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Synthesis of Modes of Ocean-Ice-Atmosphere
Covariability in the Arctic System from
Multivariate Century-Scale Observations
Martin MilesEnvironmental Systems Analysis Research Center, Boulder, CO
Mark SerrezeNational Snow and Ice Data Center, University of Colorado, Boulder, CO
James OverlandPacific Marine Environmental Laboratory, Seattle, WA
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Overall objective
Quantitatively synthesize modes of (co)variability
– and changes in these modes – in the Arctic and
subpolar North Atlantic ocean–ice–atmosphere
system in the past one to two centuries
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Specific objectives (4):
• Assemble, update and systematize the longest
continuous time series of oceanographic and
meteorological measurements, sea ice
observations and climate indices
Integrate a subset of the multidecadal to century-scale
Unaami Data Collection with a set of century-scale time
series from the Arctic and subpolar North Atlantic,
complemented by NCEP and other fields
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a b
(a) Approximate locations of multidecadal time series of climate () atmosphere (), ocean (), sea ice (), terrestrial (), biology () and fisheries () variables in the Unaami Data Collection. (b) Locations of the mostly century-scale SAT measurement series >64ºN, as in Overland et al. (2004).
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Approximate locations of century-scale time series of climate () atmosphere (), ocean () and sea ice () variables from the Arctic and subpolar North Atlantic. Color coded same as in previous figure.
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Specific objectives (cont.)
• Quantitatively characterize the ocean–ice–
atmosphere system, through identifying
recurrent modes of (co)variability –
distinguishing modes other than the AO/NAO –
in ocean, ice and climate parameters
Seasonal to multidecadal time scales
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Specific objectives (cont.)
• Quantitatively document changes in modes of
variability and covariability – i.e., re-organization
of the signals and linkages that may represent
‘regime shifts’ in the system
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Specific objectives (cont.)
• Synthesize our results together with other
observational and modelling analyses, to
develop improved understanding of the arctic
ocean–ice–atmosphere system and
interactions with the subpolar North Atlantic
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Overarching science questions
What are the modes of variability other than the
Arctic/North Atlantic Oscillation (AO/NAO) and what
is their relative importance in different regions and
seasons?
How do modes of variability change through time
and how unusual are recent changes compared to
longer-term observations or model-based results?
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Methodological approach
Data synthesis: Integrated, consistent multi-method,
multivariate statistical analysis
Reconcile previous research: heterogeneous
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Methodological approach
Data synthesis: Integrated, consistent multi-method,
multivariate statistical analysis
Simple and advanced:
time series analysis techniques in time and frequency
domains
spatial analysis – composites, correlations, EOF, SVD
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Modes of variability concept
Organized, recurring patterns (spatial and temporal)
of variability and covariability
Statistical or data modes
Physical or dynamical modes
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a) Arctic Oscillation
b) Pacific Pattern (Pacific North American - PNA)
AO amplitude smallin recent years!
20th CenturyArctic Climate Patterns
SLP-based
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Surface Air Temperature (SAT) Anomalies
Arctic Climate Patterns
1977–88 (PNA+) 1989–1995 (AO+) 2000–2005 (Arctic Warm) Pacific North American Arctic Oscillation
Modified from Overland and Wang, Geophys. Res. Lett., 2006
New Recent Pattern
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New Recent Arctic Climate Pattern (Arctic Warm)
Cross-section, zonal annual T anomalies
Temperature Anomalies 2000–2005
SAT anomalies (spring)
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Source: Semenov and Bengtsson, Geophys. Res. Lett., 2004
Primary statistical modes of 20th century SAT variability
EOF1AO/NAO
EOF2PNA
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AO/NAO Pattern: Anomalies in SAT (shown), SST, SSS
and sea ice in the Atlantic Arctic
1989-1995AO/NAO+
1969-1971AO/NAO–
EOF1AO/NAO
Source: Semenov and Bengtsson, Geophys. Res. Lett., 2004
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Date unknown
“So extensive and dangerous a work…”
12 primary stations12+ auxilary
United States
Russia
Netherlands
Sweden
Russia
UK/Canada
United States
Denmark
Germany
FinlandAustria Norway
1882-1883
Arctic Climate Patterns evident in First IPY data
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Characteristic large-scale patterns evident
Std. dev. from ref. mean 1968–1997NAO Index data provided by the Climate Analysis Section,
NCAR, Boulder, USA, Hurrell (1995).
