Lecture 9: Water on Land and in the Cryosphere

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Lecture 9 Water on Land and in the
Cryosphere Water, water, everywhere, nor any
drop to drink --Rime of the Ancient Mariner
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Outline
I. Introduction to the Hydrological Cycle II. Ch.
9- Water on the Land a. Streams and their
channels b. A stream's load c. Floods d.
Groundwater e. Geologic Work of Groundwater f.
Lakes III. Ch. 10-The World of Snow and Ice a.
Snow b. Glaciars c. Sea Ice d. Permafrost
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Introduction The Hydrological Cycle
The Hydrological Cycle includes all water storage
and transportation on Earth
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I. Water on the Land
Water- state (liquid, solid, or gas) controlled
by temperature, pressure, and salinity Although
water is always moving, estimations of volumes
over short periods of time are possible, longer
time periods can change Water has shaped the
Earth's surface via erosion and depostition, and
is a key component of the biogeochemical cycles
of Earth
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A. Streams and their Channels
Streams are controlled by 5 factors 1. Width
and depth of the channel 2. Channel gradient 3.
Velocity of the water 4. Discharge width x
depth x velocity 5. Sediment load
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B. A Stream's Load
Load consists of 3 parts- Bed Load- coarse
particles, 5-50 of the load, slower than
water Suspended Load- fine particles that float,
like silt and clay Dissolved Load- dissolved
substances, major ions bicarbonate, Ca,
sulfate, chloride, Na, Mg, and K Particulate size
decreases down slope of the river as larger
particles sink and smaller particles float
This is an oxbow!
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C. F loods
Flood occurs when a stream's discharge becomes
greater than the capacity of the channel and
water overflows the banks Flooding can create
alluvial valleys, with floodplains, terraces, and
overbank flow

Before flooding and after flooding in 1993 on the
Mississippi River, St. Louis
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D. Groundwater
i. Less than 1 of total water, yet is still
larger than all freshwater lakes, sea ice and
glaciars ii. Mostly found within 750m of
surface ii. Aerated Zone- ground where holes are
still filled with air Saturated Zone- ground is
saturated by water begins the Water Table
iv. Groundwater moves much slower than river,
1cm/day or 1m/year v. Two important
characteristics to the water in the
sediment Porosity- percentage of the volume of a
rock's open spaces Permeability- measure of how
easily a solid allows fluids to pass
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D. Groundwater
Recharge- replenishment of ground water by
rainfall of snowmelt Discharge- groundwater
reaches surface to join rivers, lakes,
etc. Springs- groundwater emerging at
surface We like.... Aquifers! Aquifers are
areas where the rock is permeable enough to allow
for a significant amount of groundwater to
springs and wells In the U.S., we use
the High Plains Aquifer, used by 170,000 wells,
which is depleting the groundwater and lowering
the water table Hard Water vs. Soft Water- most
water in the U.S. Has lots of Ca and Mg
Bicarbonates, called hard water, and deposits
minerals to your bathtub and pipes. Soft water
has less dissolutes and allows for soaping up!
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E . Geological Work of Groundwater
Dissolution- a form of chemical weathering,
attacking limestone and marble Caves and
Sinkholes- (1) dissolution occurs, (2) larger
openings are preferentially expanded, (3)
deposition of carbonate on floor,
(4)continued deposition after
stream leaves
Karst- distinctive topography of caves and
sinkholes Punkva- an underwater river in the
Moravsky Kras (near Blansko)
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Lang's cave in Malaysia
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II. T he World of Snow and Ice
a.k.a. The Cryosphere- from Greek Kryos for
freezing cold and Sphaira for sphere
(hcygmo?) Importance- aids in North Atlantic Deep
Water Formation and effects Earth's albedo
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A. Snow icky,icky,icky
Snow's importance- it recharges groundwater
storage when it melts and reflects sunlight,
cooling surface air temperatures Snow Cycle-
increases during Fall-Winter and decreases as
Spring arrives (as you might
guess) Snowline- lower limit of perennial snow
and is controlled by topography, winter
snowfall, and summer temperatures
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B. Glaciers
Types of Glaciers- (1) Cirque- circus, bowl
shaped depression, (2)Valley- cirque that moves
into a valley, (3) Fjord- a drowned seaward end
of a trough, (4) Ice caps-plateau-like coverage,
(5) Ice sheets- continental coverage, and
(6)Ice shelves- large, floating glacier attached
to land Glaciers form due to melting snow that
accumulates and condenses to form a large mass of
ice that then moves together due to gravity and
it's own weight. Distribution- dependent on
topography, low temperatures, and a moisture
supply
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B. Glaciers
Temperate glaciers- exist in equilibrium with
water, with meltwater at the rock bed, mainly
in mid and lower latitudes Polar glaciers- mean
air temperature is below freezing and no
melting is allowed to occur Glaciers move
due to- 1. gravity pulling on its mass 2.
placing stress on the ice crystals 3. crystals
align 4. stress pushes top layers more than
lower, heavy layers 5. basal sliding due to
meltwater (can be 90 of movement for a
temperate glacier)
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Larsen B ice shelf breaks up Feb.-March 2002,
caught by NASA's MODIS satellite (lost 3,250 sq.
km of ice)
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B. Glaciers
Icebergs- form when glaciers calve, the breakup
of the front of glaciers lying in water Fun
fact- ice has a density of 0.9 of water so that
when you see a iceberg floating, only 10 is
above water, try it at home! Glaciated
Landscapes- Glaciers have carved 30 of the
Earth's surface during ice ages Glaciers can
have loads, like a stream, except the loads
carry very large rocks and deposit them
randomly They can also leave glacial grooves,
due to rocks drug along on the
landscape Cirques are due to ice
wedging Humans have benefited from the rich
soils deposited by glaciers and from meltwater
deposited in groundwater
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Glacial Advance toward viewer
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C. Sea Ice
Sea ice- forms on the surface of the ocean when
the sea surface temperature reaches -1.8oC, not
0oC, because of the salinity (salt content) of
sea water Sea ice is distributed in- perennial
zones- buildup of ice seasonal zones-
annually varying ice The Arctic Ocean consists of
water surrounded by land, whereas the Antarctic
is land surrounded by water, allowing for very
different ice coverage Sea ice is mainly wind
driven, and partly ocean driven,
at 7-15km/day Leads are cracks in the ice
polynyas are larger leads
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C. Sea Ice
Sea ice's importance- In the Earth
System, sea ice influences ocean's salinity,
circulation, and heat budget through albedo
(reflectance) Sea ice is involved in the
Ice-Albedo feedback, a positive feedback that
would follow 1. Temperature drops 2. Ice
forms at a lower latitude 3. More ice increases
Earth's albedo 4. Cooling Earth 5. back to
1.... Forming, what is known romantically as, a
Snowball Earth. Has this happened in the past?
Scientists do think so, but in order to warm up
again, volcanos would contribute CO2, a GHG, to
the atmosphere
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A little bit of what Leah studies...
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D. Permafrost
Permafrost is frozen ground, not involving
water, this is ground that is below freezing
temperatures, mostly found in North America,
northern Asia, and the Tibetan Plateau, perhaps
left from the last glacial age Effect on
climate- This is very hard to measure or
understand because the definition of permafrost
and what constitutes it is not universally agreed
upon People who live with permafrost are very
conscious of it in building houses, but not
everyone is tundra can be destroyed easily and
change the landscape dramatically
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And now for something completely different....
NYCB performing Serenade at the OCPAC
To reward those who have been paying attention...
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Your Pop Quiz!!!