10/14/201011http://www.youtube.com/watch?v=AEoHz56jWGYClimate anomalies: natural climate change• El Niño (& La Niña) Southern Oscillation (ENSO) • Pacific Decadal Oscillation (PDO)• North Atlantic Oscillation (NAO)• Atlantic Multidecadal Oscillation (AMO)• El Niño-Southern Oscillation• Fisheries in Peru• Changes in pressure patterns• Changes in wind patterns• Mainly concentrated in the Pacific OceanENSO4What is El Nino?• El Nino is a climatic fluctuation in the Pacific occurring every 3-7 years (15 since 1950)• It generally occurs within a few months of Christmas, and can be seen first in Ecuador and Peru (“El Nino” = “the Christ Child”)• It is associated with a slackening of the Trade Winds over the Pacific, and a collapse in the sea surface slope across the Pacific10/14/20102El Niño and La NiñaNormal ocean temperatures10/14/20103The big slosh of warm ocean temps to the eastern Pacific.Effects of ENSOEffects of ENSOPacific Decadal Oscillation (PDO)• Discovered late 1990s by salmon fisheries community• Temperature Oscillation• Long-lived El Niño-like pattern of Pacific climate variability• Operates on longer 20 to 30 year periods10/14/20104Pacific Decadal Oscillation PDOWarm phase PDOÆ enhanced coastal ocean biological productivity in Alaska & and inhibited productivity off the west coast of the contiguous United States.Pacific Decadal Oscillation PDOCool phase PDOÆ Opposite patternNorth Atlantic Oscillation (NAO)• Large scale seesaw in atmospheric pressure between the subtropical high and the polar low• The NAO index is defined as the anomalous difference between the polar low and the subtropical high during the winter season (December through March) • Dominant mode of winter climate variability in the North Atlantic region ranging from central North America to Europe• Operates on 20 to 30 year periods, also• Positive phaseNorth Atlantic Oscillation NAO• results in warm and wet winters in Europe and in cold and dry winters in northern Canada and Greenland•Eastern US experiences mild and wet winter conditions10/14/20105North Atlantic Oscillation NAO• Negative phase• brings moist air into the Mediterranean and cold air to northern Europe•Eastern US experiences more cold air outbreaks and hence snowy weather conditions• A multidecadal (50-70 year timescale) pattern of North Atlantic ocean-atmosphere variability• Occurs in Atlantic between the equator and Greenland• When the AMO is positive (warm Atlantic) there is less rainfall over most of the United States• During warm phases of the AMO, the numbers of tropical storms that mature into severe hurricanes is much greater than during cool phases• Since the mid-1990s we have been in a warm phase• Again, note when shifts occurred…Atlantic Multidecadal Oscillation AMOAtlantic Multidecadal Oscillation AMO Atlantic Multidecadal Oscillation AMOAMO (ocean temps) may be driving periods of increased hurricane activity.10/14/20106Effects of Climate Anomalies• Associated with changes in the frequency (& sometimes intensity) of:– Extreme weather conditions (e.g. droughts, snow, floods, hurricanes, etc..)– Forest Fires – Insect Outbreaks– Extreme ocean temperatures Æ cycles of productive/ unproductive marine ecosystems– Economic success/crashes of natural resource offerÆ pricesÆ stock market!– Insurance crisis due to more frequent-severe hurricanes, & fisheries & crops crashes • Climate anomalies may obscure and exaggerate the global increase in temperatures due to human-induced global warming.• Causes that trigger these anomalies are still poorly
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