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Climate Change Teleconnections AO, NAO, ENSO, PDO. WS 2005/2006 Lecture/Seminar. Overview I. 20. Oct. Overview – General Introduction 27. Oct. Past climate variability (millions of yrs.) 3. Nov. Little Ice Age and Medival Warm Period

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Climate change teleconnections ao nao enso pdo l.jpg

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 downloads (e.g. Wikipedia.org) or as cited.

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 downloads (e.g. Wikipedia.org) or as cited.

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: downloads (e.g. Wikipedia.org) or as cited.

NAO – North Atlantic Oscillation

PDO – Pacific Decadel Oscillation

ENSO – El Nino / Southern Oscillation

Effects of or on climate change?


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AO: downloads (e.g. Wikipedia.org) or as cited.

Negative phase: H over polar regions, L at mid. lat. (45°N)

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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positive phase                    negative phase

Arctic Oscillation

Figures courtesy of J. Wallace, University of Washington


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- negative phase

+

Arctic Oscillation

Figures courtesy of J. Wallace, University of Washington


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NAO: negative phase

"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 +: negative phase

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 -: negative phase

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: negative phase


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NAO phase implications: negative phase

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: negative phase

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: negative phase

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: negative phase

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 negative phase


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SLP at North Pole negative phase

Hodges, Glenn, 2000. National Geographic


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SLP at North Pole negative phase

Hodges, Glenn, 2000. National Geographic


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NAO and CC: negative phase

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.columbia.edu/NAO/


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ENSO: negative phase

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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Teleconnections El Nino: negative phase

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: negative phase

Cooling of surface water west of S-America

Stronger Walker Ciculation

Stronger trade winds – Thermocline rise


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Teleconnections La Nina: negative phase

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: negative phase

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: negative phase

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: negative phase


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PDO negative phase and CC?


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ENSO negative phase and PDO


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ENSO and PDO negative phase


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