Uma S. Bhatt1, I. Polyakov2, R. Bekryaev3 et al.1. Geophysical Institute & 2. International Arctic Research Institute

at Univ. Alaska, Fairbanks AK3. Arctic & Antarctic Research Institute, St. Petersburg, Russia

30th Climate Diagnostics Workshop

October 24-28, 2005, State College, PA

Regional expression of Arctic multi-decadal variability

Main Points • Multi-decadal variability is evident in climate variables of the Arctic • Arctic sectors vary with North Atlantic• North Pacific displays multi-decadal variability and strongest impacts in the Alaska sector• Siberian High also displays multi-decadal variability and influences pressure variability in the Arctic

2

Motivation

• Must understand natural climate variability mechanisms in order to distinguish from trends due to anthropogenic forcing

100 cm rise sea

level

[ACIA Report, 2004]

10cm total

3

Outline

• Document Observed Arctic Multi-decadal Variability

• Regional Examination of Multi-decadal Variability in Arctic

4

Data Information

• Monthly Station Data• Surface Air Temperature• Sea Level Pressure

•Consolidated several databases

• Russian drifting stations•International Arctic Buoy Program • Land stations

• Russian Arctic fast ice thickness & ice area

•Gridded Data

5

Composite Arctic Multi-decadal SAT & SLP Variability

[Polyakov et al., 2002]

• Composite time series created from stations north of 62N• SLP peaks offset by 15 years from SAT

6

Compare with Arctic SAT Trends from Other Studies

[Polyakov et al.,2002]

7

Eastern Arctic Sea Ice Extent Displays Multi-decadal Signal and is Decreasing

•August sea ice extent (in 1000 km) in the Kara, Laptev, E. Siberian, and Chukchi, from Russian ship and aircraft observations & since 1990 satellite records. • Ice lags SAT

[Polyakov et al., 2003b]

8

April Ice Edge in Barents: Retreat since 1850

• Multi-century scale variability is prominent in Arctic

[Shapiro and Colony, 2002, Polar Record]

Ice edge since 1750, Vinje, 2002

9

Intermediate Atlantic Water Displays Multi-decadal Variability & Long Term Trend

[Polyakov et al., 2004]

Atlantic Water PathwayIce Thickness

Atlantic Water Temperature

10

Origins of this Pattern of Variability - N. Atlantic

• Monthly NAO correlated with Arctic station Surface Air Temperatures• Strongest in North Atlantic Sector• Mechanisms- thermohaline circ.- solar variability- greenhouse forcing- MLM + ozone/solar

[Polyakov et al., 2003b]

• How is multi-decadal variability expressed regionally in the Arctic?

11

Climatically Consistent Regional Divisions

1. Greenland Sea

2. Barents Sea

3. Kara-Laptev

4. Central Arctic

5. E. Siberian/Chukchi

6. Beaufort Sea

7. Canadian Archipelago

8. Greenland

12

SAT Displays Multi-decadal Variability close to N. Atlantic

= 1.1

= 0.58

= 1.05

= 1.15

• Red line is Smoothed time series • Surface Air Temperature, (Wavelet Analysis) - 1880-1920 Cool; 1920-60 Warm; 1960-80 Cool; 1980-00 Warm.

13

SAT in Regions that Display Different Variability

= 1.30

= 0.97

= 1.09

= 0.83

Hard to tell due to short data set Multi-decadal but a bit different

•More decadal variability in these sectors

14

SLP Regions That Display Multi-decadal Variability

= 1.79

= 1.44

= 1.59

= 1.76

Sea Level Pressure (Wavelet Analysis) - 1880-1900 High ; 1900-35 Low ; 1935-75 High; 1975-00 Low

15

Regions not displaying Multi-decadal Variability

= 2.26 = 1.13

= 1.12 = 1.15

• Sea Level Pressure: Regions 5-7, 1950-80 High SLP

16

Large amplitude multi-decadal oscillations impacts calculation of trends

SAT - all regions are warming

(orange) except Region 3

SLP -decreasing (green) in regions

1,2,5,6,7 & increasing in

Regions 3 & 8.

Significance of trends decreases as the record gets

shorter.

Greenland Sea

Barents

Kara-Laptev

Central Arctic Greenland

Canada

Beaufort

E.Siberian/Chukchi

17

Large amplitude multi-decadal oscillations impacts calculation of trends

SAT - all regions are warming

(orange) except Region 3

SLP -decreasing (green) in regions

1,2,5,6,7 & increasing in Regions 3 & 8.

