NACLIM Deliverable D23.15
Definition of Matrix containing key ocean quantities & ass. errors for direct modelobs. Comparison
Deliverable title
(Definition of Matrix containing key ocean quantities & ass. errors for direct modelobs. comparison: Full title: Definition of Matrix containing key ocean quantities and
associated errors to be used for a direct model-observation comparison. This
deliverable consists of a description of the rationale behind the choice of the integral
key parameters to be used when assessing the agreement between observed and
modeled estimates of fluxes and storages)
WP No.
2.3
WP title
Joint model-observational data comparison
Work duration
1)
Lead beneficiary:
12
FMI
15 Sept.
Due delivery deadline:
2013
Actual delivery date:
18
October
2013
R= report
Nature of the
deliverable
P= prototype
D= demonstrator
X
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:
Other contributing
partners:
FMI
Bert Rudels
UHAM
Detlef Quadfasel
NERC/NOC
Gerard McCarthy
Page 1
Index
1. Executive summary ........................................................................................................... 3
2. Project objectives .............................................................................................................. 3
3. Detailed report on the deliverable ...................................................................................... 4
4. References ........................................................................................................................ 8
5. Dissemination and uptake ................................................................................................. 8
5.1 Dissemination .................................................................................................................. 8
5.2 Uptake by the targeted audience .................................................................................... 10
6. The delivery is delayed:  Yes  No ........................................................................... 11
7. Changes made and difficulties encountered, if any.......................................................... 11
8. Efforts for this deliverable ................................................................................................ 11
9. Sustainability ................................................................................................................... 11
10. Dissemination activities ................................................................................................. 13
Page 2
1. Executive summary
This deliverable provides a framework for comparison between observations and model results
pertaining to the Atlantic Meridional Overturning Circulation. Since scales and resolution of data
collected from observations and those obtained from numerical model simulations differ, only
integral measures can be applied. Two classes of parameters are chosen, scalar parameters
such as temperature (heat), salinity (freshwater) and depth, heat and freshwater content in
different basins in the North Atlantic and vector parameters like fluxes of volume, heat and
freshwater. The chosen parameters are related to the local heat and freshwater exchange
between the ocean and atmosphere in the different basins such as the seasonal and annual
variations of the mixed layer depth and temperature. The selected parameters should be simple
to obtain and still provide valuable information. The model and observational time series, and
their error estimates, will be compared and the mean values, range of variability, dominant
periods and possible trends determined and compared. These comparisons constitute the main
task for the subsequent deliverables in this work package.
2. Project objectives
With this deliverable, the project has contributed to the achievement of the following objectives
(see DOW Section B.1.1):
Nr.
1.
2.
3.
4.
5.
6.
Objective
Assessing the predictability and quantifying the uncertainty in
forecasts of the North Atlantic/Arctic Ocean surface state
Assessing the atmospheric predictability related to the North
Atlantic/Arctic Ocean surface state
Monitoring of volume, heat and fresh water transports across key
sections in the North Atlantic
Quantifying the benefit of the different ocean observing system
components for the initialization of decadal climate predictions
Establishing the impact of an Arctic initialization on the forecast
skill in the North Atlantic/European sector
Quantifying the impact of predicted North Atlantic upper ocean
state changes on the oceanic ecosystem
Page 3
Yes
No
X
X
X
X
X
X
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 end users/stakeholders
11. Constructing a dataset for sea surface and sea ice surface
temperatures in the Arctic
X
7.
X
X
X
X
3. Detailed report on the deliverable
General
Observations only describe the present and past states of an investigated system and through
prolonged time series they can reveal variability on seasonal, annual and decadal time scales.
They may, if the time series are long enough, identify trends and extraordinary events. They
cannot predict the future states of the system, how stable it is and how rapidly it may evolve. To
achieve this, theoretical concepts and models are required, which from known, prescribed or
calculated, forcing can follow and project the evolution of the system. The theoretical concepts
used are, however, hypotheses, not truths, and numerical simulation models are imperfect tools
and their power and accuracy are not yet sufficiently well documented. Therefore a comparison
between observations and model performances is critical and has been given high priority in
NACLIM.
There are also fundamental differences between observations and numerical model data.
Classical ship born observations and those from moored instrumentation are limited to either
small time slots or to localized areas. They are usually concentrated on key areas such as
energetic boundary currents or sites of intense water mass modification. In contrast, model
outputs cover the ocean on a much larger scale and continuously in time, but they lack the
Page 4
usually lack the high spatial resolution to resolve the energetic features. Consequently data from
the two systems can be compared only in their integral quantities and not in a localized way.
