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

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

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

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).

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.

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

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

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

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?

Methodological approach

Data synthesis: Integrated, consistent multi-method,

multivariate statistical analysis

Reconcile previous research: heterogeneous

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

Modes of variability concept

Organized, recurring patterns (spatial and temporal)

of variability and covariability

Statistical or data modes

Physical or dynamical modes

a) Arctic Oscillation

b) Pacific Pattern (Pacific North American - PNA)

AO amplitude smallin recent years!

20th CenturyArctic Climate Patterns

SLP-based

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

New Recent Arctic Climate Pattern (Arctic Warm)

Cross-section, zonal annual T anomalies

Temperature Anomalies 2000–2005

SAT anomalies (spring)

Source: Semenov and Bengtsson, Geophys. Res. Lett., 2004

Primary statistical modes of 20th century SAT variability

EOF1AO/NAO

EOF2PNA

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

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

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

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

EOF3

2006 winter (Arctic Warm, except Bering and Siberia)

Recentmost Arctic Warmth vis-à-visEarly 20th Century Warming

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).

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).

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?

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

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

Example: Historical sea ice observations – Greenland

Regional series from ice charts,

e.g., Danish chart from 1910s.Source: DMI (Schmith and Hansen, 2003)

-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

-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

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

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”

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

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 )

Observational data:Historical observations – Nordic Seas region

Source: NPI

End of slideshow