Transcript Historical Sea Level Changes

Warmup
 How has global climate change affected the
biosphere?
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In the polar zone?
In the temperate zone?
In the tropical zone?
Ocean Acidification and Sea
Level Rise
2.6.4B & 2.6.4C
Ocean Acidification
 Ocean acidification is the name given to the ongoing
decrease in the pH of the Earth's oceans, caused by the
uptake of carbon dioxide (CO2) from the atmosphere.
 Remember the pH scale!
How does the Acid get into the Ocean in the first
place?
Ocean Acidification
 Since the industrial revolution began, it is estimated that
surface ocean pH has dropped by slightly more than 0.1
units on the logarithmic scale of pH, representing an
approximately 29% increase in H+, and it is estimated
that it will drop by a further 0.3 to 0.5 pH units (an
additional doubling to tripling of today's post-industrial
acid concentrations) by 2100.
 These changes are predicted to continue rapidly as the
oceans take up more anthropogenic CO2 from the
atmosphere.
 Over the last decade, scientists have discovered that this
excess CO2 is actually changing the chemistry of the sea
and proving harmful for many forms of marine life.
This process is known as ocean acidification.
Effects on Wildlife
 Corals, mussels, snails, sea urchins and other marine
organisms use calcium (Ca) and carbonate (CO3) in
seawater to construct their calcium carbonate (CaCO3)
shells or skeletons.
 As the pH decreases, carbonate becomes less available,
which makes it more difficult for organisms to secrete
CaCO3 to form their shells.
 A more acidic ocean
could wipe out species,
disrupt the food web
and impact fishing,
tourism and any other
human endeavor that
relies on the sea.
 The growing acidification of the oceans is a threat to
corals.
 This relatively healthy coral community on Australia's
Great Barrier Reef represents the current situation,
with atmospheric CO2 concentration of 375 ppm. Mass
bleaching has been observed in many places around
the world, and coral reefs struggle to survive. Coral
cover is currently at 60 percent or less of what it once
was.
 At an atmospheric CO2 concentration of 450-500 ppm
(which could be reached before 2050 based on current
trends), the accelerated rate of coral erosion would
lead to an overall decline worldwide, as in this location
on the Great Barrier Reef. Coral cover will drop to less
than 10 percent of what it once was. (Projections from
2007 paper in Science.)
 Once the atmospheric CO2 concentration exceeds 500
ppm, reef ecosystems will be exceedingly rare or nonexistent, robbing many marine organisms of the
habitat they need to survive. Coral reefs worldwide will
collapse into rubble, as in this reef that once grew in an
inshore region of the Great Barrier Reef. (Projections
from 2007 paper in Science.)
Carbon Emissions
The Acid Sea
The carbon dioxide we pump into the air is
seeping into the oceans and slowly acidifying
them. One hundred years from now, will oysters,
mussels, and coral reefs survive?
National Geographic Reading…
Changes in Sea Level
Sea Level and Climate change
 Between 1870 and 2004, Global average sea levels have
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risen 17 cm.
Two main factors contributed to observed sea level rise.
The first is thermal expansion: as ocean water warms,
it expands.
The second is from the contribution of land-based ice
due to increased melting. The major store of water
on land is found in glaciers and ice sheets
Glacier Calving
Vulnerable Regions
Rising waters
 Over the last several decades, evidence of people's
influences on climate change has become increasingly
clear and compelling.
 Warming of the climate system is well-documented-evident from increases in global average air and ocean
temperatures, widespread melting of snow and ice, and
rising sea levels.
 http://www.globalwarmingart.com/wiki/Special:SeaLev
el
 This Aug. 2011 photo shows a flooded road on Hatteras
Island, N.C., after Hurricane Irene swept through the
area the previous day cutting the roadway in five
locations. From Cape Hatteras, N.C., to just north of
Boston, sea levels are rising much faster than they are
around the globe.
Extra Extra…now hear this! In the news!
North Carolina tries to wish away sea-level rise
US state proposes new law that would ignore grim
projections of a one-metre sea-level rise by the end of the
century
 Some lawmakers will go to great lengths to deny the
reality of climate change. However, North Carolina
lawmakers reached new heights of denial, proposing a
new law that would require estimates of sea level rise to
be based only on historical data—not on all the evidence
that demonstrates that the seas are rising much faster
now thanks to global warming.
 Keep reading…
Is this possible?
 http://geology.com/sea-level-rise/
Historical Sea Level Changes
2.6.4D ANALYZE HOW SEA LEVEL HAS BEEN
AFFECTED BY OTHER EARTH PROCESSES
SUCH AS GLACIATIONS AND TECTONIC
MOVEMENTS. CONSIDER LONG- AND SHORTTERM CHANGES.
Glaciation
 Sea water is removed to
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form glaciers; glaciers melt
to add water to ocean
Rate: 1-15 mm/yr
Volume change: water
Can result in changes of up
to 200m!
During Pleistocene
glaciation, a drop of 106m
occurred.
Melting of Greenland and
Antarctic would produce a
sea-level rise of 60m.
Glacial Isostasy
 Sea shelf sinks under ice;
rebounds when ice melts
 Rate: 0.5-5mm/yr
 Volume change: basin
Thermal Contraction
 Approximately 2m
change in sea level for
one degree change in
surface water
temperature
 Rate: slow
 Volume change: water
 During Pleistocene,
temperatures were 5`C
lower than today,
accounting for 10m lower
sea levels just from thermal
contraction.
Juvenile water
 Addition of new water from volcanic activity; one-
way change
 Rate: very slow
 Volume change: water
Shelf Margin sinks/rises
 Affects broad areas, but not worldwide
 Rate: <0.02mm/yr
 Volume change: basin
 1964 earthquake in Alaska raised the coast by more
than 5m!
Change in rate of seafloor spreading
 Rate of seafloor spreading controls volume of
ocean basin
 Rate: <0.02mm/yr
 Volume change: basin
 The early Atlantic was shallow (thin layer, “floated”)
until the late Cretaceous (layer thicken with time,
“sunk”)
Sediment transfer to oceans
 Reduces basin size;
 Typically a one-way change, sediments can be
returned to continents through the subduction zone
 Rate: very slow
 Volume change: basin
Subduction
 Loss of sediment to the mantle or plastered to
continental block; one-way change
 Rate: very slow
 Volume change: very slow