The comparison, by necessity, involves the past, not the future. Model outputs from
specific areas and time periods, selected because of their relevance and because of the
availability of observations, are compared with existing measurements. The forcing is known
and the model derived hydrographic fields, circulation and transports can be obtained and
compared with those observed. Two basic oceanographic parameters are examined, water
mass characteristics, heat and freshwater content, and transports of volume, heat and
occasionally freshwater.
Water masses
The water mass properties are determined in the interior of different basins and eight major
areas or basins are chosen: north-eastern Atlantic, the Iceland Basin, the Irminger Basin and
the Labrador Sea in the North Atlantic, and the Norwegian Basin, the Lofoten Basin, the
Greenland Sea and the Iceland Sea north of the Greenland-Scotland Ridge. Areas in the centre
of the basins that comprise most of the available observations are selected and the overlapping
grid points in the models are used to determine the corresponding parameters.
The second step is to determine the possibly varying density surface that separates the
northward flowing warm upper limb of the Meridional Overturning Circulation from the denser
southward flowing lower limb is determined. When this is done the maximum depth and the
temperature and salinity of the mixed layer in winter are estimated. The maximum seasonal
heat content (mean temperature) above this depth is then computed, relative to the temperature
in winter. The corresponding freshwater content can also be determined. This describes the
variations in the water column taking place above the permanent pycnocline in different parts of
the North Atlantic. In addition the thickness and the heat and freshwater contents of the layer
between the permanent pycnocline and the separating density surface are estimated. This layer
Page 5
defines the properties of the water that moves northward and still may provide heat to the
atmosphere downstream of the studied position.
For the lower limb of the Meridional Overturning Circulation the thickness, heat and
freshwater content between the separating density surface and 2000 dbar, which is the
approximate depth limit of the Labrador Sea water and also the depth of the ARGO profiles,
time series are determined that show the properties of the southward flowing dense water
produced south of the Greenland-Scotland Ridge (only for the northeast Atlantic, Iceland Basin,
Irminger Basin and the Labrador Sea). North of the Greenland Scotland Ridge the winter mixed
layer is expected to penetrate through the separating density surface and directly provide water
to the lower circulation limb through the overflows.
The foci will be on how well the models capture the observed variability, but also the
mean fields, produced by the models, will be examined and compared with the mean fields
derived from the observations and from the climatology (Levitus and Boyer, 1994). The temporal
variations of the proposed parameters are evaluated from available observations and time
series, e.g. Argo floats, hydrographic stations, and the time evolutions of the same parameters
at the same positions are then determined in the models. This gives time series of the annual
variations in winter mixed layer, depth and properties, seasonal heat storage, and the properties
of the deeper part of the northward moving limb south of the Greenland-Scotland Ridge. Below
the separating density surface the variability of thickness and heat content (possibly freshwater
content) in the dense waters formed south of the Greenland-Scotland Ridge are estimated from
observation and models. North of the sill the winter mixed layer and the layers below feed
directly into the overflow water.
Variability, standard deviations, possible significant periods and possibly existing trends
in the two time series can then be compared and evaluated.
From Levitus and Boyer (1994) mean values and standard deviations of the same
parameters are determined for the entire deep part of the different basins and compared with
Page 6
the mean values and standard deviations at the chosen grid points. This allows for estimating
possible effects of lateral displacements of water masses within the basins, which may show up
and erroneously be interpreted as time evolution at the grid points.
Transports
The observations available within NACLIM comprise the northward and southward transports of
volume and heat and freshwater of the overflows across the Greenland-Scotland Ridge, the
southward flow in the deep western boundary current along the Labrador Sea slope and, in
collaboration with RAPID, the transports across 26oN. Because the exchanges across the ridge
and the flows in the deep northern/western boundary currents are very localised, the
comparison will be between the magnitudes and the variability of the transports derived by the
models. The exact location of the strongest flow will not be considered in the comparison.
The transport of warm water into the Nordic Seas, and eventually to the Arctic Ocean,
from models are perhaps best be determined at the Svinøy section just north of the ridge, where
most of the northward flow entering the Nordic Sea on both sides of the Faroe Islands is known
to pass. There also exist local observations of the transports across the Svinøy section. Another
important addition would be observations of the fluxes of the slope current across the Ellett line
south of the sill.
