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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
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
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)