Department of Atmospheric and Oceanic Sciences by mikesanye

VIEWS: 0 PAGES: 19

									   Effects of Climate Change on Arctic Observed
   April 12, 2006 — By Randolph E. Schmid, Associated Press

WASHINGTON — It's becoming harder to find the right snow to build an igloo, and melting
permafrost is turning land into mud. With climate change the nature of the Arctic is changing,
too, in ways that worry the people who live there. The Smithsonian's National Museum of
Natural History opens a pair of exhibits on Saturday: "Arctic: A Friend Acting Strangely," and
"Atmosphere: Change is in the Air," discussing what is happening to the climate and how it
affects people living in the planet's northernmost areas.

"They are truly concerned," anthropologist Igor Krupnik said Tuesday of the Arctic natives.
Indeed, the Arctic exhibit title comes from an Inuit word natives have used to describe the
changing climate -- uggianaqtuq -- suggesting unexpected behavior or "a friend acting
strangely." The ocean is eating their land as sea ice melts and storms erode shorelines and wash
away fishing communities, changing climate means new plants in some areas and changes in
migratory routes of animals people depend on for food, weather is stormier and food sources for
polar bears and caribou change.

Since the 1950s, air temperatures have warmed over much of the Arctic, rain and snowfall have
increased and sea ice is in decline. While some government scientists have reported political
pressure to limit their comments on climate change, Robert Sullivan, the museum's associate
director for public programs, said that did not happen in the development of this exhibit. "Here's
the data," Sullivan said. "This is not a political position, it's just scientific data."
"There have been some suggestions that the data is unclear; well, the data is not unclear," Sullivan
added, standing near a map of Greenland illustrating the melting of that island's giant ice cap. In
addition to Smithsonian staff, scientists from the National Oceanic and Atmospheric Administration,
NASA and the National Science Foundation took part in developing the exhibit. It will remain at the
museum until November and there are plans for it to travel to other museums.

While change is unsettling for many, it isn't necessarily all bad, the exhibit notes. For example, a
reduction in sea ice could improve navigation and industrial development, the growing season lengthens
and rich northern fisheries may expand. Adjacent to the Arctic exhibit is Atmospheres, looking at
changes in the air around us, notably the rising level of carbon dioxide which scientists say is a major
factor in trapping heat from the sun and raising temperatures. The Smithsonian Environmental Research
Center in Edgewater, Md., has been studying the effect of increasing carbon dioxide levels on plants for
years, said center director Anson H. Hines.

Plants like carbon dioxide, using it in their growth, and higher levels of the gas spurred them to grow
larger, he said. The plants also became more efficient at water use. However, Hines added, even though
the plants grew larger they were less nutritious. "Global climate change is one of the most significant
challenges humankind has ever faced," said museum director Cristian Samper. "These landmark
exhibitions bring us closer to the science that provides the foundation for understanding how the Earth
has changed through time. The exhibitions also convey the human dimension that must be considered in
addressing how to respond to the environmental changes that are taking place not just in the Arctic, but
all over the globe."
Key to ice ages – northern hemisphere summer
i.e. can you melt the snow from the previous winter?
If no, then ice sheet grows. If yes, ice sheet shrinks




                                              Figure 14-1
Are ice ages an example of a two-state climate system?




                                                Figure 14-9
Changes in climate due to changes in Earth’s orbit
Factors that influence summer insolation

Tilt (obliquity) of earth’s orbit with respect to plane of rotation
about the sun (larger tilt, less sun in winter, but more sun in
summer)


•    varies from 22 to 24.5
    degrees (i.e. the arctic
    circle oscillates north and
    south)


•   period is 41,000 years
Factors that influence summer insolation

Eccentricity – the shape (i.e., how circular it is) of the earth’s
orbit about the sun

•    varies from 1.00 (circular)
    to 1.06
•   Currently 1.017 (nearly
    circular, but closest to sun
    in Dec., farthest from sun
    in June)
•   period is 100,000 years
Factors that influence summer insolation

Precession – where the orbital axis is pointed – presently, the
north star

•    changes timing of summer
    compared to distance from
    sun
•   Is affected by Venus and
    Jupiter (like torque pulling
    on a ‘top’, making it
    wobble)
•   period is 19,000-23,000
    years
Solar insolation in June, Northern Hemisphere




                                          Figure 14-8
We need an amplifier to explain the large variations in climate
due to the 100,000 year eccentricity mode

                                   CO2/biological pump

                                   • Shelf-nutrient

                                   • Iron fertilization

                                   • Coral reef


                                   Cloud/albedo
Schematic of nutrient throughput in the ocean




                                                Figure 14-10
                  Shelf Nutrient Hypothesis
Nutrients in ocean – balance between input by river and loss by
sedimentation of organic matter




                                                         Figure 14-11
                  Shelf Nutrient Hypothesis
Nutrients in ocean – balance between input by river and loss by
sedimentation of organic matter

If CO2 in atmosphere was lower during a glaciation, either input from
rivers was down, or there was more loss by sedimentation

Glaciers     sea level    weathering        phosphate         CO2



Problem – cadmium abundances in seawater track
abundances of phosphate, but measurements of
cadmium in fossil shells show that it wasn’t higher
during glacials – implies that phosphate wasn’t
higher either!
Figure 14-13
                   Iron Fertilization Hypothesis
Iron abundances limit primary productivity (new growth) in certain
regions of the ocean (where the other limiting nutrients are plentiful).
Iron is supplied by wind-blown dust (Sarahan, Gobi deserts – wait
until next week or the week after!)

Lower CO2 during glaciations would imply more wind-blown dust, so
either dryer climate or greater average winds.

Surface temp       temp gradient     winds              iron     CO2


Evidence supports this feedback – windblown dust in
ocean sediments is higher during glacials
Iron Fertilization Hypothesis




                            Figure 14-15
                    Coral Reef Hypothesis

Ca2+ + 2HCO3-  CaCO3 + CO2 + H2O

Formation of coral increases atmospheric CO2

temp    sea level     coral    CO2        greenhouse effect




Problem – growth can keep up with changes in sea level,
but dissolution of limestone is slow, so if this occurs, the
process may be unbalanced – CO2 release may be faster
than CO2 uptake (we call this hysteresis)
Changes in terrestrial biomass




                            Figure 14-16
Even Sulfur – from life! – may play a role.




                                   Figure 14-18

								
To top