The variability of the strength and properties of the overflows observed downstream of
Faroe Bank Channel and Denmark Strait will be compared to the model outputs. Furthermore,
the evolution of the overflow water in the northern/western deep boundary current from the
Faroe Bank Channel and the Irminger Sea south of Denmark Strait to the Labrador Sea will be
estimated from both observations and models. The changes in density and TS characteristics of
the two overflows as they reach the Labrador Sea are used to estimate the entrainment of
ambient water south of the sills of the Greenland-Scotland Ridge, which are then compared with
the entrainment rates determined, or used, by the models.
Page 7
For the RAPID array the time series of the total northward and southward overturning
transports within a constraint of zero mass transport are determined as well as the northward
heat and freshwater fluxes. Volume and heat fluxes in the lower limb are also estimated, relative
to the same reference temperature, to obtain the variability of the northward heat transport.
These observational results are compared with the corresponding model results and the
variability, possible periods and trends are determined for the different time series. The time
series of the different parameters obtained from observations and models are analysed, as well
as the differences in mean values, variability and significant periods, if any, and trends, if any,
and the possible existence of extreme events.
4. References
Levitus, S., & Boyer, T. P. (1994). World Ocean Atlas 1994. Volume 4. Temperature (No. PB-95-270112/XAB; NESDIS--4). National Environmental Satellite, Data, and Information Service,
Washington, DC (United States).
5. Dissemination and uptake
5.1 Dissemination
Peer reviewed articles:
Title
Main author
All authors
Title of
the
periodica
l or the
series
Number,
date or
frequency
Publish
er
Atmosphe
re drives
recent
interannua
l
variability
of the
Altantic
C. D. Roberts;
J. Waters; K.
A. Peterson;
M. Palmer; G.
D. McCarthy;
E. FrajkaWilliams and
K. Haines
Geoph In press
ysical
Resear
ch
Letters
Amer
ican
Geop
hysic
al
Unio
n
Plac
e of
publ
icati
on
Check the NACLIM „Dissemination Plan“ on the open access requirements:
http://naclim.zmaw.de/Deliverables.2224.0.html
1
Page 8
Year of
publication
2013
Permanent
identifiers[1]
DOI
Is/Will open
access
1provided to
this
publication?
Yes, green
OA
meridional
overturnin
g
circulation
at 26.5ºN
Observed
decline of
the
Atlantic
Meridiona
l
Overturnin
g
Circulatio
n 2004 to
2012
D. A. Smeed,
G. McCarthy,
S. A.
Cunningham,
E. FrajkaWilliams, D.
Rayner, W. E.
Johns, C. S.
Meinen, M.
O. Baringer,
B. I. Moat, A.
Duchez, and
H. L. Bryden
Ocean
Scienc
e
Discus
sions
10
Europ
ean
Geop
hysic
al
Unio
n
2013
doi:10.51
94/osd10-16192013
Yes, green
OA
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?
In revision
Intra-seasonal
variability of the
deep Western
Boundary Current
in the western
subpolar North
Atlantic
Fischer, J., J.
Karstensen, R.
Zantopp, M. Visbeck,
A. Biastoch, E.
Behrens, C. Böning, D.
Quadfasel , K.
Jochumsen, H.
Valdimarson, S.
Jónsson, S. Bacon, P.
Holliday, S. Dye, M.
Rhein, C. Mertens
Progress in
Oceanography
Yes, green OA
Submitted
to Climate
Dynamics
Historical
analogues of the
recent extreme
minima observed in
the Atlantic
meridional
overturning
Adam T. Blaker; Joel J- Climate Dynamics
M. Hirschi; Gerard
McCarthy; Bablu
Sinha; Sarah Taws;
Robert Marsh; Andrew
Coward ; Beverly de
Cuevas
Page 9
Yes, green OA
circulation at 26N
In press
Chapter 17: The
Cecilie Mauritzen, Bert
Arctic and subarctic Rudels, John Toole
oceans/seas
accepted
Arctic ocean
circulation,
processes and water
masses: a
description of
observations and
ideas with focus on
the period prior to
the International
Polar Year 20072009
Circulation and
transformation of
Atlantic water in
the Eurasian Basin
and the contribution
of the Fram Strait
inflow branch to the
Arctic Ocean heat
budget.
