
Seas and mass and freshwater transport for the most important overflow branches
• To estimate the variability and identify any potential trends in these flows.
Description of work and role of the partners
The experience from previous experiments has revealed gaps in the monitoring systems, but also
indicated ways to make them less costly to run. At the project start, these changes will be implemented
and
measurements acquired during the field phase of the project. The mooring arrays for the Atlantic inflows
and
the overflows will only slightly be modified, but the arrays capturing the freshwater fluxes on the East
Greenland
Shelf and those covering the overflow sources upstream are new developments.
Task 2.1.1 Monitoring the inflow of Atlantic water to the Nordic Seas
a) The existing monitoring systems across the three Atlantic inflow branches will be modified in order
to enhance
the accuracy and make them more sustainable as long-term monitoring systems. [UiB, MRI, HAV, MSS, SAMS].
The output will be the Deliverable D8, D21, D34, D57
b) Monitoring will be maintained during the field phase of NACLIM and time series of hydrographic
properties
and volume transport of the three Atlantic inflow branches generated annually. [UiB, MRI, HAV, MSS,
SAMS].
The output will be the Deliverable D21, D34, D57
c) Based on the updated time series, variability and potential trends of the inflow branches will be
estimated and
evaluated in relation to available model results. [UniRes, UiB, MRI, HAV, MSS, SAMS] The output will be
the
Deliverable D51, D59
d) At the project conclusion, a design for a sustainable long-term inflow monitoring system will be
recommended.
[UniRes, UiB, MRI, HAV, MSS] The output will be the Deliverable D59
Task 2.1.2 Monitoring the dense water overflow across the Greenland-Scotland Ridge
a) Denmark Strait overflow. [MRI, UHAM] The output will be the Deliverable D21, D34, D57
b) The existing ADCP mooring array in the Faroe Bank Channel (FBC) will be maintained during the field
phase
of NACLIM and time series of FBC-overflow properties and transport generated annually. [HAV, UiB and
UHAM]
The output will be the Deliverable D21, D34, D57
c) The overflow across the shallow Wyville Thomson Ridge will be monitored downstream of the ridge.
[SAMS]
The output will be the Deliverable D21, D34, D57, D44, D55
d) Based on the updated time series, variability and potential trends of the monitored overflow branches
will be
Page
11
estimated and evaluated in relation to available model results. [UiB, UHAM, MRI, HAV, SAMS] The output
will be
the Deliverable D51, D59
e) At the project conclusion, a design for a sustainable long-term overflow monitoring system will be
recommended. [UniRes, UiB, UHAM, MRI, HAV, SAMS] The output will be the Deliverable D59
Task 2.1.3 Sources of the Denmark Strait Overflow
A skeleton mooring array based on the currently deployed full Kogur array will be maintained to monitor
the
deep East Greenland Current [UiB] and the North Icelandic Jet (American partner, WHOI), the two
identified
pathways of Denmark Strait Overflow Water. The eastern part of the Kogur section is regularly occupied
by CTD
cruises [MRI]. Along with the ongoing mooring program at the Denmark Strait sill [MRI, UHAM], these
concurrent
measurements will be an important step towards determining the relative contributions of the two sources
of
overflow water. The output will be the Deliverable D21, D34, D57, D44, D55
Task 2.1.4 Freshwater fluxes on the East Greenland Shelf
The extension of the Kogur array onto the Greenland shelf will be maintained and expanded in order to
measure
the transport of fresh water by the East Greenland Current [NIOZ]. The deployment will initially take
the form of
an innovative pilot project in which the technology required for upper-ocean measurements in ice-covered
waters
already employed (e.g. in the Davis Strait) will be further developed. The output will be the
Deliverable D8, D12,
D21, D32, D53, D21, D34, D57, D44, D55
Interaction with other work packages
WP2.1 addresses the exchanges of heat and mass across the Greenland-Scotland Ridge and will provide data
(input) to activities in WP’s 1.1, 1.2, 3.1, 3.2, 4.1 and 4.2.
WP 2.1 will exchange data and observations technology with WP 2.2: WP2.2 addresses the assessment and
improvement of the observing system south of the Greenland/Scotland Ridge. WP2.1 proposes to perform
similar work but for the region north of the Greenland Scotland Ridge .
For more information on interactions with WP 2.3, please see the exhaustive explanation in WP2.3.
WP 2.1 and WP 3.1 will jointly investigate the importance of initializing the density structure in the
overflow
region: the importance of initializing the density structure in the overflow region will be investigated
in
collaboration with WP 2.1 by providing the information from the “perfect” model experiments obtained
in WP3.1.
Data on exchanges across the Greenland/Scotland Ridge from WP2.1 is required as input to WP3.2.
List of deliverables
D21.12) Description of a monitoring system on the shallow East Greenland shelf: This is a report
describing the
design of a new monitoring system to be deployed on the East Greenland shelf. [month 12] Who is in
charge: NIOZ
Page
12
D21.21) Daily time series data of mass, heat and freshwater transports across the Greenland-ScotlandRidge-1:
Full title: Daily time series data of mass, heat and freshwater transports across the
Greenland-Scotland-Ridge-1st Batch This deliverable consists of time series of mass, heat and freshwater
transport across the GSR calculated on the first year of observations. [month 18] Who is in charge :
UIB
D21.32) Report on system performance: a monitoring system on the shallow East Greenland shelf: This is a
report on the performance of the monitoring system described under D12. [month 30] Who is in charge:
NIOZ
D21.34) Daily time series data of mass, heat and freshwater transports across the Greenland-ScotlandRidge-2:
Full title: Daily time series data of mass, heat and freshwater transports across the
Greenland-Scotland-Ridge-2nd Batch. This deliverable consists of time series of mass, heat and
freshwater
transport across the GSR calculated on the second year of observations. [month 30] Who is in charge:
UIB
D21.53) Assessment of the freshwater transport in the East Greenland Current at the Kogur array:
Assessment
of the freshwater transport in the East Greenland Current at the Kogur array [month 44] Who is in
charge: MRI
D21.57) Daily time series data of mass, heat and freshwater transports across Greenland-Scotland-Ridge3:
Daily time series data of mass, heat and freshwater transports across the Greenland-Scotland-Ridge- 3rd
Batch
[month 44] Who is in charge: UIB
Page
13
Person-months per participant
Person-months (PM)
Deliverable title
Lead
benef
iciary
Tot
PM
UH
AM
DQ
Description of a monitoring
system on the shallow East
Greenland shelf
NIOZ
4.5
Daily time series data of
mass, heat and freshwater
transports across the
Greenland-Scotland-Ridge1st Batch
Report on system
performance: a monitoring
system on the shallow East
Greenland shelf
Daily time series data of
mass, heat and freshwater
transports across the
Greenland-Scotland-Ridge2nd Batch
Assessment of the
freshwater transport in the
East Greenland Current at
the Kogur array
Daily time series data of
mass, heat and freshwater
transports across the
Greenland-Scotland-Ridge3rd Batch
UIB
MPG
UPMC
UiB
UniRE
S
1
1
2
28
3
9
1
NIOZ
4.5
1
1
2
UIB
27
3
9
1
MRI
11
1
1
1
UIB
27
3
9
1
Page
14
GEOM
AR
DMI
HAV
FMI
MRI
NIOZ
SAMS
NER
C/
ICPO
NERS
C
VITO
GIM
DTU
MSS
0.5
4
6
1
2
2
3
1
3
1
0.5
4
6
6
4
6
2