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Interannual-to-decadal variability of the North Atlantic from an ocean data assimilation system
Language
English
Obiettivo Specifico
4A. Clima e Oceani
Status
Published
JCR Journal
JCR Journal
Peer review journal
Yes
Title of the book
Issue/vol(year)
/23 (2004)
ISSN
0930-7575
Electronic ISSN
1432-0894
Publisher
Springer Verlag GMBH Germany
Pages (printed)
531-546
Issued date
July 28, 2004
Abstract
An ocean analysis, assimilating both surface
and subsurface hydrographic temperature data into a
global ocean model, has been produced for the period
1958–2000, and used to study the time and space vari-
ations of North Atlantic upper ocean heat content (HC).
Observational evidence is presented for interannual-to-
decadal variability of upper ocean thermal fluctuations
in the North Atlantic related to the North Atlantic
Oscillation (NAO) variability over the last 40 years. The
assimilation scheme used in the ocean analysis is a uni-
variate, variational optimum interpolation of tempera-
ture. The first guess is produced by an eddy permitting
global ocean general circulation forced by atmospheric
reanalysis from the National Center for Environmental
Prediction (NCEP). The validation of the ocean analysis
has been done through the comparison with objectively
analyzed observations and independent data sets. The
method is able to compensate for the model systematic
error to reproduce a realistic vertical thermal structure
of the region and to improve consistently the model
estimation of the time variability of the upper ocean
temperature. Empirical orthogonal function (EOF)
analysis shows that an important mode of variability of
the wintertime upper ocean climate over the North
Atlantic during the period of study is characterized by a
tripole pattern both for SST and upper ocean HC. A
similar mode is found for summer HC anomalies but not
for summer SST. Over the whole period, HC variations
in the subtropics show a general warming trend while the
tropical and north eastern part of the basin have an
opposite cooling tendency. Superimposed on this linear
trend, the HC variability explained by the first EOF
both in winter and summer conditions reveals quasi-
decadal oscillations correlated with changes in the NAO
index. On the other hand, there is no evidence of cor- relation in time between the NAO index and the upper
ocean HC averaged over the whole North Atlantic
which exhibits a substantial and monotonic warming
trend during the last two decades of the analysis period.
The maximum correlation is found between the leading
principal component of winter HC anomalies and NAO
index at 1 year lag with NAO leading. For SST anom-
alies significant correlation is found only for winter
conditions. In contrast, for HC anomalies high corre-
lations are found also in the summer suggesting that the
summer HC keeps a memory of winter conditions.
and subsurface hydrographic temperature data into a
global ocean model, has been produced for the period
1958–2000, and used to study the time and space vari-
ations of North Atlantic upper ocean heat content (HC).
Observational evidence is presented for interannual-to-
decadal variability of upper ocean thermal fluctuations
in the North Atlantic related to the North Atlantic
Oscillation (NAO) variability over the last 40 years. The
assimilation scheme used in the ocean analysis is a uni-
variate, variational optimum interpolation of tempera-
ture. The first guess is produced by an eddy permitting
global ocean general circulation forced by atmospheric
reanalysis from the National Center for Environmental
Prediction (NCEP). The validation of the ocean analysis
has been done through the comparison with objectively
analyzed observations and independent data sets. The
method is able to compensate for the model systematic
error to reproduce a realistic vertical thermal structure
of the region and to improve consistently the model
estimation of the time variability of the upper ocean
temperature. Empirical orthogonal function (EOF)
analysis shows that an important mode of variability of
the wintertime upper ocean climate over the North
Atlantic during the period of study is characterized by a
tripole pattern both for SST and upper ocean HC. A
similar mode is found for summer HC anomalies but not
for summer SST. Over the whole period, HC variations
in the subtropics show a general warming trend while the
tropical and north eastern part of the basin have an
opposite cooling tendency. Superimposed on this linear
trend, the HC variability explained by the first EOF
both in winter and summer conditions reveals quasi-
decadal oscillations correlated with changes in the NAO
index. On the other hand, there is no evidence of cor- relation in time between the NAO index and the upper
ocean HC averaged over the whole North Atlantic
which exhibits a substantial and monotonic warming
trend during the last two decades of the analysis period.
