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Class Business

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Title: Class Business


1
Class Business
  • February 15th, first in class exam

2
Isotopic ratios
  • Evaporation of vapor depletes the vapor of about
    10 of Oxygen 18 (similarly for Deutorium).
  • Of the remaining vapor, once it forms
    precipitation (either snow or rain) it is further
    depleted in Oxygen 18 (and Deuterium).
  • In Summary, water vapor has a greater proportion
    of the LIGHT element (Oxygen 16 and Hydrogen)
    relative to the Heavy elements (Oxygen 18 and
    Deuterium). And Snow is lighter than regular
    water vapor.

3
  • The coldest snow is the lightest because as air
    cools down, it loses moisture, in essence, the
    heavier isotopes drop out earlier so what is left
    when snow is finally formed is the lighter
    elements.

4
  • Scientists measure the temperature of an ice
    sheet directly by lowering a thermometer into the
    borehole that was drilled to retrieve the ice
    core. Like an insulated thermos, snow and ice
    preserve the temperature of each successive layer
    of snow, which reflects general atmospheric
    temperatures when the layer accumulated. Close to
    the surface of the bedrock, the lowest layers of
    the ice are warmed by the heat of the Earth.
    These physical temperature measurements help
    calibrate the temperature record scientists
    obtain from oxygen isotopes.

5
Vostok Ice Core
6
Review
7
Proxy data Tree rings
  • Dendroclimatology - the study of the
    relationships between climate and tree-growth
    parameters and their use in the reconstruction of
    past climates.

8
In parts of the world with four seasons, trees
usually grow best in the spring because of higher
rainfall. The cells produced are larger. As the
season progresses the cells get smaller and
smaller and then eventually as winter comes,
growth stops. Thus, trees growing in seasonal
climates exhibit growth rings. These annual
growth rings allow us to age the tree. However,
they also provide a record of what kind of year
was present during that years growth.
9
How is it done?
10
Tree core
11
Many factors can influence the width of tree rings
  • Soil and air temperatures,
  • Soil moisture conditions,
  • Sunshine
  • Wind

12
Older trees work best
Bristle cone pine tree in the Great Basin region
of western North America. These are the oldest kn
own living trees, and can live up to 5,000 years.
13
  • 400 year old Scots pine

14
Sometimes can core fossil trees
  • Fossilized tree from a lake in Scotland

15
How to analyze
  • Compare current tree cores with recent climate
    records to establish the relationship between
    climate and tree ring growth
  • Then analyze the tree rings of either older trees
    (100-400 years old) or fossilized trees

16
  • By carefully comparing, aligning and averaging
    yearly growth rings from many trees in an area,
    you can create a chronology.
  • Sometimes you can measure tree rings taken from
    old buildings, in peat bogs or lakes to extend
    the chronology backwards.

17
How is it done?
18
  • Scientists from 15 institutions in Europe and 9
    countries are working on reconstructing climate
    from trees in northern Eurasia going back several
    recent centuries
  • In some locations (N. Sweden), fossil trees are
    allowing records to go back for 7000 years

19
Other proxy measures
  • In the Ocean sediments core the ooze
  • Ooze (which is in fact the technical term)
  • Ooze contains fossil remains of living creatures
  • Types of creatures and relative abundance
  • Oxygen ratio of the calcium carbonate in the
    skeletons

20
Pollen records
  • Record of species living in different areas from
    pollen cores

21
Pollen coring
22
Pollen core
  • Species composition and relative abundance
  • Can infer climate based on species distributions

23
El Nino Southern Oscillation (ENSO)
  • Example of interaction between ocean and
    atmosphere
  • Disruption of ocean-atmosphere system in tropical
    Pacific
  • Results in redistribution of rains with flooding
    and droughts

24
How it works? (ENSO)
  • Along the equator, western Pacific has very warm
    water, but the eastern Pacific has cool water
    which wells up carrying nutrients that support
    large fish populations
  • Every 2-7 years, trade-winds subside, warm water
    moves eastward across the Pacific
  • Interrupts the upwelling of cool nutrient rich
    water

Easterncold
Western warm
25
El Nino Southern Oscillation
NORMAL
During a normal year, trade winds push warm water
west (towards Australia), cool water rises in its
wake
Trade winds push warm water west
West
East
El Nino
During El Nino year, trade winds weak and switch
direction, push warm water east and prevent cold
water from upwelling
The upwelling brings nutrients to the surface.
Trade winds weak, push warm water east
West
East
26
El Nino effect on ocean temperature
27
El Nino facts
  • El Nino is Spanish for the Christ Child.
  • First used by fisherman in Ecuador and Peru to
    refer to the warm, nutrient poor ocean currents
    appear around Christmas time
  • El Nino event can last 2-3 years
  • Following El Nino can get La Nina (colder than
    average temperatures in the Eastern Pacific)

