Climate Change Teleconnections AO, NAO, ENSO, PDO

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Climate ChangeTeleconnections AO, NAO, ENSO,
PDO

• WS 2005/2006
• Lecture/Seminar

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Overview I

• 20. Oct. Overview General Introduction
• 27. Oct. Past climate variability (millions of
  yrs.)
• 3. Nov. Little Ice Age and Medival Warm Period
• 10. Nov. The last 100 years the instrumental
  record
• 17. Nov. Teleconnections ENSO / NAO / PDO
• 24. Nov. no seminar
• 1. Dec. no seminar

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Overview II

• 8. Dec. Almuth / Katja, Clouds Olav, CC in
  NL
• 15. Dec. Mitja, CH4 Hydrates Carolyn,
  Ocean CO2 Dynamics
• 22. Dec. Michael, CC in Siberia Bettina,
  Treelines and CC Daniel, ACIA?
• 5. Jan. Case study Subtropics
• 12. Jan. Case study Tropics
• 19. Jan. Recent catastropies and CC?
• 26. Jan. Humans do not have an impact The
  climate critics

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• Following graphics either from the IPCC webpage
  or free downloads (e.g. Wikipedia.org) or as
  cited.

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Teleconnection I
Variability of atmospheric circulation
Including weather patterns at time scales days,
e.g. frontal system weeks, e.g. mid-summer wet
period months, e.g. cold winters years, e.g.
period of hot summers, droughts centuries, e.g.
climate change
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Teleconnection II
Teleconnection patterns refer to recurring and
persistent, large-scale pattern of pressure and
circulation anomalies that spans vast
geographical areas.
Preferred modes of variability
Teleconnection patterns are a naturally occurring
aspect of our chaotic atmospheric system, and can
arise primarily as a reflection of internal
atmospheric dynamics.
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Outline
NAO North Atlantic Oscillation
PDO Pacific Decadel Oscillation
ENSO El Nino / Southern Oscillation
Effects of or on climate change?
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AO
Negative phase H over polar regions, L at mid.
lat. (45N)
Cold winter air to central US and Europe
Positive phase Lower over Arctic, higher
pressure at mid. lat.
Storm tracks further N ? wetter in Alaska,
Scotland, Scandinavia drier in Mediterranean and
W US colder in Greenland and Newfoundland
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Arctic Oscillation
Figures courtesy of J. Wallace, University of
Washington
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Arctic Oscillation
Figures courtesy of J. Wallace, University of
Washington
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NAO
"In Greenland, all winters are severe, yet they
are not alike. The Danes have noticed that when
the winter in Denmark was severe, as we perceive
it, the winter in Greenland in its manner was
mild, and conversely."
Hans Egede Saabyes diary (1770-78)
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NAO
Positive phase Low low over N-Atlantic and
strong subtropical high.
Pressure difference increase ? strong westerlies
The eastern US experiences mild and wet winter
conditions
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NAO -
The negative NAO index phase shows a weak
subtropical high and a weak Icelandic low
The reduced pressure gradient results in fewer
and weaker winter storms crossing on a more
west-east pathway
Moist air in Mediterranean, cold air to N-Europe.
The US east coast snowy weather conditions.
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NAO Index
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NAO phase implications
The trend in the NAO accounts for several
remarkable changes recently in the climate and
weather over the middle and high latitudes of the
Northern Hemisphere, as well as in marine and
terrestrial ecosystems Strengthened subpolar
westerlies from the surface to the lower
stratosphere (Thompson et al. 1999). Milder
winters in Europe downstream across Asia
juxtaposed against more severe winters over
eastern Canada and the northwest Atlantic
(Hurrell 1995a Wallace et al. 1995 Hurrell
1996 Shabbar et al. 1997 Thompson and Wallace
1998).
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NAO phase implications
Pronounced regional changes in precipitation
patterns (Hurrell 1995a Hurrell and van Loon
1997 Dai et al. 1997) resulting in the advance
of some northern European glaciers (Hagen 1995
Sigurdsson and Jonsson 1995) and the retreat of
Alpine glaciers (Frank 1997). Changes in sea-ice
cover in both the Labrador and Greenland Seas as
well as over the Arctic (Chapman and Walsh 1993
Maslanik et al.1996 Cavalieri et al. 1997
Parkinson et al. 1998 McPhee et al. 1998 Deser
et al. 1999). Pronounced decreases in mean sea
level pressure (SLP) over the Arctic (Walsh et
al. 1996).
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NAO phase implications
Changes in the physical properties of Arctic sea
water (Sy et al. 1997 Morison et al. 1998
McPhee et al. 1998 Dickson 1999 Dickson et al.
1999a,b). Changes in the intensity of convection
in the Labrador and the Greenland-Iceland Seas
(Dickson et al. 1996 Houghton 1996) which in
turn influence the strength and character of the
Atlantic meridional overturning circulation.
Stratospheric cooling over the polar cap (Randel
and Wu 1999), and total column ozone losses
poleward of 40oN (Randel and Wu 1999 Thompson et
al. 1999).
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NAO phase implications
Changes in storm activity and the shifts in the
Atlantic storm track (Hurrell 1995b), changes in
within season variability such as blocking
(Nakamura 1996). Trend in North Atlantic surface
wave heights (Kushnir et al. 1997). Changes in
the production of zooplankton and the
distribution of fish (e.g., Fromentin and Planque
1996). Changes in the length of the growing
season over Europe (Post and Stenseth 1999), and
changes in the population dynamical processes of
several terrestrial species (Post et al. 1999
Stenseth et al. 1999).
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SLP at North Pole
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SLP at North Pole
Hodges, Glenn, 2000. National Geographic
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SLP at North Pole
Hodges, Glenn, 2000. National Geographic
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NAO and CC
Hurrell (1996) has shown, for example, that the
recent upward trend in the NAO accounts for much
of the observed regional surface warming over
Europe and Asia, as well as the cooling over the
northwest Atlantic over the past several decades.
source and additional info http//www.ldeo.columbi
a.edu/NAO/
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ENSO
Tropical influence
Every 3-8 years Pressure loss over E
Pacific Pressure rise over W Pacific Trade winds
decrease
Possible flip flop of Walker Circulation
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Walker Circulation flip-flop
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Teleconnections El Nino
Increased precipitation across the southern US
and in Peru,
San Francisco 1926, 1983
Drought in the West Pacific (sometimes associated
with devastating brush fires in AU)
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La nina
Cooling of surface water west of S-America
Stronger Walker Ciculation
Stronger trade winds Thermocline rise
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Teleconnections La Nina
Precip rise W-Pazific, oceanic influenced areas
(e.g. Mozambique), S-Asia (during SW-Monsoon),
N/NE-Australia, S-Africa, N-SAmerica, central
America, Hawaii.
Precip decline Equatorial Islands central
Pazific, middle E-Africa, S-SAmerica
Hurricane frequency increased
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PDO
Influences jet stream location
Multi year variability
Effect on ecosystem productivity in Pacific
Effects of or on climate change?
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PDO - phases
positive phase                            
negative phase
Image courtesy of Stepen Hare and Nathan Mantua,
University of Washington, units are degrees
Celsius
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PDO - record
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PDO and CC?
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ENSO and PDO
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ENSO and PDO
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