The maximum correlation is found between the leading
principal component of winter HC anomalies and NAO
index at 1 year lag with NAO leading. For SST anom-
alies significant correlation is found only for winter
conditions. In contrast, for HC anomalies high corre-
lations are found also in the summer suggesting that the
summer HC keeps a memory of winter conditions.
Sponsors
This work has been supported by the EU
PREDICATE Project (Contract EVK2-CT-1999-00020) and the
EU ENACT Project (Contract EVK2-CT2001-00117)
PREDICATE Project (Contract EVK2-CT-1999-00020) and the
EU ENACT Project (Contract EVK2-CT2001-00117)
References
Alexander MA, Deser A (1995) A mechanism for the recurrence of
wintertime SST anomalies. J Phys Oceanogr 25: 122–137
Bretherton FR, Davis RE, Fandry CB (1976) A technique for
objective analysis and design of oceanographic experiment ap-
plied to MODE-73. Deep Sea Res 37: 559–582
Carter EF, Robinson AR (1987) Analysis models for the estimation
of oceanic fields. J Atmos Oceanic Technol 4: 49–74
Carton JA, Chepurin G, Cao X (2000) A simple ocean data
assimilation analysis of the global upper ocean 1950–95. Part I:
methodology. J Phys Oceanogr 30: 294–309
Conkright ME, Levitus S, O’Brein T, Stephen C, Stathoplos L,
Baranova O, Antonov J, Gelfeld R, Burney J, Rochester J,
Forgy C (1998) World Ocean Database 1998. Documentation
and Quality Control. Version 2.1. National Oceanographic
Data Center Internal Report 14 OCL/NODC
Cox MD (1984) A primitive equation, 3-dimensional model of the
ocean. GFDL Ocean Group Tech Rep 1, pp 143
Curry RG, McCartney MS (2001) Ocean gyre circulation associ-
ated with the North Atlantic Oscillation. J Phys Oceanogr 31:
3374–3400
Curry RG, McCartney MS, Joyce TM (1998) Oceanic transport of
subpolar climate signals to mid-depth subtropical waters.
Nature 391:575–577
Deser C, Blackmon ML (1993) Surface climate variations over the
North Atlantic Ocean during winter: 1900–1989. J Clim 6:
1743–1753
Deser C, Alexander AM, Timlin MS (2003) Understanding the
persistence of sea surface temparature anomalies in midlati-
tudes. J Clim 16: 57–72
Frankignoul C, De Coe¨tlogon G, Joyce TM, Dong S (2001) Gulf
Stream variability and ocean-atmosphere interactions. J Phys
Oceanogr 31: 3516–3528
Grey SM, Haines K, Troccoli A (2000) A study of temperature
changes in the upper North Atlantic: 1950–94. J Clim 13: 2697–
2711
Hansen DV, Bezdek HF (1996) On the nature of decadal anomalies
in North Atlantic sea surface temperature. J Geophys Res 101:
48,749–48,758
Houghton RW (1996) Subsurface quasi-decadal fluctuations in the
North Atlantic. J Clim 9: 1363–1373
Joyce MT, Deser C, Spall MA (2000) The relation between decadal
variability of subtropical mode water and the North Atlantic
Oscillation. J Clim 13: 2550–2569
Krahmann G, Visbeck M, Reverdin G (2001) Formation and
propagation of temperature anomalies along the North Atlantic
Current. J Phys Oceanogr 31: 1287–1303
Kushnir Y (1994) Interdecadal variations in North Atlantic sea
surface temperature and associated atmospheric conditions.