Significance of trends decreases as the

record gets shorter.

Greenland Sea

Barents

Kara-Laptev

Central Arctic Greenland

Canada

Beaufort

E.Siberian/Chukchi

18

Spatial Variability in Arctic Surface Temperature Trends last 20 years: Cooling over Kara Sea?

•

•

•

( Comiso, 2003)

• Trend all months• Surface Temperature is decreasing over Taimyr Peninsula, between Kara Sea and Laptev Sea.

19

Pacific Decadal Oscillation & Arctic

• PDO is the leading PC of monthly SST

anomalies in the North Pacific Ocean.• S. Minobe  showed 15-to-25 & 50-to-70

years.

+ phase - phase

20

Annual Average SAT-Index Correlations5-E.Siberia/Chukchi

NAO (0.28)

1-GIN

2-B

aren

ts

3-Kara/L

aptev

4 -Central Arctic

6-E.A

laska/Beaufo

rt

7-Can

adian

Arch

.

8-Greenland

NAO (0.34)

NAO (0.44)

NAO (0.49)

NAO (-0.39)

NAO (-0.68)

PDO (0.41)

Black - 99.9%

Green - 95.0%

NAO is SLP index,

positive==> Icelandic

low is deeper

PDO, positive==>

Stronger Aleutian low

and more warm

southerly winds.

DJF similar

21

Siberian High

[Gong & Ho, 2002]

• October-March feature, Shallow high over Asia, 40-60N & 70-120E• Highs move out of this region into the Arctic• Trend in High since 1980, not as strong…

22

Recent Changes in Siberian High

•

•

•

• Siberian High has trend and displays some low frequency variability• What is this variability associated with? Multi-decadal fluctuations in Indian Ocean…

hPa

23

Siberian High, Arctic SLP, & NAO

•

•

•

• Recent low pressure seen in Arctic SLP follows Siberian High Anomalies

24

SLP differences between warm and cold decades in the Arctic

What may be happening?• Highs (from Siberian High) entering Arctic are weaker acting to maintain a lower SLP• NCEP reanalysis shows about half the anomaly

25

Annual Average SLP-Index Correlations5-E.Siberia/ChukchiNAO (-0.25)

1-GIN2-

Bar

ents

3-Kara/L

aptev

4 -Central Arctic

6-E.A

laska/Beaufo

rt

7-Can

adian

Arch

.

8-Greenland

NAO (-.71)

NAO (-.31)

NAO (-0.64)

NAO (-0.28)

NAO (-0.23)

Black - 99.0%

Blue - 95.0%

SHi (0.35)

SHi (0.37)

SHi (0.23)

SHi (0.24)

NAO negative correlations,

positive phase means lower

pressures

Siberian High - positive

correlations, strong high

==> higher SLP

PDO negative correlations

DJF in R 5 & 6

26

Summary

• Multi-decadal variability is more prevalent in North Atlantic sector of Arctic

• North Pacific displays multi-decadal variability that influences impacts the Alaska sector

• Siberian High also displays low frequency variability and influences pressure variability in the Arctic

• Records are short (two realizations) so we need to find analogs in GCMs to study the mechanisms (working on this)

Acknowledgements

Frontier Research System for Global Change

Geophysical Institute (GI)

International Arctic Research Center (IARC)

Others on Multi-decadal Variability Team

G. Alexeev, R. Colony, M. Johnson, H. Simmons,

L. Timokov, D.Walsh, & J. Walsh

28

29

Correlations between Indices

DJF

NAO => SiHi -0.28 (95%)

SOI => SiHi 0.26 (95%)

AO => SiHi -0.50 (99%)

NAO => SiHi : Changing Correlation over time…

1920-59: -0.05

1960-00: -0.29

30

NAO Relationship to SAT & Ice

-20

+20

More southerly (northerly) advection less (more) ice

Deser et al. 2000

Observed Sea Level Pressure pattern associated with ice anomalies (Red-less ice and Blue-more ice)

31

DJF SAT-Index Correlations Similar to Annual5-E.Siberia/Chukchi

NAO (0.38)

1-GIN

2-B

aren

ts

3-Kara/L

aptev

4 -Central Arctic

6-E.A

laska/Beaufo

rt

7-Can

adian

Arch

.

8-Greenland

NAO (0.45)

NAO (0.48)

NAO (0.66)

NAO (-0.55)

NAO (-0.4)

PDO (0.32)

Black - 99.9%