Dynamic Climate An overview of Climate Oscillations

Dynamic Climate

An overview of Climate Oscillations

WHAT is a Climate Oscillation?

• Climates are long-term weather patterns.• Climates are a product of

– Latitude, – Altitude, – Proximity to Water, – Location and distribution of nearby Highlands, and – Nearby Ocean Currents– Global Wind Patterns.

• Which of these are static? • Which of these are dynamic?

Thermohaline Circulation: The Global Conveyor Belt

How thermohaline circulation runs

How Thermohaline Circulation works

How the Thermohaline affects the atmosphere.

Thermohaline Circulation, as viewed from the North Pole

What happens in the Antarctic

What can happen?

What can happen? (cont.)

The global conveyor belt thermohaline circulation is driven primarily by the formation and sinking of deep water.

When the strength of the haline forcing increases due to excess precipitation, runoff, or ice melt the conveyor belt will weaken or even shut down.

The variability in the strength of the conveyor belt will lead to climate change in Europe and it could also influence other areas of the global ocean.

So how does it affect climate?

• http://www.pik-potsdam.de/~stefan/thc_fact_sheet.html

So what present Climate Oscillations have been noted?

• El Niño Southern Oscillation (ENSO)

• North Atlantic Oscillation (NAO)

• Arctic Oscillation (AO)

• Pacific Decadal Oscillation (PDO)

El Niño Southern Oscillation (ENSO)• Southern Pacific

• Current(s) involved: South Pacific Gyre

• General length of time for each phase: 3 – 5 years

• What phase are we currently in? La Nina is ending(?)

• Positive Phase (La Nina)– Sea surface temperatures

• Peru current cooler than normal

– Atmospheric pressure

• surface pressures tend to be low over the warm waters of the equatorial western Pacific

Weather outcomesRainy across Australia,

Indonesia, Philippines, Amazonia

Drought W. South America, Southern US

Negative Phase (El Nino)Sea surface temperatures – Peru Current cooler than normal

Peru Current warmer than normal

Atmospheric pressure •pressure over the western Pacific rises and the air pressure over the eastern Pacific falls.

Weather outcomesRainy in W. South America

Drought in Australia

El Niño Southern Oscillation (ENSO)

During El Niño, sea-surface temperatures in the eastern equatorial Pacific are warmer than usual (top), while during La Niña the same region is cooler.

El Niño Southern Oscillation (ENSO)

• http://www.pmel.noaa.gov/tao/elnino/el-nino-story.html

What results…

What results…

North Atlantic Oscillation (NAO)

• Ocean involved: North Atlantic

• Current(s) involved: North Atlantic Gyre

• General length of time for each phase: no real periodicity

• What phase are we currently in? positive

http://addins.wrex.com/blogs/weather/2011/12/lets-stay-positive-because-last-year-we-were-negative

• Positive Phase– Strong Azores High,

Iceland Low – Weather outcomes: USA

has mild winter; Europe gets snow; North Africa stays dry

• Negative Phase– Pressure centers shift

eastward, become weaker– Weather outcomes: USA

has cold winter; Europe has cold dry winter; N. Africa gets rain.

What results…

Arctic Oscillation (AO)

• Ocean involved: Arctic• Current(s) involved:

Beufort Gyre, Transpolar Drift

• General length of time for each phase – no real periodicity

• What phase are we currently in? positive

• Positive Phase– Weak Beaufort Gyre;

Stronger Transpolar Drift– Higher Atmospheric

pressure – Weather outcomes: frigid

winter air does not extend as far into the middle of North America

• Negative Phase– Strong Beaufort Gyre;

Weaker Transpolar Drift– Lower Atmospheric pressure – Weather outcomes: colder

winter in Eastern USA

Pacific Decadal Oscillation (PDO)

• Ocean involved: North Pacific • Current(s) involved: North Pacific

Gyre• General length of time for each

phase: 20-30 years! • What phase are we currently in?

entering a “cool” phase(?)

• Positive (COOL) Phase– Sea surface temperatures: Cooler

than normal – Atmospheric pressure: strong hi/lo

differential – Weather outcomes: mild

temperatures over much of North America, and unusually strong precipitation along the Gulf of Alaska and the Gulf of Mexico.

• Negative (WARM) Phase– Sea surface temperatures: warmer

than normal– Atmospheric pressure: weaker hi/lo

differential– Weather outcomes: extreme

temperatures over much of North America, and less precipitation along the Gulf of Alaska and the Gulf of Mexico.

PDO vs. ENSO