J Clim 7: 141–157
Levitus S (1989) Interpentadal variability of temperature and
salinity at intermediate depths of the North Atlantic Ocean,
1970–1974 versus 1955–1959. J Geophys Res 94: 6091–6131
Levitus S, Antonov JI, Boyer TP (1994) Interannual variability of
temperature at a depth of 125 meters in the North Atlantic
Ocean. Science 266: 96–99
Levitus S, Antonov JI, Boyer TP, Stephens C (2000) Warming of
the World Ocean. Science 287: 2225–2229
Marshall JC, Nurser AJG, Williams RG (1993) Inferring the sub-
duction rate and period over the North Atlantic. J Phys Oce-
anogr 23: 1315–1329
Masina S, Pinardi N, Navarra A (2001) A global ocean tempera-
ture and altimeter data assimilation system for studies of cli-
mate variability. Clim Dyn 17: 687–700
Mellor GL, Yamada T (1982) Development of a turbulence closure
model for geophysical fluid problems. Rev Geophys Space Phys
20: 851–875
Molinari RL, Mayer DA, Festa JF, Bezdek HF (1997) Multi-year
variability in the nearsurface temperature structure of the
midlatitude western North Atlantic Ocean. J Geophys Res 102:
23,267–23,278
Rayner NA, Kent EC, Kaplan A (2003) Global analyses of sea
surface temperature, sea ice, and night marine air temperature
since the late nineteenth century. J Geophys Res 108: No. D14,
4407, doi:10.1029/2002JD002670
Rosati A, Miyakoda K (1988) A general circulation model for
upper ocean simulations. J Phys Oceanogr 18: 1601–1626
Smagorinsky J (1993) Some historical remarks on the use of non-
linear viscosities. In: Galperin B, Orzag SA (eds) Large eddy
simulation of complex engineering and geophysical flows.
Cambridge University Press, Cambridge, UK, pp 3–36
Stammer D, Wunsch C, Giering R, Eckert C, Heimbach P, Mar-
otzke J, Adcroft A, Hill CN, Marshall J (2003) Volume, heat,
and freshwater transport of the global ocean circulation 1993–
2000, estimated from a general circulation model constrained by
World Ocean Circulation Experiment (WOCE) data. J Geophys
Res 108: No. C1, 3007, doi:10.1029/2001JC001115
Sutton RT, Allen MR (1997) Decadal predictability in Gulf Stream
sea surface temperature. Nature 388: 563–567
Talley LD, Raymer ME (1982) Eighteen degree water variability. J
Mar Res 40 (Suppl.): 757–777
Watanabe M, Kimoto M (2000) On the persistence of decadal SST
anomalies in the North Atlantic. J Clim 13: 3017–3028
Watanabe M, Kimoto M, Nitta T, Kachi M (1999) A comparison
of decadal climate oscillations in the North Atlantic detected in
observations and a coupled GCM. J Clim 12: 2920–2940
Williams RG, Spall MA, Marshall JC (1995) Does Stommel’s
mixed layer ‘‘Demon’’ work? J Phys Oceanogr 25: 3089–3102
wintertime SST anomalies. J Phys Oceanogr 25: 122–137
Bretherton FR, Davis RE, Fandry CB (1976) A technique for
objective analysis and design of oceanographic experiment ap-
plied to MODE-73. Deep Sea Res 37: 559–582
Carter EF, Robinson AR (1987) Analysis models for the estimation
of oceanic fields. J Atmos Oceanic Technol 4: 49–74
Carton JA, Chepurin G, Cao X (2000) A simple ocean data
assimilation analysis of the global upper ocean 1950–95. Part I:
methodology. J Phys Oceanogr 30: 294–309
Conkright ME, Levitus S, O’Brein T, Stephen C, Stathoplos L,
Baranova O, Antonov J, Gelfeld R, Burney J, Rochester J,
Forgy C (1998) World Ocean Database 1998. Documentation
and Quality Control. Version 2.1. National Oceanographic
Data Center Internal Report 14 OCL/NODC
Cox MD (1984) A primitive equation, 3-dimensional model of the
ocean. GFDL Ocean Group Tech Rep 1, pp 143
Curry RG, McCartney MS (2001) Ocean gyre circulation associ-
ated with the North Atlantic Oscillation. J Phys Oceanogr 31:
3374–3400
Curry RG, McCartney MS, Joyce TM (1998) Oceanic transport of
subpolar climate signals to mid-depth subtropical waters.