28
El Nino in Words (from NASA)
  • Stretching across nearly a third of the Earths
    surface, the tropical Pacific Ocean soaks up more
    sunlight than any other single system on Earth.
  • Most of the sunlight is stored in the ocean as
    heat, but the heat isn't distributed evenly.
    Winds stir the surface of the ocean, creating
    pools of warm water and stretches of cool water.
  • In the tropical Pacific, the section of the ocean
    between 23 degrees North and 23 degrees South,
    trade winds blow from east to west. The winds
    push the sun-warmed surface water west, away from
    the South American coast, to a deep pool of warm
    water east of Indonesia.
  • Along the South American coast, deep, cold water
    rises to the surface to replace the warm water
    being pushed west. As a result, waters in the
    eastern tropical Pacific are typically cool,
    while the western tropical Pacific is warm.
  • Periodically the trade winds will slow or even
    reverse directions so that warm water is no
    longer pushed west. The western Pacific cools,
    while the eastern Pacific warms. This distinctive
    reversal in the Pacifics temperature pattern is
    called El Niño. (The name, Spanish for boy
    child, arose because the pattern often becomes
    obvious around Christmas.)

29
This year
  • Satellite measurements of sea surface
    temperatures in the tropical Pacific revealed a
    clear El Niño pattern in November 2006.

30
What to expect with El Nino
  • .

31
Warmer-than-average sea surface temperatures
stretch away from the South American coast, while
cooler-than-average temperatures (blue) pool
around Indonesia and Australia
32
Effects of El Nino
  • Though El Niño is a normal climate pattern that
    develops every 3-7 years, it can cause unusual
    weather patterns around the globe.
  • Heavy rains, flooding result in South America and
    part of North America. parts of North and South
    America.
  • Loss of fish and birds around South American
    coast because there is no food supply.
  • Drought in western Pacific nations such as
    Australia and Indonesia.

33
A typical El Nino year can lead to warmer winters
in North America but warmer and drier in
Southern hemisphere
34
Biological Impacts of an El Nino Year (from NASA)
  • During normal years, when there is a steep
    thermocline tilt, the cold, deep currents flowing
    from Antarctica up the west coast of South
    America are allowed to upwell, bringing essential
    nutrients that would otherwise lie at the bottom.
    Phytoplankton living near the surface depend upon
    these nutrients for survival. In turn, fish and
    mammals depend upon phytoplankton as the very
    foundation of the marine food chain. As
    previously explained, the warm surface waters of
    an El Niño prevent this upwelling, effectively
    starving the phytoplankton population there and
    those animals higher up the food chain that
    depend upon it. Fishermen in Peru and Ecuador
    generally suffer heavy losses in their anchovy
    and sardine industries.
  • At Christmas Island, as a result of the sea level
    rise during the 1982-83 El Niño, sea birds
    abandoned their young and flew out over a wide
    expanse of ocean in a desperate search for food.
    Along the coast of Peru during that same time
    period, 25 percent of the adult fur seal and sea
    lion populations starved to death, and all of the
    pups in both populations died. Similar losses
    were experienced in many fish populations.
  • Meanwhile, over a six-month period about 100
    inches of rainfall fell in Ecuador and northern
    Peru--ordinarily a desert region. Vegetation
    thrived and the region grew lush with grasslands
    and lakes, attracting swarms of grasshoppers and,
    subsequently, birds and frogs that fed on the
    grasshoppers. Many fish that had migrated
    upstream during the coastal flooding became
    trapped in the drying lakes and were harvested by
    local residents. Shrimp harvests were also very
    high in some of the coastal flood regions, but so
    too was the incidence of malaria cases due to
    thriving mosquito populations

35
From Australian climate website
  • A regular commentary on the El Nino-Southern
    Oscillation
  • CURRENT STATUS as at 31st January 2007
  • Equatorial Pacific SSTs have cooled and are close
    to or below El Niño thresholds.
  • Negative subsurface anomalies have strengthened
    and spread further east along the thermocline and
    have nearly reached the surface in the eastern
    Pacific.
  • Trade Winds have generally been somewhat stronger
    than average apart from a weakening in the
    central-west Pacific in the middle of the month.
  • Cloudiness near the date-line has recently been
    above average.
  • Most computer models predict the decay of El Niño
    conditions in the first half of 2007.

36
El Nino events
1998 strongest on record. In general, they are th
ought to be intensifying
37
Bottom Line
  • ENSO is the largest single cause of inter-annual
    climate variability
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