SAT anomalies related to fluctuations in atmospheric circulation
Similar in scale to modern values
DEC JAN FEB
SL
PS
AT
WIN
TE
R
C
W
L
NAO +2.4
H
NAO -1.4
C
1882-1883
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Primary statistical modes of 20th century SAT variability
EOF1AO/NAO
EOF2PNA
EOF3Not related to known physical
mode of variability
-3
-2
-1
0
1
2
3
1820 1840 1860 1880 1900 1920 1940 1960 1980 2000
Early 20th centurywarming period
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EOF3
2006 winter (Arctic Warm, except Bering and Siberia)
Recentmost Arctic Warmth vis-à-visEarly 20th Century Warming
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EOF3
2006 winter (re-scaled)
Greenland–Barents Sea region unusually warm: Jan Mayen and Svalbard (+13 C) anomalies!
Recentmost Arctic Warmth vis-à-visEarly 20th Century Warming
Feedback mechanism? Barents Sea SAT amplification – BSO
pressure-gradient and sea ice? (Bengtsson et al., J. Climate (2004).
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Recentmost Arctic Warmth (cont.)
2006 winter pressure- and wind-anomalies Winter 2006 sea ice
Feedback mechanism? Barents Sea SAT amplification – BSO
pressure-gradient and sea ice? (Bengtsson et al., J. Climate (2004).
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Many science questions to be addressed:
Recent new arctic climate pattern: completely new or similar to early 20th century; seasonal aspects, feedbacks?
Decadal to interannual quasi-periodic modes of covariability: patterns, spatial and temporal; regime shifts?
Early 20th century warming: onset and underlying mechanisms?
AMO: manifestation in sea ice and other arctic records; mechanisms interactions; role in recent warming?
Atlantic Arctic: anomalous 19th-20th century vis-á-vis pan-Arctic temperature reconstructions?
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Insight into many of these science questions will be
gained in this ARCSS synthesis project
Integrated multivariate statistical analysis of long time series
of SAT, SST, sea ice and SLP
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Examples of SST data and
variability evident in Faroe-
Iceland gateway
0
2
4
6
8
1820 1840 1860 1880 1900 1920 1940 1960 1980 2000
-2
0
2
4
6
8
1820 1840 1860 1880 1900 1920 1940 1960 1980 2000
-4
-2
0
2
4
1820 1840 1860 1880 1900 1920 1940 1960 1980 2000
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Example: Historical sea ice observations – Greenland
Regional series from ice charts,
e.g., Danish chart from 1910s.Source: DMI (Schmith and Hansen, 2003)
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-4
-2
0
2
4
1820 1840 1860 1880 1900 1920 1940 1960 1980 2000
SW Greenland sea ice extension [std.anom.]
0
10
20
30
40
1820 1840 1860 1880 1900 1920 1940 1960 1980 2000
Icelandic ice [weeks]
-3
-2
-1
0
1
2
3
1820 1840 1860 1880 1900 1920 1940 1960 1980 2000
-3
-2
-1
0
1
2
3
1820 1840 1860 1880 1900 1920 1940 1960 1980 2000W Greenland SST
vs.
Storis
(negative)
[std.anom.]
Examples of variability
evident in multivariate
observations in the 19th
and 20th centuries
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-4
-2
0
2
4
1820 1840 1860 1880 1900 1920 1940 1960 1980 2000
SW Greenland sea ice extension [std.anom.]
0
10
20
30
40
1820 1840 1860 1880 1900 1920 1940 1960 1980 2000
Icelandic ice [weeks]
-3
-2
-1
0
1
2
3
1820 1840 1860 1880 1900 1920 1940 1960 1980 2000
-4
-2
0
2
4
1820 1840 1860 1880 1900 1920 1940 1960 1980 2000
Newfoundland sea iceextent [std.anom.] and NAO
Examples of variability
evident in multivariate
observations in the 19th
and 20th centuries
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Results and deliverables Data set: Time series, standardized and metrics
Synthesis papers
general: Modes of variability synthesis
focused: Multidecadal oscillation in sea ice records
Early 20th-century warming onset
Science, Nature, Geophys. Res. Lett., J. Clim., Clim. Change
Timetable based around thematic papers
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Summary
Contribution to the ARCSS Synthesis
• Long-term baseline data and information from
under-utilized multivariate observations that
bridge a gap between contemporary
measurements and paleoenvironmental data
• Self-consistent ‘metrics’ quantifying quasi-
periodic variability, covariability and changes
evident over the past ~50–200 years, thereby
“setting the record(s) straight”
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Summary
Contribution to the ARCSS Synthesis
• Improved understanding of the temporal and
spatial patterns, linkages and mechanisms of
change in the arctic system
Potential linkages to several SASS projects
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Evidence for a multidecadal
oscillation in arctic sea ice
Evident in other 20th-century sea ice analyses, e.g., Polyakov and
others (2003), Johannessen and others (2004)
Temperature and sea ice: Annual sea ice extentvs. air temperature in the Arctic (60-90°N)
Zakh
arov
ice
exte
nt (1
06 km
2 )
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Observational data:Historical observations – Nordic Seas region
Source: NPI
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End of slideshow