Nature 391:575–577
Deser C, Blackmon ML (1993) Surface climate variations over the
North Atlantic Ocean during winter: 1900–1989. J Clim 6:
1743–1753
Deser C, Alexander AM, Timlin MS (2003) Understanding the
persistence of sea surface temparature anomalies in midlati-
tudes. J Clim 16: 57–72
Frankignoul C, De Coe¨tlogon G, Joyce TM, Dong S (2001) Gulf
Stream variability and ocean-atmosphere interactions. J Phys
Oceanogr 31: 3516–3528
Grey SM, Haines K, Troccoli A (2000) A study of temperature
changes in the upper North Atlantic: 1950–94. J Clim 13: 2697–
2711
Hansen DV, Bezdek HF (1996) On the nature of decadal anomalies
in North Atlantic sea surface temperature. J Geophys Res 101:
48,749–48,758
Houghton RW (1996) Subsurface quasi-decadal fluctuations in the
North Atlantic. J Clim 9: 1363–1373
Joyce MT, Deser C, Spall MA (2000) The relation between decadal
variability of subtropical mode water and the North Atlantic
Oscillation. J Clim 13: 2550–2569
Krahmann G, Visbeck M, Reverdin G (2001) Formation and
propagation of temperature anomalies along the North Atlantic
Current. J Phys Oceanogr 31: 1287–1303
Kushnir Y (1994) Interdecadal variations in North Atlantic sea
surface temperature and associated atmospheric conditions.
J Clim 7: 141–157
Levitus S (1989) Interpentadal variability of temperature and
salinity at intermediate depths of the North Atlantic Ocean,
1970–1974 versus 1955–1959. J Geophys Res 94: 6091–6131
Levitus S, Antonov JI, Boyer TP (1994) Interannual variability of
temperature at a depth of 125 meters in the North Atlantic
Ocean. Science 266: 96–99
Levitus S, Antonov JI, Boyer TP, Stephens C (2000) Warming of
the World Ocean. Science 287: 2225–2229
Marshall JC, Nurser AJG, Williams RG (1993) Inferring the sub-
duction rate and period over the North Atlantic. J Phys Oce-
anogr 23: 1315–1329
Masina S, Pinardi N, Navarra A (2001) A global ocean tempera-
ture and altimeter data assimilation system for studies of cli-
mate variability. Clim Dyn 17: 687–700
Mellor GL, Yamada T (1982) Development of a turbulence closure
model for geophysical fluid problems. Rev Geophys Space Phys
20: 851–875
Molinari RL, Mayer DA, Festa JF, Bezdek HF (1997) Multi-year
variability in the nearsurface temperature structure of the
midlatitude western North Atlantic Ocean. J Geophys Res 102:
23,267–23,278
Rayner NA, Kent EC, Kaplan A (2003) Global analyses of sea
surface temperature, sea ice, and night marine air temperature
since the late nineteenth century. J Geophys Res 108: No. D14,
4407, doi:10.1029/2002JD002670
Rosati A, Miyakoda K (1988) A general circulation model for
upper ocean simulations. J Phys Oceanogr 18: 1601–1626
Smagorinsky J (1993) Some historical remarks on the use of non-
linear viscosities. In: Galperin B, Orzag SA (eds) Large eddy
simulation of complex engineering and geophysical flows.
Cambridge University Press, Cambridge, UK, pp 3–36
Stammer D, Wunsch C, Giering R, Eckert C, Heimbach P, Mar-
otzke J, Adcroft A, Hill CN, Marshall J (2003) Volume, heat,
and freshwater transport of the global ocean circulation 1993–
2000, estimated from a general circulation model constrained by
World Ocean Circulation Experiment (WOCE) data. J Geophys
Res 108: No. C1, 3007, doi:10.1029/2001JC001115
Sutton RT, Allen MR (1997) Decadal predictability in Gulf Stream
sea surface temperature. Nature 388: 563–567
Talley LD, Raymer ME (1982) Eighteen degree water variability. J
Mar Res 40 (Suppl.): 757–777
Watanabe M, Kimoto M (2000) On the persistence of decadal SST
anomalies in the North Atlantic. J Clim 13: 3017–3028
Watanabe M, Kimoto M, Nitta T, Kachi M (1999) A comparison
of decadal climate oscillations in the North Atlantic detected in
observations and a coupled GCM. J Clim 12: 2920–2940
Williams RG, Spall MA, Marshall JC (1995) Does Stommel’s
mixed layer ‘‘Demon’’ work? J Phys Oceanogr 25: 3089–3102
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