In revision
Bert Rudels
Bert Rudels, Meri
Korhonen, Ursula
Schauer, Sergey
Pisarev, Benjamin
Rabe, and
Andreas Wisotzki
Ocean Circulation
and Climate
A 21st century
perspective
(second edition)
Editors:
Gerold Siedler,
Stephen Griffies,
John Gould, John
Church
Progress in
Oceanography
Yes, green OA
Progress in
Oceanography
Yes, green OA
Yes, green OA
5.2 Uptake by the targeted audience
According to the DOW, your audience for this deliverable is:
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?
Page
10
The present deliverable will be implemented as modellers and observational oceanographers
provide the necessary data to fulfil the upcoming deliverables. The deliverable has been
circulated to the other core themes and presented at the NACLIM annual meeting 2013 (1-2
October 2013).
6. The delivery is delayed:  Yes
 No
7. Changes made and difficulties encountered, if any
The main difficulty has been to select the criteria to be used for the comparison. Ideally they
should also present data that, when only observation and models results are examined on their
own they still provide valuable information about the ocean circulation and processes. The
presently proposed comparisons are to be considered as roadmaps and as the
model/observation comparison proceeds throughout the project the comparison criteria will be
gradually refined. In the same vein, the disseminations reported in connection with this
deliverable spans a broad spectrum of the North Atlantic circulation, necessary to consider
when the models/observation comparison should be formulated.
8. Efforts for this deliverable
Partner
Person-months
Period covered
10
FMI
From 01/11/2012 to 18/10/2013
4
From 01/11/2012 to 18/10/2013
UHAM
1
From 01/11/2012 to 18/10/2013
NERC /NOC
15
Total
Total estimated effort for this deliverable (DOW) was 15 person-months.
9. Sustainability
 Lessons learnt: both positive and negative that can be drawn from the experiences of the
work to date and
 Links built with other deliverables, WPs, and synergies created with other projects
Page
11
Contacts with the larger scientific community working with climate related ocean circulation in
the North Atlantic and in the Arctic Ocean/Nordic Seas are necessary to formulate and later to
refine the proposed criteria.
Page
12
10. Dissemination activities
[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
Presentation
FMI
8 March 2013
Poster
FMI
Bert Rudels,
(FMI):The
circulation and
transformation
of Atlantic
water in the
Eurasian Basin
and the
contribution
from the
inflow through
Fram Strait
inflow to the
Arctic Ocean
heat budget
Bert Rudels
(FMI) The
circulation and
transformation
of Atlantic
water in the
10-16 March
2013
Page
13
Type of
audience[4]
Size of
audien
ce
Countries
addressed
Have you
sent a copy
to Chiara
(project
office) via
mail?
Naval Post
Scientific
Graduate School, Community
Monterey, CA,
USA
20
USA
Yes
Gordon
Conference on
Polar
Oceanography,
Ventura, CA,
USA
150
Internation
al
Yes
Scientific
Community
Presentation
FMI
Presentation
FMI
Presentation
NERC
Eurasian Basin
and the
contribution
from the
inflow through
Fram Strait
inflow to the
Arctic Ocean
heat budget
Bert Rudels
(FMI): The
Arctic Ocean
Climate – a
balance
between local
radiation,
advected heat
and freshwater
Bert Rudels
(FMI):
Doublediffusive
processes in
the Arctic
Ocean – are
they of
importance?
Gerard
McCarthy:
Results from
the RAPID
array
Page
14
3-5 June 2013
French Arctic
Initiative,
Collège de
France, Paris
(FR)
Scientific
Community
18 April 2013
The Arctic Hub
– Regional and
Global
Perspective,
Krakow, PL
July 2013
US-AMOC
meeting,
Baltimore, USA
250
France and
Canada
mostly
Yes
Scientific
Community
Internation
al
Yes
Scientific
Community
~200 Internation
al
Yes
Presentation
NERC
Poster
NERC
Poster
NERC
Adam Blaker
July 2013
(NERC):
Historical
analogues of
AMOC
minima
Gerard
April 2013
McCarthy: The
RAPIDAMOC 26ºN
Monitoring
Array
Adam Blaker: April 2013
Historical
analogues of
AMOC
minima
Page
15
US-AMOC
meeting,
Baltimore, USA
Scientific
Community
~200 Internation
al
Not yet
EGU General
Assembly
Scientific
Community
1000
+
Internation
al
Not yet
EGU General
Assembly
Scientific
Community
1000
+
Internation
al
Not yet
Page
16